Topic 8: Cell respiration & photosynthesis HL

8.1.1 State that oxidation is loss of electrons from element and loss of hydrogen/gain of oxygen. Reduction is gain of electrons from element and gain of hydrogen/loss of oxygen.

8.1.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation.

1. Glycolysis occurs in cytoplasm where hexose sugar is converted to two pyruvate compounds with net gain of 2 ATP and 2 NADH and H+
2. Glycolysis begins when hexose is phosphorylated, using the energy from ATP, to form hexose phosphate.
3. Hexose phosphate is then split (lysis) to form two triose molecules.
4. Each triose phosphate molecule is oxidised to form glycerate-3-phosphate. Oxidation occurs, electrons are lost and hydrogen H+ is removed from each of the triose phosphate molecules and accepted by NAD+, forming NADH and H+
5. Glycerate-3-phosphate is then further phosphorylated, whereby phosphate groups are transferred to ADP to form 2 ATP and 2 pyruvate molecules.

occurs in cytoplasm; hexose (glucose) is phosphorylated using ATP;
hexose phosphate is split into two triose phosphates; oxidation by removal of hydrogen;
conversion of NAD to NADH +H+; net gain of two ATP; pyruvate produced at the end of glycolysis;
Accept glucose/fructose/6C sugar instead of hexose.
Accept 3C sugar/glyceraldehyde instead of triose.

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs.

8.1.4 Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen.

Aerobic respiration occurs in the matrix of the mitochondrion in eukaryotes in a process termed decarboxylation, in which hydrogen is removed fro

Krebs cycle:[3 max]
occurs in matrix of mitochondrion in eukaryotes; decarboxylation;
oxidation / removal of hydrogen by NAD and FAD;
substrate level phosphorylation;
Electron transport chain:[5 max]
transfer of hydrogen to inner membrane carriers;
hydrogen ion pumped across inner membrane; creating concentration gradient;
electron transferred between carriers;
chemiosmosis; hydrogen ion passes down concentration gradient; through ATPase complex;
oxygen is final acceptor forming water;

pyruvate produced by glycolysis; pyruvate enters mitochondrion/mitochondria;
pyruvate loses CO2 in link reaction; and NADH + H+; with formation of acetyl CoA;
to take part in Krebs cycle; where two CO2 are produced per molecule of pyruvate;
one ATP from ADP + Pi; along with three NADH + H+ and one FADH2;
NADH + H+ provide electrons circulating in the electron transport
chain on the inner mitochondrial membrane;
allowing H+ to accumulate in the intermembrane space;
and come back to the matrix through ATP synthase/synthetase to produce
ATP by chemiosmosis;
presence of O2 required as the final electron acceptor for the electron
transport chain; producing water with H+;

8.1.5 Explain oxidative phosphorylation in terms of chemiosmosis.

• ATP synthase enzyme catalyses phosphorylation of ADP to form ATP, using energy from the electron transport chain and redox reactions
• NADH is oxidised to NAD

8.1.6 Explain the relationship between structure of mitochondrion and its function

• Cristae forming a large surface area for electron transport chain
• Small space between inner and outer membranes for accumulation of protons
• Fluid matrix - contains enzymes of Krebs cycle

Photosynthesis

8.2.1 Draw and label a diagram showing the structure of chloroplast as seen in electron micrographs

8.2.2 State that photosynthesis consists of light-dependent and light-independent reactions.

8.2.3 Explain light-dependent reactions (including photoactivation of photosystem II, photolysis of water, electron transport, cyclic and non-cyclic photophosphorylation,photoactivation of photosystem I, and reduction of NADP+)

Chlorophylls within Photosystem II absorb light energy and pass it to two chlorophyll molecules, This light absorption (photoactivation) causes an electron in one of the chlorophylls to jump to a high energy level. Excited electron passes along chain of electron carriers, at the end of which electrons are passed on to ferredoxin, causing NADP+ to be reduced to NADPH + H+.
Absorption of light in photosystem II provides electron for photosystem I
Photolysis of water produces H+ and O2, termed non-cyclic photophosphorylation.
In cyclic photophosphorylation, electron returns to chlorophyll, producing ATP by H+ pumped across thylakoid membrane by chemiosmosis.

(chlorophyll/antenna) in photosystem II absorbs light;
absorbing light/photoactivation produces an excited/high energy/free electron;
electron passed along a series of carriers;
reduction of NADP+ / generates NADPH + H+;
absorption of light in photosystem II provides electron for photosystem I;
photolysis of water produces H+ / O2; called non-cyclic photophosphorylation;
in cyclic photophosphorylation electron returns to chlorophyll;
generates ATP by H+ pumped across thylakoid membrane / by
chemiosmosis / through ATP synthetase/synthase;

8.2.4 Explain photophosphorylation in terms of chemiosmosis.

8.2.5 Explain the light-independent reactions (include the roles of ribulose bisphosphate (RuBP) carboxylase, reduction of glycerate 3-phosphate (GP) to triose phosphate (TP), NADPH + H+, ATP, regeneration of RuBP, and subsequent synthesis of more complex carbohydrates.



8.2.6 Explain the relationship between the structure of the chloroplast and
its function.

• large surface area of thylakoids for light absorption,
• small space inside thylakoids for accumulation of protons
• fluid stroma for the enzymes of the Calvin cycle.

8.2.7 Explain the relationship between the action spectrum and the absorption
spectrum of photosynthetic pigments in green plants.



8.2.8 Explain the concept of limiting factors in photosynthesis, with reference
to light intensity, temperature and concentration of carbon dioxide.