Unit 1 – Cell Biology
Pupil Course Notes
St Ambrose High School
Biology Department
Unit 1
Cell Biology
Pupil Notes
(complete)
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Page 1 of 23
Unit 1 – Cell Biology
Topic 1 – Cell Structure
Unit 1
1.
Pupil Course Notes
Cell Structure
Cells are the basic units of life. All living things are made of cells.
Cell wall
Cells contain different structures that do different jobs.
Cell membrane
Animal
cell
Plant
cell
Cytoplasm
Mitochondria
o
Vacuole
Nucleus
ribosome
s
Circular DNA
Chloroplast
Fungal
cell
Ribosomes
Cell wall
mitochondria
vacuole
nuclei
Bacterial
cell
Cell wall
cytoplasm
Plasmid
Cell membrane
Part
Function
Cell wall
Provides support and gives structure
Mitochondria
Site of aerobic respiration
Chloroplasts
Site of photosynthesis
Cell membrane
Controls the entry and exit of materials
Vacuole
Contains sap and is involved in water balance
Nucleus
Contains DNA and controls cells activities
ribosomes
Site of protein synthesis
plasmid
Extra pieces of bacterial DNA
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Unit 1 – Cell Biology
Pupil Course Notes
Bacteria

Bacteria are single celled micro-organisms.

They have a cell wall and ribosomes, but no other parts.

The cell wall has a different structure to plant and fungal cell walls.

They have one large circular piece of DNA and extra little pieces called plasmids.

Plasmids give bacteria extra properties such as the ability to resist antibiotics.

Bacteria can be used in biotechnology to make yoghurt and cheese.

They can also be used to produce biofuels.
Fungi

Fungi are organisms which are not quite plants or animals.

Their cells are similar to other plant and animal cells but have a different cell wall.

Some fungi such as yeast are simple, unicellular organisms.

Yeasts are important in biotechnology, where they are used in baking and brewing.

They use sugar to make alcohol and carbon dioxide.

Other complex fungi are used in biotechnology to produce a variety of enzymes and
for production of antibiotics such as penicillin.
Summary
Structure
Type of cell
Animal
Plant
Bacteria
Fungus
Ribosome
X
X
X
X
Mitochondrion
X
X
Circular DNA
Vacuole
X
X
Cell Wall
X
X
X
X
X
Nucleus
X
X
Chloroplasts
X
X
Plasmids
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X
X
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Unit 1 – Cell Biology
Unit 1
a)
Pupil Course Notes
Topic 2 – Transport across cell membranes
Function and Structure of the Cell Membrane
The cell membrane allows the transport of materials in and out the cell.
It is composed of lipids and protein molecules.
The cell membrane is said to be selectively permeable because it lets small molecules
through but not big ones.
b)
Diffusion
Molecules move from an area of high concentration to an area of low concentration.
Area of High
Concentration
Area of Low
Concentration
A concentration gradient is the difference in concentration between two areas. In diffusion
molecules move down a concentration gradient from high to low.
This process does not need energy and so it is said to be passive.
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Unit 1 – Cell Biology
c)
Pupil Course Notes
Importance of Diffusion
Diffusion is a vital process in the survival of living organisms. In multicellular organisms it
allows the movement of oxygen from the lungs into the blood, it also moves oxygen and
glucose into cells for respiration and allow waste products such as carbon dioxide to be
excreted from the body. In a unicellular organism diffusion is the means by which it obtains
food and oxygen from its surrounding environment.
d)
Osmosis
Osmosis is the movement of water molecules from a region of high water concentration to a
region of low water concentration across a selectively permeable membrane.
When water enters and leaves cells by osmosis it changes their appearance.
e)
Animal Cells

Animals cells placed in a solution with a low water concentration will lose water and
shrink.

Animals cells placed in a solution with a high water concentration will gain water and
burst.
In high water concentration  Cell Bursts
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In low water concentration  Cell shrinks
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Unit 1 – Cell Biology
Pupil Course Notes
Plant Cells

Plant cells placed in a solution with a low water concentration will lose water and
become plasmolysed.

Plant cells placed in a solution with a high water concentration will gain water and
become turgid.

