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S4 N4/5 Biology
Unit 1- Cell biology
Part B-‘Through a microscope’
NAME:
CLASS:
2
LEARNING OUTCOMES
N I can now….. Track
CELL STRUCTURE
1 5 Identify and state the functions ; cell wall, mitochondria, chloroplast,
cell membrane, vacuole, nucleus and ribosome
2 5 Understand fungal and bacterial cell structures compared to plant
cells and the different cell wall structure (not cellulose)
3 5 Use magnification scales to work out actual sizes of cells
4 TRANSPORT ACROSS CELL MEMBRANES
5 5 State that cell membranes consist of proteins and phospholipids
6 5 State that the cell membrane is selectively permeable
7 5 State that passive transport occurs down a concentration gradient
and does not require energy.
8 State that diffusion and osmosis are examples of passive transport
9 5 State that diffusion is the movement of molecules down a
concentration gradient from a higher to a lower concentration.
10 5 Give examples of molecules which move by diffusion
11 5 Explain the benefit of diffusion to cells
12 5 State that osmosis is the movement of water molecules from a high
water concentration to a lower water concentration through a
selectively permeable membrane.
13 5 Draw diagrams to represent cells when placed in high and low water
concentration solutions
14 5 Describe how animal cells can burst or shrink and plant cells can
become turgid or plasmolysed.
15 5 Describe the relationships between different concentrations of
solutions and their effect on cells
16 5 State that active transport requires energy for membrane proteins
to move molecules and ions against the concentration gradient.
DNA AND THE PRODUCTION OF PROTEINS
17 5 Describe the structure of DNA: double-stranded helix held by
complementary base pairs.
18 5 State that DNA carries the genetic information for making proteins.
19 5 State that the four (Adenine, Thymine, Cytosine and Guanine) bases
make up the genetic code and that A always pairs with T and C always
pairs with G.
17 5 State that the base sequence determines the amino acid sequence in
proteins.
18 5 State that a gene is a section of DNA which codes for a protein.
19 5 State that Messenger RNA (mRNA) is a molecule which carries a
complementary copy of the genetic code from the DNA in the nucleus
to a ribosome, where the protein is assembles from amino acids.
PROTEINS
20 5 State that the variety of protein shapes and functions arises from
the sequence of amino acids.
3
21 5 State that proteins may have functions such as structural, enzymes,
hormones, antibodies and receptors.
22 5 State that enzymes function as biological catalysts and are made by
all living cells.
23 5 State that enzymes speed up cellular reactions and are unchanged in
the process.
24 5 Describe how the shape of the active site of an enzyme is
complementary to its specific substrate(s).
25 5 State that enzyme action results in product(s).
26 5 Describe the difference between synthesis and degradation
reactions. Giving examples of the different substrates, enzymes and
products involved.
27 5 Explain that each enzyme is most active in its optimum conditions.
28 5 Describe the effect temperature and pH can have on enzymes and
other proteins.
29 5 Describe how enzymes can become denatured, resulting in a change in
their shape which will affect the rate of reaction.
RESPIRATION
30 5 State that respiration is a series of enzyme controlled reactions in all
cells where the chemical energy stored in glucose is released.
31 5 State that the energy released from glucose is used to generate ATP.
32 5 State that the energy transferred by ATP can be used for cellular
activities such as muscle cell contraction, cell division, protein
synthesis and transmission of nerve impulses.
33 5 State that glucose is broken down to two molecules of pyruvate,
releasing enough energy to yield 2 ATP molecules.
34 5 State that further breakdown of pyruvate depends on the
presence/absence of oxygen.
35 5 State that if oxygen is present, aerobic respiration takes place.
36 5 State that during aerobic respiration each pyruvate is broken down to
carbon dioxide and water, releasing enough energy to yield a large
number of ATP molecules.
37 5 State that in the absence of oxygen the fermentation pathway takes
place.
38 5 Describe how the fermentation pathway in animals involves the
pyruvate molecules being converted to lactate.
39 5 Describe how the fermentation pathway in plants and yeast involves
converting the pyruvate molecules to carbon dioxide and ethanol.
40 5 State that the breakdown of each glucose molecule via the
fermentation pathway yields only the initial two molecules of ATP.
