A2 Bio Processes And Stuff

Question 1

3 stages of respiration and their locations + net values

Answer 1

1. Glycolysis - cytoplasm - 2ATP, 2NADH, 2 pyruvate (some atp lost for active transport)
2. Linking step - matrix - 2NADH, 2ACOA
   + krebs cycle - matrix - ATP, 3NADH, FADH
3. Oxidative phosphorylation - CRISTAE

Question 2

Glycolysis process

Answer 2

• occurs in cytoplasm
  1. Hydrolysis of 2ATP
  2. Allows for phosphorylation of glucose to 2TP (triose phosphate)
  3. 2 TP is oxidised to 2 pyruvate
  4. Allowing for reduction of 2NAD to 2NADH
  5. Energy surplus allows for phosphorylation of 4ADP to 4ATP
• Net 2ATP, 2NADH, 2 Pyruvate

Question 3

Link reaction

Answer 3

-mitochondrial matrix
1. 2 pyruvates oxidised, with the loss of proton allowing for the reduction of 2NAD into 2NADH
2. Pyruvate also decarboxylised, with the addition of CoA
3. Releasing C02, with 2ACoA as the final product
Net - 2NADH, 2ACoA, (2CO2)

Question 4

Oxidative decarboxylation/ Krebs cycle

Answer 4

-matrix
1. ACoA condensed with 4C compound to make a 6C compound
2. This then undergoes a series of oxidation and decarboxylation reactions, returning to a 4C compound
3. At each decarboxylation step, CO2 is released
4. Each new oxidation step releases H+ ions to reduce NAD to NADH
5. 1 step releases energy to phosphorylate ADP to ATP and FAD reduced to FADH
Net - ATP, 3NADH, 1FADH (X2)

Question 5

Oxidative phosphorylation

Answer 5

Cristae

1. NADH is reoxidised, donating H+/e-
2. electrons passed between carriers down a decreasing energy gradient
3. carriers use energy to pump protons across the membrane from the matrix to the intermembrane space
4. This generates a PH gradient (PMF)
5. Protons diffuse via chemiosmosis into the matrix via ATPase allowing the phosphorylation of ADP to ATP
6. Oxygen acts as the final electron acceptor where it joins with H+/e- to form water

Question 6

Options for how to recycle built up lactate

Answer 6

1. (+02) lactate to pyruvate + respire as normal (28ATP)
2. Lactate to pyruvate + reverse glycolysis (more short term store)
3. Lactate to pyruvate + reverse glycolysis then glycogen formed from glucose (long term store)

Question 7

Anaerobic respiration in animals (Lactate fermentation)

Answer 7

1. 02 not present - no final electron acceptor in oxidative phosphorylation
2. NADH can’t be removed
3. Lack of NAD, prevents oxidation reactions in link reaction/ Krebs cycle
4. Reduction of pyruvate to lactate by lactate dehydrogenase oxidises enough NADH to allow glycolysis to still proceed (2NAD produced)
   - 2 ATP produced

Question 8

How is anaerobic respiration different in yeast and plants compared to in animals?

Answer 8

1. Ethanol acts as hydrogen acceptor instead of pyruvate
2. 2 enzymes used (pyruvate decarboxylase and ethanol decarboxylase) animals use lactate dehydrogenase
3. Formation of ethanol cannot be reversed- high enough levels can kill an organism (Lactate can be recycled when oxygen is available)

Question 9

Alcohol fermentation process

Answer 9

1. Pyruvate is decarboxylised to ethanol by pyruvate decarboxylase
   - Giving off CO2
2. NADH is oxidised to NAD - releasing 2H+
   - 2H+ accepted by ethanal - reducing it to ethanol

Question 10

stages of light independent reaction

Answer 10

• stroma
  1. enzyme rubisco catalyses the CARBON FIXATION of RuBP with CO2 to form an unstable 6 carbon molecule which breaks down into 2 GP (glycerate - 3 - phosphate) molecules
  2. hydrolysis of ATP to ADP and oxidation of NADPH provide the reducing power for reduction of 2GP into 2TP (Triose Phosphate)#
  3. 5/6 of the carbon is then recycled as the hydrolysis of ATP to ADP provides energy + phosphate for the PHOSPHORYLATION of TP back into RuBP to repeat the calvin cycle
  4. Remaining carbon condensed into organic molecules and hexose sugars that can be used for energy storage and for growth (can form carbs, amino acids etc)

Question 11

Why plants produce fruit in the summer

Answer 11

1. in midday summer (peak light intensity), cyclic phosphorylation occurs
2. The rate of of the light dependent reaction becomes far greater than the rate of the calvin cycles
3. There is a buildup/ excess of ATP + NADPH
4. The protons and electrons from ldr is recycled down the etc, only using photosystem 1
5. This stops the production of NADPH but increases ATP production
6. LDR now has higher ATP production than respiration, so respiration stops
7. Meaning glucose and starch not needed so can be stored
8. The plant can now use the starch to produce fruits and vegetables

