Download Hyndland Secondary Page 1 09/10/2011 Credit Material in italics

Hyndland Secondary
Credit Material in italics
Page 1
09/10/2011
Biology Department
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Hyndland Secondary
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09/10/2011
INVESTIGATING CELLS
INVESTIGATING LIVING CELLS
Cell Structure & function
All living things are made of cells.
Microscopes are used to study the structure of cells.
The MAGNIFICATION of a microscope is found by multiplying the strength of the two
lenses together:
Magnification = eyepiece X objective
Stains are coloured solutions used to show up the internal structure of cells more clearly e.g.
Iodine stains nuclei yellow.
Diagrams of Animal and Plant Cells
ANIMAL CELL
PLANT CELL
Similarities and Difference between Plant & Animal cells
FOUND IN BOTH PLANT AND ANIMAL CELLS
Structure
Nucleus
Cytoplasm
Description
Function
Contains chromosomes made of DNA
Clear, jelly like substance
Controls ALL cell’s activities
Site of cell’s chemical reactions e.g.
respiration
Controls what enters/ leaves the cell
Cell Membrane Flexible
FOUND IN PLANT CELLS ONLY
Cellulose
wall
Vacuole
Chloroplast
cell Rigid , made of cellulose
Gives cell shape, prevents plant cells
bursting when swollen
large, membrane bound cavity filled with Provides support, storage
sap (watery solution of salts and sugars)
contains the green pigment chlorophyll
traps light for photosynthesis
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WHAT YOU SHOULD NOW KNOW
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.
Credit Material in italics
Investigating cells
Cells
Stains make parts of the cell stand out so that they are
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 wall (always) 5- A vacuole (most)
6-Chloroplasts (some)
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INVESTIGATING DIFFUSION
Diffusion
Diffusion is the movement of a substance from a HIGH concentration to a LOWER
concentration
Diffusion continues until the concentrations are equal.
A concentration gradient is a difference in concentration between two areas. Diffusion is said
to occur down a concentration gradient.
Importance of Diffusion
Substance needed by the cell pass INTO the cell by diffusion e.g. oxygen & dissolved food (glucose)
Waste substances pass OUT of the cell
e.g. carbon dioxide (from respiration), urea (from the breakdown of amino acids)
In the body diffusion occurs in the lungs, kidneys and small intestine:
Lungs (see S4 notes): oxygen into blood, carbon dioxide out of lungs
Kidney: useful substances e.g glucose, amino acids are reabsorbed from the tubule into the blood capillary
Small intestine : products of digestion are absorbed into the blood stream.
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Cell Membrane
The cell membrane controls the passage of materials into & out of the cell
It has tiny pores (holes).
Small molecules (e.g. glucose, carbon dioxide, urea) can pass through these pores, but larger
(e.g. sucrose, starch, proteins) or charged molecules (sodium or potassium ions) cannot.
Substances which are not dissolved cannot diffuse through the membrane (e.g. carbon dioxide
and oxygen need to dissolve in a layer of mucus before diffusing into the blood from the lung
see p). In the leaf a layer of moisture is found on the spongy mesophyll cells into which
carbon dioxide diffuses.
Osmosis
Osmosis is a special case, the diffusion of water across membranes.
Osmosis = the movement of water from a higher water concentration (HWC) to a lower water concentration
(LWC) across a selectively permeable membrane*.
*The cell membrane is a selectively permeable membrane (only small molecules can pass
through them)
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In the diagram below:
Water moves by osmosis from a HWC outside the bag to a LWC
Visking tubing
(a man made
material containing
tiny pores).
inside the bag
Glucose is at a high concentration inside the bag, so diffuses out.
Starch is too large to move through the pores in the membrane so stays
in the bag.
Starch and glucose
solution
water
Osmosis in Plant Cells
cytoplasm
LIQUID OUTSIDE
WATER GAIN or LOSS
CHANGE to CELL
CELL
Water
Cell gains water
Cell swells
Solution equal to cell solution
No net gain or loss of water
Cell does not change
Solution stronger than cell sap
Cell loses water
Cell shrinks
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When plant cells take in water by osmosis, they swell
and become TURGID.
When plant cells lose water by osmosis they become
FLACCID.
PLASMOLYSIS occurs when a cell becomes very
flaccid. So much water has been lost that the cell
membrane shrinks away from the cell wall. This
usually starts at the corners
The membrane surrounding the vacuole is also
selectively permeable and so the vacuole shrinks and
expands with osmosis.
Osmosis in Animal Cells
Animal cells contain weak solutions of salt and sugar and only have a cell membrane. Consequently they
BURST if too much pressure is placed on it.
Animal cells can gain or lose water by osmosis:
Changes in red blood cells due to osmosis
Solution outside cell
Water gain or loss
Change to cell
Water
Cell gains water
Cell swells & bursts
Solution weaker than cell solution
Cell gains water
Cell swells & bursts
Solution equal to cell solution
No loss/ gain
Cell does not change
Solution stronger than cell sap
Cells loses water
Cell shrinks
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WHAT YOU SHOULD NOW KNOW
Investigating diffusion
4- State what diffusion is
It is the movement of a substance from an area of high
concentration to an area of low concentration.
5- Give examples of substances which enter Glucose, oxygen, carbon dioxide and water
and leave the cell by diffusion
6- (C) Explain the
diffusion to organisms
importance
of Diffusion allows gases to move in and out of cells.
In small organisms (e.g. bacteria, amoeba), gases diffuse
through the cell membrane.
In larger organisms: most cells are 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.
7- Describe the function of cell The cell membrane: controls the passage of
membrane
substances in and out of the cell.
8- Explain what osmosis is.
Osmosis is a special case of diffusion: the molecule
which diffuses across the membrane is water
9- Give the name use to describe plants swollen up: turgid
cells which have swollen up by osmosis shrunk: plasmolysed
and those which have shrunk
10- (C) Explain osmosis in terms of a Osmosis is the movement of water through a selectively
selectively permeable membrane and of a permeable membrane (size of membrane holes
concentration gradient
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.
11- Explain osmosis in terms of water
Osmosis is the movement of water through a
concentration of the solution involved.
selectively permeable membrane from an area of high
water concentration to an area of lower water
concentration.
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INVESTIGATING ENZYMES
Enzymes
Within living cells many CHEMICAL REACTIONS occur. However, at body temperature
these reaction would be too slow for life to be possible. The reactions are speeded up by
enzymes which act as catalysts.
CATALYSTS:

