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CELLS UNIT
Chapter 6: Chemistry in biology
Chapter 7: Cellular structure and function
Chapter 8: Cellular energy
Chapter 9: Cellular Reproduction
6.1 Atoms, Elements, & Compounds



Chemistry will help you learn about biology because
organisms are made up of different chemicals.
Everything is made
up of matter and
matter is made up
of atoms.
Atoms are the smallest
chemical units of matter.
3 kinds of particles


The nucleus is the core part of an atom
Proton
Positive charge (+)
 Found in the nucleus


Electron
Negative charge (-)
 Travels around the nucleus


Neutron
Neutral charge
 Found in the nucleus

Elements




A scientist named Mendeleev created the Periodic
Table which lists all of the known elements on Earth
An element is a pure substance made of only one
kind of atom
Each element is represented by a one or two letter
symbol
http://www.dayah.com/periodic/


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Common elements include carbon, oxygen,
hydrogen, helium, nitrogen…
Elements differ in the number of protons their atoms
contain.
Hydrogen only contains one proton
Oxygen contains eight protons
How many protons does uranium have?
Atomic Number and Atomic Mass


Atomic number tells us
how many protons are in
an element.
Atomic mass tells us
how many protons and
neutrons are in the nucleus
(how heavy the element is)
Compounds


A stable substance made up of two or more
elements.
Every compound is represented by a chemical
formula. Each element may have a subscript that
tells how many there is of that element.
Water H2O
H= white
O= red
How to count #’s of elements in compounds

Examples:
salt (NaCl, 1 sodium and 1 chlorine)
 water (H2O, 2 hydrogen and __ oxygen)


carbon dioxide
(CO2, __ carbon and __ oxygen)
sugar
(C6H12O6, __ carbon, __ hydrogen __ oxygen)

Bonding (2 types)



Covalent bond – when two or more atoms share electrons
and form a molecule.
A molecule is a group of atoms put together.
The number of protons found in the nucleus should equal
the number of electrons floating around the nucleus. This
makes an element stable.



Ionic Bond – A bond formed between molecules when
electrons are transferred.
Sometimes atoms or molecules gain or lose electrons
This transfer causes one atom to be positive and one
atom to be negative. When combined they form a stable
molecule (like salt, NaCl).
6.2 Chemical Reactions




Chemical reactions allow living things to grow,
develop, reproduce, and adapt.
Chemical reaction – process by which atoms or
groups of atoms in substances are reorganized into
different substances.
Energy is the ability to move or change matter.
Energy can be stored or released by chemical
reactions.
Chemical Equations


The starting materials for a chemical reaction are
called reactants.
The newly formed substances created after a
reaction are the products.
REACTANTS
C6H12O6 + O2


PRODUCTS
CO2
+
H20
glucose and oxygen react to form carbon dioxide and water
Circle the reactant(s) and box the product(s)

H2O + NaCl (salt) ----------> Na+ + Cl-

H2CO3 (carbonic acid) <------- H2O + CO2

HCl + NaOH -----------------> NaCl + H2O
Balanced equations



In chemical reactions, matter cannot be created or
destroyed.
This means that the number of atoms of each
element on the reactant side must equal the number
of atoms of the same element on the product side.
Balance this equation:
C6H12O6 +
O2

CO2
+
H20
Energy of Reactions


Living things cannot undergo chemical reactions without
energy.
Activation energy – the maximum amount of energy
needed for reactants to form products in a chemical
reaction.
Enzymes


Enzymes are proteins that
speed up chemical
reactions in the body by
lowering the activation
energy.
Enzymes are never used
up in the reaction. They
can be used again and
again.
Lock-and-Key Model of Enzymes


The reactants that bind to the enzyme are called
substrates.
The specific location where a substrate binds on an
enzyme is called the active site.
Factors that Affect Enzyme Function
Enzymes operate best within certain
temperature ranges. Temperatures outside this
range make the reaction move slowly or not at
all.
 Enzymes operate best within a certain range of
pH values. Too low of a pH (acidic) or too high
of a pH (basic) will slow or stop a reaction.

