Download Cells Investigating cells 1- State what are the basic units of all living

Cells
1- State what are the basic units of
all living cells
2- Explain the purpose of staining
animal and plant cells
3-State the structure of a typical
plant and animal cell and list the
differences between them.
4- State what diffusion is
5- Give examples of substances
which enter and leave the cell
6- (C) Explain the importance of
diffusion to organisms
7- Describe the function of cell
membrane
8- Explain what osmosis is.
9- Give the name use to describe
plants cells which have swollen up by
osmosis and those which have shrunk
10- (C) Explain osmosis in terms of a
selectively permeable membrane and
of a concentration gradient
11- Explain osmosis in terms of water
concentration of the solution
involved.
Investigating cells
Cells
Stains make parts of the cell stand out so that it is
easier to see with a microscope
Plant and animal cells have in common:
1-Nucleus
2-Cell membrane
3-Cytoplasm
In addition, plant cells have:
4- Cell walls(always)
5- A vacuole (most)
6-Chloroplasts(some)
Investigating diffusion
It is the movement of a substance from an area of
high concentration to an area of low
concentration.
Glucose, oxygen, carbon dioxide and water
Allow gases move in and out of cells.
Small organisms (e.g. bacteria, amoeba), gases
diffuse through the cell membrane.
Larger organism: most cells not in direct contact
with air. Gas exchange takes place through specific
organs: e.g. lungs in humans, gills in fish and leaves
in plants.
The cell membrane: controls the passage of
substances in and out of the cell.
Osmosis is a special case of diffusion: the
molecule which diffuses across the membrane is
water
swollen up: turgid
shrunk: plasmolysed
Osmosis is the movement of water through a
selectively permeable membrane (size of
membrane holes determines which molecules can go
through it) along the concentration gradient, from
an area of high water concentration to an area of
low water concentration.
Osmosis is the movement of water through a
selectively permeable membrane from an area of
high water concentration to an area of lower water
concentration.
12- State the function of cell division
13- State the biological name for cell
division
14- State the function of the nucleus
15- State what is the store of
hereditary information?
What is meant by “chromosome
complement”?
16- Describe how the daughter cells
compare to the original cell
17- (C) Describe the stages of
mitosis in animal and in plant cells
18- Recognise the stages of mitosis
in an animal cell
and in a plant cell
1
6
2
5
Investigation cell division
To increase the number of cells in an organism so
that growth and cell replacement can take place.
Mitosis
- control cell activities including cell division.
- store of hereditary information
Chromosomes, DNA
Number of chromosomes characteristic to a
species, e.g. humans have 46 chromosomes
They have an identical set of chromosomes which
carry the same information as the original cell.
To obtain two identical sets of chromosomes, the
genetic material contained in a nucleus is replicated
(copied) before mitosis.
Plants
Animals
1- Nuclear division
yes
yes
2- Division of cytoplasm
yes
yes
3- New cell wall forming
yes
no
4- Separation into two daughter
yes
yes
cells
1- Chromosomes get shorter and fatter. The cell is
ready for mitosis.
2- Chromosome are attached to spindle fibres and
positioned at the equator (plane at the centre of
the cell). They can be seen to be made of two
chromatids.
3- Spindle fibres contract, chromatids are pulled
apart towards opposites poles.
4- Two nuclei form at each end of the cell
5- The cytoplasm start to divide
6- Two daughter cells are formed
Same as above except for 5:
5- New cell wall forms on a plane at the centre of
a cell.
3
4
19- (C) Explain why it is important
that the chromosome complement of
daughter cells in multi-cellular
organisms is maintained
20- Describe a chemical reaction in
general terms
21- Explain the meaning of the term
“catalyst”.
22- Explain why enzymes are
required for the function of living
cells.
23- State what an enzyme is.
24- Give an example of an enzyme
involved in the chemical breakdown
of a substance
25- Give an example of an enzyme
involved in synthesis (building up)
26- (C) Explain the word “specific” as
applied to enzymes and their
substrate
27- State what type of molecule
enzymes are.
28- Describe the effect of
temperature on enzyme activity
If cells don’t inherit exactly the same set of
chromosome (e.g. too many or too few), it does not
behave as any other cell and die grow and/or
function abnormally.
Investigating enzymes
A substrate is chemically altered into a product
A catalyst is a substance which speeds up the rate
of a chemical reaction without being changed or
used up.
(i.e. a catalyst is neither a substrate nor a product
as it is unaffected by chemical reactions).
A large number of chemical reactions take place in
every living cell continuously. These are controlled
enzymes which are the catalysts produced by the
cells themselves.
The cell processes necessary for life would happen
too slowly without enzymes
An enzyme is a biological catalyst.
C-L-A-P
- Catalase: breaks down hydrogen peroxide into
water and oxygen
- Lipase: breaks down fats into fatty acids and
glycerol
- Amylase: It breaks down starch into maltose.
- Pepsin: breaks down proteins into polypeptides
and amino acids.
Potato phosphorylase: in potatoes, joins molecules
of Glucose-1-phosphate to form starch.
Each enzyme only works on one substrate. E.g.
Amylase only breaks down starch. Enzymes and
substrates have matching shapes like a “lock and
key”.
Enzymes are proteins.
At low temperatures, enzymes do not work
effectively (molecules move too slowly). Enzymes
increase the rate of reaction (i.e. speed up) most
effectively at a temperature called the optimum.
Beyond that temperature, an enzyme becomes
denaturated.
29- Describe the effect of a range
of pH on the activity of pepsin and
catalase
30- (C) Explain the term “optimum”
as applied to the activity of enzymes
31- State three reasons why living
cells need energy.
32- Give an example of an energy
transformation in a plant and in an
animal.
33- State what cells need in order to
release the energy from food.
34- Describe aerobic respiration in
terms of a word equation
35- State where the carbon dioxide
released from food comes from.
36-State what may be produced by
respiration in addition to carbon
dioxide
37- (C) State which contain more
energy per gram: proteins, fats,
carbohydrates.
38- (C) Explain the importance of
energy released from food during
respiration to the metabolism of
cells.
Each enzyme has a specific pH, i.e. a pH at which it
works most effectively (faster rate of reaction).
Enzyme may work at other pH but the rate of the
chemical reaction that they control is usually not
as fast.
Pepsin works most effectively at pH 2.8 (acidic
condition found in the stomach). It has a narrow
range of pH at which it works well (± 0.5 pH units).
Catalase works most effectively at pH 7 and
larger range of pH than pepsin at which it works
well (± 1 pH units).
The conditions at which enzymes work most
effectively are called optimum conditions: optimum
pH and optimum temperature.
Investigating aerobic respiration
Cell division, movement (muscle cells), synthesis
reactions.
Plants: light energy → chemical energy (starch)
Animal: chemical energy (fat) → heat energy
Cells need oxygen (found in air) to release the
energy from food in “aerobic respiration”
glucose + oxygen → energy + carbon dioxide + water
The carbon dioxide released as a waste product of
respiration comes from food.
Heat energy and water will be produced by aerobic
respiration.
Fats contain about twice as much energy as
proteins and carbohydrates (sugars, starch)
Cell metabolism is all the chemical reactions which
take place inside a cell. The energy released from
food is needed for many chemical reactions and
therefore it is needed for cell metabolism.