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06/05/2017
AQA Additional Science
Biology 2
A typical plant cell:
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Cell wall – made
of cellulose which
strengthens the cell
Cell membrane
– controls what
comes in and out
Large vacuole –
contains sap and
helps support the
cell
Chloroplasts (containing
chlorophyll) – this is needed
for photosynthesis
Nucleus – controls
what the cell does and
stores information
Cytoplasm –
Chemical reactions
happen here
A Typical Animal Cell
1) Cytoplasm - this is
where the reactions
happen and these are
controlled by enzymes
2) Nucleus –
controls the
cell’s activities
3) Cell Membrane –
controls what
comes in and out
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4) Ribosomes – protein
synthesis happens
here
5) Mitochondria energy is released
here
More specialised animal cells
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I.D:
Red Blood Cell
Function:
Carries oxygen around
the body
Features:
No nucleus and large
surface area
Ciliated
epithelial cell
White blood cell
Nerve cell
(neurone)
Egg cell (ovum)
Diffusion
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Diffusion is when something travels from an area of high
concentration to an area of low concentration. For example,
consider the scent from a hamburger…
The “scent particles” from
this hamburger are in high
concentration here:
Eventually they will
“diffuse” out into this area
of low concentration:
Oxygen passes into cells by diffusion
Diffusion Summary
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Diffusion is when particles spread from an area of high
concentration to an area of ___ concentration. The particles
move along a “concentration _____” and this process takes no
_____ (it’s a “passive” process”). Diffusion can be accelerated
by increasing the _______ of the particles, which makes them
move _______.
Words – faster, low, gradient, temperature, energy
Osmosis
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Osmosis is a “special kind of ___________”. It’s when water
diffuses from a __________ area to a less concentrated area
through a partially permeable _________ (i.e. one that allows
water to move through but not anything else):
Water
Sugar solution
In this example the water
molecules will move from
left to right (along the
concentration ______) and
gradually _____ the sugar
solution.
Words – membrane, concentrated, dilute, diffusion, gradient
Potato cells
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Strong
sugar
solution
Medium
sugar
solution
Weak
sugar
solution
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Photosynthesis – the 4 things you need
SUNLIGHT
Gives the plant energy
CHLOROPHYLL
WATER
Travels up
from the roots
CARBON DIOXIDE
Enters the leaf through small
holes on the underneath
The green
stuff
where the
chemical
reactions
happen
Leaf Structure
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Palisade
cells
Photosynthesis equations
Carbon dioxide + _____
Sunlight
Chlorophyll
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glucose + _____
Sunlight
6CO2
+ 6H20
Chlorophyll
C6H12O6 + 6O2
The GLUCOSE produced by photosynthesis is used by the
plant for _______ (through ____________). It is stored
in the plant as ___________.
Words – respiration, starch, water, oxygen, energy
Three factors can affect photosynthesis:
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1. Temperature – the best temperature is
about 300C – anything above 400C will
slow photosynthesis right down
2. CO2 – if there is more carbon dioxide
photosynthesis will happen quicker
3. Light – if there is more light
photosynthesis happens faster
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Drawing graphs of these factors
1. Temperature
Photosynthesis is controlled by
enzymes – these are destroyed
at temperatures above 400C
2. Carbon dioxide
Photosynthesis increases at
first but is then limited by a
lack of increase in temp or light
3. Light
Photosynthesis increases at
first but is then limited by a
lack of increase in temp or CO2
What is the glucose used for?
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Glucose (sugar) can be used to make long chains of starch…
Glucose
molecules
Starch
molecule
This glucose is then used by the plant as a store of _____ and
some of it may be used for _________. The energy released
from respiration can be used to make ______ acids or to build
up fats and _____ as a food store in a _____.
