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EXAM QUESTIONS Flashcards

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1
Q

Describe the hydrolysis reactions involved in the digestion of triglycerides. Do not write about the activity of lipase.

A
  • breaking ester bonds by adding water
  • produces 3 fatty acids and a glycerol
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2
Q

All mammals produce a lipase called CEL. CEL digest triglycerides. CEL is activated by bile salts binding to the enzyme. Describe two other functions of bile salts?

A
  1. They emulsify lipids
  2. Form micelles
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3
Q

Mammals feed their young on milk. CEL digests the triglycerides in milk. The ability to produce CEL occurred due to a gene mutation. Describe how natural selection may have led to all mammals in a population producing CEL.

A
  • random mutation results in producing a new allele, those with new allele produce more CEL
  • they are more likely to survive now that they are able to digest milk so can reproduce more and pass on that allele
  • directional selection then increases the frequency of this surviving allele in the population
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4
Q

What is a species?

A

A group of similar organisms that can interbreed and produce fertile offspring

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5
Q

Name two biological molecules that can be coded for by a gene, do not include a polypeptide or a protein

A
  • tRNA
  • rRNA
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6
Q

Rough - 46.8 (% of endoplasmic reticulum made of phospholipids)
Smooth - 52.5 (% of endoplasmic reticulum made of phospholipids)
Use the date above to suggest how the structure of RER is different from the structure of SER and how this is related to there function

A
  • less phospholipids in RER so there is more room for ribosomes for protein synthesis
  • more phospholipids in SER so they can transport more lipids
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7
Q

Give the two types of molecule from which a ribosome is made

A
  • rRNA
  • ribosomal proteins
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8
Q

Give 4 structural differences between a DNA molecule and an mRNA molecule

A
  1. DNA is double stranded, mRNA is single stranded
  2. DNA is longer, mRNA is shorter
  3. DNA has the base thymine, mRNA has the base uracil
  4. DNA has a deoxyribose sugar, mRNA has a ribose sugar
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9
Q

Scientists produced a short, single stranded, artificial nucleic acid, called PNA. The PNA binds to a small section of DNA. The scientist introduced PNA into cells and discovered that these cells produced less mRNA than cells that did not contain PNA, suggesting that how PNA affected the transcription of the section of DNA

A

Because PNA is complementary to DNA it forms complementary base paring with it. This prevents RNA polymerase working on it and pre mRNA getting made

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10
Q

Describe the role of ATP in the process of translation in protein synthesis

A

It provides energy for peptide bonds to form between amino acids creating polypeptides and then proteins

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11
Q

Describe a biochemical test to show that raffinose solution contains a non - reducing sugar (3)

A
  • add acid and neutralise
  • add Benidicts solution
  • place in hot water bath for 5 minutes
  • turns orange is non reducing sugar is present
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12
Q

Explain the arrangement of phospholipids in a cell surface membranes (2)

A
  • bilayer (water is present inside and outside the cell)
  • hydrophobic tails point inwards (away from water)
  • hydrophilic heads point outwards
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13
Q

Describe how an ester bond is formed in a phospholipid molecule

A
  • condensation reaction
  • between glycerol and fatty acids
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14
Q

State and explain the property of water that helps to prevent temperature increase in a cell (2)

A
  • property = high specific heat capacity
  • buffers any change in temperature
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15
Q

Describe how a phagocyte destroys a pathogen present in the blood

A
  • engulfs (endocytosis)
  • forming a vesicle which fuses with a lysosome
  • lysosomes digestive enzymes lysozymes will digest/hydrolyse the pathogen
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16
Q

Give two types of cell, other than pathogens, that can stimulate an immune responce

A
  • cancer cells
  • transplanted cells
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17
Q

What is the role of the disulphide bridge in forming the quaternary structure of an antibody? (1)

A

Joins two different polypeptides together

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18
Q

Outline the role of organelles in the production, transport and release of protiens from eukaryotic cells. Do not include details of transcription and translation in your answer

A
  • DNA in nucleus is code for proteins
  • Ribosomes on RER produce proteins
  • mitochondria produce ATP for protein synthesis
  • Golgi apparatus package and modifies
  • vesicles transport
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19
Q

Suggest why a nucleus might not be visible in a figure

A
  • its a section of the cell where the nucleus isn’t there - it might be in another part of the cell
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20
Q

Give one advantage of viewing a biological specimen using a transmission electron microscope compared with using a scanning electron microscope