SPEED UP chemical reactions

Remain UNCHANGED during the reaction

REPEAT the reaction over and over again
Enzymes are CATALYSTS in living cells.
Enzymes are made form PROTEIN. They perform two types of reaction:

BUILDING UP of small molecules into larger molecules

BREAKING DOWN of large molecules into small molecules.
Enzymes are needed in cells to:

Synthesise useful products

Release energy during cell respiration

Change poisonous wastes into safer materials

Change substances into a form that can be stored or used

Reactions of photosynthesis, on which all life depends.
SUBSTRATE – the substance on which an enzyme acts
PRODUCT – the substance produced by the action of the enzyme
enzyme*
SUBSTRATE
PRODUCT
*The enzyme itself is not changed by the chemical reaction
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Examples of Enzymes:
Name of Enzyme
Where found
What it Does
Test for Activity
Degradation reaction (Breaking down reactions)
CATALASE
In plant and animal Breaks
tissues
hydrogen
down Glowing
splint
peroxide relights in the gas
into OXYGEN and given off
WATER
AMYLASE
In digestive juices STARCH is broken Benedict’s
(saliva,
pancreatic down
juice)
reagent
into turns orange
MALTOSE
Synthesis reactions (Building up Reactions)
PHOSPHORYLASE In potato tubers
Builds special
Iodine
turns
blue
reactive glucose
black as starch is built
(GLUCOSE – 1 –
up
PHOSPHATE) into
STARCH
How Enzymes Work
Enzymes have a particular
shape. On their surface is
a groove called the active site
(see over). The shape of the
active allows the substrate (S) to fit into it exactly, like a key in a lock. When the substrate binds to the active
site a chemical reaction occurs.
Other molecules, because they have a different shape, cannot fit into the active site. Because of this enzymes can
work on only one substrate molecule – they are said to be SPECIFIC.
As each enzyme is specific for a single substrate molecule, a different enzyme is required for each chemical
reaction.
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Effect of Temperature on Enzymes
At low temperatures enzymes work slowly –
(Their reaction rate is at a MINIMUM)
As the temperature increases, they work faster,
up to a MAXIMUM RATE.
The temperature at which an enzyme works at
its maximum rate (not best!) is called the
OPTIMUM TEMPERATURE.
Any further increase in temperature causes the enzyme protein to be damaged. The enzyme’s shape changes, so
the rate decreases again, because the enzyme no longer works.
Denaturation of enzymes
When an enzyme is unable to work because its shape has
changed it is said to be DENATURED. As the
temperature rises above the optimum, the enzyme becomes
denatured and the activity rapidly decreases to zero.
It can non longer work because the shape of the active site no
longer fits the shape of the substrate and the substrate can no
longer fit in.
The effect of pH on enzymes
An enzyme will work only in a narrow range of pH.
If the conditions become too acid or alkali, the enzyme
becomes denatured.
The OPTIMUM pH is the pH at which the enzyme
has most activity. The optimum pH is different for different enzymes. Pepsin is found in the stomach (acidic)
and so has an optimum pH which is acidic.
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WHAT YOU SHOULD NOW KNOW
20- Describe a chemical reaction in general terms
21- Explain the meaning of the term “catalyst”.
22- Explain why enzymes are required for the
functioning 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
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-(C) Explain what a control is.
Credit Material in italics
Investigating enzymes
A substrate is chemically altered into a product
A catalyst is a substance which speeds up the rate (i.e.
the speed) 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 takes place in
every living cell continuously. These are controlled by
enzymes which are 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, i.e. it is
irreversibly damaged
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 7-9 and has a
larger working range of pH than pepsin (± 1 pH units).
The conditions at which enzymes work most effectively
are called optimum conditions: optimum pH and optimum
temperature.
A repeat of an experiment to show that the effect
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Biology
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observed is only due to
the factor
being investigated
(e.g. activity of an enzyme)
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INVESTIGATING AEROBIC RESPIRATION
Need for Energy
Living cells are the site of a number of chemical reactions. Together these chemical reactions are called
metabolism. Some of these reactions release energy. Living cells need energy for:

Cell division e.g. growth & repair

Maintaining body temperature (birds & mammals)

Movement

Chemical reactions e.g. making enzymes, digesting food
RESPIRATION is the process by which cells release ENERGY from GLUCOSE. It happens in all
living cells (plant & animal) all the time.
Aerobic Respiration
Oxygen is required for aerobic respiration. Two waste products, water and carbon dioxide are
made.
Equation for aerobic respiration:
GLUCOSE + OXYGEN
WATER + CARBON DIOXIDE + ENERGY
Reactants
waste products
useful product
The carbon dioxide released can be detected by

Turning limewater milky

Turning bicarbonate indicator from red to yellow
Aerobic respiration occurs in many small steps, each controlled by an enzyme. This allows the
energy to be released in small amounts.
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The energy in food molecules such as glucose is CHEMICAL ENERGY. Green plants
capture LIGHT ENERGY and convert it into chemical energy in photosynthesis (Error!
Bookmark not defined.). Animals obtain their food from plants (Error! Bookmark not
defined.).
The quantity of energy contained in foods can be found by burning a measured mass of food
and using the heat energy released to heat a measured volume of water.
The energy content of different foods differs:
Fats contain TWICE as much energy as proteins or carbohydrates (e.g. glucose & starch)
Respirometers
A
respirometer
can
be
used
to
measure
the
rate
of
respiration
The use of respirometers depends on three factors:

The volume of oxygen used up is equal to
the volume of carbon dioxide produced

The carbon dioxide can be absorbed by a
chemical (e.g. soda lime, potassium
hydroxide) and so the uptake of oxygen is
seen as a drop in the volume of air in the
respirometer

