biology processes

Question 1

aerobic respiration

Answer 1

GLYCOLYSIS- CYTOPLASM-aerobic+ anaerobic
1.Phosphorylation of glucose -2x adp+pi + 1glucose=hexose biphosphate
Phosphate + glucose=unstable splits into 2 triose phosphate
2. 2 NAD oxidises TP = 2 NADH
2x pi +4adp+ 2 phosphate from TP =4x ATP
Overall -Net 2 ATP produced

Pyruvate is actively transported into mitrochondrial envelope
Link reaction-
Pyruvate- hydrogen reduces NAD and 1 carbon is removed-decarboxylation+dehydrogenation
Acetyl is formed 2 carbon – CoA+acetyl
Krebs cycle-
de na de na a fa na
6 -4c+2c =6c
Oxidative phosphorylation- mitochondrial matrix
Most ATP produced
Reduced coenzyme is releases hydrogen splitting in protons and electrons- which electrons are carried along etc- releasing energy aas they move across inner casuong hydrogen to move over mitochondrial membrane into intermembrane space- creates an electrochemical gradient-protons moves through facilaitated diffusion along atp synthase to create atp -34 atp made
Oxygen picks up electron and hydrogen to form water – terminal electron acceptor

Question 2

heart rate

Answer 2

SAN releases wave of depolaristion across atria =contraction of atrial muscle
When depolarisation wave reaches the avn this causes the AVN to release another wave of depolarisation- there is an inulative layer between atria and venrtiale meaning depolarisation wave cannot reach ventricles straight away
The bundle of His carries wave of depolarisation to septum and purkyne fibres at very bottom of ventricle.it contracts from the bottom meaning all the blood is forced out of the heart
Ventricles contract
Short delay before ventricles contracts allowing the atria pump all blood in before ventricles contract
cells repolarise

Question 3

maintaining resting potential

Answer 3

Maintaining a resting potential
-60 mv- electrical difference across membrane when neurone is at rest
Outside is more pos. than inside- membrane becomes permeable to na + k pump- protein+ atp- active transport
3na+ in – 2 k+ out – 1 loss of charge
Membrane more to permeable to k+ as some k+ channels are permanently open + there are more of them- allows k+ to move out faster than Na+ move in maintaining -70mv

beacuaestherell be permanent na+ ion channels opne

Question 4

cause of a.p.

Answer 4

Action potential- stimulus
-Outside of neurone is more pos. charge than inside
-depolarisation-exceeds threshold of -55mv- Na+ channels open – Na+ flood in neuron reaching +30mv
Repolarization- sodium ion channels close-k+ channels open- negative
Hyperpolarisation/refractory period– 80mv -overshoots decrease in voltage –

Question 5

transcription

Answer 5

Transcription- DNA to pre mrna- -uracil replaces thymine
DNA helicase breaks hydrogen bonds between complementary bases –
One strand is used as a template – free nucleotide line up by completer base pairing -join by phosphodiester bond caused by the rna polymerase =mrna
Eukarytoic cells pre mrna splices introns out leaving eoxns-moves thorigh nuclear pores and attaches to ribosome in cytoplasm

Question 6

translation

Answer 6

Translation-ribosome attaches to start codon on mRNA molecule-anticodon binds to complimentary codon -TRNA brings specific amino acid -amino acids join by a peptide bond with the use of atp -TRNA is then released-ribosome moves a long mRNA forming a polypeptide.

Question 7

mitosis

Answer 7

-Prophase- chromosomes condense and become visible – centrioles separate-releasexd to both pole of the cell
-Metaphase-chromosomes align in centre -spindle fibres released -attach to chromatid
-Anaphase- spindle fibres contract-pulling chromatids to opposite poles -chromatids move to opposite ends of cell
-Telophase- chromosomes are different poles of cell-longer and thinner -spindles disintegrate- cytoplasm splits – 2 genetically identical cells form
Cytokinesis- cytoplasm divides and new cell membrane forms

Question 8

cardiac cycle+valves

Answer 8

Cardiac cycle
Vena cava-deox blood into right atrium
Pulmonary vein-oxygenated blood from lungs to left atrium
Pulmonary artery – deox blood from right ventricle to lungs becoming oxygenated
Aorta-oxygenated blood from left ventricle to rest of body

Valves-opens when pressure is higher behind the valve and shuts if not
bicuspid-semi lunar valves -aorta+ pulmonary aorta
Atrioventricular valves-tricuspid-between atria and ventricles