Words – seed, amino, glucose, respiration, oils
2 common nutrients…
Nitrates:


Used to make proteins
Lack of it leads to stunted growth
Magnesium:


Used to make chlorophyll
Lack of it leads to yellow leaves
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Food chains
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A food chain shows where the energy goes in a food chain (in
other words, “what gets eaten by what”):
Cabbage
Rabbit
Plants convert the
sun’s energy into food
Stoat
Fox
The arrows indicate where
the energy is going
Pyramids of biomass
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In this food chain we can see that the mass of organisms in
each stage is less than in the previous stage:
Cabbage
Rabbit
Stoat
Fox
We can draw a “Pyramid of Biomass” to show this pattern:
Mass of foxes
Mass of stoats
Mass of rabbits
Mass of cabbages
Energy flow in a food chain
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Consider the energy flow in this food chain:
100%
10%
Cabbage
Rabbit
1%
Stoat
0.1%
Fox
Clearly, not all of the ___’s energy that becomes stored in the
_______ will end up in the fox. Only around ______ is passed
on to the next stage in each food chain.
Energy is lost at each stage because of a number of reasons:
1) Each organism has to ____, keep warm etc
2) Energy is lost through faeces (______)
Words – 10%, move, sun, waste, cabbage
Sankey Diagrams for animals
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Cold blooded animal
Warm blooded animal
Faeces
Movement
Heat
Faeces
Movement
Heat
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Improving the efficiency of a food chain
Clearly, food chains aren’t very efficient. How could the
efficiency of a food chain be improved?
1) Reduce the number of stages in the chain:
Cabbage
Rabbit
2) Limit an animal’s movement
or keep it warm:
3) Use plant hormones to
regulate the ripening of fruit
Stoat
Fox
Farming Methods
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There are basically two types of farming method; “intensive”
and “organic”:
Intensive
Cost
Produce
Fertilisers/
food
Space
Organic
Recycling ourselves
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Microbes are the key to this – they break down waste and
dead bodies so that the products can be used by plants for
growth. Microbes work best in warm, moist conditions where
there is plenty of oxygen.
The Carbon Cycle
6. These
microbes also
release CO2
through
respiration
CO2 in air
4. Animals
release CO2
through
respiration
5. Animals (and plants)
die and their remains
are fed on by microbes
and detritus feeders
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2. Plants release
CO2 through
respiration
1. CO2 is taken in
by plants for
photosynthesis
and turned into
carbohydrates
3. The carbon
taken in by plants
is then eaten by
animals
Introduction to Enzymes
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Enzymes are biological catalysts. They help the reactions
that occur in our bodies by controlling the rate of reaction.
An enzyme is basically a protein molecule
made up of long chains of amino acids. These
molecules are then “folded” to create a
certain shape:
The enzyme’s shape helps another
molecule “fit” into it:
Enzyme
This shape can be destroyed by
high temperatures or the wrong
pH:
Substrate
Enzyme use in nature
Cells use glucose to generate
energy – this process is called
“respiration”. Respiration
happens in mitochodria and is
catalysed by enzymes.
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Photosynthesis is
catalysed by enzymes
in the cells.
(Aerobic) Respiration
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All living organisms have to move, _____, reproduce etc. Each
of these life processes needs ENERGY. ___________ is the
process our bodies use to produce this energy:
Glucose + oxygen
water + carbon dioxide + ENERGY
The glucose we need comes from ______ and the oxygen from
_________. Water and carbon dioxide are breathed out.
The MAIN product of this equation is _________.
