bio questions Flashcards by jananie sukkarnan

Suggest and explain why the combined actions of endopeptidases and
exopeptidases are more efficient than exopeptidases on their own

Endopeptidases hydrolyse internal (peptide
bonds)
More ends or increase in surface area (for
exopeptidases);

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The addition of a respiratory inhibitor stops the absorption of amino acids.
Use Figure 1 to explain why.

No/less ATP produced
Sodium (ions) not moved (into/out of cell);
No concentration gradient for sodium (to
move into cell with amino acid);

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Give two reasons why it was important that the student counted the number of
stomata in several parts of each piece of leaf tissue.

So it is a representative sample
To obtain a (reliable) mean;

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Other than the distribution of stomata, suggest and explain two xerophytic
features the leaves of this plant might have.

Hairs so ‘trap’ water vapour
and water potential gradient
decreased;
2. Stomata in pits/grooves so
‘trap’ water vapour and water
potential gradient decreased;
3. Thick (cuticle/waxy) layer so
increases diffusion distance;
4. Waxy layer/cuticle so reduces
evaporation/transpiration.
5. Rolled/folded/curled leaves so
‘trap’ water vapour and water
potential gradient decreased;
6. Spines/needles so reduces
surface area to volume ratio;

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Suggest two reasons why the rate of water uptake by a plant might not be the
same as the rate of transpiration.

Water used for
support/turgidity;
Water used in photosynthesis;
Water used in hydrolysis;
Water produced during
respiration;

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The species of tubifex worm in Figure 3 has 50% saturation of their
haemoglobin with oxygen at 0.08 kPa.
Explain how this enables this species to survive in water polluted with sewage.

High/50% saturation (with oxygen)
below (pO2 of) 0.2 kPa;
(Oxygen) for respiration;

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Species of tubifex worm that live in ponds, lakes and rivers cannot survive in
seawater.
Use your knowledge of water potential to explain why they cannot survive in
seawater.

Water potential higher in worm
Water leaves by osmosis (and
worm dies);

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Suggest two reasons why an increase in phosphate can be linked to growth of
the embryo.

(Phosphate required) to make RNA;
2. (Phosphate required) to make DNA;
3. (Phosphate required) to make
ATP/ADP;
4. (Phosphate required) to make
membranes;
5. (Phosphates required) for
phosphorylation;

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The chilling requirement of seeds of certain plant species is considered to be an
adaptation for survival in countries with seasonal changes in environmental
conditions.
Suggest how this adaptation may enable these plant species to survive and
respond to seasonal changes.

Seeds/embryo remain
dormant/inactive in winter/cold

Seeds/plants develop in
spring/summer

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HIV attaches to a specific protein receptor on helper T cells. A low percentage
of people have a mutation of the CCR5 gene which codes for this protein
receptor. This mutation results in a non-functional protein receptor.
Explain how this mutation can result in the production of a non-functional protein
receptor.

Change in DNA base/nucleotide
(sequence);
2. Change in amino acid
(sequence)/primary structure;
3. Alters (position of)
hydrogen/ionic/disulfide bonds;
4. Change in tertiary structure (of
receptor);

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People with the CCR5 mutation show a greater resistance to developing AIDS.
Explain why.

Receptor) is not complementary
OR
(HIV) cannot bind/attach and
enter/infect (helper) T cell;
2. No replication (of virus)
OR
No destruction of (helper) T cell;

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Some people produce a much higher ventricular blood pressure than normal.
This can cause tissue fluid to build up outside the blood capillaries of these
people.
Explain why.

More fluid forced/filtered out of
capillary/blood (due to high
pressure);
2. Less return of fluid (into
capillary/blood) due to pressure

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Describe how the structures of starch and cellulose molecules are related to their
functions.

Starch (max 3)
1. Helical/ spiral shape so compact;
2. Large (molecule)/insoluble so
osmotically inactive;
3. Branched so glucose is (easily)
released for respiration;
4. Large (molecule) so cannot leave
cell/cross cell-surface membrane;

Cellulose (max 3)
5. Long, straight/unbranched chains of
β glucose;
6. Joined by hydrogen bonding;
7. To form (micro/macro)fibrils;
8. Provides rigidity/strength;

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Describe the processes involved in the transport of sugars in plant stems.

