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AS Biology > MISTAKES FROM PAPER 2 > Flashcards

MISTAKES FROM PAPER 2 Flashcards

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1
Q

Explain what is meant by a closed double circulation

A
  • blood is contained in blood vessels, heart, arteries, arterioles, veins
  • There is systemic (oxygenated blood) and pulmonary circulation (deoxygenated blood)
  • Blood passes through the heart twice
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2
Q

Explain why arteries have thicker walls than veins

A
  • Arteries have more layers of muscle: elastic tissue, fibrous tissue, smooth muscle that maintains blood pressure
  • Arteries need to withstand high pressure blood and prevent bursting
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3
Q

Short term effects of carbon monoxide on the cardiovascular system

A
  • Haemoglobin has a higher affinity for carbon monoxide than oxygen which forms carboxyhaemoglobin
  • This means that less oxygen is transported in the blood and percentage saturation of haemoglobin with oxygen is reduced
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4
Q

Short term effects of nicotine on the cardiovascular system

A
  • increases blood pressure
  • increases heart rate
  • constricts arteries
  • makes platelets sticky so increases the chance of blood clotting
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5
Q

Function of permanent sap vacuole

A
  • stores cell sap, water, ions, minerals

- gives turgidity to the cell

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6
Q

Describe the role of DNA in the production of polypeptides

A
  • A length of DNA codes for a gene

- DNA is used for protein transcription

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7
Q

Why do competitive inhibitors increase the Km of enzymes?

A
  • The affinity of the enzyme to substrate becomes lower

- The enzyme needs a higher concentration of substrate to saturate active sites to reach Vmax

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8
Q

Outline how mutations can cause healthy cells to become tumour cells

A
  • There would be a mutation in the gene causing cell division
  • Mutation of the tumour supressing gene
  • This leads to a disruption of the cell cycle leading to shortened interphase
  • This leads to uncontrolled cell division and it divides indefinitely
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9
Q

Describe the process of DNA replication

A
  • DNA unwinds by DNA helicase
  • Hydrogen bonds are broken between strands, catalysed by DNA polymerase
  • Both DNA strands act as templates
  • Free nucleotides from the nucleus attach to their complementary nucleotides on both DNA strands sequentially
  • This occurs along the whole DNA strand
  • This DNA replication is semi-conservative
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10
Q

Name the structure that synthesises rRNA and combines it with proteins

A

Nucleolus

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11
Q

Explain how the structure of the variable region of an antibody molecule is related to its function

A
  • The variable region is the antigen-binding region which is complementary to the antigens
  • The variable region is specific to an antigen
  • The R groups and side chains (tertiary structure) give the antibody its specific shape
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12
Q

Outline how monoclonal antibodies are produced

A
  • Antigens are injected into a mouse or other small organism
  • Immune response is stimulated and plasma cells are produced
  • Plasma cells are taken from the mouse’s spleen
  • Plasma cells are fused with myeloma cells to form hybridoma cells
  • The hybridoma cells which can also secrete antibodies, clone and increase in numbers
  • There is a screening to find the hybridoma cell that produces the desired antibody
  • What follows is large scale production - fermenter
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13
Q

Suggest the advantages of using monoclonal antibodies in diagnosis of disease

A
  • Monoclonal antibodies used all have the same specificity
  • Detects only 1 antigen
  • Diagnosis is fast
  • Can distinguish between different pathogens and strains
  • Can be fluorescently labelled to see where these antibodies go - useful in locating cancer cells
  • Can detect location of tissues expressing antigen like cancer cells or blood clots
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14
Q

Describe the function of telomeres

A
  • Prevent the loss of genetic material (genes) from chromosomes
  • Permits continued replication
  • Prevents shortening of chromosomes
  • Length of telomere determines lifespan of cells
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15
Q

Describe the function of ribosomes in protein synthesis

A
  • Ribosomes are the site of DNA translation of polypeptides
  • Ribosomes are a binding site for mRNA
  • They are a binding site for 2 tRNA molecules
  • They hold 2 amino acids close together to form peptide bonds
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16
Q

