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A level- Biology > Hard questions > Flashcards

Hard questions Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Describe why facilitated diffusion requires no metabolic energy

A
  1. Particles have their own kinetic energy

2. Move down the concentration gradient

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2
Q

Explain why glucose cannot pass through a cell membrane by simple diffusion

A
  1. Phospholipids act as a barrier

2. The molecules are too large

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3
Q

Suggest how the leaf of pondweed is supported

A
  1. Air spaces give buoyancy

2. Supported by surrounding water

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4
Q

Suggest why antibodies specific to nuclear proteins are not normally made

A
  1. Nuclear proteins normally hidden in the nucleus
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5
Q

Suggest how water is being lost from the cut stem when leaves have been treated with petroleum jelly in a potometer experiment

A
  1. Evaporation form upper leaf surfaces
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6
Q

Suggest two sources of error in a potometer experiment

A
  1. Not all lower leaf surfaces covered
  2. leaks in apparatus
  3. Shoot not cut under water
  4. Error in reading position of the meniscus
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7
Q

Explain why bone is described as a tissue and gills are described as organs

A
  1. Tissue has few types of cells and performs one function
  2. Bone has a few types of cells and performs one function
  3. Organs consist of several tissues
  4. Gills contain blood, bones, epithelial and connective tissue
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8
Q

How would the calculated rate differ form the true initial rate of reaction in an enzyme reaction

A
  1. Initial rate is likely to be greater

2. Because higher concentration of substrate at start, so more chance of substrate entering the active site

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9
Q

Give ways to refine an experiment so reproducible results would be obtained

A
  1. Specify volumes of reactants added
  2. Specify volume that should be removed for testing
  3. Stir before taking the sample
  4. Test with iodine- for starch, or other chemicals
  5. Carry them all out at the same temperature
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10
Q

Explain why vaccinations are examples of active immunity

A
  1. Antibodies are produced
  2. Activation of lymphocytes
  3. Memory cells remain
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11
Q

State 3 properties of fibrous proteins that are different to globular proteins

A
  1. Insoluble
  2. Strong
  3. Unreactive
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12
Q

How could haemoglobin be identified in urine

A
  1. Add biurets reagent
  2. Colour change from blue to purple
  3. Compare with control
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13
Q

Outline how the difference in lumen size between arteries and veins is related to their function

A
  1. In arteries small lumen maintains high pressure
  2. In veins large lumen- low resistance needed because of low pressure
  3. Same flow rate is achieved by having a larger volume
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14
Q

Why is movement of molecules from the plasma membrane towards the centre of living cells greater than in an experiment

A
  1. Involvement of vesicles/ cytoskeleton
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15
Q

Stem cells can specialise to form a variety of cell types. What other feature is shown by stem cells but not specialised cells

A

Ability to continue dividing

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16
Q

Why do cells need to be stained

A
  1. Provide contrast

2. Identify components

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17
Q

State why the structure of enzyme molecules allows them to be detected in solution using the biuret test

A
  1. Enzymes are globular proteins

2. Hydrophilic groups on outside of enzyme

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18
Q

Some enzymes work better in the presence of other molecules or ions. Explain how these molecules or ions increase the activity of enzymes

A
  1. Cofactors/ coenzymes
  2. Bind to enzyme temporarily
  3. They change the shape of the active site and change the charges on the active site
  4. They bind to substrate
  5. Increased likelihood of substrate binding to active site
  6. Carry chemicals between enzymes
19
Q

Explain the benefits to agriculture of maintaining plant biodiversity

A
  1. Maintaining genetic variation- useful source of genes
  2. Used for genetic engineering
  3. Used for selective breeding
  4. Variety might be useful in changing climate
  5. Habitat for pollinators
  6. Agents for biological control
  7. Source of new medicine for livestock
20
Q

Suggest 3 reasons why the three-domain classification system is now used in preference to the five-kingdom system

A
  1. 3 domain system fits phylogeny better- reflects evolutionary history better
  2. Number of important differences between bacteria and ekaryotes
  3. Eukaryotes all have a nucleus and 80s ribosomes
  4. Many fundamental differences between archaea and bacteria
  5. They have different cell membrane/ flagella/ enzymes
21
Q

Explain why some foods are stored in a freezer

A
  1. Decay/ food spoilage is slower
  2. Molecules have little kinetic energy
  3. Fewer collisions between substrate and active site
  4. Water availability reduced.
22
Q

What is the name of a limiting level for a population in a particular area

A

Carrying capacity

23
Q

Why might vegetative propagation be less effective against enabling a tree to survive a disease compared to surviving fire or high wind

A
  1. New sprouts are clones so no genetic variation

2. They are as susceptible as to the disease as the parent plant is

24
Q

What can show the development controlled by homeobox genes in a human embryo

A
  1. Head/tail orientation
  2. Position/ development of limbs
  3. Segmentation
  4. Development of eyes
25
Q

What is the benefit of bacteria being able to transmit plasmids from one cell to another

A
  1. Can take up useful genes
  2. Such as antibacterial resistance
  3. Faster/ without waiting for mutation
26
Q

Suggest a way other than extracting a gene from one organism or from cDNA libraries to obtain a gene

A
  1. Chemical synthesis/ polynucleotide synthesising.
27
Q

Suggest two ethical arguments for and against genetic manipulating a plant

A
  1. Relief of particular vitamin deficiency
  2. Expense of seed for growers and consumers
  3. Uncontrolled hybridisation with other species
  4. Unknown long-term health effects on consumers’ health
28
Q

