Paper 2- processes

Question 1

Method for producing cultures from cauliflower explants

Answer 1

1. Wipe all surfaces with disinfectant and soak all apparetus- no fungi contamination which would mean we see fungal growth, not explant
2. Break of a small floret of cauliflower using scalpal- cut a thin section
3. steralise the explant by soaking in solution for 15 mina- make sure to swirt
4. add to agar growth medium
5. leave for 3 weeks on sunny windowsill

Question 2

Oestrogen Stimulation Pathway

Answer 2

1. Oestrogen diffuses through the cell surface membrane into the cytoplasm
2. Oestrogen diffuses through nuclear pore and attaches to a ERa receptor causing it to undergo a change
3. The new shape of the ERa receptor allows it to detach from the protein complex and diffuse toward gene to be expressed
4. Receptor binds to cofactor enabling it to bind to the promotor region stimulating RNA polymerase binding and gene transcription

Question 3

Steps of making recombinant DNA

Answer 3

Identification- of gene
Isolation
Multiplication
Transfer- using vector
Identification- using marker gene

Question 4

Polymerase Chain Reaction Process

Answer 4

Denaturation- he double-stranded DNA is heated to 95°C which breaks the hydrogen bonds that bond the two DNA strands together

Annealing- the temperature is decreased to between 50 - 60°C so that primers (forward and reverse ones) can anneal to the ends of the single strands of DNA

Elongation- the temperature is increased to 72°C for at least a minute, as this is the optimum temperature for Taq polymerase to build the complementary strands of DNA to produce the new identical double-stranded DNA molecules

Question 5

In vivo method of DNA replication

Answer 5

• isolation
• Inserted into vectors
• transported into bacterial host cells
• bacteria multiply in number
• marker genes help identify
• remaining bacteria are cultured

Question 6

how to use DNA probes to locate specific alleles

Answer 6

• sample is taken from patient
• DNA extracted and purified
• amplified
• restriction endonucleases digest amplified test DNA
• rest is separated in gel electrophoresis
• bands transfered to nylon membrane and labelled DNA probes complementary to harmful allele is added
• washed

Question 7

Gel Electropherisis

Answer 7

1. pipette DNA samples into wells on the gel plate
2. connect the negative electrode to the end of the plate with the wells and cconnect positive at far end
3. the smaller mass/ shorter pieces of DNA will move faster and further from the wells than larger fragments
4. proves added so UV light can view the DNA samples

Question 8

Non-Cyclic phosphorylation

Answer 8

1. photoionisation- energy is absorbed by PSII which excites the electrons to a higher energy level to be released from the chlorophyll
2. these need to be replaces- photo-lysis of water into protons and electrons and oxygen
3. excited electrons move down the chain loosing energy to PSII. This energy transports H+ into thylakoids making a higher concentration than the stroma. Protons now move down via ATP synthase molecules making ATP
4. at PSI, more energy absorbed which excited electrons to an even higher energy level so they are transfered to NADP reducing it

Question 9

Cyclic Phosphorylation

Answer 9

Produces ATP using energy from PSI- doesnt pass hydrogen to NADP

Question 10

Calvin Cycle

Answer 10

1. CARBON DIOXIDE FIXATION- Carbon dioxide combines with ribulose bisphosphate catalysed by the enzyme rubisco. This forms an unstable 6 carbon molecule which immediatley splits into two G3P
2. Molecules of G3P are reduced by NADP with energy provided by ATP forming 2 molecules of triose phosphate. this step uses some ATP and all the NADP
3. The rest of the ATP is used to regenerate the ribulose bisphosphate or combined with fructose to form glucose

Question 11

Investigating the effect of light intensity on photosynthesis in pond weed

Answer 11

ensure all the water is well aerated before use by bubbling air through ensuring oxygen produced isnt absorbed