1)(At source) sucrose is actively
(transported) into the phloem/sieve
element/tube;
2. By companion/transfer cells;
3. Lowers water potential in
phloem/sieve element/tube and
water enters by osmosis;
4. (Produces) high (hydrostatic)
pressure;
5. Mass flow/transport towards
sink/roots/storage tissue;
6. At sink/roots sugars are
removed/unloaded;

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The food eaten by a rabbit is digested mainly by microorganisms in its caecum.
The caecum is a section of intestine attached between the ileum and the large
intestine. The resulting semi-digested material leaves the anus of a rabbit as soft,
caecal droppings. The rabbit then eats these caecal droppings.
Use this information and Figure 2 to suggest how eating its own caecal droppings
helps a rabbit’s digestion and absorption of dietary protein.

More/remaining/undigested (protein) broken
down;
(So more) amino acids absorbed;
(Because) protein/food passes again through
stomach/ileum;

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Role of single-stranded DNA fragments

Template;
Determines order of nucleotides/bases;

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Role of DNA nucleotides

Forms complementary pairs / A – T, G - C

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The scientists hypothesised that memory B cells had formed in the mice 180 days
after the 3rd injection.
Suggest and explain a practical method the scientists could use to test this
hypothesis.

Inject vaccine (again)/meningitis antigen/
inactive antigen/dead/living bacteria/
pathogen/use a booster;
(Memory cells present if) faster/more
rapid production/higher concentration
antibody (than 1st injection)
Add enzyme attached to (second)
antibody against memory cell;
Colour change shows memory cell
present;

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Explain why coloured water moved up the stalks.

Water evaporates/is transpired (from leaves/
stalk/celery/plant);
Water potential gradient/lower water potential
creates tension/pulls up wate
Hydrogen bonds/cohesion/adhesion maintains
column;

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Circle the most appropriate measure for this set of measurements.
Give a reason for your choice and find the value using the measurements from all
eight stalks.

why median

(Presence of) outliers/80/70
OR
Small sample size/8 (measurements);

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Describe the roles of iron ions, sodium ions, and phosphate ions in cells.

. -Haemoglobin binds/associates with
oxygen

Co-transport of glucose/amino
acids (into cells);
3. (Because) sodium moved out by
active transport/Na – K pump;
4. Creates a sodium
concentration/diffusion gradient;
5. Affects osmosis/water potential;

-Affects osmosis/water potential;
7. Joins nucleotides/in
phosphodiester bond/in backbone
of DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
9. Phosphorylates other compounds
(usually) making them more
reactive;
10. Hydrophilic/water soluble part of
phospholipid bilayer/membrane;

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The movement of substances across cell membranes is affected by membrane
structure. Describe how.

-phospholipid bilayer allows diffusion of non polar/lipid soluble substances
- Phospholipid bilayer prevents diffusion of polar/charged/lipid soluble substances
- carrier proteins allow active transport
- channel/carrier proteins allow facilitated diffusion/co-transport
- shape/charge of carrier protein determines which substances are transported/moved
-number of channel/carrier proteins determine how much movement
- membrane surface area determines how much movement
- cholesterol affects fluidity/permeability

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Describe how a phosphodiester bond is formed between two nucleotides within a DNA
molecule

Condensation (reaction)/loss of water;
(Between) phosphate and deoxyribose;
(Catalysed by) DNA polymerase;

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In the process of semi-conservative DNA replication, the two strands within a DNA molecule are separated. Each then acts as a template for the formation of a new complementary strand.
Describe how the separation of strands occurs.

DNA helicase;
Breaks hydrogen bonds between base pairs/ AT
and GC/complementary bases
OR
Breaks hydrogen bonds between polynucleotide
strands;

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Explain how an arteriole can reduce the blood flow into capillaries

1. Muscle contracts; 2. Constricts/narrows arteriole/lumen;

What can you conclude from the appearance of valves in Figure 1 about heart muscle activity and blood movement between: 1. ventricles and arteries?

1. Ventricle (muscles) relaxed No (blood) backflow (into ventricles)

What can you conclude from the appearance of valves in Figure 1 about heart muscle activity and blood movement between: . atria and ventricles?

