Download CELLS structure and function

CELLS
STRUCTURE
AND
FUNCTION
Important Characteristics:
Chemically and structurally unique
 Need energy
 Have a life span
 Are capable of growth and reproduction
 Respond to their environment

Organisms are organized
The substances from which organisms are
made are carefully organized.
 Organization determines the kind of
organism.

Each new cell contains the same kind of
molecules and the same amount of water
as the ‘parent’cell.
 Some cells are very short-lived – only
days

◦ Ex. Scavenger white blood cells

At any instant only certain genes in a cell
are on or expressed giving orders for the
function of that cell.
The basic unit of life. All living organisms are made up of
one or more cells. Cells are the smallest unit that we say is
alive. All cells come from the division of preexisting cells.
CELL THEORY
Tiny Building Blocks
Organisms are made of cells
 The basic structure of life.
 A microscope is required to see the
structure

Structural Units
Cell – the basic structure of all living
things
 Cell specialization – differences in cells so
they can perform unique activities
 Tissue – groups of cells that are alike in
activity and structure
 Organ – collections of tissues that work
together to perform certain functions
 Organ systems – several organs that
work together to perform an acitivity

TYPES OF CELLS
Prokaryotic
Genetic material
contained is held
within a single
molecule
 Smallest of all cells
 Bacteria and bluegreen algae
 Used in
biotechnology

Eukaryotic
Genetic material held
within a nucleus
 Animal and plants are
made of these

ANIMAL CELLS
Animal Cell Structure
Animal cells are typical of the eukaryotic
cell, enclosed by a plasma membrane and
containing a membrane-bound nucleus
and organelles. Unlike the eukaryotic cells
of plants and fungi, animal cells do not
have a cell wall.
 Most cells, both animal and plant, range in
size between 1 and 100 micrometers and
are thus visible only with the aid of a
microscope.

The lack of a rigid cell wall allowed animals to
develop a greater diversity of cell types, tissues,
and organs.
 Specialized cells that formed nerves and muscles
gave these organisms mobility. The ability to move
about by the use of specialized muscle tissues is a
hallmark of the animal world, though a few
animals, primarily sponges, do not possess
differentiated tissues.
 Notably, protozoans locomote, but it is only via
nonmuscular means, in effect, using cilia, flagella,
and pseudopodia.

The animal kingdom is unique among
eukaryotic organisms because most
animal tissues are bound together in an
extracellular matrix by a triple helix of
protein known as collagen.
 Plant and fungal cells are bound together
in tissues or aggregations by other
molecules, such as pectin.

Structure
3 COMPONENTS
Cell membrane
 Cytoplasm
 Organelles

Structure
CELL MEMBRANE
CELL MEMBRANE




All living cells have a plasma membrane that
encloses their contents.
In prokaryotes, the membrane is the inner
layer of protection surrounded by a rigid cell
wall.
Eukaryotic animal cells have only the
membrane to contain and protect their
contents.
Contains protein receptors that control the
flow of substances into and out of the cell.
Structure
CYTOPLASM
CYTOPLASM
A jellylike substance of which 90 percent
is water.
 Found within the cell membrane and
surrounds the nucleus.

Structure
ORGANELLES
NUCLEUS


Highly specialized organelle that serves as
the information processing and
administrative center of the cell.
This organelle has two major functions:
◦ it stores the cell's hereditary material, or DNA,
and
◦ it coordinates the cell's activities, which include
growth, intermediary metabolism, protein
synthesis, and reproduction (cell division).

The nucleus is a two-layered membrane with
pores.
Nucleolus

an organelle within
the nucleus - it is
where ribosomal
RNA is produced.
Some cells have
more than one
nucleolus.
CENTRIOLES
Located near the center of the cell are
two cylinders
 Self-replicating organelles
 Each is made of nine pairs of hollow
tubules.
 Important role in cell division.

MITOCHONDRIA
 The
cell’s powerhouse
 Site of both respiration,
(exchange of oxygen and carbon
dioxide), and the breakdown of
fats and sugars to convert oxygen
and nutrients into energy.
Mitochondria
Oblong shaped organelles that are found
in the cytoplasm of every eukaryotic cell.
 Inner folds contain enzymes that produce
adenosine triphosphate (ATP)

◦ Provides energy needed for many cell
functions.
ENDOPLASMIC RETICULUM
Network of tubules and thin, curved sacs
- manufactures, processes, and transports
chemical compounds for use inside and
outside of the cell.
 2 types:

◦ Rough – is covered with ribosomes that give
it a rough appearance. Play a role in protein
synthesis and transport.
◦ Smooth – site of calcium storage and fat
production.
Rough ER
Smooth ER
RIBOSOMES
All living cells contain ribosomes
 Small, granular structures function
in the assembly of proteins.
 Tiny organelles composed of
approximately 60 percent RNA and
40 percent protein.
 In eukaryotes, ribosomes are made
of four strands of RNA.
 In prokaryotes, they consist of three
strands of RNA.