1. set up in a dark room, add distilled water and sodium hydrogencarbonate to a boiling tube
   2.cut pondweed stem at an angle
2. place light at a set distance from the tube and measure the volume of gas collected in the gas syringe over a set period of time
3. repeate
4. repeate over a range of distances

Question 12

Glycolysis

Answer 12

1. Glucose is phosphorylated into glucose phosphate using 2 molecules of ATP
2. GP splits into two molecules of triosephosphate
3. TP is oxidized into pyruvate where the electrons and hydrogens are transported to NAD

Produces- 2x pyruvate, 2x ATP, 2x NADH

Question 13

Ethanol Fermentation

Answer 13

1. pyruvate is decarboxylated to ethanal giving off Co2
2. ethanal is reduced to ethanol from NADH

Question 14

Lactate Fermentation

Answer 14

pyruvate accepts hydrogen from NADH forming lactate

Question 15

The Link Reaction

Answer 15

1. pyruvate is oxidised to acetate making NADH and oxygen
2. acetate combines with coenzyme A forming acetyl CoA

Question 16

The Krebs Cycle

Answer 16

1. Acetyl CoA releases oxyloacetate 2C to combine with a four carbon molecule making a 6 carbon molecule
2. The CoA returns to the link reaction
3. A series of oxidation reduction reactions convert this molecule back to 4C and it reduces NAD and FAD as well as produces ATP and looses Co2

Question 17

Nitrogen Cycle

Answer 17

Ammonification- where microbes known as saphrobionts break down organic matter to ammonia in a two stage process: Proteins are broken down into amino acids with the use of extracellular protease enzymes. These are broken down further to remove amino acid groups with the use of deaminase enzymes. The products of decomposition are used for repsiration

Nitrification- where nitrifying bacteria convert ammonia to nitrate ions. NO3- in an oxidation reaction, with a nitratie ion. Most plants can take up nitrate ions through their roots.

Denitrification- where nitrate ions are converated to nitrogen gas by the denitrifying bacteria. This process is wasteful and can be prevented from occuring by soil being well drained

Nitrogen Fixation- Where nitrogen gas is fixed into other components by bacteria with nitrogen fixing ability. They do so by reducing nitrogen fas to ammonia which dissolbes to form ammonium ions. Nitrogen fixing bacteria live in root nodules of leguminous plants.

Question 18

Phosphorus Cycle

Answer 18

phosphorus in rocks is released into the soil and into water sources in the form of phosphate ions (PO₄³⁻) due to weathering

Phosphate ions are taken up from the soil by plants, or absorbed from water by algae

Phosphate ions are transferred to consumers during feeding

Phosphate ions in waste products and dead organisms are released into the soil or water during decomposition by saprobionts

The phosphate ions can be taken up and used again by producers, or may be trapped in sediments that may turn into phosphorus-containing rock once again

Question 19

Eutrophication

Answer 19

Leaching can lead to a process called eutrophication, which occurs as follows:

mineral ions enter water bodies, causing rapid growth of algae at the surface

This is known as an algal bloom

algae block sunlight, which prevents aquatic plants below the surface from photosynthesising

these plants, and eventually the algae, begin to die and dead organic matter accumulates

bacteria decompose the dead matter, respiring aerobically and using up the oxygen dissolved in the water

oxygen levels fall and aquatic animals such as fish and insects can no longer survive

Question 20

Investigating IAA + responses

Answer 20

1. cut root tip and mark at 2mm levels
2. divide into 3 groups:
   - A- remove tips
   - B- light proof container
   - C- directional light to one side
3. leave all roots in their conditions for 3 hours and determine growth

A- grow evenly but low
B- even, more
C- bend away from light

Question 21

Pacinian Corpuscle stimulation

Answer 21

1. lamellae deform and press on the sensory nerve endings
2. neurone streaches and streach mediated sodium ion channels open
3. sodium ions move in via facilitated diffusion
4. the positive sodium ions increase the charge of axon generator potential- threshold, action

