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Biology
Science 10
Cycling of Matter in Living Systems
p.254-359
In this unit we will explore:
 microscope technology
 the cell theory
 cellular structures and function
 cellular transport
 The specialized cells of multicellular
organisms
 plant cell mechanisms (gas exchange,
water transport)

7.1 Life From Life

The development of the theories of
the origin of living matter:

Aristotle (384 BC – 322 BC) – a Greek
philosopher whose theory of abiogenesis or
spontaneous generation was accepted for over
2000 years.
Abiogenesis – living things could arise
from non-living matter
 Examples:






a) eels came from the slime in river mud
b) rats came from garbage or dirty laundry
c) maggots came from rotting material
d) mice came from a pile of wheat husks
e) frogs came from mud

Aristotle created his theories on the origin
of life based on his many observations,
however, he did not conduct any scientific
experiments to test his ideas.

Q: Choose one of the above examples
and describe how to refute the idea
using scientific experimentation.

Francesco Redi (1626 – 1697) – Italian
physician who used controlled scientific
experiments to refute the theory of
spontaneous generation
Redi’s experiment: see figure 7.2 p.259
(see next slide)

Why did maggots appear in jar 1 & 2?
Jar 1:
Meat covered 
No maggots
appeared

Jar 2 & 3
Meat, left uncovered
 Maggots
appeared

NOTE: Within a few years, the discovery
of microscopic single celled organisms,
renewed the idea of abiogenesis. People
believed a “vital force” or “active principle”
in the air created these micro-organisms.


Louis Pasteur (1822 – 1895) – French scientist
who finally settled the continued debate of the
theory of abiogenesis.
Pasteur’s experiment:
< --------- airborne particles
settled here
Tutorial 3.3 Pasteur’s Experiemnt

http://bcs.whfreeman.com/thelifewire/con
tent/chp03/0302003.html

a swan-neck glass flask (figure 7.3) full of
nutrient-rich broth was boiled to force out air
and kill any microbes

flask was cooled and broth remained clear even
after many days because any microbes entering,
settled with gravity in the neck of the flask.

When flask was tipped so broth reached neck,
soon broth became cloudy.

As a result: The accepted theory became
biogenesis – living things could only
arise from other living organisms
(suggested by Vichow in 1858)
*WORD
CONNECT
Biogenesis - Latin root “bio” = of
living
things and “genesis” = origin
Discovering Cells

Prior to seeing bacteria, the common
assumption was that curses or
supernatural spirits caused diseases!

The invention of the microscope allowed
scientists to magnify objects and examine
the microscopic world, and as a result,
cells were discovered.

Cell – the smallest functional unit of life
found in all living organisms
TRIVIA
 (p.265) * The largest cells are egg cells
(largest: ostrich eggs which are 1.2 kg, 14
cm wide)
 * The longest cells are nerve cells (longest
is the sciatic nerve that runs down your
leg)

Onion cell
Developing the Cell Theory

the cell theory explains and defines the
boundary between the living and nonliving and is integral to our understanding
of life on Earth

The molecules that are food for a cell and
the organic molecules that make up a cell
are non-living, yet the cell is ALIVE!

Robert Hooke (1635 – 1703) – looked at
cork with a compound light microscope
(30X magnification) and was the first to
see and name “cells”.
Cork cell

Antony van Leeuwenhoek (1632 – 1723)
– Dutch linen merchant who first
described single-celled microorganisms.
He used a single lens microscope (500X
magnification) to study blood cells, pond
water & teeth scrapings

called his sightings “animalcules”
Blood cells

Matthias Schleiden (1804 – 1881) and
Theodor Schwann (1810 – 1882) –
German scientists who studied cells in
hundreds of plants and whose research
contributed to the cell theory, stating
that “all organisms are made of cells ”

(NOTE: they still believed that cells were
created by spontaneous generation.)
Plant cell

Rudolf Vichow – German physician who
made microscopic observations of cells
dividing and completed the cell theory still
accepted today.
The Cell Theory

All organisms are composed of one or
more cells.

The cell is the smallest functional unit of
life.

All cells are produced from other cells.
Complete:

Textbook p. 265 #2, 5, 6, 7, 9, 11
Video: discovering the cell (national
geographic)

https://www.youtube.com/watch?v=qTPd
wSG0-5A
7.2 Cells and Technology

Light Microscopes – use to view objects
illuminated by visible light

Simple microscope – used only one
lens (similar to a magnifying glass)

Compound microscope – uses two or more
lenses placed one on top of the other

first created on 1595 by Zacharias Janssen, a
Dutch maker of reading glasses

commonly has one lens in the eyepiece and one
in each objective

can magnify as much as 2000 X
Label the microscope in
Your workbook

Electron microscope – specimens are
illuminated with a beam of electrons
instead of a beam of light

magnifies up to 1.2 million times

electron micrograph – the photograph
of the image produced by an electron
microscope
An Ant &
Pollen Grains (1000X)

TEM – transmission electron microscope

built in 1931 in Germany

specimens are thinly sliced, then placed
under a vacuum to remove moisture &
particles. Electrons are then transmitted
through the specimen to view 2-D
internal structures & details.