A

A TEM has a higher resolving power than a SEM

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21
Q

Describe and explain the mechanism that causes lungs to fill with air

A
  • as you breath in the diaphragm contracts and the external intercostal muscles contract
  • decreasing the pressure in the lungs
  • pressure of air outside the lungs is higher so it flows in down a concentration gradient
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22
Q

Name the type of

A
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23
Q

Name the type of bond between complementary base pairs

A

Hydrogen bonds

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24
Q

Name the type of bond between adjacent nucleotides in a DNA strand

A

Phosphodiester bonds

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25
Describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule
1.tRNA is in a clover shape, mRNA is linear 2.tRNA has anti codons mRNA has codons
26
In a eukaryotic cell, the structure of the mRNA used in translation is different from the structure of the pre - mRNA produced by transcription. Describe and explain a difference in the structure of these mRNA molecules.
- pre - mRNA has both exons and introns and has more nucleotide bases so is longer - mRNA has only exons, has less nucleotide bases so is shorter
27
Describe how HIV is replicated
- attachment proteins bind to receptors on t -cells (lymphocytes) - releases its nucleic acid into the host cell - reverse transcriptase turns its RNA into DNA - which is injected into the host cells DNA - its viral proteins are made during protein synthesis - they are then assembled and leave the cell
28
Explain why is is not possible to determine the identity of the structures labelled X using a optical microscope
- resolution is too low - because light wavelength is too long
29
U. Marinum cells ingest bacteria and ingest them in the cytoplasm. Describe the role of one named organelle in digesting these bacteria
- lysosomes - fuse with vesicle - lysozymes hydrolyse the bacteria
30
Describe the arrangement of the genetic material in a cell during prophase
- chromosomes are becoming visible because they are sill condensing - no spindle activity
31
Name the fixed position occupied by a gene on a DNA molecule
- because base/nucleotide sequence in triplets determine sequence of amino acids primary structure in a polypeptide
32
Describe how the structure of glycogen is related to its function
- branched so compact - polymer of glucose so easily hydrolysed - branched so more ends for faster hydrolysis - glucose provides respiratory substrate for energy
33
Give the pathway a red blood cells takes when travelling in the human circulatory system from a kidney to the lungs.
- renal vain to vena cava - vena cava to right atrium - right atrium to right ventricle - right ventricle to pulmonary artery
34
Describe how mRNA is produced from an exposed template strand of DNA
- Nucleotides form complementary base pairing - phosphodiester bonds from - by action of RNA polymerase
35
Define the term exon
Base sequence coding for polypeptide
36
Describe binary fission in bacteria (3)
- circular DNA replicated - replication of plasmids - cytoplasm divides
37
Suggest and explain two environmental variables that could be changes to increase the growth of bacteria cells (4)
- increases conc of glucose - increases respiration - increase conc of oxygen - increase respiration
38
What is a gene?
A stretch of DNA containing a specific sequence of bases with a particular function
39
Describe how the production of mRNA in a eukaryotic cell is different from the production of mRNA in a prokaryotic cell
In a eukaryotic cells transcription occurs to produce pre - mRNA which is spliced to remove introns which then turns into mRNA, In prokaryotic cells transcription produces mRNA directly.
40
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation
- the tRNA brings a specific amino acid to the ribosome, on the ribosome the mRNA has a codon which is specific to the anticodon on the tRNA, they bind by complementary base pairing. The amino acid on top of the tRNA will join to another one on a another tRNA molecule by a peptide bond
41
Describe how monomers join to form the primary structure of a protein
- condensation reaction between amino acids which creates peptide bonds and creates a specific sequence of amino acids
42
Describe and explain one similarity and one difference between the induced fit model of enzyme action and the lock and key model of enzyme action
Similarity = both create enzyme sub straight complexes Difference = induced fit - enzymes are able to change shape to fit when bonded to a sub straight, lock and key model - the active site is fixed and doesn’t change
43
State how enzymes help reactions to proceed quickly at lower temperatures
They reduce the activation energy
44
A competitive inhibitor decreases the rate of an enzyme controlled reaction explain how
- attaches to the enzymes active site because it has a similar shape to the substrate so has a complementary structure to the active site - causes the active site to be blocked from the sub-straight preventing it from binding - prevent enzyme sub straight complexes forming and decreasing the rate of reaction