Explain why it is recommended that antibiotics should not be given to people with mild cases of cholera or to protect people from cholera

A
  • Bacteria resistance due to selection pressures from antibiotics
  • There could be horizontal transmission of resistance
  • Oral Rehydration Therapy is already effective
  • Antibiotics kill gut bacteria
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17
Q

Suggest why an enzyme free in solution (pH 7) has a different optimum pH compared to an immobolised enzyme (pH 4)

A
  • Immobilised support material affects enzyme action
  • Enzymes free in solution has greater exposure to hydrogen ions
  • Immobilised enzymes have a slightly altered active site
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18
Q

Suggest an advantage of immobilising enzymes for commercial use

A
  • Less time-consuming
  • Can be re-used
  • Easily recovered
  • More productive
  • Longer shelf-life of enzyme
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19
Q

Outline the role of the mosquito in the transmission of malaria

A
  • The mosquito is a vector of the disease
  • Mosquito takes blood meals
  • Infective cells enter with saliva and anticoagulent of mosquito into blood
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20
Q

Describe what happens in the stage cytokineses of cell division

A
  • A cell plate is formed across equator of the cell
  • Organelles are shared out
  • The cytoplasm is divided (into two)
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21
Q

State what is meant by a sink in a plant

A

An area of plant which receives assimilates / sucrose

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22
Q

Explain the mechanism by which water is transported in the xylem of the leafy twig

A
  • There is cohesion tension of water molecules in the xylem due to the upwards transpiration pull which causes tension on the xylem vessels
  • This produces a continuous column of water
  • Water molecules are held together by hydrogen bonds in the form of cohesion.
  • Water molecules have hydrogen bonds with the xylem wall in the form of adhesion, as the water molecules ‘stick’ to the cellulose because it is hydrophilic.
23
Q

Describe and explain how carbon dioxide and hydrogen ions play a role in the unloading of oxygen from haemoglobin

A
  • Carbon dioxide diffuses into the red blood cells from respiring tissue
  • Carbon dioxide reacts with water to form carbonic acid, catalysed by carbonic anhydrase
  • Carbonic acid dissociates into a hydrogen ion and hydrogen carbonate
  • Therefore, when there is an increase in carbon dioxide, there is an increase in hydrogen ions and so an increase in acidity
  • Haemoglobin has a higher affinity for hydrogen ions (higher acidity) than oxygen and so releases oxygen more readily.
  • Haemoglobinic Acid is formed when hydrogen ions combine with haemoglobin and when this happens, haemoglobin releases oxygen
  • At higher partial pressures of carbon dioxide, oxygen is more readily released due to the Bohr Effect
24
Q

Explain how water was lost from the leaves of a leafy twig.

A
  • Water evaporates from the moist spongy mesophyll cells cell walls into air spaces in a leaf until the air within the leaf is fully saturated
  • Then the water vapour diffuses through the stomata to air down the water potential gradient
25
Q

Define Transpiration

A

Transpiration is the loss of water through the stomata of a leaf

26
Q

State and explain three ways in which the structure of xylem vessels is adapted to transport water.

A
  • Xylem is a hollow tube with no cytoplasm so there is faster flow of water (NOT DEAD CELLS)
  • Xylem has a lack of end walls (NOT NONE)
  • Cellulose cell wall lining allows adhesion of water
  • Thick cellulose cell wall prevents collapse of xylem
  • Xylem cell wall is impregnated with lignin for waterproofing and preventing water loss, and also supports the xylem
27
Q

Why is mitosis important?

A
  • Replacement of dead or old cells
  • Tissue repairment
  • Asexual reproduction where genetically identical cells are produced
28
Q

Function of Centrioles

A

Organise microtubules to form spindle fibres during mitosis

29
Q

Describe the appearance of the lining of the bronchus in a long-term smoker

A
  • Destroyed Cilia
  • Shorter Cilia
  • Enlarged goblet cells
  • Accumulated mucus
  • Scar tissues
  • Inflammation of lining (lining of phagocytes)
  • Tar deposits on the lining
30
Q

Measles is caused by what pathogen?

