A-level biology > 6 markers > Flashcards

6 markers Flashcards

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1
Q

structure and function of glycogen?

A
  • helix/coiled/branched so compact
  • polymer of glucose so easily hydrolysed
  • branched so more ends for faster hydrolysis
  • glucose (polymer) so provides respiratory substrate for energy release
  • insoluble so does not effect the water potential/osmosis
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2
Q

structure and function of starch?
4

A
  • helical/ spiral shape so compact
  • larger molecule
  • insoluble so osmotically inactive
  • branched so glucose is easily released for respiration
  • large molecule so cannot leave the cell
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3
Q

structure and function of cellulose?

A
  • long, unbranched chains of beta glucose
  • joined by hydrogen bonding
  • to form micro/macro fibrils
  • provides rigidity and strength
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4
Q

structure of proteins?

A
  • amino acids joined by peptide bonds
  • by condensation reaction
  • secondary structure is formed by hydrogen bonding
  • tertiary structure formed by R group interactions including hydrophobic interactions, hydrogen bonds, ionic bonds, and disulphide bridges
  • quaternary structure when multiple polypeptide chains are present
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5
Q

structure of DNA?

A
  • polymer of nucleotides
  • nucleotide consists of deoxyribose , phosphate and an organic/nitrogenous base
  • phosphodiester bonds between nucleotides
  • DNA double helix held by H bonds
  • hydrogen bonds between thymine-adenine and cytosine-guanine
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6
Q

describe semi-conservative replication?

A
  • DNA helicase unwinds double helix/breaks hydrogen bonds
  • both strands act as templates
  • free DNA nucleotides line up in complementary pairs (T-A G-C)
  • DNA polymerase joins nucleotides of new strand
  • forming phosphodiester bonds
  • each new DNA molecule consists of one old/original/template and one new strand
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7
Q

why are enzymes specific?

A
  • tertiary structure/ 3D shape of enzyme
  • active site complementary to substrate
  • induced fit model
  • enzyme is a catalyst/ lowers activation energy
  • by enzyme substrate complex
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8
Q

describe competitive and non-competitive enzyme inhibition

A
  • inhibitors reduce binding of enzyme to substrate/ prevent formation of ES complex

(competitive inhibition)
- inhibitor similar shape to substrate
- binds to active site of enzyme/complementary to active site

(non competitive inhibitor)
- inhibitor binds to allosteric site of enzyme
- prevents formation of active site/ changes active site shape
- cannot be overcome by adding more substrate

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9
Q

describe the role of ions

A

iron:
- haemoglobin binds/associates with oxygen

sodium ions:
- co-transport of glucose/amino acids
- sodium moved out by active transport
- creating a sodium concentration gradient
- affects osmosis/water potential

phosphate ions:
- affects osmosis/water potential
- joins nucleotides via phosphodiester bonds in DNA backbone
- used in/to produce ATP
-phosphorylates other compounds making them more reactive
- hydrophilic/water soluble part of the phospholipid bilayer

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10
Q

structure of ATP and how it is formed/broken down?

A
  • ribose, adenine and 3 phosphates
  • ATP to ADP + Pi by ATP hydrolase
  • in hydrolysis reaction
  • ADP + Pi to ATP by ATP synthase
  • in condensation reaction
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11
Q

why is ATP useful?

A
  • releases energy in small/manageable amounts
  • broken down in one step/ single bond broken so immediate energy is available
  • phosphorylates substances to make them more reactive/ lower activation energy
  • reformed/made again (regeneration)
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12
Q

properties that make water important for organisms

A
  • metabolite in condensation/hydrolysis/photosynthesis/respiration
  • a solvent so metabolic reactions can occur / allowing transport of substances
  • high specific heat capacity so buffers changes in temperature
  • large latent heat of vaporisation so provides a cooling effect
  • cohesion so supports columns of water in plants
  • cohesion between water molecules so produces surface tension supporting small organisms
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13
Q

describe how organelles are involved in making enzymes for secretion

A
  • DNA in nucleus codes for enzyme/protein
  • ribosomes/rough endoplasmic reticulum produce enzyme/protein
  • mitochondria produce ATP
  • golgi apparatus modifies, processes and packages enzymes/proteins
  • vesicles fuse with cell surface membrane (exocytosis)
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14
Q

how can substances move across membranes?