The cell wall prevents the cell from bursting.
In high water concentration
In low water concentration
 Cell gains water and swells becoming
 Cell loses water, vacuole shrinks and
turgid
membrane pulls away from wall becoming
plasmolysed.
f)
Active Transport
Active transport is movement of molecules from a region of low concentration to a region of
high concentration against a concentration gradient. As this process moves against the
concentration gradient it requires energy in the form ATP (see topic 1.8).
Area of High
Concentration
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Area of Low
Concentration
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Unit 1 – Cell Biology
Unit 1
a)
Pupil Course Notes
Topic 3 – Producing New Cells
Mitosis
Normal cells in humans contain 46 chromosomes in the nucleus, which is 23 pairs of
chromosomes. In other words normal body cells contain two sets of chromosomes. Any cell
that contains two matching sets of chromosomes is said to be diploid.
Chromatid Chromatid
chromosome
centromere
Cell division is essential to allow organisms to grow and repair damaged parts. During cell
division, the parent cell divides to produce two identical cells, which contain the same
number of chromosomes as the parent cell.
Cancer is uncontrolled cell division.
The sequence of events of mitosis ensures that no genetic information is lost.
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Unit 1 – Cell Biology
Stage
b)
Pupil Course Notes
Description
1-2
The chromosomes replicate to form two identical chromatids.
The chromosomes coil up and become short and thick.
2-3
The chromosomes line up along the equator of the cell, the spindle fibres form
and the nucleus disappears. The spindle fibres attach to the chromosomes
3-4
The spindle fibres pull the chromatids of each chromosome apart to opposite
poles of the cell
4-5
The cytoplasm divides and new nuclear membranes form
5-6
Two daughter cells are formed, each containing the same number of
chromosomes as the original cell. These cells are identical
6-1
The cell grows before it repeats the process
Cell Culture
The cell culture technique is an artificial way of producing new cells.
Cell culturing must be carried out under sterile conditions using aseptic techniques in order
to prevent contamination.
i) Aseptic Techniques
When working in the laboratory it is very important to take precautions. These
precautions help to prevent contamination or avoid the escape of micro-organisms.
Some of the main precautions include:
 Hand and surface washing with disinfectant
 Sterilise glassware
 Use Bunsen burner to sterilise equipment
 Seal all petri dishes
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Unit 1 – Cell Biology
Pupil Course Notes
ii) Growth Media
 Agar is a growth medium that micro-organisms can grow on. It contains a jelly
that provides a surface that microorganisms can stick to and nurtrients they
use as food.
 Nutrient broth is also a growth medium that can be a that can support the
growth of cells or micro-organisms. This growth medium contains nutrients but
no agar.
Micro organisms need to be kept in conditions that are favourable for growth. For example;
control of temperature, pH and oxygen concentration.
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Unit 1 – Cell Biology
Unit 1
a)
Pupil Course Notes
Topic 4 – DNA and the Production of Proteins
Structure of DNA
Genetic information is found in the nucleus of
cells. It is organised into genes and these are
found on chromosomes. Genes are made of
DNA. DNA contains all the information needed
for normal cell function. Each individuals DNA is
unique.
DNA is a molecule that is made of two strands
held together by complementary base pairs. The
double stranded DNA molecule is then twisted to form a coiled shape described as a
double helix.
There are four different bases; the bases are called A, C, G, and T. These bases make up
the genetic code.
A always bonds with T and G always bonds with C.
T A C T G T G G
A T G A C A C C T G T A T A G G A T G A C G C C A T
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Unit 1 – Cell Biology
b)
Pupil Course Notes
DNA and Proteins
DNA carries the genetic information for making proteins. Proteins are made of molecules
called amino acids.
The base sequence in a gene determines the amino acid sequence in a protein.
To make a protein the code from the DNA in the nucleus has to be carried to a ribosome
where proteins are made.
A molecule called messenger RNA (mRNA) carries a copy of the code from the DNA in the
nucleus to a ribosome in the cytoplasm.
The protein is assembled from amino acids.
DNA
membrane
cytoplasm
nucleus
Amino acid
mRNA
Protein
Ribosome
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Unit 1 – Cell Biology
Unit 1
a)b)
Pupil Course Notes
Topic 5 – Proteins and Enzymes
Proteins and their Functions
This sequence of amino acids determines the protein’s shape and function.
Proteins have a variety of functions including
Structural – involved in the membrane
Enzymes – are involved in chemical reactions
Hormones - act as chemical messengers
Antibodies - defend the body against infection
c)
Enzymes
Enzymes function as biological catalysts and are made by all living cells. They have three
main features:
o They speed up the rate of all cellular reactions, both build up and break down.
o They are unchanged in the process.
o They have an active site with a specific shape that complements the
substance they act on.
Each enzyme is able to act on only one type of substance (its substrate) since this is the
only substance whose molecules exactly fit the enzyme's active site.
The enzyme is said to be specific to its substrate and the substrate's molecular shape is
said to be complementary to the enzyme's active site.
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Unit 1 – Cell Biology
d)
Pupil Course Notes
Factors Affecting Enzyme Activity
Temperature
Each enzyme works best in its optimum conditions. Enzymes and other proteins can be
affected by temperature and pH.
Enzymes are proteins and the structure of proteins is easily changed by heating, e.g. as
seen when boiling an egg. This results in a change in their shape. This effect is permanent.
The protein is said to be denatured, and this is irreversible.
pH
The term pH is used to describe whether a solution is acid, alkaline or neutral.
Enzymes work within a range of pH values. Each enzyme works best at its optimum pH.
The shape of an enzyme, or protein, can be changed by changes in the pH of the solution it
is in. This will affect the rate of reaction between the enzyme and substrate and may result
in the enzyme becoming denatured.
e)
Enzymes and Industry
Biotechnological industries also use enzymes to produce useful products:

Biological Washing Powders:
Digestive enzymes are added to detergents. These enzymes break up the stains
on clothes, allowing them to be washed at lower temperatures. These
temperatures cause less damage to fabrics and save energy, making them better
for the environment.

Cheese
Cheese is produced from milk by adding the digestive enzyme rennet. This is the
same enzyme that is found in a calf’s stomach while it is still feeding from its
mother.
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Unit 1 – Cell Biology
Pupil Course Notes
Enzyme summary table
Name of enzyme
Substrate
Products
Catalase
Hydrogen peroxide
Oxygen and Water
Amylase
Starch
Maltose
Pepsin
Protein
Polypeptides
Invertase
Sucrose
Glucose and Fructose
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Unit 1 – Cell Biology
Unit 1
a)
Pupil Course Notes
Topic 6 – Respiration
Respiration
Respiration is a series of enzyme controlled reactions by which chemical energy from
glucose is released. As it involves enzymes, respiration is affected by temperature.
b)
ATP Generation & Energy Storage
The energy released from the breakdown of glucose is used to regenerate a molecule
called ATP which stores chemical energy.
ATP
breakdown
As the bond is formed energy is stored
Energy is released as the bond breaks
synthesis
ADP + energy + phosphate
The energy released by ATP can be used for cellular activities including:
o Muscle cell contraction
o Cell division
o Protein synthesis
o Transmission of nerve impulses
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Unit 1 – Cell Biology
Pupil Course Notes
Respiration
There are two types of respiration