There is no change in the temperature of the
apparatus. (changes in temperature cause
changes in the volume of gases!)
In the apparatus above, the taps are closed at the start of the experiment. As the oxygen is
removed the volume of air in the tube decreases and this sucks the coloured liquid up the tube
towards the earthworm’s tube.
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The control should be a non respiring material (i.e. dead animal or glass beads) and of the
same volume as the respiring animal.
The syringe is used to return the volume back to its original level. In this way, the volume of
oxygen taken in can be measured and if the time taken to produce the change is known, the
rate of respiration (oxygen uptake per minute) can be calculated.
Energy release
During respiration some of the energy is released as heat energy. As a result in a confined
space the temperature of the surroundings is raised. The heat can be detected using an air
thermometer.
The heat released by the
respiring animal expands the air
in the tube and pushes the
coloured liquid. There is no
expansion in the control side.
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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 is produced by respiration in
addition to carbon dioxide
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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.
37- (C) State which type of food contains more Fats contain about twice as much energy as
energy
per
gram:
proteins,
fats, proteins and carbohydrates (sugars, starch)
carbohydrates.
38- (C) Explain the importance of the energy Cell metabolism is all the chemical reactions
released from food during respiration to (i.e. breakdown as well as synthesis reactions)
the metabolism of cells.
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.
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PROBLEM SOLVING
Percentage Calculations.
PERCENTAGE CALCULATIONS
3 Types of percentage calculation can be asked:
Percentage change (increase or decrease):
To find the
change
End value—start value
Percentage change =
X 100
To change to a
percentage
Start value
STEP 1
STEP 2
STEP 3
(use a calculator!!!!!):
Find the START Value (in the question)
Find the END value (in the question)
FIND OUT HOW MUCH IT HAS CHANGED
END VALUE – START VALUE
STEP 4
-
Divide this answer by the START VALUE
STEP 5
-
Multiply that answer by 100
If the answer is negative the factor has decreased, if it is positive the factor has increased
e.g. Calculate the percentage change in blood flow to the skeletal muscles during exercise, if it rises from 10 l/min to 30l /min.
Percentage change = 30-10 ÷ 10 X 100 = 20÷10 X 100 = 200% change (increase).
Percentage of:
To calculate the proportion the subset forms of the total
This asks what percentage a subset is of the total
Percentage of =
Size of subset
To change to a
percentage
X100
Total
e.g. What percent of the whole population has blood group AB?
Blood Group
A
B
AB
O
Number
24
45
33
86
Total = 24 + 45 + 33 + 86 = 188
Subset = 33
Percentage = 33 ÷ 188 X 100 = 17.6%%
How many, if the percentage is already given:
Total X Percentage
Number =
100
e.g. If 20% of a class of 40 have blue eyes, how many of the class has blue eyes?
Total =40
Number = 40 X 20 ÷ 100
= 800 ÷ 100 = 8
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Ratios
A ratio is a way of showing the relationship between two or more values.
For example a forest contains two types of deer, Roe deer and Fallow deer. The deer are counted and
360 Roe deer are found, but only 120 Fallow deer are present. To express this as a ratio a number of
steps can carried out.
 each by 120
1. Try to divide the large number by the small number 360 : 120
3:1 this is the simplest whole number ratio.
Second example.
The head teacher wishes to know the ratio of male staff to female staff in the school. There are 32
male staff and 56 female staff