SEM – scanning electron microscope

designed in 1930’s in Germany

a beam of electrons sweeps over an
object to create a 3-D image (only the
surface can be detected)

CLSM – confocal laser scanning microscope

invented in the 1960’s

a laser beam directed at numerous planes
creating a series of 2-D images or “optical
slices”

computer software then “stitches” images
together
Tetrahymena cells

STM – scanning tunnelling microscope

invented in the mid-1900’s

enables scientists to obtain an image of atoms
on an object’s surface (eg. DNA molecule)

a fine metal probe emits electrons towards
specimen’s surface and information is
interpreted by a computer producing a 3-D
image
How to use a microscope video
(5 min)

https://www.youtube.com/watch?v=SUo2
fHZaZCU

How to calculate actual Size of specimens
& How to calculate scale notes

Complete: workbook: microscope, actual
size drawing & scale calculations
7.2 A Molecular World
Genes – sections of DNA that direct the
activities of our cells
 changes in the gene can cause improper
cell function
 eg. Sickle cell anemia


DNA – carries all genetic information of the
organism, coiled to form chromosomes, found
in the nucleus of every cell

constructed of 4 bases:



Adenine pairs with Thymine
Cytosine pairs with Guanine
the order of thousands of pairs of bases make up
each organism’s unique genetic code

Q: Fill in the missing bases on this piece of
DNA.

Gene sequencing – mapping the order of all of
a gene’s bases

Human Genome Project (HGP) – an
international projec to sequence all 30,000 to
40,000 human genes

sequence information can be used to diagnose
and treat genetic disorders

eg. gene therapy – human gene is “corrected”
to help cure a disorder or cancer

Cancer - most cancers are caused by
gene damage, some of which create
mutations


cancerous cells divide indefinitely and form
layers upon layers to form a tumor
Mutations – changes in the base
sequence of a gene

- some mutations may cause a cancer where
cells grow and divide uncontrollably forming a
tumor
Living or Not?
Life needs energy, produce waste &
reproduce
 Virus – non-cellular structure made of a
piece of genetic material enclosed in a
protein coat


in order to reproduce, a virus must infect
a cell and use this host cell’s organelles
(cell parts)
Prion – a protein that can convert into a
harmful particle which can reproduce in
living tissue
 causes BSE (bovine spongiform
encephalopathy) or “mad cow disease”

Culturing Cells

Cell culture – isolated cells are given
nutrients and their growth and division are
studied
Cell lines – the generations of cells
produced from a culture; can be grown
indefinitely in a lab
 Eg. HeLa cells

Stem cells – “blank slate” cells that divide
to produce all other types of specialized
cells
 found in:






one week old embryos (fetuses)
adult bone marrow (these form different types
of blood cells ~ most abundant stem cells in adults)
unused embryos from in vitro fertilization
treatments
cord blood (from umbilical cord after birth)
genetically engineered from human egg cells

mature into specialized cells which can
only reproduce to form more of their own
kind (liver cells -> liver cells)

scientists hope to grow tissues and organs
for transplants and to cure diseases using
stem cells (eg. Parkinson’s, Alzeimer’s,
diabetes & spinal cord injuries)

Rudolf Virchow – the first scientist to link
illnesses to malfunctioning cells
The wacky history of Cell theory
video ( 6 min)

https://youtu.be/4OpBylwH9DU
Complete: check your understanding
p. 276#3-6
What’s in a Cell?

Cells – sustain life by performing the
tasks essential for the cell to function:






obtain food & energy
convert energy (eg. photosynthesis)
construct & maintain the molecules making up
the cell structure
carry out chemical reactions
eliminate wastes
reproducing

Organelles – internal cell parts that carry
out specific functions
Prokaryotes – one-celled organisms
lacking a membrane-bound nucleus &
organelles (do contain ribosomes) are the
most abundant cells on Earth
 eg. bacteria and algae

Eukaryotes – cells with a more complex
internal structure including a membranebound nucleus & organelles
 eg. most plant and animal cells

In Latin:
“karyon” means nucleus
“pro” means before
“eu” means true
therefore: prokaryote means before nucleus.
eukaryote means true nucleus.
Cell Organelles