Words – breathing, energy, grow, respiration, food
Uses for this energy
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Animals and plants have many uses for the energy they
generate from respiration:
1) To perform the life processes, such as moving, _____ etc
2) To build up body _______
3) To maintain a constant body ___________ (warm-blooded
mammals only)
4) To build up sugars, ________ and other nutrients in plants
5) To build up amino acids and ________
Words – nitrates, tissue, proteins, respiration, growing,
temperature
Enzymes in digestion
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Carbohydrase (produced in the mouth,
pancreas and small intestine) breaks
_______ (a carbohydrate) down into
glucose:
Protease (produced in the stomach,
pancreas and small intestine) breaks
_______ down into amino acids:
Lipase (produced in the pancreas and
small intestine) breaks fats (_____)
down into fatty acids and glycerol:
Words – blood, lipids, proteins, digestion, starch, smaller
Bloodstream
Enzymes can be produced by the body to help _______. When they come
into contact and react with food they break it down into ______ pieces
which can then pass into the ______:
Bile and The Liver
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Bile is a chemical produced in the
liver and stored in the gall
bladder. It has 2 functions:
1) It neutralises stomach acid
and produces alkaline
conditions for enzymes to
work in
2) It emulsifies (“breaks down”
fats:
Fat
globules
Fat
droplets
Enzymes
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Enzymes work best in certain conditions:
Enzymes are
denatured
beyond 40OC
Enzyme
activity
400C
Temp
Could be
protease (found
in the stomach)
pH
Could be amylase
(found in the
intestine)
pH
Industrial uses of enzymes
1) Enzymes are used in washing powders
to help digest fats and proteins in food
stains. Biological washing powders will
only work on 400C or lower.
2) Enzymes are used in baby foods to
“pre-digest” the proteins.
3) Enzymes are used to convert starch
into sugar which can then be used in
food.
4) Conversion of glucose into fructose
– glucose and fructose are “isomers”
(they have the same chemical formula),
but fructose is sweeter.
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Homeostasis
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Homeostasis means “controlling internal conditions”:
Waste products that need to be removed + how
CO2
Produced by respiration, removed via lungs
Urea
Produced by liver breaking down amino acids,
removed by kidneys and transferred to bladder
Internal conditions that need controlling + how
Temperature
Increased by shivering, lost by sweating
Ion content
Increased by eating, lost by sweating + urine
Water content
Increased by drinking, lost by sweating + urine
Blood glucose
Increased and decreased by hormones
Controlling Body Temperature
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Wow it’s hot!
The thermoregulatory centre in the
brain detects “warm blood”.
Also, temperature sensors in the skin
detect the heat and send information
to the brain.
When the brain detects the high
temperature it takes two main steps....
Maintaining Body Temperature
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Cold
Hot
Vasodilation
Vasoconstriction
Controlling Blood Sugar levels
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We need glucose in our bodies to help our cells to respire and
produce energy. What happens if we have too much glucose?
If blood sugar is too high the
pancreas releases insulin
The liver then converts
glucose into insoluble
glycogen and is removed
from the blood
Diabetes
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Diabetes is a ________ in which a person’s blood sugar
(i.e. glucose) level may rise to a _______ level. This is
because the ______ doesn’t produce enough _________.
Diabetes can be treated by __________ carefully or by
injecting extra insulin when needed. Diabetics have to
test their blood sugar level before they decide how much
insulin to _______ themselves with.
Words – insulin, disease, inject,
dangerous, eating, pancreas
Modern Genetics
Guten tag! My name is Gregor Mendel. I
am the father of modern genetics because
of the work I did on pea plants in 1865…
Mendel’s experiment:
Take two plants; one which is
pure-bred for tallness and one
pure-bred for shortness, and
cross them:
X
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Modern Genetics
All the plants produced
were tall.
Now cross two of these plants…
3 out of every 4 plants
were tall, leading Mendel
to hypothesise that “for
every characteristic
there must be two
determiners”
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Modern Genetics
Achtung! Unfortunately, nobody knew
about chromosomes or genes when I
published my findings so no one believed
me until after my death, when more
powerful microscopes were available.
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Mitosis
Each daughter cell has
the same number of
chromosomes and genetic
information as the parent.
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Meiosis
Each daughter cell has half
the number of chromosomes
of the parent.
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Mitosis:
1.