Question 22

Resting potential

Answer 22

The Resting Potential- When a nervous system receptor is in resting state, there is a difference in charge between the inside and the outside of the cell. The inside is negatively charged relative to the outside. This means there is a voltage across the membrane, or a potential difference. The potential difference when a cell is at rest is called its resting potential. This is generated by ion pumps and ion channels

Question 23

Generator potential

Answer 23

Generator Potential- When a stimulus is detected, the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell, altering the potential difference. The change in potential difference due to a stimulus is called the generator potential. A bigger stimulus excites the membrane more, causing bigger movement of ions and a bigger change in potential difference

Question 24

Action Potential

Answer 24

Action Potential- If the generator potential is big enough, it will trigger an action potential. an action potential is an electrical impulse along a neuron. This is only triggered if the generator potential Reese’s a certain level called the threshold level.

Question 25

Rods and Cones action potential

Answer 25

1. light causes the chemical breakdown of optical pigments 2. this results in generator potential 3. if threshold, impulse send along bipolar neurone to optic nerve to brain

Question 26

heart contraction

Answer 26

1. SAN initiates a wave of depolarisation accross atria so they contract 2. depolarisation wave reaches non- conducting tissue seperating atria and ventricle before passing to AVN. This causes a delay allowing atria to empty and ventricle to fill 3. electrical activity passes from bundle of HIS to purkyne so ventricles contract from base up

Question 27

Heart rate- autonomic NS- decrease

Answer 27

1. impulse sent along sensory neurones to medulla 2. parasympathetic relays to SAN 3. aceylcnoline released and binds to SAN receptors

Question 28

Heart Rate- autonomic NS- increase

Answer 28

1. impulse sent along sensory neurones to medulla 2. sympathetic relays to SAN 3. noradrenaline released

Question 29

Action potential in neurone

Answer 29

1. **DEPOLARISATION-** a stimulus excited a membrane on cell-surface so membrane becomes more permeable to sodium ions 2. Sodium ion channels open and sodium diffuses in while potassium doesnt so inside is less negative 3. **REPOLARISATION-** Sodium ion channels close while potassium open so potassium diffuses out of neurone and the inside becomes more negative and voltage returns to normal level 4. **HYPERPOLARISATION-** Voltage gated potassium ion channels are still open for a short time meaning too many ions diffuse out of neurone and voltage becomes more negative than resting potential 5. Potassium ion channels close restoring resting potential

Question 30

ACh Synapse

Answer 30

1. Action potential arrives at presynaptic membrane causing depolarisation opening voltage- gated calcium ion channels 2. calcium ions diffuse into presynaptic neurone down electrochemical gradient 3. influx causes ACh vesicles to fuse with presynaptic membrane releasing ACh into cleft 4. ACh diffuses accross and ACh binds to ligand- gated sodium ion channels on post causing conformational change opening channels 5 sodium ions diffuse in causing depolarisation- threshold 6. ACh breaks into choline and acetate, choline is reabsorbed into presynaptic neurone and choline combines with acetyl CoA to resynthesis ACh

Question 31

Sliding Filament model

Answer 31

Action potential travels along the muscle cell This triggers the sarcoplasmic reticulum to release calcium ions (Ca²⁺) into the muscle cell. Calcium ions bind to a protein called troponin on the actin (thin filament). This causes tropomyosin (another protein) to move and uncover myosin-binding sites on the actin. Myosin heads (on thick filaments) bind to the actin → forming a cross-bridge. ATP has already been broken down to ADP + Pi to "cock" the myosin head. Power stroke: Myosin head pulls the actin filament toward the centre of the sarcomere. ADP and Pi are released. A new ATP molecule binds to the myosin head. This makes the myosin detach from the actin. ATP is broken down again (ATP → ADP + Pi) to re-cock the myosin head. The cycle can now repeat as long as Ca²⁺ and ATP are present.