. Atria (muscle) contracted; 4. Blood movement from atria (into ventricles);

When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch. Scientists have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine. Assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain.trrrrrr

1. Less hydrolysis of starch; 2. (To) maltose; 3. (So) less absorption (of glucose)

Phloem pressure is reduced during the hottest part of the day. Use information in Figure 6 along with your understanding of transpiration and mass flow to explain why

. High (rate of) transpiration/evaporation; 2. Water lost through stomata (Causes) less water movement from xylem to phloem

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.

Micelles contain bile salts and fatty acids/monoglycerides; 2. Make fatty acids/monoglycerides (more) soluble (in water) Fatty acids/monoglycerides absorbed by diffusion; 4. Triglycerides (re)formed (in cells); 5. Vesicles move to cell membrane;

Describe how the structure of a protein depends on the amino acids it contains

1. Structure is deternmined by (relative) position of amino acid/R group/interactions; 2. Primary structure is sequence/order of amino acids; 3. Secondary structure formed by hydrogen bonding (between amino acids); 4. Tertiary structure formed by interactions (between R groups); 5. Creates active site in enzymes OR Creates complementary/specific shapes in antibodies/carrier proteins/receptor (molecules); 6. Quaternary structure contains >1 polypeptide chain

Explain why it is not possible to determine the identity of the structures labelled X using an optical microscope.

1. Resolution (too) low; 2. Because wavelength of light is (too) long;

Describe how HIV is replicated.

Attachment proteins attach to receptors on helper T cell/lymphocyte; 2. Nucleic acid/RNA enters cell; 3. Reverse transcriptase converts RNA to DNA; 4. Viral protein/capsid/enzymes produced; 5. Virus (particles) assembled and released (from cell);

Describe how a gene is a code for the production of a polypeptide. Do not include information about transcription or translation in your answer.

1. (Because) base/nucleotide sequence; 2. (In) triplet(s); 3. (Determines) order/sequence of amino acid sequence/primary structure (in polypeptide);

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs.

. Renal vein; 2. Vena cava to right atrium; 3. Right ventricle to pulmonary artery;

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.

1. (Plasma) proteins remain; 2. (Creates) water potential gradient 3. Water moves (to blood) by osmosis; 4. Returns (to blood) by lymphatic system;

Describe how mice injected with human EPO produce anti-human EPO antibody

(Human) EPO/antigen displayed on antigen- presenting cells/phagocytes/B cells (in mice); 2. (Specific) helper T cell stimulates B cell to divide/clone; 3. Plasma cells produce/release/secrete antibody;

non overlapping

each base read only once

degenerate

more than one codon codes for each amino aicds

decribe yhe mechanism pf breathing enetring the lungs

diaphram contracts and flattens external intercostal muscles contracy and ribcage pulled up vol inc and pressure decreases in thoracic cavity

suggest how bacteria with thicker capsules are more likely to surive and so cause lung disease

thicker capsule to phagocytes less liely ro bind to muerin reduced phagocytosis so more bacyerial growth

explain why phopholiupids can form a bilayer but triglycerides cannot

ohopsholipid both hydrophobic and hydrophillic triglycerides only hydrophobic hydrophilic phosphate grou[ attracts water

role of trna in translation

anticodon binds to comp codon on mrna trna brings spe amino aicd to ribsomes

definition of species richness and index of diveristy

numver of species in a community relo between number species and number ind in each species

in recent years our knowldge of prokarytoic biodiversity in the soil has increased explain why

dna /genome sequencing now used now can alasyse evry proakrytose speies rather than just recording measurable characteristics

potstoe plans with fewer ducrose transport protiens produce fewerr potatoes s and accumulate usgars in their leaves why

carbs made by photo less sucrsose transported into phloem at leaf/source

two reasons why glucose uptake by muscle cells increases significantly during excerise

inc rep to provide more atp for muscle contrcation more glucose being used up sp conc gradient for glucose so glucose enters by facillitated diffusion

ribosomes are used in

translation catalyse joining of amino acids by condensation reactions

two biological molecules coded by a gene

mrna trna

how the shape of atp synthase allows it to have these two functions - catalyse synthesis of atp allow the movement of h+ ions

