Download VJJ Class - 6 Mark Question File

Enzymes
• Describe enzymes as biological catalysts
• Enzymes catalyse chemical reactions occurring inside and
outside living cells, including:
a DNA replication
b protein synthesis
c digestion
• Describe the factors affecting enzyme action, including:
a temperature
b substrate concentration
c pH
• Enzymes are highly specific for their substrate
• The action of enzymes in terms of the ‘lock-and-key’
hypothesis
• Describe how enzymes can be denatured due to changes in
the shape of the active site
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A student carried out an investigation to study the effect of pH on the activity of
catalase.
In the presence of catalase, hydrogen peroxide breaks down to release oxygen gas.
The student set up five test tubes, as shown in the diagram, and observed the
amount of oxygen gas released.
Explain the effect of pH on the enzyme catalse.
Markscheme
• more oxygen given off at pH 7
• pH 7 is the optimum pH for this enzyme
• reaction is faster/enzyme more active in neutral solution
• very little oxygen given off at pH 5 and pH 9
• enzyme / catalase less active
• no oxygen given off at pH 1 and pH 14
• no enzyme activity
• enzyme denatured
• shape of active site is changed
• due to strong acid / low pH/strong alkali / high pH
• no longer binds to hydrogen peroxide / substrate
Digestion
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Describe the functions of the parts of the digestive system, including:
a mouth
b oesophagus
c stomach
d small and large intestines
e pancreas
f liver
g gall bladder
Explain the role of the muscular wall of the alimentary canal in peristalsis
Explain the role of digestive enzymes, including:
a carbohydrases, including amylase, which digest starch to simple sugars
b proteases, including pepsin, which digest proteins to amino acids
c lipase, which digests fats to fatty acids and glycerol
Explain the role of bile in neutralising stomach acid and emulsifying fats
Explain how the structure of villi (large surface area, single layer of cells and capillary
network) allows efficient absorption of the soluble products of digestion
Describe how the action of the mouth,
oesophagus and stomach contribute
to the digestion of food.
Markscheme
mouth
• teeth chew food/break food down into smaller pieces
• increasing its surface area
• (and) mixes food with saliva so it can be swallowed more easily
• enzyme action in mouth / amylase
• Digests starch to sugar/glucose
• tongue helps to roll food into a ball/bolus (so it can be swallowed more easily)
oesophagus
• swallowing
• muscular contractions/peristalsis in oesophagus
• pushes/moves food towards the stomach
stomach
• contraction of muscle tissue in the stomach mixes food with acid and digestive juices
• enzyme action in stomach / protease
Digests protein to amino aciids
• hydrochloric acid contributes to the breakdown of food
The diagram shows how visking tubing can be used to model the small
intestine. This model does not fully represent the structure and functions of
the small intestine. Evaluate the strengths and weaknesses of this model.
Markscheme
Strengths
• thin membrane
• permeable membrane
• presence of amylase
• presence of (large) starch molecules
• digestion into glucose
• glucose diffuses out
• concentration gradient
• water represents the blood
weaknesses
• membrane not one cell thick
• not a large surface area
• shorter length / not same size
• no villi /micro villi
• only carbohydrate digestion
• no other enzymes present
• no peristalsis
• no blood movement
• other factors e.g. pH
Describe the roles of the enzymes
involved in digestion.
Markscheme
Names of enzymes:
• carbohydrases
• eg amylase
• proteases
• eg pepsin
• lipases
General points about enzyme action:
• breakdown of large / insoluble / named molecules into small soluble molecules
• for absorption
• catalysts
• speeds up reactions
• active sites that bind to substrate
• idea of specificity – each enzyme can only break down 1 food type
• Due to shape of active site only matching 1 food type
Specific points:
• carbohydrates/ starch are broken down into sugars / glucose
• proteins /named protein are broken down into amino acids
• fats / oils / lipids / named lipid are broken down into fatty acids /glycerol
Describe the role of the small
intestine in digestion
Markscheme
Digestion
• Makes enzymes
• Receives enzymes from pancreas
• Enzyme amylase
• Breaks down starch into sugar
• Enzyme protease
• Breaks down protein into amino acids
• Enzyme lipase
• Breaks down fats into fatty acids and glycerol
• Receives bile from gall bladder
• Bile emulsifies fats
• Increasing SA
• Enzymes breaks fat down faster
Absorption
• By diffusion
• Into blood stream
• Villi
• Increase SA so faster diffusion
• single layer of cells
• Short distance for substances to travel before getting into blood
• Good capillary network
• Maintains concentration gradient so diffusion happens quickly
Explain how the structure of the small
intestine allows efficient absorption of the
soluble products of digestion
Markscheme
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Long
Villi
Increase SA
For diffusion
single layer of cells
Short distance for substances to travel before getting
into blood
Good capillary network
Blood carries digested food around body
Maintains concentration gradient
So diffusion happens quickly
Transport in Plants
• Explain how the loss of water vapour from leaves
drives transpiration
• Explain how water, glucose and mineral salts are
transported through a plant, including:
a mineral uptake in roots by active transport
b the role of the xylem and phloem vessels
• Describe how root hair cells are adapted to take up
water by osmosis
• Define osmosis as the movement of water molecules
from an area of higher concentration of water to an
area of lower concentration of water through a
partially permeable membrane
Explain how water, glucose and
mineral salts are transported
through a plant.