Cell membrane (plasma membrane)



a protective barrier for the cell allowing
transport of needed materials in and out
consists of protein molecules imbedded in a
lipid bilayer
Vesicles – small membrane sacs pinched
off of the cell membrane

store or transport materials in and out of the
cell
Cell Organelles

Cytoplasm – jelly-like cell contents


70% water with suspended organelles
Nucleus – contains DNA, the genetic
material of the cells (genes)


directs all cellular activities
materials leave the nucleus through nuclear
pores in the nuclear membrane (or nuclear
envelope)
Cell Organelles

Nucleolus – region of the nucleus where
ribosomes are produced

Ribosomes – dense granules that may
be found attached to rough ER or free in
the cytoplasm

are the site of protein synthesis – where
amino acids are assembled into proteins
according to the information stored in the
DNA
Cell Organelles

Endoplasmic reticulum (ER) – network
of tubes branching from the nucleus
through which materials can be
transported



rough ER – has ribosomes on the surface
smooth ER – has no ribosomes, produces and
packages lipids
Lysosomes – vesicles containing
digestive enzymes

function to break down food particles, kill
bacteria & destroy old or damaged cell parts
Cell Organelles

Golgi apparatus – flat disc-shaped sacs that
sort, modify & replace molecules sent from the
ER; the needed materials are pinched off into
vesicles and sent to other parts of the cell or to
the cell membrane for transport out of the cell


lysosomes are produced here
Mitochondria – rod-shaped organelle with
folded inner membranes

site of cellular respiration in which chemical energy
stored in sugars is converted into useable energy for
the cell (ATP)
Cellular Respiration

C6H12O6 + 6O2  6CO2 + 6H2O + energy
Cell Organelles

Centrioles – cylindrical structures
located just outside the nucleus of animal
cells


- during cell division, centrioles help direct
the separation of genetic material
Vacuoles – balloon-like vesicles that
store water, food, minerals, or wastes

animal vacuoles are smaller; plants usually
have one large central vacuole
Cell Organelles

Cell wall – rigid structure that protects and
provides shape and support to plant, fungi &
some bacterial cells


composed of cellulose, a complex carbohydrate (a.k.a.
fibre or roughage in our diet)
Chloroplasts – found only in green plants


contain stacks of flattened discs containing the green
pigment chlorophyll
are the site of photosynthesis in which the Sun’s
energy is converted into chemical energy (sugars)
Photosynthesis

6CO2 + 6H2O ----------- > C6H12O6 + 6O2
Animal cell
Plant cell
Plant cells



Plants cells always
have a cell wall
Plant cells may have
chloroplast
Mature plant cells
have very large
vacuoles occupying
most of the cell
volume
/
Animal cells




Animal cells never
have a cell wall
Animal cells never
have chloroplast
Animal cells have very
small vacuoles
Animal cells have a
centriole
Basic Differences Between Plant and
Animal Cells
Plant cell
 Have membrane,
cytoplasm & nucleus
 Have a cells wall
 Vacuoles big
 Nucleus large & near
the cell membrane
 Usually ‘squarish”
 Structurally rigid
Animal cell
 Have membrane,
cytoplasm & nucleus
 No cell wall
 Vacuoles small &
dispersed
 Nucleus small & near
the center of the cell
 Usually ‘roundish”
 Structurally flexible
Cell Organelles
Cell Membrane
Cell Wall
Cytoplasm
Endoplasmic Reticulum
Ribosomes
Golgi Bodies
Chloroplasts
Nuclear Membrane
Mitochondria
Nucleus
DNA
RNA
Nucleolus
Lysosomes
Vacuole
Protoplasm
Chromosomes
Proteins
City Analogies
City border
City Wall
Lawns
Highway or road system
Lumber or brick yard
Post Office or UPS
Solar Energy Plants
City Hall Fence with security guard
Energy Plants
City Hall
Original Blueprints or the city
Copies of Blueprints
Copy Machine
Waste Disposal/ Recyclers
Warehouses, water towers or
garbage dumps
Air or atmosphere
Rolled up blueprints
Lumber or bricks
Complete:

P. 284 # 2, 3, 4, 6, 7, 8

Complete: Animal cell & plant cell in
workbook
END OF CHAPTER 7
Membrane Properties

The activities of a living cell depend on
the ability of its membrane to:
 transport raw materials into the cell
 transport manufactured products and
wastes out of the cell
 prevent unwanted matter from entering
the cell
 prevent the escape of matter needed to
perform cellular functions
Cell Membrane Structure

phospholipid bilayer – each
phospholipid molecule has a head that is
hydrophilic (water-loving) and two tails
that are hydrophobic (water-fearing)
These molecules are arranged in a
bilayer two molecules thick

proteins – are embedded throughout
the membrane serving the following
functions:





moving substances across the membrane
carrying out chemical reactions (they act as
enzymes)
some have “marker” molecules (carbohydrate
chains) on their surface allowing cells to
recognize each other
allow messenger molecules (such as
hormones) to attach
assist in cell-to-cell communication and
control of cell functions