6.3 Acids and Bases




Acids – any substance that releases hydrogen ions
(H+) when dissolved in water.
Bases – any substance that releases hydroxide ions
(OH-) when dissolved in water.
The amount of hydrogen or hydroxide ions
determines the strength or weakness of the
substance.
The pH scale is used to determine if a substance is
an acid or base.




The pH scale
ranges from
0 to 14.
Acids have values
from
0 – 6.
Bases have values
from
8 – 14.
Anything with a
value of 7 is
considered neutral.
6.4 Carbon Compounds



Carbon compounds are also known as organic
compounds.
They make up most of what living things are made
of.
These compounds are made up of many carbon
molecules covalently bonded to each other and to
other elements (usually hydrogen & oxygen)
Carbohydrates





also known as sugars
made up of carbon, hydrogen and oxygen molecules in a
ratio of 1:2:1
glucose is a common biological sugar (C6H12O6)
examples: sucrose, lactose, glycogen, cellulose
functions: provide energy, structural support
Lipids





include fats and oils
they do not dissolve in water
made up of lots of carbon and hydrogen connected in
long chains
examples: phospholipids, steroids
functions: store energy, provide support, insulation


Some lipids contribute
to cardiovascular
disease by lining the
blood vessels with
plaque.
Plaque build up can
block blood flow
causing a stroke or
heart attack.
Proteins


made up of smaller molecules called amino acids
enzymes are a type of protein used to speed up
chemical reactions.
 salivase
is an enzyme in the mouth that helps to break
down food that you chew
 lactase is an enzyme in the stomach that helps to break
down lactose found in dairy products

functions: transport substances, speed reactions,
structural support, control cell growth
Nucleic Acids

made up of smaller
molecules called
nucleotides
 nucleotide
= sugar +
phosphate + base


examples: DNA, RNA
function: store and
transmit genetic
information
7.1 Cell Discovery and Theory

Robert Hooke
discovered cells
using a simple
microscope in
1665. He
called them
cells because
they reminded
him of small
rooms where
monks live.
Cell Theory



In 1838, Matthias Schleiden and Theodor Schwann
concluded all living things are made of one or more
cells.
In 1855, Rudolph Virchow proposed all cells come
from other living cells.
Many years later, scientists concluded that cells give
living organisms structure.
Characteristics of Microscopes
Since cells are not able to be seen by our eyes,
we need microscopes to magnify them.
 Microscopes enable biologists to examine the
details of cell structure and to understand how
organisms function.

Types of Microscopes
Compound Light Microscopes have a low
magnification and can be used to examine living
cells.
 Electron Microscopes have a high magnification but
cannot be used to examine living cells.
 Scanning Tunneling Microscopes use a computer to
generate a three-dimensional image of the object.

Basic Cell Types
Prokaryotic cells are the smallest and simplest
cells on Earth. The best example of a
prokaryote is bacteria.
 Characteristics of Prokaryotes

 surrounded
by a cell wall
 DNA moving freely inside the cell
 some have flagella to help them move
 don’t have a nucleus
Eukaryotic cells are larger and more complex.
They have a nucleus and other organelles.
 Cell Animation

7.2 Cell Membrane




The cell membrane helps to maintain a cell’s
homeostasis.
The cell membrane is selectively permeable meaning
it allows only certain substances into and out of the
cell.
The cell membrane is made up of a double fat layer
called a phospholipid bilayer.
Draw a diagram of a cell membrane in your notes.
Membrane Proteins

Proteins in cell membranes include:
 enzymes which help with chemical reactions inside
the cell
 receptor proteins which pull substances into the
cell when the cell needs it
 transport proteins which help move substances
across the membrane either into or out of the cell
7.3 Organelles
cytoskeleton: eukaryotic cells have a cytoskeleton
of microscopic protein fibers that provide structure
and support for the cell and its organelles
 nucleus: tells the cell what to do and stores DNA

 the
nucleus is surrounded by a double membrane called the
nuclear envelope that helps protect the DNA inside
 when a cell prepares to divide, the DNA inside the nucleus
forms chromosomes. This helps genetic information get
transferred from the old cell to the new cell.