41 5 State that respiration begins in the cytoplasm.
42 5 State that the process of fermentation is completed in the cytoplasm
but aerobic respiration is completed in the mitochondria.
43 5 Describe how a respirometer is used to measure the rate of
respiration.
44 4 State that respiration is enzyme controlled so its rate is affected by
temperature.
4
Cells and cell structure All organisms are made up of cells, the basic unit of life.
Some organisms such as amoeba are made up of only one
cell and others, like dogs are made up of millions of cells,
each one designed to do a specific job.
Cell structure
A stain is used to examine cell structure under a microscope.
Amoeba
Revision:
From the introduction to
Biology topic in S3 can you
remember what we call:
1. An organism made up of
only one cell?
2. An organism made up of
lots of cells?
Mitochondrion
Nucleus
Cytoplasm
Ribosome (black dot)
Cell membrane
ANIMAL CELL
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Nucleus
Cytoplasm
Mitochondrion
Ribosome (black dot)
Cell membrane Cell wall (cellulose)
Chloroplasts
Vacuole
PLANT CELL
Mitochondrion
Cell wall (not made from cellulose)
Ribosome (black dot)
Cell membrane
Nucleus
Vacuole
Plasmid
Chromosome
FUNGAL CELL
(FUNGUS)
BACTERIAL CELL
(BACTERIUM)
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Use the table below to note the functions of the different parts of the cells.
Part of cell Function
Cell wall
Cell membrane
Ribosome
Mitochondria
Vacuole
Chloroplast
Nucleus
Cytoplasm
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Use this table to compare the four different cell types. Using a tick or a cross
to show which structures are present or absent.
Fungi and _________ also have many of the same structures as plant cells,
however their cell _______ are not made of ____________ which plant cell
walls are. Bacterial cells may also have extra rings of DNA called ‘__________’
Estimating Cell Size
Cell structure Animal Plant Fungal Bacterial
Field of View = 8 mm
Length of one cell in field of view =
Diameter of field of view/ Estimated
number of cells across the field of view
8
Using the example above, What is the length of one cell?
Space for working:
Now try the examples below:
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Activity: Try the past paper questions on cell structure shown below.
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Transport across membranes
The cell membrane
The cell membrane is made up of _____________
and __________________. It is described as being
______________ permeable as only smaller
molecules can travel across it.
The cell membrane is thought to consist of two layers of _________________
with protein molecules embedded (like a mosaic).
Phospholipid molecules
Revision:
What is the function of
the cell membrane?
Activity 1: Using a mini white board, practise drawing and labelling the structure of
the cell membrane. Make sure you can identify proteins and phospholipids from
memory.
Activity 2: Using paper or playdough (whichever your teacher decides) make a
model of the cell membrane, correctly labelling the proteins and phospholipid
molecules.
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Movement of molecules and the concentration gradient
The molecules of a liquid (or a gas) move about freely all the time.
Your teacher will drop a crystal of purple potassium permanganate into a beaker
of water. Use the space below to draw a diagram of what happened.
The purple particles moved from a region of high concentration (the crystal) to
a region of low concentration (the surrounding water) until the concentration of
purple particles was evenly spread throughout the beaker.
The _____________ in concentration that exists between the area of
_______ concentration and the area of ________ concentration is called the
_____________ _____________.
Diffusion
_____________ is the name given to the
movement of molecules _______ a
concentration gradient from a _________
to a __________ concentration.
Experiment A: Potassium permanganate in a beaker of water:
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Diffusion is the main way substances move over short distances in organisms.
__________, dissolved food, and _________ ________ are examples of some
substances that move by diffusion.
We can use visking tubing as a model of the cell membrane and conduct an
experiment to investigate diffusion.
Start: End:
Experiment B: The model cell
Your teacher will explain the instructions.
Use the two diagrams below to record what was inside and outside the tubing at the
start and the end of the experiment.
Write a conclusion to explain the results of the model cell experiment.
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Diffusion is an example of a __________ process. This means that is does NOT
require __________.
Osmosis
During osmosis, water molecules move from an area of __________ water
______________ to an area of lower ____________ concentration down a
concentration gradient through a selectively _____________ membrane.
Osmosis is another example of ____________ transport as no __________ is
needed.