A

A species of Morbillivirus

31
Q

Describe the signs and symptoms that enable diagnosis of COPD

A
  • shortness of breath
  • persistent coughing
  • chest tightness
  • wheezing
  • weight loss
  • fatigue
32
Q

Explain one feature that enables the surrounding body cells to receive adequate supply supply of oxygen from the blood supplied by the capillary

A
  • red blood cells close to body cells
  • endothelium/ capillary wall, one cell thick
  • short distance
  • diameter / size, red blood cell and capillary (lumen) similar
33
Q

Describe the damage caused of tuberculosis on the trachea and how this will affect the functioning of the epithelial tissue of the trachea

A
  • Cilia damaged, so this leads to presence of scar tissue
  • Affects coordinated movement of cilia
  • Mucus accumulates
  • Bacteria trapped in the mucus (good growth medium for pathogens)
34
Q

Name and describe the cell structure in which the synthesis of triglycerides and other lipids
takes place

A

smooth endoplasmic reticulum

  • membranous / membranes
  • tubular
  • fluid filled channels
  • no ribosomes
35
Q

State the term used to describe an enzyme that functions within the cell.

A

intracellular

36
Q

Explain, with reference to the structure of xylem vessel elements, why water does not take a
symplastic pathway in the xylem to the leaves.

A
  • Xylem has no cytoplasm / symplast pathway is cytoplasmic (and vacuolar)
  • xylem (vessel elements) are dead cells / symplastic through living cells
37
Q

State precisely where the sinoatrial node is located

A

wall of right atrium

38
Q

Explain the role of the atrioventricular node in the coordination of heart action

A
  • passes the, impulse / wave of excitation, to the Purkyne fibres / down the septum
  • allows a (short) delay
  • so atria contract before ventricles
  • allows ventricles to fill
  • so atria have, emptied / contracted, before ventricular - contraction begins
  • so atria and ventricles don’t contract at the same time
39
Q

Explain how the structure of triglycerides makes them more suitable for energy storage than carbohydrates

A
  • Long hydrocarbon chain
  • Higher proportion of hydrogen
  • Generates twice as much energy as carbohydrate
  • Compact shape
  • Can be stored in anhydrous form
40
Q

State 3 functions of the water stored in the vacuoles of plant cells

A
  • (raw material) for photosynthesis
  • maintains turgidity
  • pushes chloroplasts to edge of cell
  • used in hydrolysis reactions
  • solvent for, ions / pigment
41
Q

Describe the advantages for organisms in storing polysaccharides, such as glycogen, rather than storing glucose

A
  • compact so large quantity can be stored ;
  • insoluble so no osmotic effect ;
  • glucose would lower water potential ;
  • (so) water would enter and cell volume would increase ;
  • (so) plant cells would need thicker cell walls / animal cells might burst ;
  • glucose reactive molecule ;
42
Q

State and explain the similarities and differences between the graph of blood pressure of the right ventricle and the graph of blood pressure for the left ventricle during the same cardiac cycle

A

Similarities
- increases and decreases in pressure at same time - starts at same point and ends at same point
- events in cardiac cycle occur are coordinated - impulses pass up both ventricles at the same
time, ventricles both contract at same time

Differences

  • left venntricle reaches higher, blood pressure / peak, (than RV)
  • systolic pressure higher in LV (than RV)
  • left ventricle pumps blood to (whole) body
  • walls of left ventricle, thicker so more force exerted by LV
43
Q

State what is meant by a STOP codon

A

Codon that:

  • terminates translation and protein synthesis
  • does not specify any amino acid
  • has no complementary, tRNA / anticodon
  • causes the release of the (completed) polypeptide chain
44
Q

