3.5 energy transfers in and between organisms

what is respiration

process by which complex molecules are used to generate ATP

equation for respiration

C6H1206 + 6O2 —> 6CO2 + 6H20 +36ATP

what is a co enzyme

aids the function of an enzyme

name the 3 co enzymes and their roles

NAD = transfers hydrogen from one molecule to another

FAD = transfer hydrogen from one molecule to another

Co-enzyme A = transfers acetate between molecues

oxidation

loss of hydrogen

reduction

gain of hydrogen

overview of respiration

glycolysis (cytoplasm) —> link reaction (matrix) —> krebs cycle (matrix) —> oxidative phosphorylation (inner membrane)

explain glycolysis process

1. glucose is phosphorylated using 2 ATP to produce hexose bisphosphate

2. hexose bisphosphate splits into triose phosphate

3. trisose phosphate is oxidised, NAD is reduced to NAHD

4. 4 ATP produced via substrate level phosphorylation (net gain of 2)

5. pyruvate is produced

what is produced per glucose molecule in glycolysis

X2 pyruvate (goes to mitochondria)

X2 NADH (mitochondria)

net gain of 2 ATP

how many Link reactions per glucose

2

describe the Link reaction process

1. pyruvate is decarboxylated releasing a CO2 molecule (3c) using enzyme decarboxylate

2. pyruvate is oxidised and NAD is reduced to NADH using dehydrogenase

3. produces acetate (2c)

4. acetate joins to Co Enzyme A to from Acetyl CoA

what is produced per glucose molecule in the Link reaction

2X CO2

2X NADH

2X Acetyl CoA

define producer

autotroph. produce organic molecules from simple inorganic materials

define consumer

heterotroph. gains nutrients from complex organic molecules. dependant on autotrophs. obtain energy by feeding on other organisms

define detritivore

feeds on broken down tissues (detritus) to increase surface area for decomposers. important for nutrient cycling

define decomposers

break down organic compounds in dead material + waste products into co2, h20 and simple inorganic ions. releases minerals absorbed by plants

how is energy lost by organisms

through respiration, parts of an organism not eaten, waste heat. lost between each trophic level and remaining energy used to form biomass

units for rate of primary productivity

KJ/ha-1/year-1

what is the GPP

gross primary production is the total quantity of light energy converted to chemical by plants in a given area resulting from photosynthesis

what is NPP

net primary production is the chemical energy store in plant biomass (energy available for growth and reproduction)

equation for working out NPP

GPP - R

equation for net production

N = i - (R + F)

i = chemical energy from food

f= energy lost in environment (secretion)

r = respiratory loss

define biomass

mass of living material in an organism. the energy transferred through living organisms of an ecosystem when organisms eat other organisms

how can you measure biomass

• mass of carbon organism contains

• dry mass of its tissue per unit area

explain the process of measuring dry mass

1. dry a sample in a low temperature oven until mass is constant

2. scale up sample for total population or area (Kgm-2)

3. 50% assumed to be carbon

explain the process of calorimetry

• can estimate the amount of chemical energy stored in biomass. the amount of heat given off tells you how much energy is in a sample

  1. sample is burnt

  2. energy released is used to heat a known volume of water

  3. change in temperature used to calculate chemical energy of dry biomass

equation for efficiency

energy used in growth (output) / energy supplied (input)

explain the Krebs cycle

• 4c compound combined with acetyl CoA. decarboxylated using decarboxylase removing CO2 and CoA to form a 6C compound

• 6C compound is decarboxyated releasing CO2 and reduction of NAD to NADH. forms a 5C compound

• 5C compound is decarboxylated, NAH reduced to NADH twice, FAD reduced to FADH2. one ATP produced via substrate level phosphorylation

• 4C compound regenerated

products of Krebs cycle per glucose

4 X CO2

6 X NADH

2 X FADH2

2 X ATP

describe the process of oxidative phosphorylation

1. NADH is oxidised releasing H+ into matrix and donates an electron to carrier protein,, electron is accepted by carrier protein on inner membrane

2. electrons move along the electron transfer chain via a series of redox reactions which release energy

3. energy released is used to pump protons into intermembrane space to create a proton gradient

4. protons diffuse back into matrix through ATP synthase to generate ATP (chemiosmotic theory)

5. oxygen is a terminal electron acceptor forming water

6. FADH2 donates electrons futher along the ETC so fewer protons transported across, less ATP generated

products of oxidative phosphorylation

NADH which has the potential to make 2.5 ATP

FADH potential to make 1.5 ATP

so overall 4 ATP net gain

10 NADH = 25 ATP

2 FADH2 3 ATP

net gain of 32 ATP

reasons for lower actual ATP yield

• proton leakage through bilayer and don’t pass through ATP synthase

• some ATP is used to actively transport pyruvate and NADH

• ECT can be uncoupled to use energy for heat

describe anaerobic respiration in animals

• glycolysis happens as usual but without oxygen, no oxidative phosphorylation, so NADH cannot be oxidised to glycolysis stops

• pyruvate is reduced into lactate to oxidise NADH so glycolysis can continue

• lactate is acidic and causes pain and fatigue so sent to liver to be metabolised

describe anaerobic respiration in plants (fermentation)

• pyruvate is decarboxylated to form ethanal

• ethanal reduced to ethanol to oxidise NADH into NAD so glycolysis can continue

• ethanol is toxic as it dissolved membranes so used as a fuel and in brewing or baking

what is a respirometer used for

used to measure the rate of anaerobic respiration

describe the apparatus used in respirometer experiment for aerobic respiration

two flasks set up with pipe joining them

in one flask there is a soda lime and a platform with specimen on

in the other flask there is an object of equal mass

describe what happens in a respirometer experiment when investigating aerobic respiration

1. O2 taken up by aerobic respiration and releases CO2 absorbed by soda lime

2. decrease in volume, decrease in pressure

3. causes liquid to move down pressure gradient

describe the respirometer experiment when investigating anaerobic respiration

no soda lime

measures using CO2. more CO2 produced increases the pressure