Markscheme
water
• through the xylem
• capillary action
• osmosis into cells in the leaf
• evaporation from leaves
• transpiration stream
• diffusion into the atmosphere
• through stomata
glucose
• converted to sucrose
• dissolved in water
• through the phloem
• bidirectional
mineral salts
• dissolved in water
• through the xylem
• from root to tip
Describe how water enters plants
from the soil and is transported to
the leaves.
Markscheme
• (water moves into) root hair cells
• by osmosis
• from a high concentration (of water)
• to a low concentration (of water)
• down a concentration gradient
• through a partially permeable membrane
• through xylem vessels
• by capillary action
• (into leaves) and out through the stomata
• reference to transpiration/transpiration stream
Photosynthesis
• Describe how the structure of a leaf is adapted for
photosynthesis, including:
a large surface area
b containing chlorophyll in chloroplasts to absorb light
c stomata for gas exchange (carbon dioxide, oxygen and water
vapour)
• How photosynthesis uses light energy to produce glucose
and how this process can be modelled using the word
equation for photosynthesis
• How limiting factors affect the rate of photosynthesis,
including:
a light intensity
b CO2 concentration
c temperature
Describe how the structure of
leaves is adapted for
photosynthesis
Markscheme
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leaves have a large surface area
contain (many) chloroplasts/chlorophyll
for maximum absorption of light
waxy cuticle to reduce water loss
stomata/pores
gas exchange/to take in carbon dioxide and
release oxygen
• guard cells that control size of stoma
• xylem vessels throughout the leaf deliver water
and mineral ions
Revision
DNA and Protein
Synthesis
In pairs……………….
• What is a gene?
• Describe the structure of DNA
• Name the scientists to discovered the structure
of DNA
• What did they do?
DNA
• Recall that a gene is a section of DNA and that it codes
for a specific protein
• Describe a DNA molecule as:
– a two strands coiled to form a double helix
– b strands linked by a series of complementary base
pairs joined together by weak hydrogen bonds:
i adenine (A) with thymine (T)
ii cytosine (C) with guanine (G)
• Explain how the structure of DNA was discovered,
including the roles of the scientists Watson, Crick,
Franklin and Wilkins
• Investigate how to extract DNA from cells
Describe the structure of DNA,
including the roles of the scientists
involved in its discovery.
Markscheme
DNA structure (max 3)
• two strands
• twisted into a double helix
• (contains) bases A, T, C, G
• adenine / A paired with thymine / T
• guanine / G paired with cytosine / C
• hydrogen / H bonds joining bases
Contributions from Scientists (max 3)
• Franklin & Wilkins - X-ray (crystallography) being used
– to show helical structure
– to show diameter of molecule
– how base pairs are arranged was shown
– how strands are arranged was shown
• Watson &Crick - Building models
– Used Franklin and Watsons X rays to work out shape
DNA
• Recall that a gene is a section of DNA and that it codes
for a specific protein
• Describe a DNA molecule as:
– a two strands coiled to form a double helix
– b strands linked by a series of complementary base
pairs joined together by weak hydrogen bonds:
i adenine (A) with thymine (T)
ii cytosine (C) with guanine (G)
• Explain how the structure of DNA was discovered,
including the roles of the scientists Watson, Crick,
Franklin and Wilkins
• Investigate how to extract DNA from cells
Protein Synthesis
• Demonstrate an understanding of the stages of protein synthesis transcription and translation:
– a the production of complementary mRNA strand in the
– nucleus
– b the attachment of the mRNA to the ribosome
– c the coding by triplets of bases (codons) in the mRNA
– for specific amino acids
– d the transfer of amino acids to the ribosome by tRNA
– e the linking of amino acids to form polypeptides
• Describe each protein as having a specific number and sequence of
amino acids, resulting in different-shaped proteins that have
different functions, including enzymes
• Demonstrate an understanding of how gene mutations change the
DNA base sequence and mutations can be harmful, beneficial or
neither
Describe how the order of bases in a
section of DNA decides the order of
amino acids in the protein
Markscheme
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Transcription
mRNA made
In nucleus
Complimentary copy of gene
By complimentary base pairing
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Translation:
mRNA attaches to the ribosome
Each 3 bases (codons) in the mRNA codes for
specific amino acids