Production of Proteins
 proteins
are made or created inside ribosomes which are
found on another cell organelle called the endoplasmic
reticulum (ER)
 proteins are important because they help with chemical
reactions

Distribution of Proteins
 proteins
must be programmed so they know what job to
perform inside the cell
 the Golgi apparatus is the organelle that programs
proteins

Lysosomes
 some
proteins are special because they help
breakdown and digest substances inside the cell

Mitochondria
 make
and store energy from carbon compounds
(carbohydrates, lipids, proteins)
 The energy stored is ATP
 Which
types of body cells would need the most
mitochondria to make energy for the body?
Structures in Plant Cells

Cell Wall
used for support and protection
 maintains an upright shape for all plants


Chloroplasts
structures that give plants their green color
 help to capture energy from the Sun to make food


Central vacuole
used to store excess water for the plant when the
environment gets dry
 also helps give a plant it’s shape

7.4 Cellular Transport



Cells have to maintain a stable internal environment
in order to survive. We call this homeostasis.
Cells are constantly bombarded by their external
environment.
The cell membrane’s job is to control what goes in
and what comes out of the cell.
Passive Transport



Passive transport - when something passes through
the cell membrane without using any energy
Equilibrium – state of balance when a substance on
one side of the cell membrane equals the amount on
the other side
Concentration gradient – when one side of the
membrane has a higher concentration of substances
than the other side
Diffusion




Particles or substances inside and around the cell
constantly move.
Diffusion – when substances move from an area
of high concentration to an area of low
concentration.
The cell does not have to use any energy for a
substance to diffuse into or out of a cell.
Remember that the cell membrane is selectively
permeable; that means it only allows certain
substances to pass through.
Facilitated Diffusion




Most cells have membrane proteins embedded in their
cell membrane that help to bring in or carry out
substances.
A carrier protein is a molecule that typically carries
amino acids and sugars across the cell membrane. (too
big to move on their own).
Another word for facilitate is “to help”.
The cell does not have to use any energy for a
substance to diffuse into or out of a cell.
Osmosis



Osmosis is the diffusion of water across a selectively
permeable membrane.
Water is always needed by the cell, so it passes
easily through the cell membrane.
A cell always wants to be stable, so water will move
into and out of a cell until the inside of the cell is
neutral (pH of 7)
How does water move?

There are three possibilities for the direction of
water movement across a cell membrane:
 Water
moves out
 Water moves in
 Water does not move
Isotonic Solutions



When water is equal on either side of the cell
membrane, there is NO MOVEMENT of water into
or out of the cell.
The cell shape remains unchanged.
This is the condition most cells try to maintain in
order to survive.
Hypotonic Solutions



When the concentration of water outside of the cell
is greater than inside the cell, the water MOVES
INTO the cell.
When water moves in, the cell swells and sometimes
bursts.
Because plant cells are more rigid than animal cells,
they typically don’t burst.
Hypertonic Solutions


When the concentration of water outside of the cell
is less than inside the cell, the water MOVES OUT of
the cell.
When water moves out, the cell shrinks.
Active Transport




Active transport requires the cell to use energy to move
substances against a concentration gradient.
The energy the cell uses is ATP.
Substances have to move from an area of low
concentration to an area of high concentration.
Swimming pool, going up a down escalator, kayaking
demo...
Types of Active Transport