Mitosis vs. Meiosis
Used for growth and repair of
cells
2. Used in asexual reproduction
3. Cells with identical number of
chromosomes and genetic
information are produced
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Meiosis:
1.
Used to produce gametes for
sexual reproduction
2. Each daughter cell has half the
number of chromosomes of the
parent
Sexual Reproduction
The human egg and
sperm cell
(“GAMETES”) contain
23 chromosomes each
and are created by
meiosis.
When fertilisation happens the
gametes fuse together to make a
single cell called a ZYGOTE. The
zygote has 46 chromosomes (23
pairs) and continues to grow through
mitosis.
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Boy or Girl?
X
Y
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X
“Allele”
Girl
XX
XY
Boy
Mother
Boy or Girl?
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Son
Father
Daughter
Gamete
Zygote
Key words
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•This allele determines the development of a
characteristic
•This is formed when an egg is fertilised by a sperm
Allele
•This allele will determine a characteristic only if
there are no dominant ones
Dominant
•This word refers to a pair of chromosomes being
made of two different alleles of a gene
Recessive
•An egg or a sperm are called this
Homozygous
•This word refers to a pair of chromosomes being
made of two of the same alleles of a gene
•An alternative form of a gene
Heterozygous
Genes, Chromosomes and DNA
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How genes work
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Some facts:
- Made up of paired bases
- Contain instructions on what a cell does, how the organism
should work etc
- The instructions are in the form of a code
- The code is made up from the four bases that hold the
strands together
- The bases represent the order in which amino acids are
assembled to make proteins
- Everyone (apart from identical twins) has different DNA
and people can be identified by “DNA finger printing”
Eye colour
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In eye colour the brown eye allele is dominant, so we call it
B, and the blue eye is recessive, so we call it b:
BB
Bb
bb
Homozygous
brown-eyed
parent
Heterozygous
brown-eyed
parent
Blue-eyed parent
What would the offspring have?
Eye colour
Example 1: A homozygous
brown-eyed parent and a
blue-eyed parent:
X
BB
Parents:
Gametes:
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Example 2: 2 heterozygous
brown-eyed parents
bb
Bb
X
Bb
B
B
b
b
B
b
B
b
Bb
Bb
Bb
Bb
BB
Bb
bB
bb
(FOIL)
Offspring:
All offspring have brown eyes
25% chance of blue eyes
Eye colour
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Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
Bb
bb
B
b
b
b
Bb
Bb
bb
bb
Equal (50%)
chance of
being either
brown eyed or
blue eyed.
Another method
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
B
b
b
Bb
bb
b
Bb
bb
Father
Mother
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Example questions
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1) In mice, white fur is dominant. What type of offspring
would you expect from a cross between a heterozygous
individual and one with grey fur? Explain your answer with a
genetic diagram.
2) A homozygous long-tailed cat is crossed with a homozygous
short-tailed cat and produces a litter of 9 long-tailed kittens.
Show the probable offspring which would be produced if two
of these kittens were mated and describe the characteristics
of the offspring (hint: work out the kitten’s genotype first).
Inherited diseases
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1) Cystic fibrosis – a disease that causes thick and sticky
mucus to coat the lungs, gut and pancreas. It’s caused by
recessive alleles:
Ff
X
Ff
2) Huntingdon's disease – a disease of the nervous system
that causes shaking and eventually dementia. It’s caused by a
dominant allele:
Cc
X
cc
Embryos can be screened for alleles that cause
these diseases before birth.
Stem Cells
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A while ago we considered examples of specialised cells:
Ciliated
epithelial cell
White blood cell
Nerve cell
(neurone)
Egg cell (ovum)
A “stem cell” is a cell that hasn’t yet become specialised and
can be found in embryos or bone marrow. These cells can be
used to treat certain conditions but the use of these cells is
very controversial.
Research tasks
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Task
Present an argument concerning one of these two topics:
1) Use of stem cells from embryos in medical research
2) The use of embryo screening to identify deformities