Protein position within a membrane:

Peripheral proteins – are partially embedded
in the inside or outside surface of the
membrane

Integral proteins – extend through the entire
bilayer and project from both surfaces

The Fluid-Mosaic Model

Cell membrane molecules are in constant
motion (drifting past each other) resulting
in:


membrane flexibility
cell’s ability to change shape
Fluid mosaic model cell membrane
https://www.youtube.com/watch?v=Qqsf_
UJcfBc
 (2 min)

Complete:

BLM 8-1 cell membranes
Cell Membrane Function





A Biological Barrier
a cell membrane prevents many
materials from entering the cell. Name
6:
- salts
- atoms
- viruses
- sugar
- ions
- bacteria
- proteins

most organelles are surrounded by
membranes with the same structure as a
cell membrane

Apoptosis – when the lysosome bursts
and releases it’s digestive enzymes into
the cell, resulting in cell destruction
The final clean up
Apoptosis under a microscope (30sec)

https://www.youtube.com/watch?v=NU0M
3uqGCuw
A Selective Filter

Cell membranes are semi-permeable,
allowing some materials to cross, while
excluding others. They can select




by particle size
small enough to enter membrane - O2, H2O
too large to cross - sugar
particular materials to transport across (they
bind to chemicals based on their size, shape or
charge)

p. 296 Cool Tools – Describe the freezefracture method and how it provided
evidence for the fluid mosaic model.

[specimens are frozen in liquid nitrogen
then cracked with a cold knife. The lipid
bilayer can be separated, exposing the
membrane proteins. Can coat with
platinum and examine with electron
microscope]
Complete p. 296 # 1-6
Transport Across Cell Membranes

Selective Transport – the movement of
only certain substances across the cell
membrane

Particle Model of Matter – all matter is
made of tiny particlesp.297 Find Out
Activity – Brownian Motion

Brownian Motion – in a liquid or gas,
particles are in constant, random motion

Concentration Gradient – the difference
in concentration between two areas for
any given molecule produces a gradient
or path of movement in which molecules
move toward areas where the
concentration of particles is lower

- molecules move down a concentration
gradient

Equilibrium – a state at which molecules
are evenly distributed (the concentration
is equal throughout the medium)

molecules continue moving but equilibrium
is maintained
Types of Transport Across Membranes

Passive Transport – movement across
cell membranes without an input of
energy

Q. Name 2 reasons molecules move.


1. Brownian Motion
2. Concentration gradients

Diffusion – the net movement of
particles from an area of high
concentration to an area of low
concentration


no energy is expended
in a cell, very small particles can cross the
cell membrane by moving between the
phospholipid molecules

Q: Why does oxygen diffusing into
the cell never reach equilibrium?


A: Your cells continually consume oxygen for
cellular respiration, making the concentration
inside always lower than the outside
Q: Describe the concentration
gradient of carbon dioxide.

A: Higher concentrations in the cell so net
movement is out of the cell.
complete

BLM 8-3 particle model of matter and
diffusion

Osmosis – the diffusion of water
molecules across a membrane (water
molecules move from where they are
more highly concentrated to where they
are less concentrated)

Solutions are described in terms of their
concentration relative to another solution

Hypotonic solution – has a lower
concentration of solute compared to
inside the cell

Water is therefore more concentrated outside
the cell and water enter the cell (cell swells)

Hypertonic solution – has a higher
concentration of solute compared to the
inside of the cell

Water is therefore less concentrated outside
the cell and water will leave the cell (cell
shrinks)

Isotonic solution – has the same solute
concentration on both sides of the cell
membrane. Equilibrium has been
reached. EQUAL FLOW of water into and
out of the cell

Q: a) What happens when a cell is
placed into distilled water?


A:
The cell is hypotonic and water moves
into the cell & the cell may burst
Q: b) What is turgor pressure?

A:
The cell wall of a plant resists the
pressure of a water-filled vacuole keeping the
plant firm
Complete: BLM 8-4 concentration
gradients

Q: c) What happens when a cell is placed
into strong salt water?


Q: d) What is plasmolysis?


A:
The solution is hypertonic and water leaves the
cell. The cell shrinks and may die (plasmolysis)
A: Loss of water in a plant cell resulting in WILTING
Q: e) Why would drinking saltwater pose a
problem?Do BLM 8-4 Concentration
Gradients

A: Hypertonic solution outside cells would cause cells to
lose water, shrink and die (dehydration)

Facilitated Diffusion – diffusion of molecules
across the cell membrane by way of transport
proteins.

- necessary for glucose, ions, and other
substances that cannot cross the membrane by
simple diffusion

Transport proteins have 3-D shapes that
make them highly selective, recognizing atoms
or molecules by shape, size or charge.
Two types of transport proteins:
 carrier proteins – facilitate the diffusion
of glucose across the cell membrane


Q: Explain how glucose enters the
cell.