don’t include co-transport

A

osmosis:
- movement of water
- from high water potential to a low water potential/ down water potential gradient
- through aquaporins/ water channels
- passive process

simple diffusion:
- movement of small/non polar molecules only
- crosses the phospholipid bilayer
- down concentration gradient
- passive process

facilitated diffusion:
- movement of large/charged substances
- channel/carrier protein
- down the concentration gradient
- passive process

active transport:
- carrier proteins
- against concentration gradient
- using ATP/ energy from respiration

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15
Q

describe process of co-transport?

A
  • Na+ ions leave the epithelial cell and enter the blood
  • by active transport via carrier protein using ATP
  • so Na+ concentration is lower than in the lumen
  • Na+ ions diffuse in from high to low area of concentration through a co-transport protein
  • glucose is absorbed with Na+ ions against their concentration gradient
  • glucose then moves into the blood via facilitated diffusion
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16
Q

describe how membrane structure affect transport?

A
  • phospholipid bilayer allows movement/diffusion of non-polar/lipid soluble substances
  • phospholipid bilayer prevents movement/diffusion of polar/lipid insoluble substances
  • carrier protein allow active transport
  • channel/carrier proteins allow facilitated diffusion/co-transport
  • shape or charge of channel and carrier proteins determines which substances move
  • number of channels/carriers determine how much movement
  • cholesterol affects fluidity/rigidity/permeability of membrane
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17
Q

how are cells adapted for co-transport?

A
  • microvilli provide a large/increased surface area
  • many mitochondria produce ATP/ release or provide energy
  • carrier proteins for active transport
  • channel/carrier proteins for facilitated diffusion
  • co-transport of sodium ions and glucose by carrier proteins
  • membrane bound enzymes digest disaccharides/ produce glucose
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18
Q

describe viral replication

A
  • viral attachment protein attaches to cell receptors
  • viral nucleic acid enters into cell
  • viral nucleic acid is replicated in the cell/ reverse transcriptase produces DNA from RNA
  • viral protein is produced
  • viral components assembled and released from cell
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19
Q

describe the appearance and behaviour of CHROMOSOMES in mitosis?

A

Prophase:
- chromosomes coil/condense and become visible
- chromosomes appear as two sister chromatids joined at the centromere

Metaphase:
- chromosomes line up on the equator
- chromosomes attached to spindle fibres
- by their centromere

Anaphase:
- the centromere splits/divides
- sister chromatids/chromosomes are pulled to opposite poles

Telophase:
- chromatids/ chromosomes uncoil

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20
Q

how do phagocytes destroy bacteria?

A
  • phagocyte attracted to bacteria by chemicals/recognise antigens on bacteria as foreign
  • engulf/ingest bacteria
  • bacteria in vacuole/vesicle
  • lysosome fuses with/empties enzymes into vacuole
  • bacteria digested/hydrolysed
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21
Q

describe how a vaccine works?

A
  • vaccine contains antigen from pathogen
  • macrophage presents antigen on its cell surface
  • T cell with complementary receptor protein binds to antigen
  • T cell stimulates B cell
  • with complementary antibody on its surface
  • B cell secretes large amount of antibody
  • B cell divides to form clones all secreting/producing same antibody
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22
Q

describe the difference between active and passive immunity?