45
When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch. Scientist have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine. Assuming the scientist are correct, suggest how eating stale bread could help to reduce weight gain
Because there is less hydrolysis of starch to maltose this means there is less absorption of glucose so more egested starch
46
Nucleic acids such as DNA are polymers made up of many repeating monomer units. Name the monomer from which nucleic acids are made
Polynucleotide chain
47
Explain 5 properties that make water important for organisms
- adhesion - adhere to cellulose molecules in plant cell walls allowing water to move - solvent properties - they can dissolve many other substances like salt - high specific heat capacity - creates a stable environment - cohesive - important for moving water up the xylem - high latent heat - important for cooling down (sweat)
48
Explain why if one cell in the body has a mutation all the cells in the body will have this mutation
The mutation happens int eh gamete which goes on to produce a zygote and then you when it replicated to grow into you the DNA replication that occurs all the genes will be replicates exactly so when the cell divides by mitosis the products are 2 genetically identical cells to the original one so the mutation is passed on
49
Describe how crossing over occurs during meiosis 1
When they chromosomes line up alongside its homogulus partner it allows the chromatids to become twisted around one another, the chromatids break and rejoin to chromatid on sister chromosome (recombination)
50
What is the biological importance of reducing the chromosome number when the cell divides by mitosis
When the sperm and egg fertilise because they have half the number of chromosomes each you get the right amount of chromosomes after fertilisation
51
Give 4 differences between mitosis and meiosis
1. Meiosis - reduces the chromosome number, mitosis - maintains the same chromosome number as in the parent nucleus 2. Meiosis - 4 daughter cells are produced, mitosis - 2 daughter cells are produced 3. Meiosis - cells are genetically different, mitosis - cells are genetically identical 4. Meiosis - crossing over, mitosis - no crossing over
52
Where does transcription occur in a eukaryotic cell
Nucleus
53
Pressing downwards on a coverslip allowed the student to observe the stages on mitosis clearly, why?
Flattened it to make it one cells thick so that light could pass through
54
Name the type of blood vessel that controls blood flow to muscles and explain how these blood vessels change blood flow during exercise
Arterioles - the muscle wall relaxes - vasodilation increases blood flow
55
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels
- lipids molecules combine with bile salts to form micelles which transport them to the epithelial cells of the ileum, the micelles diffuse into the epithelial cells because they are non polar. Inside the cells, they are recombined into triglycerides and packaged with proteins and cholesterol into chylomicrons - then released by exocytosis into the lymph vessels
56
The movement of Na plus out of the cells allows the absorption of glucose into the cell lining the ileum explain how
The active transport of Na out of the cells allows lowers the sodium concentration inside the cell. This creates a concentration gradient causing NA to diffuse back into the cell from the ileum through the SGLT1 co transporter. As Na moves in, it brings glucose into the cell via co transport
57
Describe and explain two features you would expect to find in a cell specialised for absorption
1. Microvilli - increase surface area of cell membrane - more efficient absorption of nutrients 2. Lots of mitochondria - provide ATP for active transport processes e.g pumping NA ions out of the cell
58
Describe the role of enzymes in the digestion of proteins in a mammal.
Enzymes break down proteins into smaller, absorbable molecules in mammals . Endopeptidases hydrolyse peptide bonds within the protein hydrolysing it into smaller polypeptides. Exopeptidase then remove amino acids from the ends of these polypeptides. Finally, dipeptidases hydrolyse dipeptides into individual amino acids, which can be absorbed into the bloodstream
59
Tissue fluid is formed from blood at the arteriole end of a capillary bed. Explain how water from tissue fluid is returned to the circulatory system (4)
- plasma proteins remain - creates water potential gradient - water moves to blood by osmosis - returns to blood by lymphatic system
60
Describe how mice injected with human EPO produce anti - human EPO antibody (3)
- antigen displays on antigen presenting cells - helper T cell stimulates B cells to divide - plasma cells produce antibody
61
Cells lining the ileum of mammals absorb the monosaccharide glucose by co - transport with sodium ions. Explain how (3)
- sodium ions are actively transported from ileum cell to blood - this forms a concentration gradient so, facilitated diffusion happens two sodium ions diffuse into the cell from the ileum taking a glucose molecule with it
62
The sports drink contains sodium chloride. Sodium chloride increases uptake of glucose in the small intestine. Explain how?