High water
concentration
Low water
concentration
Experiment C: Investigating osmosis
Aim- to find out what happens to the mass of cells placed in different solutions
with different concentrations of water.
Use your jotter to write up your experiment correctly, remember:
Aim
Method
Results/Graph
Conclusion
Evaluation
Experiment D: The model cell
Your teacher may allow you to further investigate osmosis by drowning gummy
bears.
14
Osmosis in animal cells
Movement of water by osmosis occurs between cells and their immediate
environment. The direction depends on the water concentration of the liquid in
which the cell is immersed compared to that of the cell.
If animal cells ___________ water, they swell up and ____________ as they
don’t have a cell __________ to support the cell.
If animal cells ____________ water, they _______________.
Osmosis in plant cells
If plant cells lose water, they shrink and become ___________________.
If plant cells gain water, they swell up and become ___________. They don’t
burst as they have a cell ___________ for support.
15
Active transport
Active transport requires
__________ for __________ in the
cell membrane to move molecules and
ions ___________ the concentration
gradient from an area of
___________ concentration to an
area of _________ concentration.
Use the table below to summarise the different ways that molecules can be
move across cell membranes.
Process Examples of molecules
which move by this method
Active or passive
Activity: Try the past paper questions below on transport across cell
membranes.
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DNA and the production of proteins
The order of the bases in a DNA molecules contains the instructions to make
proteins.
Each protein is made up of long chains of amino acids. Each group of three
bases carries the code for one amino acid. The order of the base sequence of
the DNA determines the amino acid sequence in the protein.
Revision: In S3 you learned about the structure of DNA.
Try and answer the questions below using your prior knowledge:
DNA is found in structures called ____________.
DNA is made up of two strands twisted into a structure called a
____________ ____________.
A section of DNA which codes for a particular protein is called a
____________.
What are the names of the 4 bases that make up DNA?
A___________
T___________
C___________
G___________
What is the complementary base pair rule? Which bases always pair with
each other?
18
So…. if the instructions to make the proteins (found in the DNA) are contained
within the nucleus and proteins are actually made at the ribosome in the
cytoplasm then there must be some way of getting the instructions to the
ribosome. It is therefore necessary to make a copy of the instructions.
1. The DNA is too ___________ to leave the nucleus, so it makes a
complementary copy of itself called ___________ RNA (mRNA).
2. mRNA carries a copy of the code from the DNA in the nucleus to the
___________.
3. At the ribosome, the correct amino acids are joined together in the correct
order to make a ___________.
Quick questions:
Where in the cell is DNA found?
Where in the cell is the site of protein synthesis?
19
Activity: Try the following past paper questions on the structure of DNA and
protein synthesis.
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Enzymes
Respiration
Revision:
What are the different functions of proteins?
1. Antibodies
2.
3.
4.
5.
Enzymes are BIOLOGICAL CATALYSTS, what does this mean?
What is the difference between a SYNTHESIS and a DEGRADATION
reaction? –Use small diagrams to help with your explanation
Activity:
Label the enzyme to
show its active site.
What would this
enzymes substrate look
like?
22
Factors affecting enzyme activity
The rate of enzyme reactions depends on several factors including
___________________ and ______.
Effect of temperature
As the temperature increases, enzyme activity also ___________, however
only until their _____________ temperature. This is the temperature where
enzmyes are most active and is usually around 37 oC. After the optimum
temperature enzyme activity ____________. This is because the enzyme
becomes ________________, this is permenant damage to the enzymes active
site.
As pH is increased, enzyme activity ________ so rate of reaction is quicker,
but only up to pH___ . The pH the enzyme is most active at is called its
optimum. Above this, enzyme activity ___________ as the enzyme was
denatured (destroyed).
Note that different enzymes will have different optimum pH’s. Look at the
diagram below:
Experiment E: Investigating the effect of temperature on enzyme activity
Using liver as a source of catalase, investigate the breakdown of hydrogen peroxide
at different temperatures
Experiment F: Investigating the effect of pH on enzyme activity
Using starch-agar, amylase and different pH buffer solutions, investigate the
effect of pH.
Activity:
What is pepsin’s
optimum pH?
What is catalase’s
optimum pH?