Proteins and large sugars are too large to pass
through the membrane or be moved by
membrane proteins.
These substances are moved across a cell
membrane by vesicles (large pockets in the cell
membrane).
Draw diagrams in your notes
active transport demo
8.1 Obtaining Energy


In order for your body to function properly, you
need energy to perform daily activities.
All energy comes from the Sun.
 Autotrophs
make their own food by using the Sun’s
energy
 Heterotrophs need to ingest food to obtain energy
Metabolism


Metabolism – all the
chemical reactions that
take place in a cell
Two important chemical
reactions involve:
 photosynthesis
 cellular
respiration
ATP


Adenosine triphosphate is the most important
biological molecule that provides energy for living
things.
ATP releases energy when the bond between
phosphates is broken.
8.2 Photosynthesis


Photosynthesis – describes the process of how the
Sun’s energy is trapped and converted into energy
Overall equation:
SUNLIGHT

6CO2 + 6H2O


C6H12O6 + 6O2
Plants have special organelles called chloroplasts that
help to capture the Sun’s energy.
8.3 Cellular Respiration


Cellular respiration – describes the process of how
living organisms obtain energy by breaking down
organic molecules
Overall equation:
C6H12O6 + 6O2

 6CO2 + 6H2O + energy
Animals have special organelles called mitochondria
that help to breakdown sugars into useable energy.
carbon dioxide
and water
glucose
and oxygen
9.1 Cellular Growth



Cell size is limited by its ratio of surface area to its
volume.
Surface area – the area covered by the cell
membrane.
Volume – space taken by the inner contents of the
cell.
Importance of Small Cell Size


As a cell grows, its volume increases much more
rapidly than the surface area.
By remaining small, cells can function better.
 Substances
can move in and out easily
 The cell can communicate across smaller distances
The Cell Cycle



Once a cell reaches its size limit, something must
happen—either it will stop growing or it will divide.
Most cells will eventually divide.
Cell cycle – a repeating sequence of events that
allow a cell to grow and divide.
How do cells know when to divide?

Just as traffic lights control the flow of traffic, cells
have a system that controls the phases of the cell
cycle.



Cells have a number of “red light-green light”
switches that regulate information traveling
through the cell.
Cells can’t divide unless they pass all checkpoints
with green lights.
Yellow or red lights would slow or stop cell
division.
Stages of the Cell Cycle
Chromosomes

How many cells do you think are produced by the
human body everyday?
2

trillion cells, that’s 25 million cells every second
Why do cells divide?
 Cells

need to grow, develop and repair themselves
When a cell divides, the DNA must be copied
before the genetic information is distributed
Prokaryotic Cell Reproduction


Bacteria have a single circular strand of DNA that
“floats” around the cell; the DNA is not contained
within a nucleus
Prokaryotes reproduce by a type of cell division
called binary fission.
Binary Fission
Eukaryotic Cell Reproduction



In eukaryotes, DNA is organized into units called
genes
Genes are small segments of DNA
A single molecule of DNA has thousands of genes
lined up next to each other
Chromosomes




When a cell prepares to divide, the DNA coils up
into a structure called a chromosome.
Each chromosome has two strands; each strand is an
exact copy of the other.
Each individual strand is called a chromatid.
The two chromatids are connected by a point called
a centromere.
Chromosome Structure



Homologous
chromosomes are those
that are identical in
structure.
Most humans have 23
pairs of chromosomes
(46 total).
There are two types of
cells: somatic (body
cells) and gametes
(sex cells).
Cancer


Sometimes cells have mutated chromosomes
that lead to cancer. These cancer cells can
change all the checkpoints to green lights
and they coast through the cell cycle
reproducing rapidly.
All cancers are different, but if scientists
can figure out what changes all the
checkpoints to green lights we could cure
cancer.
Causes of Cancer

Carcinogens – substances that are known to cause
cancer.
 Asbestos
 Tobacco


products
Ultraviolet radiation and other forms of radiation
Genetics