A: Glucose fits into a groove on the carrier, the
protein’s shape changes, and glucose is
released on the inside of the cell

channel proteins – have tunnel-like
pores filled with water that allow charged
ions in and out of the cell
A. Channel protein
B. Carrier proteins

B. Active Transport – the movement of
molecules and ions against the
concentration gradient which requires ATP
energy and carrier proteins to pump
these molecules from an area of low
solute concentration to an area of high
solute concentration.

used to accumulate nutrients, or remove toxic
materials or wastes
Complete:
BLM 8:6 types of transport across cell
membranes
 6-7 Role of cell membrane in endocytosis
& exocytosis


Most cells use 40% of their energy on
active transport; kidney cells use 90% of
their energy on using active transport to
filter wastes out of your blood!

Bulk Transport – the use of vesicles to
facilitate movement of substances that are too
large to enter or exit the cell via transport
proteins

Two types:


ENDOCYTOSIS – the cell membrane forms a pocket
around the material to be transported, then either
pinches off as a vesicle or a vacuole. (moves stuff in)
Q: Differentiate between a vacuole &
vesicle.

A: Vesicle transports contents; vacuole stores the
ingested material
Endocytosis
Two types of Endocytosis:
 phagocytosis - when cells “eat” by
taking in large particles or other cells


Q: What happens after a new vesicle
enters the cytoplasm of a cell?

A: It fuses with a lysosome and the enzymes
would digest the material

pinocytosis – when cells “drink” by
taking in droplets of fluid

Receptor – mediated endocytosis –
receptors, like antennae, detect specific
compounds or cells and bind with them,
triggering endocytosis.

Q: Give 2 examples of molecules entering by
R.M.E.

Cholesterol & HIV

EXOCYTOSIS – the reverse of endocytosis,
whereby the membrane of vesicles or vacuoles
fuses with the cell membrane and the stored
contents are expelled from the cell.

Q: Give 2 examples of expelled materials.Do
BLM 8-6 Types of Transport Across Cell
Membranes

A: Wastes, enzymes, hormones
Exocytosis
Video: amoeba feeds

https://www.youtube.com/watch?v=W6rn
hiMxtKU
Complete:

BLM 8-7 The role of cell membranes in
Endocytosis and exocytosis
Membranes at Work

Water Purification

Reverse osmosis – uses pressure to
force contaminated water through a
membrane with fine pores that will not
allow bacteria, salts, and other dissolved
molecules through, resulting in water
with fewer impurities

Kidney Dialysis - filters toxic wastes
that accumulate in the blood while
retaining necessary proteins, glucose,
amino acids & ions

- the patient’s blood is pumped through
dialysis tubing, a synthetic, semi-permeable
membrane. When immersed into a salt
solution, needed salts don’t diffuse, but
wastes, which are hypertonic to the
dyalysate, diffuse out of the blood.

Controlled Delivery of Medications –

medication can be placed in a flat
transdermal patch that sticks to the skin. A
semi-permeable membrane lining the inner
surface allows drugs to diffuse out of the
patch at a slow, constant rate.
Q: Give 4 examples of medications
available in patches.
 A: Nicotine (to quit smoking)






hormones for imbalances
- motion sickness drugs
contraceptive hormones
- pain reducers
- weight-loss

Liposomes – artificial vesicles that can
safely transport medications from one
part of the body to another

Two examples:


used to transport anti-cancer medications to
tumours in cancer patients
liposomes, coated with the gene needed to
cure cystic fibrosis, are sprayed into the
patient’s nostrils
Complete:
Test pg.307 # 2-5
 Movie: membranes

Cell Size and Function

Particles entering the cell reach more to
other areas of the cell by diffusion, due to
a differing concentration gradient in the
two areas.

Q. Compare rate of diffusion across a
cell membrane with diffusion within a
cell.

A. Concentration gradient within a cell is lower
so diffusion in a cell is slow and inefficient.

Two reasons an amoeba could not function
were it human-sized:

substances could diffuse through the cell
membrane in less than a second, but would
take more than a week to reach the centre of
the cell.

It would have a very low surface area – to –
volume ratio making it difficult for adequate
amounts of oxygen and nutrients to diffuse in

Q. What do scientists believe was the
reason that the Paleozoic Era could sustain
the existance of giant insects?

A. The air was believed to be 35% oxygen
(now 21%) making the concentration gradient
of oxygen much steeper and O2 was able to
efficiently move through longer tracheoles.
Surface Area to Volume Ratio

***As a cell grows, volume increases
faster than surface area.

Eg. If cell size is doubled, it would require
eight times more nutrients and produce
eight times more waste, but surface area
would only have increased four times.