A
  • active involves memory cells passive does not
  • active involves production of antibody by plasma and memory cells
  • passive involves antibody introduced into body from outside
  • active is long term because antibody produced is in response to antigen
  • passive is short term because antibody given is broken down
  • active can take time to develop and work whilst passive is fast acting
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23
Q

describe how B-lymphocytes would respond to vaccination against a virus

A
  • B cell (antibody) binds to viral specific receptor/antigen
  • B cell clones/divides by mitosis
  • plasma cells release/produce monoclonal antibodies against the virus
  • B/plasma cell release/produce monoclonal antibodies
  • B/plasma cells produce/develop memory cells
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24
Q

how i a capillary adapted for exchange of a subtance

A
  • permeable capillary wall/membrane
  • single cell thick/thin walls reduce diffusion distance
  • flattened endothelial cells reduce diffusion distance
  • fenestrations allow large molecule through
  • small diameter gives a short diffusion distance
  • narrow lumen reduces flow rate giving more time for diffusion
  • red blood cells in contact with wall/pass singly allowing more time for diffusion
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25
describe the role of haemoglobin
- loads/associatrs oxygen in the lungs - at high partial pressure of oxygen - binding of an oxygen molecule makes binding of another molecule easier - unloads/dissociates oxygen in respiring cells - at low partial pressure of oxygen - or high partial pressure of CO2
26
describe how tissue fluid is formed?
- hydrostatic pressure of blood is high at arterial end - fluid/water/soluble pass out - proteins and large molecules remain - lowering the water potential - water moves back into venous end of the capillary by osmosis - lymph system collects any excess tissue fluid which returns to blood/ circulatory system
27
describe the adaptations of gills for exchange? 4
- filaments/lamella = large surface area to maintain a gradient - large number of capillaries = to remove oxygen/ maintain a gradient - thin epithelium = short diffusion pathway - pressure changes = to bring in more water/ maintain gradient - counter current flow = maintains concentration gradient along the whole length of the lamella as blood and water travel in opposite directions ensure equilibrium is never reached
28
describe how fish make water flow across gills
- mouth opens and operculum/opercular valve shuts, floor of mouth is lowered - water enters due to decreased pressure/increased volume - mouth closes, operculum/opercular valve opens - floor raised results in increased pressure/decreased volume - high/ increased pressure forces/pushes water over gills
29
describe insect gas exchange ?
- spiracles allow diffusion of oxygen - tracheoles are highly branched so large surface area for exchange - tracheole walls are thin so short diffusion - tracheole walls are permeable to oxygen/air - chitin exoskeleton is impermeable so reduce water loss - spiracles can close so less water loss/ have valves - hairs around spiracles reduce water loss
30
describe the adaptations of mammalian breathing systems?
- alveoli provide a large surface area - walls of alveoli are thin to provide a short diffusion pathway - walls of capillary are thin and close to the alveoli to shorten diffusion distance - walls of capillaries/alveoli are have flattened cells - cell membrane is permeable to gases - many blood capillaries maintain concentration gradient and increase surface area - intercostal muscle maintain a diffusion/ concentration gradient - wide trachea/ branching bronchi for efficient flow of air - cartilage rings keep airways open
31
describe cohesion tension theory of water transport in xylem
- water lost from leaf due to transpiration - lowers water potential of mesophyll/leaf cells - water pulled up xylem creating tension - water molecules cohere due to hydrogen bonds - continues water column - adhesion of water molecules to walls of xylem
32
describe transcription
- DNA strands separate by H bonds breaking between complementary DNA bases - By DNA helicase - one of the strands is used as a template and transcribed - Nucleotides align by complementary base pairing A-U T-A C-G G-C - RNA nucleotides joined by RNA polymerase - by phosphodiester bonds between adjacent nucleotides - pre-mRNA is formed - splicing removes introns
33
describe translation
- mRNA attaches to ribosomes - tRNA anticodons bind to complementary mRNA codon - tRNA brings specific amino acid - amino acids join by peptide bonds - amino acids join together with the use of ATP - tRNA released after amino acid joined to polypeptide - ribosomes move along the mRNA to form the polypeptide
34
ways in which genetic variation is increased within a species other than mutation