Describe how R groups can contribute to the globular structure of a protein

A
  • R group interactions and, folding / coiling, of polypeptide chain (to give globular structure)
  • (charged / polar R groups) forming, ionic / hydrogen, bonds
  • (amino acids with), hydrophobic / non-polar, R groups, on the inside
  • (amino acids with), hydrophilic / charged / polar, groups on outside
  • ionic R groups can interact with water, hydrogen bonds form with water
  • promotes stability / helps to maintain globular structure
45
Q

Describe two differences between the vessels that transport phloem sap in flowerinig plants and the vessels that transport blood in mammals

A
  • only sieve tubes / one type versus arteries, veins and capillaries
  • sieve tubes are composed of cells v blood vessels composed of tissues
  • sieve tubes, have cytoplasm or blood vessels are, hollow
  • sieve tubes have sieve plates
  • sieve tubes have companion cells (to fully function)
  • veins have valves
  • idea of transport open (phloem plasmosdesmata) v closed (blood vessels)
46
Q

Explain why the wall of the left ventricle in the heart is thicker than the wall of the right ventricle

A
  • to generate a high(er) blood pressure (during systole)
  • to overcome high(er) resistance (in systemic circuit than in pulmonary circuit)
  • to transport blood a greater distance/ greater distance in systemic circuit
  • ref. to right ventricle generating low pressure to avoid damaging (capillaries in the) lungs
47
Q

Describe the role of macrophages in lungs

A
  • prevention of infections (of, gas exchange system / named part)
  • prevent (named) pathogen entering, rest of body / blood
  • idea that macrophages patrol /move around /AW, alveoli /lungs
  • phagocytosis / endocytosis
  • engulf /remove / destroy / kill/ digest , pathogens
  • phagocytes are antigen presenting cells
48
Q

Suggest why neutrophils secrete elastase

A
  • breakdown of elastin and elastic tissue
  • makes a pathway, to alveolus /through alveolar wall
  • to reach, pathogens / site of infection, in alveoli /AW/ implied
49
Q

Explain why malaria is very difficult to control

A
  • No effective vaccine
  • Plasmodium is eukaryotic / antigens differ in different life stages
  • Drug resistance in Plasmodium - chloroquine
  • insecticide resistance in Anopheles
  • problems with, funding research
  • lack of knowledge
50
Q

Explain how knowledge of transmission of V.Cholerae is used to control the spread of the disease in the human population

A
  • Pathogen is most vulnerable when in transfer between hosts
  • Do not use human faeces as fertiliser
  • Drink purified / chlorinated water
  • Bottled water
  • Antibiotic treatment
51
Q

When Benedict’s solution is added to a sucrose solution and put into a boiling bath, no change in colour is observed. Why?

A
  • sucrose is a non-reducing sugar

- no (hydrochloric) acid used (to break down sucrose to reducing sugars)

52
Q

Describe and explain how sucrose is transported from the phloem in the leaves or sugar beet to storage tissues in the root

A
  • diffusion, into phloem sieve tube (element), from companion cell (through plasmodesmata) ;
  • presence of sucrose (in phloem sieve tube element), lowers water potentia
  • water enters (sieve tubes), by osmosis / down water potential gradient (into sieve tubes)
  • increase in, hydrostatic, pressure
  • low hydrostatic pressure in, storage tissues / root / sink, by removal of sucrose
  • movement of, (phloem) sap / sucrose (in solution), down hydrostatic pressure gradient / from high to low hydrostatic pressure
  • Mass flow
53
Q

Explain why Myasthenia Gravis is known as an autoimmune disease

A
  • failure to distinguish between self and non-self
  • specific B-,lymphocytes / cells, are not destroyed
  • antibodies are produced against receptors on nerve cells
  • antibodies bind to receptors
  • impulses are not transmitted across synapse
  • causes muscle weakness
54
Q

Describe the role of Golgi Body in secretory cells

A
  • modification / process / described, of, proteins / polypeptides
  • examples of modification:
    folding of polypeptides / protein folding
    assembly of polypeptides to form quaternary structure
  • packaging into vesicles
  • formation of (primary) lysosomes

AS Biology (9 decks)

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