1. Try to divide the large number by the small number 32: 56  each by 32
1:1.75, not a whole number ratio so move to next step
2. Divide both sides by the largest number which goes in evenly,
32:56
 each by 4
8: 14
 each by 2
4:7 This is the simplest whole number
ratio, the two numbers cannot be divided evenly by the same number!
Third example
The EU fishery minister suggested that the North Sea contained very little cod, but much more
herring. The survey shows that there were 175 cod, and 1,260 herring. What is the ratio of cod:
herring.
1. Try to divide the large number by the small number 175 : 1260
 each by 175
7.2:1, not a whole number so move to next step
2.Find a number that will divide evenly into both sides (the same number for each side)
175: 1260
 each by 5
35:252 can they be divided again?
35:252
5:36
 each by 7
This is the simplest whole
number ratio, the two numbers cannot be divided evenly by the same number!
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Chemical
Tests
TESTS
pH Scale (Acidity/ Alkalinity)
The pH Scale gives a measure of how acidic or alkaline a solution is:
1
COLOUR of
pH indicator
2
RED
3
4
5
6
7
GREE
pH
ORANG YELLOW
8
9
10
11
BLUE
12
13
14
PURPLE
pH is measured using pH indictor or paper
The pH falls (becomes more acidic) when fats are broken down to fatty acids (& glycerol), or protein
are broken down (to give amino acids)
Carbon Dioxide
Carbon dioxide is the gas used up in photosynthesis and produced in aerobic respiration in animals and
plants (along with water) and in anaerobic respiration in plants (along with alcohol). In experiments it
can be absorbed by soda lime or potassium hydroxide.
Carbon dioxide turns limewater milky.
Bicarbonate indicator can be used to tell how much carbon dioxide is present
Carbon Dioxide
Colour of Bicarbonate Indicator
Zero
Normal (0.03%
High
Purple
Red
Yellow
Experimental Design
In a scientific experiment a test is only fair if only one variable factor has been changed at a time.
Examples of variable factors are time, lengths, volumes, weights and concentrations. If more than one
is is
changed between experiments the test is not fair. A fair test is also a VALID test.
Experiments are repeated to make them more RELIABLE or REPRESENTATIVE. To make an
experiment more accurate better equipment must be used e.g. a more accurate balance or replace a
ruler having centimetre divisions with one having millimetre divisions.
Food Tests
Food Type
Reagent
Procedure
Positive result
Glucose (sugar)
Benedict’s
Heat with sample at 95°C
Turns from blue to orange
Starch
Iodine
Add to sample
Turns from orange to blue/
black
Protein
Biuret
Heat with sample
Turns from to violet
Fats
Alcohol and
water
Shake with sample.
Solution goes cloudy
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CHARTS
Charts/Graphs
In Biology two types of chart are used:
the BAR chart and the LINE GRAPH
Usually a question tells you which to draw.
BAR CHART
When data concerns the numbers in various groups, then a bar chart is used
Number
RED
37
40
BLUE
15
35
YELLOW
7
30
WHITE
3
GREEN
24
Number
Colour of Flower
25
20
15
10
Germination (%)
0
7
80
10
24
70
20
59
60
30
74
40
37
50
2
Germination (%)
Temperature (ºC)
GREEN
WHITE
YELLOW
BLUE
RED
Label; axes names and units (if any)
5
copy the column headings. The first set of
0
information goes on the horizontal axis, the
second on the vertical axis.
Devise a scale (divide the axis up evenly).
Find the highest value in your data.
37
Colour of Flower
Count the number of large squares on your vertical axis 8
Divide the highest value by the number of squares,
37/8 = 4.625
round your answer up to the nearest easy* number. i.e. 5 Each large square is worth 5
*easy numbers are usually 1, 2, 5, 10, 50, 100 etc.
Draw the bars (you should make each bar the same width and leave a gap between the bars (you won’t
lose marks if you don’t)
LINE GRAPH
Line graphs are used when both sets of data are numbers. A scale must be used on both axes.