Question 32

Talk about what happens when glucose is too high

Answer 32

- The rise in glucose concentration is detected by **beta cells** found in the Langerhans in the pancreas. - Insulin is secreted by beta cells inhibiting the action of alpha cells - Binding of insulin to the receptors on the plasma membrane causes vesicles with glucose transport proteins to fuse with the membrane - This increases the permeability of the cells to glucose increasing the rate of glucose uptake into the cell. This is then converted to glycogen or fats and subsequently used for respiration.

Question 33

Talk about when glucose is too low

Answer 33

- Alpha cells in the islets of Langerhans in the pancreas detect a fall in glucose and secretes the hormone glucagon - Glucagon secretion inhibits beta cell action - glucagon stimulates hepatocytes to convert glycogen to glucose - Glucose diffuses out of hepatocytes into the blood - cells use fatty acids and amino acids for respiration insted

Question 34

Adrenaline with glucose

Answer 34

1. Adrenaline fuses to a receptor on the cell surface membrane of liver cells and causes the receptor to change shape on the inside of the membrane 2. the changing shape on the inside of the membrane activates the enzyme adenyl cyclase converting ATP to cAMP which acts as a second messenger. 3. The cAMP then changes shape and activates the protein kinase enzyme which catalyses the converson of glycogen into glucose.

Question 35

Fasting Oral Glucose Tolerance test

Answer 35

1. Fast for 8 hours 2. A sample of your blood is taken and blood sugar levels are measured. 3. Drink 100g if sugar in a glucose solution 4. Blood sugar is takeb again after 1 hour, 2 hours and 3 hours.

Question 36

describe co transport of glucose/ amino acids with sodium occurs in kidney

Answer 36

Sodium pumped into blood from epithelial cells Low Na⁺ inside cells causes Na⁺ to diffuse in from filtrate via co-transporters Glucose/amino acids move in with Na⁺ Solutes then diffuse into blood

Question 37

normal blood glucose concentration

Answer 37

Glucose enters the nephron during ultrafiltration at the glomerulus → it’s small enough to pass into the Bowman's capsule. Glucose is reabsorbed in the proximal convoluted tubule (PCT) by: Co-transport with sodium ions via co-transporter proteins Followed by diffusion into the blood in nearby capillaries In a healthy person, all glucose is reabsorbed, so no glucose is found in the urine.

Question 38

Blood glucose too high

Answer 38

Blood glucose concentration rises above the kidney’s reabsorption threshold Not all glucose can be reabsorbed in the PCT Excess glucose remains in the filtrate Glucose is excreted in the urine

Question 39

filtration and reabsorption

Answer 39

1. ultrafiltration- high hydrostatic preassure causes water and small molecules to be forced out of the glomerulus capillaries into renal capsule 2. selective reabsorption happens here in the proximal convuluted tubule 3. loop of hemle maintains a sodium ion gradient so water can be reabsorbed into blood 4. water moves out of diastal convuluted tubule and collecting duct back to blood 5. the collecting duct carries urine

Question 40

natural selection

Answer 40

Variation exists within a species population This means that some individuals within the population possess different phenotypes (due to genetic variation in the alleles they possess; remember members of the same species will have the same genes) Environmental factors affect the chance of survival of an organism; they, therefore, act as a selection pressure Selection pressures increase the chance of individuals with a specific phenotype surviving and reproducing over others The individuals with the favoured phenotypes are described as having a higher fitness The fitness of an organism is defined as its ability to survive and pass on its alleles to offspring Organisms with higher fitness possess adaptations that make them better suited to their environment When selection pressures act over several generations of a species they can cause a change in the allele frequency and the phenotype frequency in a population through natural selection Natural selection is the process by which individuals with a fitter phenotype are more likely to survive and pass on their alleles to their offspring so that the advantageous alleles increase in frequency over time and generations The allele frequency and the phenotype frequency in a population can also change due to isolation