transfer of amino acids to the ribosome by tRNA
the linking of amino acids to form polypeptides
Describe the effect of a
mutation
Markscheme
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Change in a gene
Change to sequence/order of bases
Changes order or type of amino acid
Changes shape of protein
Function of protein changes
Enzymes active site changes shape
Substrate can’t fit into it
May have useful effect eg new characteristic
May have harmful effect – eg cancer
May have no effect on characteristic
Gene Technology
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The process of genetic engineering, including the removal of a gene from the DNA of one
organism and the insertion of that gene into the DNA of another organism
Advantages and disadvantages of genetic engineering to produce GM organisms,
– a beta carotene in golden rice to reduce vitamin A deficiency in humans
– b the production of human insulin by genetically modified bacteria
– c the production of herbicide-resistant crop plants
Recall that cloning is an example of asexual reproduction that produces genetically identical
copies
The stages in the production of cloned mammals, including:
– a removal of diploid nucleus from a body cell
– b enucleation of egg cell
– c insertion of diploid nucleus into enucleated egg cell
– d stimulation of the diploid nucleus to divide by mitosis
– e implantation into surrogate mammals
The advantages, disadvantages and risks of cloning mammals
Stem cells in the embryo can differentiate into all other types of cells, but that cells lose this
ability as the animal matures
The advantages, disadvantages and risks arising from adult and embryonic stem cell research
Genetic engineering can be used to
produce GM organisms. Describe
process of genetic engineering
Markscheme
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removal of a gene
from the DNA of one organism
Cut out using an enzymes
gene inserted into the DNA of other organism
using enzymes
Gene codes for new protein
Evaluate the use of genetic
engineering to produce GM organisms
Markscheme
Advantages
beta carotene in golden rice
to reduce vitamin A deficiency in humans
Of bacteria to produce human insulin
To treat diabetes
Production of herbicide-resistant crop plants
Easier for farmers to spray fields to get rid of weeds
Disadvantages
Unexpected effects
Makes crops poisonous
Bacteria – new diseases
herbicide-resistant gene gets into wild plants
Evaluate the use of adult and
embryonic stem cells in research.
Markscheme
Advantages
• Stem cells can differentiate
• into any cell type
• Can lead to treatments for disease
• Eg fix damaged heart muscle
Disadvantages
• Embryonic stem cells – have to kill embryo. Some people think this is
wrong as it is an unborn baby
• Adult stem cells – not many in an adult, hard to get
• Adult stem cell treatment don’t always work
• body destroys them
• Stem cells injected into body could cause cancer
A cloned animal contains genetic
information that is identical to its
parent. Describe the stages in the
production of a cloned mammal.
Markscheme
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use of body cell
nucleus removed from body / parent cell
use of egg cell - nucleus removed from egg cell
nucleus (from body cell) transferred to empty egg
electric shock; to stimulate cell division
Mitosis happens
formation of embryo;
embryo implanted
into womb of female – pregnancy happens
normally
Describe the processes that take
place in the formation of the
foetus from a sperm cell and an
egg cell.
Markscheme
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fertilisation of egg by sperm
fusion of nuclei
forming diploid cell
Forms zygote
(zygote) divides by mitosis
to form identical cells
several mitotic divisions - growth of foetus
examples of how fetus grows eg in height, mass
stem cells in embryo
specialisation / differentiation of (stem) cells into different
cell types
• examples of different cell types eg neurones, skin cells
Cell Division
• Describe the division of a cell by mitosis as
– the production of two daughter cells
– each with identical sets of chromosomes in the nucleus to the
parent cell
– this results in the formation of two genetically identical diploid
body cells
• Mitosis occurs during growth, repair and asexual reproduction
• At fertilisation, haploid gametes combine to form a diploid zygote
• Describe the division of a cell by meiosis as the production of
– four daughter cells,
– each with half the number of chromosomes
– results in the formation of genetically different haploid gametes
Mitosis and meiosis are types of cell
division. Compare these two types of
cell division.
