Cell Respiration and Photosynthesis

Cell respiration
Define cell respiration.
Cell respiration -- controlled release of energy in the form of ATP from organic compounds in cells.
State that in cell respiration glucose in the cytoplasm is broken down into pyruvate with a small yield of ATP.
Explain that in anaerobic cell respiration pyruvate is converted into lactate or ethanol and carbon dioxide in the cytoplasm, with no further yield of ATP.
Mention that ethanol and carbon dioxide are produced in yeast whereas lactate is produced in humans.
Explain that in aerobic cell respiration pyruvate is broken down in the mitochondrion into carbon dioxide and water with a yield of ATP.
State that oxidation involves the loss of electrons from an element whereas reduction involves gain in electrons, and that oxidation frequently involves gaining oxygen or losing hydrogen; whereas reduction frequently involves loss of oxygen or gain in hydrogen.
Outline the process of glycolysis including phosphorylation, lysis, oxidation and ATP formation.
In the cytoplasm, one hexose sugar is converted into two three-carbon atom compounds (pyruvate) with a net gain of two ATP and two NADH + H+ . Phosphorylation is a process in which ATP is made in vivo (in glycolysis the process is substrate level phosphorylation).
Draw the structure of a mitochondrion as seen in electronmicrographs.
Explain the relationship between the structure of the mitochondrion and its function.
Limit this to cristae forming a large surface area for the electron transport chain, the small space between inner and outer membranes for accumulation of protons and the fluid matrix containing enzymes of the Kreb cycle.
Explain aerobic respiration including oxidative decarboxylation of pyruvate, Krebs cycle, NADH + H+ , the electron transport chain and the role of oxygen.
In aerobic respiration (in mitochondria in eukaryotes) each pyruvate is decarboxylated (CO2 removed). The remaining two carbon molecule acetyl group reacts with reduced coenzyme A, and at the same time one NADH + H+ is formed. This is known as the link reaction.
In Krebs cycle each acetyl group (CH3CO) formed in the link reaction yields two CO2. The names of the intermediate compounds in the cycle are not required. Thus it would be acceptable to note: C2 + C4 = C6 --> C5 --> etc. Students should also note that the hydrogen atoms removed are collected by 'hydrogen-carrying co-enzymes'.
Explain oxidative phosphorylation in terms of chemiosmosis.
Cross reference with 7.2.4. The synthesis of ATP is coupled to electron transport and the movement of protons (H+ ions) - the chemiosmotic theory. Briefly, the electron transport carriers are strategically arranged over the inner membrane of the mitochondrion. As they oxidize NADH + H+ and FADH2 , energy from this process forces protons to move, against the concentration gradient, from the mitochondrial matrix to the space between the two membranes (using proton pumps). Eventually the H+ ions flow back into the matrix through protein channels in the ATP synthetase molecules in the membrane. As the ions flow down the gradient, energy is released and ATP is made.
Describe the central role of acetyl CoA in carbohydrate and fat metabolism.
Acetyl CoA is an intermediate in carbohydrate (glucose) metabolism. In lipid metabolism the oxidation of the fatty acid chains results in the formation of two-carbon atom (acetyl) fragments which then pass through Krebs cycle.
Photosynthesis
State that photosynthesis involves the conversion of light energy into chemical energy.
State that white light from the sun is composed of a range of wavelengths (colours).
Reference to actual wavelengths or frequencies is not expected.
State that chlorophyll is the main photosynthetic pigment.
Outline the differences in absorption of red, blue and green light by chlorophyll.
Students should appreciate that pigments actively absorb certain colours of light due to their structure. The remaining colours of light are reflected and give rise to the colour perceived by the brain of the observer. It is not necessary to mention wavelengths or the structure responsible for the absorption.
State that light energy is used to split water molecules (photolysis) to give oxygen and hydrogen, and to produce ATP.
State the ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules.
Draw the action spectrum of photosynthesis.
Explain the relationship between the action spectrum and the absorption spectrum of photosynthetic pigments in green plants.
A separate spectrum for each pigment (chlorophyll a, chlorophyll b, etc) is not required.
Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by the increase in biomass.
The recall of details of specific experiments to indicate that photosynthesis has occurred or to measure the rate of photosynthesis will not be expected.
Outline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis.
The shape of the graphs is required.
Explain the concept of limiting factors with reference to light intensity, temperature and concentration of carbon dioxide.
Draw the structure of a chloroplast as seen in electronmicrographs.
Explain the relationship between the structure of the chloroplast and its function.
Limit this to the large surface area of thylakoids for light absorption, the small space inside thylakoids for accumulation of protons and the fluid stroma for the enzymes of the Calvin cycle.
State that photosynthesis consists of light-dependent and light-independent reactions.
Not 'light' and 'dark' reactions.
Explain the light-dependent reactions.
Include the photoactiviation of photosystem II, photolysis of water, electron transport, cyclic and non-cyclic photophosphorylation, photoactivation of photosystem I and reduction of NADP+.
Explain photophosphorylation in terms of chemiosmosis.
Electron transport causes the pumping of protons to the inside of the thylakoids. They accumulate (pH drops) and eventually move out to the stroma through protein channels in the ATP synthetase enzymes. This provides energy for ATP synthesis. Cross reference 7.1.5.
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 synthesis of carbohydrate.