23
Each enzyme is most active in its _________________ conditions. If the
conditions change beyond an enzyme’s optimum, the shape of the enzyme's
active __________ changes permanently so the ________________ can no
longer fit in. This means that the enzyme cannot work. The enzyme is described
as being ____________________.
Activity:
Try the questions below on factors affecting enzyme activity
24
25
Respiration
The chemical energy stored in ____________ must be
released by all cells through a series of reactions controlled
by ________________. This is called respiration.
Respiration carried out in the presence of oxygen is called _____________
respiration.
This is the word equation for aerobic respiration:
GLUCOSE + OXYGEN CARBON DIOXIDE + WATER + ENERGY
ATP
When respiration occurs, it releases energy (see word equation above) which is
used to generate a chemical called ______. ATP stores this
___________________ energy.
The energy transferred by ATP can be used for cellular activities including:
1. ______________ cell contraction
2. Cell _________________
3. Protein _________________
4. Transmission of __________________ impulses
R=
E=
S=
P
I
R
A
T
I
O
N
Experiment G: Burning food to determine its energy
content
26
Aerobic respiration
The first stage of aerobic respiration
happens in the ________________.
No ________________ is required for
this stage to happen. Glucose is broken
down into two molecules
of________________. This releases
enough energy to yield ___ molecules of
ATP.
If oxygen is present:
The second stage of aerobic respiration
happens in the _______________.
Each pyruvate from the first stage is
broken down into carbon dioxide and
water.
This releases enough energy to yield a
large number of ATP molecules.
The more mitochondria a cell has, the
more energy it will require.
Stage 1 of aerobic respiration yields a
total of ____ ATP for each glucose
molecule, whereas stage 2 yields a large
number.
Aerobic respiration
27
Fermentation
There will be times when oxygen is absent or in short supply (e.g. during
strenuous exercise in animal cells and in microbes) and when this is the case
______________takes place.
Fermentation in animal cells
The first stage of fermentation in animal
cells happens in the cytoplasm.
No oxygen is required for this stage to
happen.
Glucose is broken down into two
molecules of a chemical called
_____________________.
___ ATP are produced.
The second stage of fermentation also
happens in the _________________.
No oxygen is present for this stage.
The pyruvate from the first stage is
converted into _________.
No more ATP is produced.
Fermentation produces a total of ___
ATP for each glucose molecule.
Fermentation in animal cells
28
Fermentation in plant and yeast cells
The first stage of _______________ in
plant and yeast cells happens in the
cytoplasm.
_____ oxygen is required for this stage
to happen.
Glucose is broken down into two
molecules of a chemical called
__________________.
__ ATP are produced.
The second stage of fermentation also
happens in the ________________.
No oxygen is present for this stage.
The pyruvate from the first stage is
converted into ________________
(alcohol) and carbon
__________________.
No more ATP is produced.
Fermentation produces a total of ___
ATP for each glucose molecule.
Factors affecting respiration
Respiration is a series of steps controlled by ___________. Since enzyme
activity can be affected by temperature, temperature also has an effect on the
rate of respiration.
Fermentation in plant and yeast
cells
29
Measuring the rate of respiration
It is possible to measure the rate of respiration using a respirometer. A simple
respirometer that can be set up in the classroom is shown below
In the experimental set up the coloured liquid creates a sealed environment
that the snail is in.
As the snail respires it will use up some of the available____________and
produces carbon dioxide. As the liquid in the bottom of the test tube absorbs
the carbon dioxide the pressure inside the equipment decreases and the
coloured liquid is drawn up the tube.
There are two ways that this can be used to measure respiration.
1. Time how long it takes for the liquid to travel a set distance (e.g. 0.4 cm3).
2. Measure how far the liquid travels in a set period of time (e.g. 5 minutes)
Tap
Glass tube
Rubber stopper
Scale
(cm3)
Wire mesh platform
Solution to absorb
carbon dioxide
Snail
Coloured liquid
0.0
0.2
0.4
SQA Higher 2012 Section B Q4
30
To make sure that the change in liquid levels is due to the snail respiring you
would set up a control.
This allows results to be compared and all variables would be kept the same
except the one you are investigating.
Activity: Discuss with your group or as a class a possible control for this experiment.
Activity: Try the past paper questions below on respiration
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