Result:

1. not enough surface area for oxygen,
nutrients, and waste exchange

2. cell would starve

3. cell would be poisoned from a buildup of
waste products
OR

Cells want to maximize surface area to
volume ratio (amount of membrane to size of
cells)

A surface area to volume is a 2 digit
expression


Surface area: volume
As a cell grows its volume increases much
faster then its surface area.

A cell with a surface area-to-volume ratio
of 30:6 has to acquire 3 times the
nutrients of a cell with a ratio of 10:2.

A cell with a surface area-to-volume ration
of 18:6 requires 6 times the nutrients as a
cell with a ratio of 3:1

The human body has more than 10 trillion
cells. If 1000 average-sized cells were
lined up, they would total less than 2 cm
in length!
Cell Shape and Surface Area

Certain cell shapes increase surface areato-volume ratio’s

Eg.



Enfolding of membrane
Flattened cells
The higher the surface ratio to volume the
better!
From One Cell to Many Cells

How do some organisms function at
enormous sizes?


They are multicellular and grow by adding
more cells instead of simply growing larger
cells,
Result: Rapid diffusion within cells exists

Cell specialization – in multicellular
organisms, cells are organized into tissues
that do specific jobs.

Q: Give an examples of cell specialization
in your body



Lungs – gas exchange
Heart & blood vessels – transport O2, nutrients
& wastes
Kidneys – water regulation & excretion of
wastes
Complete:
P. 314 # 2, 4, 7
 Workbook surface area to volume ration &
cell size

End of chapter 8!

Cell Specialization – in multicellular organisms,
cells are organized into tissues that do specific
jobs.

Give an example of cell specialization in
your body.




- lungs – gas exchange
- heart & blood vessels – transport of O2, nutrients &
wastes
- kidneys – water regulation and excretion of wastes
- digestive system – nutrient digestion and absorption
Specialized and Organized

Q. What functions need to be carried out
by the leaf of a plant?





A. gas exchange
release water
protect leaf cells
photosynthesis
transport water & nutrients through leaf

In single-celled organisms, one cell
performs all the functions of life.

In multi-cellular organisms, groups of
similar cells (called tissues) are specialized
to perform specific tasks.

Q. Name 4 specialized cells in the human
body.




A. cells of the intestinal lining
nerve cells
muscle cells
skin cells
 Photosynthesis
occurs in the
chloroplasts of plant cells
6CO2(g) + 6H2O(l)  C6H12O6(s) + 6O2(g)
Cellular respiration occurs in the mitochondria
of plant and animal cells.
C6H12O6(s) + 6O2(g)  6CO2(g) + 6H2O(l)

During cellular respiration in animals
and plant cells, exhaled air contains
lower O2 levels and higher CO2 level
than inhaled air.
Complete BLM 9-1
photosynthesis & respiration in
plants
Cells that make up the leaf

Epidermal Cells – make up the
epidermis




Description - flat, single cell layer covering
the upper and lower surfaces of the leaf
- transparent, which allows solar energy to
pass through to cells beneath
- a waxy cuticle coats the cells to prevent
evaporation of water
Function – to protect the leaf, therefore do
not contain chloroplasts

Palisade Tissue Cells


Description – long and narrow (columnar)
cells packed closely together lying just below
the epidermis
Function – major photosynthesis,
therefore packed with chloroplasts

Spongy Tissue Cells


Description – round, loosely packed cells
found just below palisade layer; contain
chloroplasts
Function – gas and water exchange, minor
photosynthesis
Stomata and Guard Cells



Description –
stomata (singularstoma) are tiny
openings on the
underside of a leaf
- each stoma is
controlled by 2
guard cells
Function –
stomata allow
exchange of carbon
dioxide, oxygen
and water vapor

Vascular Tissue Cells


Description – a series of tubes or leaf veins
called phloem and xylem, which are arranged
together in vascular bundles
Function –


XYLEM – carries water and minerals from
roots to leaves
PHLOEM – carries sugars made by the leaves
to other parts of the plant

Do an analogy of leaf tissues and
human body tissues


skin = epidermis; circulation system =
vascular tissue;
lungs = stomata
Complete BLM 9-2

Cell specialization in leaves
Cell, Tissue, Organ, System

Name 3 advantages multicellular
organisms have over single-celled
organisms.




– larger size
- a variety of specialized cells
- an ability to thrive in a broader range of
environments
Multicellularity, however, requires a high degree
of organization of the numerous cells in order to
perform their functions efficiently. (The human
body contains approx. 100 trillion cells.)

Cells – basic unit of organization



eg.
Human – stomach cell
Plant - phloem cell
Tissues – many cells with the same
structure and functions clustered together


eg. Human – muscle tissue of stomach
Plant – epidermal tissue

Organs – multiple tissues working
together to perform a specific function



eg. Human – stomach
Plant – leaf
Systems – organs working together to
perform a complex function


eg. Human – digestive system
Plant – vascular system
Complete:

P. 324 check your understanding #1-4
9.2 Gas Exchange in Plants

During cellular respiration in animal and
plant cells, exhaled air contains lower O2
levels and higher CO2 level than inhaled
air.