-1)active site complimentary to adp+pi 2)enzymes substrate forms 3)channel proteins 4)allos facilliatted diffusione

gos are polymers of galactose explain why gos are described as polysaccharide

-galactose is a monosaccharide -polysaccharide carbohydrate golymer -condensation reactions

two differences between the structures of gos and lactose

lactose contains alpha glucose lactose is a disaccharide and gos is polysaccharide

explain why amylase produced in the human digestion system does not digest gos

active site only comp to starch due to tertiary structure

pathway of blood

1)pul vein 2)left atrium 3)left arrivemtricular valves 4)left ventricle 5)left semilunar 6)aorta

blood vessel controlling blood floe to muscles and explain how these blood vessels change blood flow during excursive

arteriole muscle relaxes vasodilation increases blood flow

suggest similarities and differences in the causes of genetic variation within these rice populations

-both pop have independent segregation -both have further mutations -corssing over causes variation in non mutations only

describe the hydrolysis reactions involved in the digestion of triglycerides

breaking of ester bonds addition of water

functions of bile salts

emulsify lipds inc sa for lipase activity form micelles

describe how natural selection may have led to all mammals in a pop producing CEL

mutation new allele those with new allele digits milk more likely to survive and reporudce directionalnseelction inc freuwnecy

similarities and diff in dna and rna

-polymers of nucleotides -nucleotides have pentose base and phopshate cga phophodiester bonds differences deoxyribose v ribose thymanie vs uracil long vs shprt double helix vs single stranded

similarities and differences between the structures of chloroplasts and mitochondria

similarities -double membrane both circular dna both ribsokmes differences -thylakoids stoma vs metric pigment v no pigrment starch grainsvs no

lipid testing

Add ethanol/alcohol then add water and shake/mix White/milky (emulsion)

suggest and explaian how a reduced tidal volume affects the exchange of co2 between blood and alveoli

shallow conc gradient less co2 moves out of lungs slower movement of co2 out of blood

term used to decribe this method of naming organisms

binomial

one other way of generic variation within a soecies isincreased

ranom fusion of gametes new allele combo

suggest one explanation for the faster rate ofnplasmid rep in cells growing in a culture with a high amino productioj

-used in protrin synthesis -so more enxymes for plasmid rep

the enxyme encoded by the adf allele cataslyses the breakdown of alc faster than the enzyme encoded by the adf allele suggest why

diff primary strucutre diff tertiary strucutee enzye sub comp more lielly to form

describe how atp moelculebis formed from its coponent moleule

-adp and pi -condensation atp synthase

exp,ain five properties that make water important for orgamism

1. A metabolite in condensation/hydrolysis/ photosynthesis/respiration; 2. A solvent so (metabolic) reactions can occur 3. High (specific) heat capacity so buffers changes in temperature; 4. Large latent heat of vaporisation so provides a cooling effect (through evaporation); 5. Cohesion (between water molecules) so supports columns of water (in plants); 6. Cohesion (between water molecules) so produces surface tension supporting (small) organisms;

decribe the process of semi conservative replication of dna

1. DNA helicase unwinds DNA/double helix 2. Both strands act as templates; 3. (Free DNA) nucleotides line up in complementary pairs/A-T and G-C; 4. DNA polymerase joins nucleotides (of new strand); 5. Forming phosphodiester bonds; 6. Each new DNA molecule consists of one old/original/template strand and one new strand;

outline a method a student could use to find the rate pf waterless per mm2 of surface area

1)method for measuring area eg.draw around leaf on a graph paper and count squares 2)divide rate of water losss by total surface area of leaves

The rate of water movement through a shoot in a potometer may not be the same as the rate of water movement through the shoot of a whole plant. Suggest one reason why

plants have roots

suggest two reasons why water molecules and carbon dioxide molecules can both move through PIP1

they are both small and have smilier shapes

loading sucrose sequwence

1)h+ ions actively transported out of companion cells 2)diffuse back in coupled with scores via co transport protein 3)sucrose diffuses thprigh plasmodesmata into sieve tube element 40THIS LOWER SWATER POT IN SIEVE TUBES 5)water enters from yhr xylem increasing hydrostatic pressure