50
40

30
20

10
Label axes by copying the column headings

(first 1st—horizontal, 2nd column—vertical)

0
Devise scales for both axes
0
10
20
30
40
50
Horizontal 50/10 = Each big box is worth 5 ºC
Temperature (ºC)
Vertical 74/8 = 9.25, Each big box is worth 10%
Plot the points and join with a straight line (Only join 0,0 if that point is in the data)
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GLOSSARY
Active Site
Amylase
Atom
Catalase
Catalyst
Cell wall
Chloroplast
Concentration
Concentration Gradient
Cytoplasm
Denatured
Diffusion
Distilled water
End product(s)
Enzyme
(Cell) Membrane
Molecule
Nucleus
Optimum conditions
Osmosis
Pepsin
pH
Phosphorylase
Selectively permeable
Solute
Solvent
Specific Activity
Stain
Substrate
Synthesis
Vacuole
part of an enzyme molecule to which the substrate attaches
an enzyme which speeds up the breakdown of starch
the smallest part of an element which can exist chemically
an enzyme which speeds up the breakdown of hydrogen peroxide
a substance which speeds up a reaction but remains unchanged
cellulose layer around the outside of a plant cell
structure within a plant cell which contains chlorophyll
the number of solute molecules in a specific volume of solvent
the difference between two concentration levels
the fluid part of a cell
permanent damage caused to an enzyme by high temperature
movement of molecules from high to low concentration
pure water consisting of 100% water molecules
compound formed at the end of a reaction
chemical found in living cells which acts as a catalyst
selectively-permeable layer surrounding the cytoplasm in all cells
two or more atoms joined together by chemical bonds
control centre of a cell
conditions in which an enzyme works most efficiently
diffusion of water molecules across a semi- permeable membrane
an enzyme which breaks down protein
a measure of acidity/alkalinity
an enzyme which synthesizes starch
allows some molecules to pass through but not others
substance which is dissolved in a liquid
liquid used to dissolve another substance
each enzyme only acts on one substrate
coloured dye used to show up cell structure more clearly
the molecule on which an enzyme works
building up a larger molecule
cavity in the cytoplasm of a plant cell