Aerobic – requires oxygen

Anaerobic – does not require oxygen
Aerobic respiration involves the breakdown of glucose via pyruvate to form carbon dioxide
and water.
Carbon Dioxide
+
water
pyruvate
Glucose
This requires oxygen and gives 38 molecules of ATP. Aerobic respiration starts in the
cytoplasm and is completed in the mitochondria. Cells such as muscle and sperm have
many mitochondria as they require a lot of energy.
Anaerobic Respiration
Anaerobic respiration is the release of energy from glucose in the absence of oxygen.
This happens differently in plant and animal cells.
Animal cells
Glucose
Lactic Acid
pyruvate
Plant cells
Ethanol and
Carbon dioxide
This does not require oxygen and gives 2 molecules of ATP.
This occurs in the cytoplasm and can also be called fermentation.
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Unit 1 – Cell Biology
Pupil Course Notes
Comparison of Aerobic and Anaerobic Respiration
Type of
Aerobic
Respiration
Respiration
Location(s)
Cytoplasm and
Mitochondria
Final
Carbon Dioxide
Products
and Water
ATP Yield
38 molecules
Anaerobic
Anaerobic
Respiration
Respiration
in Animals
in Plants
Cytoplasm
Cytoplasm
Lactic Acid
2 molecules
Ethanol and
Carbon Dioxide
2 molecules
Summary:
Aerobic Respiration
Glucose + Oxygen
Energy + Carbon Dioxide + water
Anaerobic Respiration (also called fermentation)
In Plant cells
In animal cells
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Glucose
Glucose
Alcohol + Carbon dioxide + Energy
Lactic Acid + Energy
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Unit 1 – Cell Biology
Unit 1
Pupil Course Notes
Topic 7 – Genetic Engineering
Genetic information can be transferred from one cell to another naturally or by genetic
engineering.
This can occur naturally between bacterial cells and often involves the bacterial plasmids
and sometimes viruses.
In genetic engineering, a piece of chromosome containing the required gene from the cell of
one organism (e.g. a human) can be transferred into a bacterial cell. The bacterial cell may
then produce a substance normally made by the other organism.
Genetic engineering is of medical value because useful substances which can be produced
include: human insulin used by people suffering from diabetes to control their blood sugar
levels, and human growth hormone.
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Unit 1 – Cell Biology
Pupil Course Notes
The stages in genetic engineering are shown below:
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Unit 1 – Cell Biology
Pupil Course Notes
Therapeutic Use of Cells
Genetic engineering is a relatively easy, cheap and fast method to produce crucial proteins
for therapeutic medical use, such as insulin, human growth hormone or Factor VIII – a
blood clotting protein used to treat haemophilia. The technique can also be used on
agricultural crops to produce greater yield, resistance to disease or a longer shelf life.
DNA Profiling: the Benefits and Risks
We can use our understanding of genetics to create DNA Profiles. These are commonly
used today in many ways:

to determine paternity.

by forensic teams to identify suspects in police investigations.

by archaeologists to identify the genetic heritage of mummified human remains.

to identify genetically linked health issues, such as haemophilia, sickle cell anaemia
or haemochomatosis.
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Unit 1 – Cell Biology
Unit 1
a)
Pupil Course Notes
Topic 8 - Photosynthesis
Photosynthesis
Green plants make their own food in a process called photosynthesis.
Photosynthesis is a series of enzyme controlled reactions in two stages
Light Reaction

First stage of photosynthesis

Light energy from the sun is trapped by chlorophyll in a chloroplast

The energy is used to split water into hydrogen and oxygen

The light energy is changed into chemical energy in the form of ATP
Light energy from
the sun trapped by
chlorophyll
Water
Hydrogen
Light
energy
Carbon Fixation
Oxygen
diffuses
from the cell
ADP + Pi
ATP
This is the second stage of photosynthesis. It involves a series of enzyme controlled
reactions joining together carbon dioxide and hydrogen to form sugar. This reaction
requires ATP and hydrogen, passed on from the light reaction.
Carbon
Dioxide
Enzyme
controlled
Sugar
Hydrogen
ATP
ADP + Pi
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Unit 1 – Cell Biology
b)
Pupil Course Notes
The Fate of the Energy
The chemical energy in sugar is available for:
1. respiration
2. conversion to starch for storage.
3. conversion to cellulose for structural use
c)
Limiting Factors
A factor in short supply limits the rate at which a reaction happens and is called a
limiting factor. In photosynthesis these are:

Light Intensity

Temperature

Carbon dioxide concentration
Increasing light intensity or carbon dioxide concentration should increase the rate of
photosynthesis, until the plant is receiving as much as it can use at which point they
stop being a limiting factor
C - 0.50% CO2
Y
B - 0.10% CO2
X
A - 0.01% CO2

At the points labelled Y the limiting factor is light intensity

At the points labelled X the limiting factor is carbon dioxide concentration

Temperature acts as a limiting factor as enzymes involved in photosynthesis
are temperature dependant.
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Unit 1 – Cell Biology
Pupil Course Notes
Summary:
Light Energy
Carbon Dioxide + Water
Sugar + Oxygen
Chlorophyll
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