Question 9

LIR

Answer 9

LIR-Calvin cycle- stroma
Rubisco enzyme sensitive to temperature

-C02 reacts with RuBP forming 2 gp-carboxylation
-GP is reduced by NADP to NADPH and ADP-ATP to form TP
-Some of the carbon as a hexose sugar from the TP Is used in a organic substance like fatty acids or cellulose
-1 ATP regenerates RuBP from the TP

Question 10

ldr

Answer 10

LDR-
Chloroplast structure- grana thylakoid
Photolysis- water splits- h+ ,2e-,oxygen
e- is passed along chain of electron carrier proteins
oxygen is used in respiration later
h reduces nad into nadh
photoionization of chlorophyll- light energy absorbed by chlorophyll – energy results in electrons becoming excited and raising to leave chlorophyll
chlorophyll becomes ionised – some of the energy pumps over hydrogen thylakoid membrane-
electrons move along electron protein channel which pumps protons over thylakoid membrane-
electrochemical gradient is created- protons pass through enzyme atp synthase- produces atp

Question 11

phagocytosis

Answer 11

receptors bind to macrophage-phagocyte changes shape to engulf pathogen
pathogen fuses with vesical forming a phagosome-lysosome binds releasing digestive enzyme-hydrolysing pathogen

Question 12

cell mediated response

Answer 12

after phagocytosis-antigens are present on cell surface-helper t cells attach causing them to divide rapidly by mitosis - cloning
purpose of t cells-
activate b lymphocytes + stimulate microphages to engulf +become memory cells

Question 13

b cell activation

Answer 13

antigen collides with complemtary- b-lymphocyte - takes in antigen by endocytosis-present on cell surface then colides with helper t to go through clonal expansion

Question 14

memory b cells-

Answer 14

live for decades-divide rapidly by mitosis if they come in contact with antigen previously encountered-large number of antibodies produced -pathogen destroyed before symptoms occur

Question 15

cytotoxic t cells

Answer 15

cause cell to become abnormal release protein(perforin) creates a pore in cell membrane-disrupts cells w.p. sp a,y shrink or burst

Question 16

describe how altered DNA may lead to cancer ? (6)

Answer 16

1. (DNA altered by) mutation;
2. (mutation) changes base sequence;
3. Of gene controlling cell growth / oncogene / that monitors cell division;
4. Of tumour suppressor gene;
5. Change protein structure / non-functional protein / protein not formed;
6. (Tumour suppressor genes) produce proteins that inhibit cell division;
7. Mitosis;
8. Uncontrolled / rapid / abnormal (cell division);
9. Malignant tumour;

Question 17

nstursl selection

Answer 17

natural selection? (6)

1) variation of phenotypes in population due to random mutations
2) individuals that do not show behaviour die
3) change in selection pressue- environmental change
4) allele frequency increases in population
5) those who have the advantageous alleles, survive and reproduce and pass on their alleles giving a selective advantage to their offspring
6) until all individuals show the phenotype frequency of alleles in the population changes

Question 18

tissue fluid

Answer 18

high b.p/h.p
forces h2o out
large proteins remain in capillary
low w.p in capillary
due to plasma proteins
h2o enters capillary by osmosis

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Question 19

meisosiis

Answer 19

describe what happens to chromosomes in meiosis? (8)

chromosomes shorten/ condense
chromosomes associate in homologous pairs/ formation of bivalents
crossing over / chiasmata forms
join to spindle fibres
at equator
join via centromere
homologous chromosomes move to opposite poles/ chromosomes separate
pair of chromatids separated in 2nd ÷

Question 20

gills adaptations

Answer 20

Explain how the gills of fish are adapted for efficient gas exchange ? (6)

many lamallae on many filaments provide a large s.a increases diffusion
thin epithelium of lamellae short diffusion pathway increases rate of diffusion
blood flows over the gills in the opposite directions to blood flowing in the capillaries ( countercurrent flow)
maintains a steep diffusion gradient along whole length of gill lamellae- equilibrium is not achieved as water always meets blood with higher o2 conc
large n.o of capillaries and circulation replaces oxygenated blood with deoxygenated blood to maintain steep conc gradient-increases rate of diffusion
pressures change due to ventilation replaces deoxygenated h2o as oxygenated h2o maintains steep diffusion gradient increase rate of diffusion

Question 21

bohr effect/02 taking o n haemogloni

Answer 21

Describe how haemoglobin loads and unloads o2 in the body? (dissociation curve fetus left to mother)

loading of o2 at high p.p of o2
in lungs ( haemoglobin) had a high affinity for o2
dissociates o2 at low p.p of o2
unloading linked to higher co2 conc ( bohr effect)
higher affinity loads more o2 at same high p.p
therefore o2 moves from mother to foetus