GOLGI APPARATUS
(also called the Golgi body
or Golgi complex)
 Stacks of flattened sacs
receive and process small
vesicles of protein from
the rough reticulum.
 The proteins are modified
and repackaged into larger
vesicles and released at the
cell membrane for body
functions
 The distribution and
shipping department for
the cell's chemical
products

LYSOSOME

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The main function of these microbodies is
digestion.
This organelle produces powerful enzymes
that degrade dangerous materials taken into
the cell.
Break down cellular waste products and
debris from outside the cell into simple
compounds, which are transferred to the
cytoplasm as new cell-building materials.
Dispose of any unwanted substances or
worn out organelles.


Lysosomes are
about 1 μm in
diameter, are
surrounded by a
single membrane,
and have a densely
staining, featureless
interior.
There may be
dozens of
lysosomes in a cell,
depending on its
needs.

http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__lysosomes.html
Peroxisome

A membrane-bound
organelle that
contains specific
enzymes imported
from the cytoplasm
(cytosol).
CHROMATIN

A granular material
composed of DNA.
(the cell’s genetic
material)
VACUOLE
Storage Bins to the Cells
 Sac stores and transports water, ingested
materials and waste products.

MICROVILLI

Some cells have projections that increase
their surface area to aid absorption.
◦ Lining of the small intestine
Flagella and cillia

http://programs.northlandcollege.edu/biol
ogy/Biology1111/animations/flagellum.htm
l
CYTOSKELETON

The internal framework of the cell has 2
main types of structure.
◦ Actin Filaments – provide support and
contraction
◦ Microtubules – hollow tubes that aid
movement of substances through the cell’s
cytoplasm
◦ Structural strength
 all eukaryotic cells (prokaryotes don't have them)
There are many different types of
cells.
Each cell has a shape, and size adapted for
its function.
Types of Cells
SIZE
Major difference in cells occurs between plant cells and
animal cells.
While both plant and animal cells contain the structures
discussed before plant cells have some additional specialized
structures.
PLANT CELL
Cell Wall

Many animals have skeletons to give their
body structure and support. Plants do
not have a skeleton for support and yet
plants don't just flop over in a big spongy
mess.
cell wall
This is because of a
unique cellular structure
called the cell wall. The
cell wall is a rigid
structure outside of the
cell membrane composed
mainly of the
polysaccharide cellulose.
 They become thicker with
age.

Vacuoles
One or a few very large ones are found in
each cell.
 As the cells mature the vacuoles tend to
get larger and fuse into a single vacuole
that is up to 90% of the cell’s volume.
 Contain large quantities of water and
dissolved substance.

storing foods (e.g., proteins in seeds)
 storing wastes
 storing malic acid in CAM plants
 storing various ions (e.g., calcium, sodium,
iron) which, among other functions, helps
to

Water flows in and creates osmotic
pressure which is responsible for the
rigidity (“turgor”) of plants
 When water is in short supply the
vacuoles lose their osmotic pressure and
the plant wilts.
 Holds solid crystals of substances that
color flowers.

PLASTIDS
Can color a plant
 They are usually disk-shaped and about
5-8 µm in diameter and 2-4 µm thick. A
typical plant cell has 20-40 of them.



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The chloroplast allow plants to harvest
energy from sunlight. Specialized pigments
in the chloroplast (including the common
green pigment chlorophyll) absorb sunlight
and use this energy to complete the
chemical reaction:
6 CO2 + 6 H2O + energy (from
sunlight) C6H12O6 + 6 O2
In this way, plant cells manufacture glucose
and other carbohydrates that they can store
for later use.
Chloroplast
Membrane-bound organelle and the site of
photosynthesis and ATP production
Leucoplasts are whitish in color and store
starch, lipid or protein.
 Chromoplasts produce and store other
pigment, the carotenoids which give color
to particular parts of a plant.