During photosynthesis, plants consume
CO2 and H2O and produce O2.
Leaves

Gases diffuse into stomata of plant leaves
and move through air spaces between the
spongy and palisade tissue cells. CO2
dissolves into the watery film around the
cells and diffuses into the cells of the leaf
where chloroplasts use the CO2 for
photosynthesis. O2 produced diffuses
out of the leaf cells and leaves through the
stomata.
Roots and Stems

- some gas exchange occurs in surface
cells

- in woody plants, layers of dead cork cells and
waxy substances prevent gas exchange

- Lenticels, which appear as slashes on stems
of trees and herbaceous plants, are natural
pores through which gas exchange can occur.
Gas Exchange is Tied to Water Loss

Q. How do plants carry out evaporative
cooling?


A. By transpiration.
Q. How can this process function as a survival
mechanism for plants?

A. Can cool leaf 10-15C and prevent heat damage

Transpiration is the evaporation of water from
leaves of plants. This can be as much as 99% of
the water absorbed by the roots.

Transpiration and gas exchange are
controlled by the shape of guard cells which
open stomata to allow CO2 in and O2 and H2O
out. More photosynthesis occurs when stomata
are open.

OPENED STOMATA – occurs when high water
pressure, called turgor pressure, causes water to
move into the guard cells by osmosis. The guard
cells swell and the stomata open, allowing
transpiration. (Occurs most during the day).

CLOSED STOMATA – occurs when the
amount of water in the guard cells
decreases and they shrink and the
stomata close. (Occurs most during the
night, except in desert plants where
stomata only open at night due to dry
conditions).

WILTED PLANTS – result from reduced
turgor pressure as a result of water loss.
Complete BLM 9-3

Complete p. 330 #1
Water Transport in Plants

Xylem Vessels and Phloem Vessels

Xylem and phloem make up the vascular tissue
of plants, transporting water, minerals, and
sugars through a series of interconnected
tubes through the leaves, stems and roots.

XYLEM – transports water and dissolved
minerals from soil to leaves.


in mature plants, most xylem cells are dead,
only cell walls remain, forming hollow tubes
called xylem vessels.
Detailed Structure of Xylem Vessels –
consists of long hollow cells called
tracheids or vessel elements, which are
joined by small pits, allowing water to flow
through.

PHLOEM – transports sugars produced during
photosynthesis from leaves to roots. Cylindrical
cells joined end to end form phloem vessels,
which are living cells with porous cell walls.
Sugary sap flows down the phloem vessels and
passes through these pores.

Detailed Structure of Phloem Vessels –
consists of sieve tubes, cylindrical cells joined by
a sieve plate. A companion cell lies alongside
each sieve tube cell, offering support because the
sieve tube cell lacks many organelles.

Water Uptake in Roots


Roots are covered with epidermal tissue which
is permeable to water only at the root tip.
Water enters the root tips by osmosis until it
reaches the xylem.
Root hairs – increase surface area for
absorbing water & dissolved minerals.

are each an outgrowth of a single epidermal
cell

- minerals enter the root by facilitated
diffusion or active transport

- the solution of water & minerals in root
xylem is called xylem sap.

- xylem carries the xylem sap up to stems
& leaves (branching into leaf veins)
eventually being absorbed by all cells of
the plant
Properties of Water

Two properties of water allow xylem sap
to rise great distances against gravity

Cohesion – the attraction of water
molecules to other water molecules due to
their polar nature. (Observed as water
forms droplets)

- the column of xylem sap can be broken
by a break in the vessel or a bubble in the
sap.

Q: Explain how each of these
situations could be caused.


A: Break – cut in root, stem or leaf
Bubble – freezing in winter

Adhesion – the attraction of water
molecules to molecules of other
substances. (Observed as water sticks to
the glass in a graduated cylinder, forms a
meniscus)

- water also clings to the cellulose wall of a
xylem vessel, preventing the sap from falling
back towards the roots, thus helping to fight
the force of gravity.

The two main mechanisms that aid the
upward movement of water in plants are
root pressure and transpiration.

A. Root Pressure Pushes

Root pressure occurs when root cells actively transport
minerals into the xylem. This causes water to diffuse
into this hypertonic area, building root pressure in the
xylem which forces fluid up the xylem vessels.

Fluid seeping from a cut stem of a plant occurs due to
root pressure.

Q: Will all transport cease due to a
cut halfway up the stem?

A: Xylem sap will still flow upwards above
the cut (compare to a cut straw)
B. Transpiration Pulls
 Transpiration of water from leaf stomata
generates a pulling force, aiding the
upward transport of water –


1) The energy for xylem transport ultimately
comes from the heat of the Sun.