- independent segregation of homologous chromosomes - crossing over between homologous chromosomes within bivalents - random fertilisation of gametes - produces new combinations of alleles
35
describe and explain the processes that increase genetic variation in meiosis
- homologous chromosomes pair up - independent segregation - maternal and paternal chromosomes are re-shuffled in any combination - crossing over leads to exchange of parts of non-sister chromatids/alleles between homologous pairs - both create new combinations of alleles
36
describe what a mutation is and what effects it can have
- gene mutation is defined as: change in the base/nucleotide sequence of DNA - may have no effect because: genetic code is degenerate so amino acids may not change OR mutation occurs within introns OR new allele is recessive so does not influence phenotype - may result in change because: results in changes in properties of the protein
37
describe what happens to chromosomes in meiosis
- chromosomes condense - chromosomes associate with homologous pairs and bivalents are formed - crossing over/ chiasma are formed - join to spindle fiberes - at the equator - join via centromere - homologous chromosomes move to opposite poles - pairs of chromatids are separated in the second division
38
how does meiosis produce variation
- crossing over - independent segregation of homologous chromosomes in meiosis - independent/random assortment
39
describe the light independent reaction
- carbon dioxide reacts with ribulose bisphosphate RuBP - produces two glycerate-3-phosphate using enzyme Rubisco - glycerate 3 phosphate is reduced to triose phosphate - using reduced NADPH - using energy form ATP - triose phosphate is converted to 1/6 hexose sugar and then RuBP is regenerated
40
describe the light dependent reaction
- light energy excites electrons/electrons removed from chlorophyll - electrons move along carrier proteins/ electron transfer chain releasing energy - electrons reduce carriers - energy is released - energy used to join ADP + Pi --> ATP - photolysis of water produces protons, electrons and oxygen - NADP is reduced by electrons
41
how is ATP made in mitochondria
- substrate level phosphorylation - Krebs cycle and link reaction produces NADH and FADH - electrons released from FADH and NADH - electrons pass along carriers/ electron transport chain through redox reactions - energy released - H+ ions move into the intermembrane space - ATP synthase causes ADP + Pi ---> ATP
42
describe how microorganisms produce nitrates from waste/remains
- proteins or amino acids are converted into ammonium compounds - by saprobionts - ammonium is converted into nitrites - nitrites into nitrates - by nitrifying bacteria
43
how do bacteria make the nitrogen in dead leaves available for growing plants
- protein/amino acids broken down into ammonium compounds - by saprobionts - undergo extracellular digestion - ammonium converted into nitrites - nitrites into nitrates - via oxidation - by nitrifying bacteria - nitrogen to ammonia - by nitrogen fixing bacteria in root nodules
44
how does nitrate cause the death of fish in water
- growth of algae/surface plants/algal bloom blocks light - reduced photosynthesis causing submerged plants to die - saprobiotic organisms - aerobically respire - less oxygen for fish to respire - causing aerobic organisms to die
45
how does farming increase crop yield
- fertilizers added to soil - nitrate/nitrogen for proteins and phosphate for ATP/DNA - selective breeding/ genetic modification of crops - ploughing or aeration allows for nitrification - benefit of crop rotation in terms of soil nutrients
46
describe how exercise causes an increase in heart rate
- chemoreceptors detect a decrease in pH from rise in CO2 - more impulses are sent to cardiac centre centre/medulla - more impulses sent to the SAN - by sympathetic nervous system
47
describe the control of heart rate
- SAN releases wave of excitation - both atria contract in atrial systole - AVN relays/ passes wave of depolarisation after a short delay - via purkyne tissues and bundle of his - so ventricles contract at the same time from bottom upwards
48
sequence the events in transmission across a cholinergic synapse
- depolarisation of presynaptic membrane - calcium ion channels open and calcium ions enter - synaptic vesicles move to/fuse with the presynaptic membrane and release acetylcholine/ neurotransmitter diffuses across the synaptic cleft - acetylcholine attaches to receptors on the postsynaptic membrane - sodium ions enter leading to depolarising
49
describe the role of calcium and ATP
- ca+ ions diffuse into myofibrils from the sarcoplasmic reticulum - ca+ ions cause movement of tropomyosin - movement causes exposure of the binding sites on the actin - myosin heads attach to binding sites on actin - hydrolysis of ATP on the myosin heads cause them to bend - bending pulling actin molecules - attachment of new ATP molecule to each myosin head causes myosin heads to detach from actin sites - hydrolysis of the ATP releases energy which cocks the myosin head back to its original position