Markscheme
Mitosis
• (genetically) identical cells produced
• two daughter cells
• one division
• diploid daughter cells
• occurs in the formation of body cells
• for growth and repair (of body tissues)
Meiosis
• (genetically) non-identical cells
• four daughter cells
• 2 divisions
• haploid daughter cells
• half the number of chromosomes
• occurs in the formation of gametes
• results in genetic variation
Sperm cells and egg cells are needed
for human sexual reproduction.
Describe in detail the type of cell
division that produces sperm cells.
Markscheme
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meiosis
2 divisions
4 cells produced
haploid (cells)
cells have half the number of chromosomes
cells are genetically different (genetically) nonidentical cells
Heart and Circulation
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How the structure of the heart is related to its function, :
a four blood vessels of the heart (pulmonary artery, pulmonary vein, aorta, vena cava)
b left atrium and ventricle to pump oxygenated blood
c right atrium and ventricle to pump deoxygenated blood
d valves to prevent backflow
e why the left ventricle has a thicker muscle wall than the right ventricle
f the direction of blood flow through the heart
Structure and function of arteries, veins, capillaries.
a arteries transport blood away from the heart
b veins transport blood to the heart
c capillaries exchange materials with tissues
Structure and function of the parts of the blood, :
a red blood cells
b white blood cells
c plasma
d platelets
glucose and oxygen diffuses from capillaries into respiring cells, carbon dioxide diffuses from
respiring cells into capillaries
Define diffusion as the movement of particles from an area of high concentration to an area of
lower concentration
Markscheme
• two sides to prevent mixing of blood
• left side deals with oxygenated blood
• thicker wall of left ventricles
• pump blood to body
• right side deals with deoxygenated blood
• pumps blood to lungs
• muscular wall of ventricles which contract
• atria receive blood
• valves to prevent backflow
• correct reference to (named) arteries/veins
Explain why heart rate and
breathing rate increase during
exercise.
Markscheme
• increased muscle contraction
• blood is pumped faster around the body/to muscles
• more oxygen/glucose delivered to cells/muscles
• for aerobic respiration
• which releases energy
• rate of gas exchange increases
• more carbon dioxide in the blood
• more oxygen inhaled/into body
• more carbon dioxide exhaled/from body
• reduce build up of lactic acid
Exercise
• Investigate the effect of exercise on breathing
rate and heart rate
• Explain why heart rate and breathing rate
increase with exercise
• Calculate heart rate, stroke volume and cardiac
output, using the equation, cardiac output =
stroke volume x heart rate
• Why during vigorous exercise, muscle cells may
not receive sufficient oxygen for their energy
requirements and start to respire anaerobically
A reduced cardiac output would affect
the performance of an athlete.
Explain the effects that a reduced
cardiac output would have on the
muscle cells of an athlete.
Markscheme
• there will less blood flow (to the muscles)
• because less blood leaving the heart
• less oxygen (reaching muscle)
• less glucose (reaching muscle)
• reduced rate of aerobic respiration
• less energy released
• less carbon dioxide removed
• greater rate of anaerobic respiration
• glucose broken down without oxygen
• reduced muscle contraction
• build up of lactic acid (in muscle cells)
• causing cramp / fatigue
Respiration
• Aerobic respiration uses oxygen to release energy from
glucose
• Word equation for aerobic respiration
• During vigorous exercise, muscle cells may not receive
sufficient oxygen for their energy requirements and so start to
respire anaerobically
• Anaerobic respiration releases energy from glucose
• Word equation for anaerobic respiration
• The process of anaerobic respiration releases less energy than
aerobic respiration
• The build-up of lactic acid requires extra oxygen to break it
down. This is called excess post-exercise oxygen consumption
or EPOC (formerly known as oxygen debt)
• Explain why heart rate and breathing rate remain high after
exercise
Compare aerobic and
anaerobic respiration
Markscheme
Aerobic
• Use oxygen
• To release energy from glucose
• Makes carbon dioxide and water
• Happens in all cells
Anaerobic
• Does not use oxygen
• Releases less energy from glucose
• Makes lactic acid
• Happens in muscle cells
• During vigorous exercise
• When there is not enough oxygen
Explain why heart rate and
breathing rate remain high after
exercise
Markscheme
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rate of gas exchange increases in lungs
more oxygen into body
blood is pumped faster to muscles
Red blood cells carry oxygen
more oxygen gets to muscles
Used to break down lactic acid
made by anaerobic respiration
called excess post-exercise oxygen consumption
or EPOC