2) Water molecules evaporate leaving the air
within the leaf slightly drier

3) Water then diffuses out of leaf cells into
intracellular fluid where solutes are more
concentrated

4) As evaporation from the leaf continues, the
cohesion of water molecules draws the water up
the xylem vessels, replacing evaporated water.

Adhesion of water molecules to the walls of
xylem vessels aids the process.

Transpiration increases as temperature
rises, increasing water movement through
xylem. Xylem transport speed can be up
to 50 meters/hour
Sugar Transport in Phloem
 Sugars produced by the palisade and
spongy tissue cells of the leaf are
transported to the stems and roots by
phloem vessels


1) Sugar, minerals, and other nutrients enter
phloem by active transport

2) Water flows by osmosis, causing phloem
cells to swell with turgor pressure. ( Sugar +
nutrients + water = phloem sap)

3) Phloem sap flows down the
concentration gradient and the fluid
pressure forces the sap through pores in
phloem cell walls and into surrounding
cells

4) The nutrients are continually used up
by tissues of the stem and root resulting
in a pressure gradient that causes a
continual flow of solution from leaf to
root.

Phloem transport ranges from 20 cm/hr to
100 cm/hr

Q: How do aphids help researchers study
phloem?

A: After they probe a phloem cell with their
stylet, researchers cut off the stylet. Phloem
continues to ooze out and can be studied.
NOTE: – artificial probes injure the phloem
cells.
Phloem & xylem video ( 5 min)

https://www.youtube.com/watch?v=60Sg
ZgK3Gss
Complete

Textbook p. 340 #1-7
Plant Control Systems

Tropisms are plant responses in which the plant
grows towards or away from a stimulus.

Phototropism is the growth of a plant toward a
light source.

WHY? This maximizes light absorption for
photosynthesis which fuels plant growth

HOW? Plant cells respond to light by growing at
different rates. When cells on one side of a stem grow
more elongated than cells on the other side, the stem
curves.

SKETCH AND LABEL a plant bending towards the Sun,
indicating area of elongation.
The Mechanism

Charles and Francis Darwin concluded that the tip
of the seedling detects light, transmits that
information to the stem, and the rate of growth
of stem cells is affected. The Darwins suspected a
chemical signal triggered the growth.

Decades later, Peter Boysen-Jensen tested the
presence of a chemical signal, finding that the
chemical could pass through gelatin but not mica.
(See Fig. 9.19, p.344)
The Hormone

In 1926, Frit Went confirmed that a chemical he
named “auxin” (meaning to grow”) was produced
in the plant tip. Auxin is actively transported
through the cells towards the shaded side of the
stem causing cells there to grow longer than cells
on the lighted side, resulting in bending towards
the light.

Q: Summarize Went’s experiment on p.345,
Fig. 9.20

A: Agar containing auxin caused cell elongation in
stems on which ever side it was placed (light not being a
factor)

Gravitropism – is the growth of a plant
in response to the force of gravity

1)Negative gravitropism – stem grows
towards sunlight and against the force of
gravity

2)Positive gravitropism – roots grow into the
soil & towards the force of gravity
The Mechanism

Gravitropism occurs as soon as seeds
germinate and the response of the stems
and roots is consistent regardless of how
the seed is oriented when it is planted.

Auxin is responsible for the plant growth
response to gravity.

IN THE STEM – when a plant is placed on its
side, more auxin collects in the cells on the
stems lower side. These cells then grow longer
resulting in the stem curving upward.

IN THE ROOT – increased auxin concentration
inhibits root growth. When a root is placed
sideways, auxin collects along the lower side but
cell growth is inhibited here. Cells on the upper
side, however, continue to grow longer,
resulting in the root growing downward.

Another theory of positive gravitropism
is that dense starch grains in the root tip
cells may settle at the low point in cells
signalling the direction of gravity and
influencing the direction of growth.

3. Nastic Response is a plant’s response
to touch. The stimulus of touch sends an
electrical signal to certain leaf cells
resulting in a drop in turgor pressure. This
causes the leaf to collapse.

Q: Give two examples of plants
exhibiting a nastic response (See
p.344)

A: Mimosa, Venus Fly Trap

4. Thigmotropism is a rapid growth of
certain plant cells in response to touch. It
is seen in plants that use tendrils to wrap
around supports or other plant stems.

Eg. The tendrils of a pea plant that come
in contact with a chain-link fence will wrap
around it, gaining support as it grows.
Tropism song

https://www.youtube.com/watch?v=uX5e
oxKbzHE
complete
BLM 9-6 discovering tropisms
 Review p. 348 Q1-7
 P. 350 #1-8, 10, 11
 BIO unit review