- sodium ions and glucose are absorbed by co transport - co transport happens via a cotransporter protein - sodium ions are removed via active transport - this maintains a low concentration gradient of sodium ions
63
Explain why the diffusion of chlorine ions involves a membrane protein and the diffusion of oxygen does not. (5)
- chloride ion is a polar molecule therefore it cant cross the phospholipid bilayer by simple diffusion - chloride ion transported via facilitated diffusion, which requires a transmembrane protein - oxygen in non - polar - therefore can diffuse straight through the phospholipid bilayer
64
Describe how phospholipids are arranged in a plasma membrane (2)
- Phospholipids are arranged in a bilayer - they hydrophilic heads are to the outside and the hydrophobic tails to the inside
65
Describe how the RER is involved in the production of enzymes (2)
The RER has ribosomes on its surface and therefore synthesises proteins. An enzyme is a specialised protein
66
Describe how the Golgi apparatus is involved in the secretion of enzymes
Modifies proteins
67
Describe two functions of phospholipids
- Makes cells selectively permeable - maintain different concentration either side
68
Give one similarity in the way in which active transport and facilitated diffusion transport substances across the membrane (1)
They both use transmembrane proteins
69
Give one way in which active transport differs from facilitated diffusion
Active transport requires ATP
70
Explain why an electron microscope shows more detail of a cell structure than a light microscope (2)
- greater resolution - electron beam has a shorter wave length
71
Explain how three features of a plasma membrane adapt it for its functions (6)
- phospholipid bilayer that acts as a barrier to prevent polar substances from entering the cell - the membrane contains cholesterol, increasing the strength and stability of the membrane - glycoproteins that act as receptors in cell signalling
72
Describe the mechanism for the absorption of amino acids in the ileum (4)
- facilitated diffusion of amino acids into cell when higher concentration in lumen - co-transport - sodium ions actively transported from cell to blood - creating sodium ion concentration gradient - facilitated diffusion of amino acid in blood
73
Give two types of molecule from which a ribosome is made?
- rRNA - protein
74
Describe and explain the difference between photos from TEM and SEM
Describe - 3D with SEM, but 2D with TEM Explain - because electrons are deflected off
75
The resolution of an image obtained using an electron microscope is higher than the resolution of an image obtained using a optical microscope
Shorter wavelength between electrons
76
A student determined the size of a cell structure from a photograph obtained using an electron microscope. He used a ruler and a calculator and gave the answer in pm describe how the student determine the size of the structure
- measure length and divide by magnification - x 10000 from cm
77
Name two structure found in all bacteria that are not found in plant cells
- circular DNA - murine cell wall
78
Describe how monomers join to form the primary structure of a protein
- condensation reaction to from peptide bonds between amino acids - creating specific sequence of amino acids
79
Explain a property of iron ions that enables these ions to carry out their role in red blood cells
- is charged / polar - so binds with oxygen
80
What is a tumor
- mass of cells - made by uncontrolled mitosis
81
Describe how you would determine a reliable mitotic index from tissue observed with an optical microscope
- count cells in mitosis in field of view - divide this by total number of cells in field of view - repeat at least 5 times
82
Describe the primary structure of all proteins
- the specific sequence of amino acids - joined by peptide bonds
83
Define universal, non-overlapping and degenerate
Universal - the same codon will always code for the same amino acids Non overlapping - each base is only part of one codon Degenerate - multiple codons code for the same amino acids
84
Describe one difference between the structure of DNA in a prokaryotic cell and in eukaryotic cell
Circular not linear
85
Suggest how bacteria with a thicker capsule are more likely to survive and so cause lung disease
- less likely to bind to murein cell wall - reduced phagocytosis so more bacterial growth
86
Describe two differences between the structure of the triglyceride and a phospholipid
- has 2 fatty acids not 3 - has 3 eater bonds not 2
87
Explain why phospholipids can form a bilayer but triglycerides cannot
- phospholipids are polar - triglycerides are non polar - hydrophilic group attracts water
88
Describe the role of tRNA in translation (2)
- anti codon binds to codon - brings specific amino acids
89
Describe how gas exchange occurs in single celled organisms and explain why this method cannot be used by large, multicellular organisms
- diffusion across the cell surface membrane - large organisms have small SA:vol ratio - diffusion pathway would be too long - too slow
90
Name two enzymes that are involved in replicating the DNA of a virus and their roles in the replication process
DNA polymerase - condensation reaction to join nucleotides DNA helicase - breaks hydrogen bonds