50
how does ultrafiltration produce glomerular filtrate
- blood pressure/hydrostatic pressure - small molecules - pass through basement membrane - protein too large to go through
51
how does glucose end up in urine of diabetics
- high concentration of glucose in the blood - high concentration in tubule/in filtrate - reabsorbed by facilitated diffusion - requires proteins/carriers - these are working at maximum rate/are all saturated - not all glucose is reabsorbed/some is lost in urine
52
how does the loop of Henle maintain ion gradient
- epithelial cells of tubule cells carry out active transport - transport chloride ions out of filtrate - against the concentration gradient - into surrounding tissue - creates/maintains water potential gradient for water reabsorption - counter current multiplier
53
role of the loop of Henle in water absorption
- the ascending limb allows sodium ions to be actively removed - ascending limb is impermeable to water - in the descending limb sodium ions diffuse in - descending limb water moves out/ membrane is permeable to water - low water potential/high concentration of ions in the medulla/tissue fluid - the longer the loop of Henle the lower the water potential in the medulla - water leaves collecting duct - by osmosis down the water potential gradient
54
describe the role of ADH in producing concentrated urine
- when water potential of the blood is too low - detected by receptors in the hypothalamus - pituitary secretes more ADH - ADH increases the permeability/recruitment of aquaporins in the DCT - more water is reabsorbed/leaves the nephron and moves into the blood - by osmosis down the water potential gradient
55
how does ADH control the volume of urine produced
- if water potential of blood falls - detected by receptors in the hypothalamus - leads to ADH released from the pituitary gland - ADH makes cells of collecting ducts more permeable to water - water leaves filtrate by osmosis - smaller volume of urine is produced
56
describe evolution of species due to separation (e.g. different islands)
- geographical isolation/separation - allopatric speciation due to isolation/separation - different selection pressures - variation due to mutation - reproductive isolation/separation OR - separate gene pools - change in allele frequency in each population/ different allele frequency in each population - different species can no longer interbreed to produce fertile offspring
57
describe speciation (general question)
- reproductive separation/isolation - no gene flow different selection pressures/different abiotic factors - variation due to mutations in different populations - different advantages allele is passed on/selected for - change in frequency of alleles - eventually different species cannot interbreed to produce fertile offspring
58
describe succession
- colonisation by pioneer species - death/decomposition - change in environment/examples of change caused by organisms present (e.g. formation of soil/humus) - enables other species to colonise/survive - change in biodiversity - increase the number of species/diversity - stability increase/ less hostile environment created - climax community is reached
59
what limits the size of a climax community
- phosphorus or nitrogen availability - number of producers providing energy/light intensity affecting the rate of photosynthesis - disease killing (weaker) members of species - space for niches - competition intra or interspecific for food/named resources
60
describe PCR
- DNA heated to 90-95c - H-bonds between complementry bases is separated - cooled to 55c - primers added and bind through annealing - nucleotides attach by complementary base pairing - temperature to 72c - DNA polymerase joins nucleotides together - phosphodiester bonds formed - cycle repeated
61
how a gene can be cut from one organisms and inserted into other
- cut desired gene from DNA - using restriction endonucleases at the recognition site to create sticky ends - using plasmid open with same restriction endonuclease and join plasmid and gene with DNA ligase for multicellular organisims: - introduce vector via micropipette for bacteria: - return plasmid to bacterial cells - use cold shock
62
explain how modified plasmids are made by genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected
- isolate wanted gene/DNA from another organism - using restriction endonucleases to produce sticky ends - use ligase to join wanted gene to plasmid - also include marker gene such as antibiotic resistance or fluorescenceF - add plasmid to bacteria to grow colonies then replica plate onto medium where the marker gene is expressed - colonies not killed have antibiotic resistance gene and probably the wanted gene
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