Question 12

What are GPP and NPP

Answer 12

Gross primary production = total quantity of chemical energy store in plant biomass in a given area of volume in a given time.
Net primary production = chemical energy store left in plant biomass after (-20 - 50%) loss to respiration taken into account. - Available for plant growth and reproduction or to other trophic levels in the ecosystem
NPP = GPP - R (respiratory loss)

Question 13

Nitrogen cycle in full

Answer 13

1. nitrogen fixation
   -nitrgogen gas (n2) into ammonium ions/ ammonia (NH4+/NH3)
   -by RHIZOBIUM - aerobic or anaerobic - increases fertility of the soil
2. nitrification (2 steps)
   -Ammonium ions/ ammonia into nitrite by NITROSOMONAS
   -Nitrite into nitrate by NITRO BACTER
   (Both increase 02 and fertility in soil) - A.T by root hair cells
3. ammonification (decomposition)
   -nitrogenous waste into ammonium ions/ ammonia
   -by SAPROBIONTS
   - requires 02, increased fertility again
4. denitrification
   - nitrate into nitrogen gas (N2)
   -by PSEUDOSOMONAS
   - decreases soil fertility and 02

Question 14

Biomass definition

Answer 14

mass of carbon or dry mass of tissue per given area per given time

Question 15

How to estimate chemical energy stored in dry biomass

Answer 15

Bomb colorimetry:

1. sample of dry material is weighed then burned in pure oxygen within a sealed chamber called a bomb
2. the bomb is surrounded by a water bath and the heat of combustion causes a small temperature rise in water
3. using cpecific heat capacity of water, and knowing volume of water, we can calculate the energy released from the mass of burnt biomass in JKg-1

Question 16

nutrient cycle sequence

Answer 16

1. nutrient taken up by producers as simple, inorganic molecules
2. the producer incorporates the nutrient into complax organic molecules
3. when the producer is eaten, the nutrient passes into consumers
4. it then passes along the food chain when these animals are eaten by other consumers
5. when the producers and consumers die, their complex molecules are broken down by saprobiontic microorganisms that release the nutrient in its simplest form

Question 17

Describe the response when blood glucose levels fall

Answer 17

1. Receptor cells in the pancreas ( alpha cells in islets of langerhan) detect fall in blood glucose levels
2. alpha cells release glucagon hormone by exocytosis
3. glucagon travels in the blood to target cells in the liver, muscles and other cells
4. glucagon binds to complimentary receptors in hepatocytes
5. () Enzymes involved in glycogenolysis activated
   () Enzymes involved in gluconeogenesis
   () Glucose released into blood stream from cell via facilitated diffusion

Question 18

Describe the response when blood glucose levels rise

Answer 18

1. Receptor cells in the pancreas ( beta cells in islets of langerhan) detect rise in blood glucose levels
2. beta cells release insulin hormone by exocytosis
3. insulin travels in the blood to target cells in the liver, muscles and other cells
4. insulin binds to complimentary receptors in hepatocytes
5. cyclic AMP released
6. () genes coding for proteins involved in facilitated diffusion switched on - move to membrane + increase glucose uptake
   () Enzymes involved in respiration (glycolysis) activated
   () Enzymes involved in glycogenesis activated
   () enzymes involved with converting glucose into fatty acids are activated

Question 19

Describe the heart beat in terms of atrial systole and ventricular systole

Answer 19

• myogenic ( electrical activity required for contraction is initiated from within itself )
• ——–Atrial systole:
  1) electrical activity initiated from the SAN
  2) Impulse passes across the ATRIA, causing CONTRACTIONS and blood mvmt
  3) The activity reaches the AVN. A delay between the SAN and AVN becoming active allows atrial systole
• ——-Ventricular systole:
  4) activity passes from the AVN down the BUNDLE OF HIS FIBRES that are non-conductive (fully myelinated)
  5) at the base of the septum, activity passes to the PERKINJE FIBRES which STIMULATE THE VETRICLES
  6) a wave of excitation passes up the ventricles, causing them to contract
  7) Blood is forced out of the ventricles from the bottom due to a decreased volume and increased pressure - ventricular systole

Question 20

control of the heart rate during exercise

Answer 20

1) chemoreceptors in the AORTIC and COROTID BODIES detect FALL in ph due to increased CO2 from increased aerobic respiration
2) negative feedback control switches off CARDIO INHIBITORY CENTRE of MEDULLA
- action potential sent to CARDIO ACCELERATORY CENTRE of medulla
3) increased frequency of a.p sent to SYMPATHETIC neurone
4) NOR-ADRENALIN is released
5) to the SAN - increased frequency of impulse - increased contractions

Question 21

control of heart rate AFTER exercise

Answer 21

1) chemoreceptors in the aortic and corotid bodies detect a RISE in ph due to decreased levels of CO2
2) negative feedback control switches off cardio- acceleratory centre of medulla
- AP sent to cardio- inhibitory centre of medulla
3) Increased frequency of APs sent to parasympathetic neurone
4) ACETYLCHOLIN is released
5) to the SAN - decreased frequency of impulse/ contractions