On a sunny day more pondweed is at the surface of the water but on a cloudy day, less pondweed is at the surface of. Explain this

A
  1. Greater light intensity on sunny day
  2. Oxygen produced during photosynthesis
  3. Oxygen trapped within the weed created buoyancy.
29
Q

ATP is produced in two different ways
1. Produced in Krebs cycle
2. Produced using reduced NAD and FAD on the inner mitochondrial membrane
Outline the differences in the two ways by which ATP is produced in respiration

A
  1. By substrate level phosphorylation
    - By removing phosphate from a compound
  2. By chemiosmosis
    - Hydrogen lost from redNAD / redFAD
    - electrons pass down electron transport chain
    - ref to proton gradient / electrochemical gradient
    - ref to ATP synth(et)ase
30
Q

Suggest why it can be deduced that hormones act on the SAN rather than on individual cardiac muscle cells

A
  1. Stimulation of individual muscle cells would result in uncoordinated response
  2. Stimulation of individual muscle cells will not result in a change in heart rate
  3. receptors only present on the SAN
31
Q

Describe how the guard cells surrounding leaf pores are adapted to their roles

A
  1. Unevenly thickened walls
  2. Able to bend and change shape
  3. Transport proteins into plasma membrane
  4. Presence of chloroplasts- energy
32
Q

Describe how the structure of cell walls in xylem vessels would differ from undifferentiated plant cells cell walls

A
  1. Thicker
  2. Lignified
  3. Contains pits
33
Q

Describe how alveoli create a surface for efficient gaseous exchange

A
  1. Wall is one cell thick for shorter diffusion distance
  2. Squamous epithelium provide short diffusion distance
  3. Elastic so recoil which helps with venitlation
  4. Create / maintain, concentration gradient
  5. Large number of alveoli provide larger surface area ;
  6. Small size of alveoli provide larger surface area to volume ratio
  7. Cells secrete surfactant to maintain surface area
34
Q

Describe the effect of high temperature on the structure of yeast cell membrane

A
  1. Phospholipids have more kinetic energy
  2. Increases gaps between phospholipids
  3. Bilayer becomes more fluid
  4. Proteins/glycoproteins denature
35
Q

Define the term parasite

A
  1. Lives in host
  2. Gains nutrition from host
  3. At the expense of the host
36
Q

Outline significance of low value of Simpson’s Index of Diversity

A
  1. Dominated by one/ few species

2. Ecosystem is unstable

37
Q

Define the term phylogeny and explain how phylogeny is related to classification

A
  1. Phylogeny is the evolutionary relationship between organisms
  2. Phylogeny is the basis of classification
  3. Base sequence used to classify
  4. Species / organisms within the same group have shared phylogeny
38
Q

Explain how selective breeding of wheat could be done

A
  1. Cross-breed high-yielding wheat plants
  2. Assess the yield
  3. Cross breed high-yielding offspring
  4. Over several generations
  5. Prevent self-pollination/ unwanted cross-pollination
39
Q

Describe how the structure of antibodies allows them to perform their function

A
  1. 2 light chains and 2 heavy chains / 4 polypeptide
    chains
  2. Variable region allows binding to antigen
  3. Two variable regions allow binding of more than one (of the same) antigen
  4. Variable region on different antibodies allows specificity to different antigens
  5. constant region allows recognition by / attachment to /binding to phagocytes
  6. Hinge (region) allows flexibility
  7. Disulfide bonds hold polypeptides together
40
Q

Describe how antibodies carry out neutralisation and agglutination

A 
Neutralisation
1. Block binding site on pathogen
2. Bind to toxins
3. Prevent entry to host cell
Agglutination
1. Clump together many pathogens
2. Too large to cross membranes
3. Increase likelihood of being consumed by phagocyte
41
Q

After the initial release of insulin from the beta cell, insulin secretion continues even when there is no further glucose intake.
Explain why

A
  1. Continues to be secreted) as long as blood glucose (concentration) remains high than normal
  2. ATP is still present and so K+ channels remain closed
  3. Exocytosis still being triggered by calcium ions
42
Q

Why does aerobic respiration yield fewer molecules of ATP than the theoretical maximum

A
  1. some ATP used to (actively) transport pyruvate
  2. some ATP used to (actively) transport H(+) from (reduced) NAD formed in glycolysis
  3. Some energy in electron transport chain is released as heat
  4. Not all the H+ movement (back across membrane) is used to generate ATP
  5. Not all the, reduced NAD / red NAD / NADH is used to feed into the ETC
43
Q

Why does the dialysis fluid in peritoneal dialysis contain dextrose solution rather than water alone

A
  1. Dialysis is replicating function of kidney and part of kidney’s function is to remove (excess) water from blood
  2. Reduces water potential of dialysis fluid
  3. Water moves from blood (into dialysis fluid) by osmosis
  4. Prevents water moving into the blood from dialysis fluid by osmosis
  5. If it was water alone cells would swell / burst
44
Q

Suggest why patients receiving peritoneal dialysis usually need to have the peritoneal dialysis fluid replaced four times a day, but those receiving haemodialysis only need treatment 4 times a week

A
  1. Peritoneal dialysis can remove less waste than haemodialysis
  2. In haemodialysis dialysis fluid is constantly refreshed but not in peritoneal dialysis
  3. Haemodialysis uses counter-current flow
  4. In peritoneal dialysis the concentration gradient reduces / is lower
  5. In peritoneal dialysis the fluid reaches equilibrium with the blood

A level- Biology (46 decks)

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