91
Potato plants with fewer sucrose transport proteins produce fewer potatoes and accumulate sugars in their leaves
- carbohydrates made by photosynthesis - less sucrose into phloem at leaf source
92
Give two reasons why glucose uptake by muscle cells increases significantly during exercise
- increased respiration - to provide more ATP for muscle contraction - more glucose being used so concentration gradient for glucose increases - glucose enters by facilitated diffusion
93
Use your understanding of the mass flow hypothesis to explain how pressure is generated inside the phloem tube?
- sucrose actively transported into phloem - lowering water potential - water moves into phloem by osmosis
94
Explain why coloured water moved up the stalks?
- water evaporates - water potential gradient creates tension - hydrogen bonds maintains column
95
Explain how arteriole can reduce the blood flow into capillaries
- muscle contracts - constricts lumen
96
Describe the advantage of the bohr effect during intense exercise (2)
- haemoglobin affinity for oxygen decreased due to CO2 in the blood - more oxygen is released so can be used in aerobic respiration
97
Describe how the products of the light dependant reaction are used in the light independent reaction to produce triose phosphate - do not include the role of RuBP in your answer (3 marks)
1. ATP and reduced NADP are products 2. ATP provides energy 3. GP is reduces to triose phosphate
98
Describe the light independent reaction of photosynthesis (6 marks)
- carbon dioxide combines with RuBP - produces two GP using Rubisco - GP reduced to TP - Using reduced NADP - using energy from ATP - triose phosphate converted into hexose sugars or regenerated back into RuBP
99
State the key difference between kinesis and taxis (1 mark)
- kinesis is a non directional response whereas taxis is a directional response to a stimulus
100
Describe hoe spatial summation results in the propagation of a new action potential in the postsynaptic neurone? (2 marks)
- summation means there are several presynaptic neurones realising neurotransmitters molecules at the same time - this leads tot eh release of sufficient neurotransmitters molecules to reach the threshold level required to trigger an action potential
101
State why it is important that neurotransmitters, such as acetylcholine, are broken down and removed from the synapse
- they will continue to bind to the receptors on the postsynaptic membrane - this will result in a continuous state of depolarisation of the postsynaptic membrane
102
Define the term tropism
A directional growth response of a plant in response to a directional stimulus
103
Why are amyloplasts at the bottom of the root tip
- they contain high concentrations of starch - therefore are very heavy and dense - they ill therefore sink to the bottom of the root due to gravity
104
One method of transferring RNAi molecules into cells involves combining these molecules with a lipid. Suggest why this increases the uptake of RNAi molecules into cells walls
To allow it to cross the phospholipid bilayer - allows lipid soluble substances to cross
105
Steroid hormones are hydrophobic, explain why they an rapidly enter a cell by passing through its cell surface membrane
It is lipid soluble therefore can diffuse through the phospholipid bilayer
106
In the cytoplasm, testosterone binds to a specific androgen receptor (AR) suggest and explain why testosterone binds to a specific androgen receptor
- has a specific tertiary structure - this makes them complementary to each other
107
The binding of testosterone to an AR changes the shape of the AR. This AR molecule now enters the nucleus and stimulates gene expression, suggest how
- AR is a transcription factor - then binds to DNA or a promotor region - this stimulates RNA polymerase to start transcription
108
Define what it is ment by epigenetics
Heritable changes in gene function without changes to the base sequence of DNA
109
Explain how increased methylation could lead to cancer
- methyl groups could be added to a tumour suppressor gene - the transcription of tumour suppressor gene is inhibited - leading to uncontrolled cell division
110
Inhibitory synapses cause hyperpolarisation in postsynaptic neurones. Explain how this inhibits synaptic transmission
- axon is more negative - more sodium ions needed for depolarisation
111
Describe how stimulation of a pacinian corpuscle produces a generator potential (3)
- stretch mediated sodium channels in membrane - increases pressure deforms membrane - sodium channels open - sodium ions diffuse in - causes depolarisation
112
Explain how a resting potential is maintained across the axon membrane in a neurone (3)
- higher concentration of potassium ions inside and a higher concentration of sodium ions outside the neurone - membrane more permeable to potassium ions leaving then sodium ions entering - sodium ions actively transported out and potassium ions in
113
A scientist investigated the effect of inhibitors on neurones she added a respiratory inhibitor to a neurone. The resting potential of the neurone changes from -70 to 0 mV, explain why (3)
- no ATP produced - no active transport - electrochemical gradient not maintained
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