http://www.biology.ualberta.ca/facilities/m
ultimedia/uploads/cell_biology/plantcell_D
D.html
An Overview of Photosynthesis
Photosynthesis converts light energy into the
chemical energy of sugars and other organic
compounds. This process consists of a series of
chemical reactions that require carbon dioxide
(CO2) and water (H2O) and store chemical
energy in the form of sugar. Light energy from
light drives the reactions. Oxygen (O2) is a
byproduct of photosynthesis and is released into
the atmosphere. The following equation
summarizes photosynthesis:
 6 CO2 + 6 H2O → 6(CH2O) + 6 O2
 sugar


http://www.stolaf.edu/people/giannini/flash
animat/metabolism/photosynthesis.swf
Calvin cycle
These 3-carbon molecules serve as the
starting material for the synthesis of
glucose and other food molecules.
 The process is called the Calvin cycle
and the pathway is called the C3 pathway.

The graphic shows the steps in the
fixation of carbon dioxide during
photosynthesis.

http://highered.mcgrawhill.com/sites/0070960526/student_view0/
chapter5/animation_quiz_1.html
Transports molecules in and out of the cell
MEMBRANE
TRANSPORT SYSTEMS
2 Types
PASSIVE TRANSPORT
Diffusion
It is diffusion that causes a smell (expensive
perfume or smelly socks) in one part of the
room to gradually move through the room
so it can be smelt on the other side.
Diffusion occurs in the air and in liquids.
 In the animal’s body diffusion is important
for moving oxygen and carbon dioxide
between the lungs and the blood, for moving
CO2
digested food molecules from the gut into
the blood and for the removal of waste
products from the cell.

O2
Diffusion through a Liquid


In the body, diffusion causes molecules
that are in a high concentration on
one side of the cell membrane to
move across the membrane until they
are present in equal concentrations
on both sides. It takes place because
all molecules have an in-built vibration
that causes them to move and collide
until they are evenly distributed.
Small molecules like oxygen, carbon
dioxide, water and ammonia as well as
fats, diffuse directly through the
double fat layer of the membrane. The
small molecules named above as well
as a variety of charged particles (ions)
also diffuse through the protein-lined
channels. Larger molecules like
glucose attach to a carrier molecule
that aids their diffusion through the
membrane.This is called facilitated
diffusion.
Diffusion

http://www.northland.cc.mn.us/biology/Bi
ology1111/animations/transport1.html
Osmosis

Osmosis is the
diffusion of water
across a membrane
that allows water
across but not larger
molecules. This kind
of membrane is
called a semipermeable
membrane.
Osmosis
The movement of water molecules from
an area of high concentration to an area
of low concentration.
 It is osmosis that plumps out dried fruit
when you soak it before making a fruit
cake or makes that wizened old carrot
look almost like new when you soak it in
water.

Osmosis

http://www.stolaf.edu/people/giannini/flash
animat/transport/osmosis.swf
Active transport


When a substance is transported from a low
concentration to a high concentration i.e.
uphill against the concentration gradient,
energy has to be used. This is called active
transport.
Active transport is important in maintaining
different concentrations of the ions sodium
and potassium on either side of the nerve
cell membrane. It is also important for
removing valuable molecules such as glucose,
amino acids and sodium ions from the urine.

http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__how_facilitated_diff
usion_works.html
Phagocytosis


Phagocytosis is sometimes
called “cell eating”. It is a
process that requires energy
and is used by cells to move
solid particles like bacteria
across the plasma membrane.
Finger-like projections from
the plasma membrane
surround the bacteria and
engulf them as shown in
diagram 3.10. Once within the
cell, enzymes produced by the
lysosomes of the cell
(described later) destroy the
bacteria.
The destruction of bacteria
and other foreign substance
by white blood cells by the
process of phagocytosis is a
vital part of the defense
mechanisms of the body.

http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__phagocytosis.html
To make the function of the parts of the cell easier to
understand and remember you can compare them to a
factory.
THE CELL AS A
FACTORY
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The nucleus (1) is the managing director of the factory
consulting the blueprint (the chromosomes) (2);
The mitochondria (3) supply the power
The ribosomes (4) make the products;
The chloroplasts of plant cells (5) supply the fuel (food)
The Golgi apparatus (6) packages the products ready for
dispatch;
The ER (7) modifies, stores and transports the products
around the factory;
The plasma membrane is the factory wall and the gates (8);
The lysosomes dispose of the waste and worn-out
machinery.
http://www.wisconline.com/objects/index_tj.asp?objID=A
P11403
 http://www.wisconline.com/objects/index_tj.asp?objID=A
P11604
