Revision:Cell Respiration

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Outline that change in electrons during oxidation and reduction

• OIL RIG
  • Oxidation is loss of electrons (normally H)
  • Reduction is gain of electrons (normally H)

Outline what is achieved by the process of glycolysis

• glucose is broken down step by step in a series of nine enzymatic reactions, each successive reaction involving an intermediate sugar containing phosphate
• Phosphorylation
• Lysis
• Oxidation
• ATP formation
• In the cytoplasm, one hexose sugar is converted into two three-carbon atom compounds 2-oxoproponoate (pyruvate) with a net gain of two ATP and two NADH+ + H+
• Phosphorylation is a process where ATP is made in vivo (in glycolysis the process is substrate level phosphorylation

Outline Aerobic Respiration

Outline Aerobic Respiration including oxidative decarboxylation of 20oxopropanoate (pyruvate), Krebs cycle NADH, NADH + H⁺, and electron transport chain.

• Aerobic respiration, each pryuvate is decarboxylated (CO₂ removed), the remaining two-carbon molecule (ethanoyl or acetyl group) reacts with reduced Coenzyme A, and at the same time one NADH+ and HADH+ is formed. This is known as the link reaction.
• CH₃ CO COOH + CoA-S-H + NAD+ ---> CO₂ + NADH + CH₃CO-S-COA
• In Krebs cycle each ethanyol (acetyl) group (CH₃CO) formed in the link reaction yields two CO₂
• Hydrogen atoms are removed by hydrogen carrying co-enzymes
• ETC transports two hydrogens and two electrons from either FADH2 or NADH eventually to molecular oxygen forming water and in doing so, making ATP.
• Aerobic respiration occurs only if there is sufficient oxygen available

Describe Oxidative phosphorylation in terms of chemiosmosis

Describe Oxidative phosphorylation in terms of chemiosmosis including proton pumps, a proton gradient and ATP synthetase Chemiosmotic Theory

• The synthesis of ATP is coupled to electron transport and the movement of protons (H⁺ ions)
• the way in which ATP is formed from ADP and phosphate as electrons pass down the electron transport chain
• The process is powered by a gradient of protons, H⁺ ions, established across the inner mitochondrial membrane. This is known as chemiosmotic coupling. The proton gradient is established as electrons move down the electron transport chain. At three transition points in this chain, significant drops occur in the amount of potential energy held by the electrons. As a consequence, a relatively large amount of free energy is released at each of these steps. This energy powers the pumping of protons from the mitochondrial matrix through the inner membrane to the intermembrane space.
• In brief
  • The ET carriers are strategically arranged over the inner membrane of the mitochondrion and as they progressively oxidise 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, a proton pump. The pH therefore drops between the membranes (pH8-pH7, a 10x increase) and a potential difference is created. Eventually the H₊ ions flow back into the matrix through special gates in the ATP synthetase molecules in the membrane. As the ions are flowing down the gradient, energy is released and ATP is made.

Draw the structure of a mitochondrion as seen in electromicrographs

Explain the Relationship between structure and function of mitochondrion

• Aerobic respiration
  • takes place in the mitochondria.
• They are surrounded by two membranes
  • the outer one is smooth
  • inner one folds inward.
• folds are called cristae
  • Within the inner compartment of the mitochondrion, surrounding the cristae, is a dense solution known as the matrix. It contains a bunch of molecules involved in respiration (like enzymes, coenzymes, water phosphates etc.)

Explain the role of ethanol in Carbohydrate and fat metabolism

• Fats
• To get energy from them, the fats are first split into their glycerol and fatty acid components. The fatty acids are then chopped up into two-carbon fragments and slipped into the Krebs cycle as acetyl CoA. Proteins: broken down into their constituent amino acids. The amino acids are deaminated (amino groups removed) and the residual carbon skeleton is either converted to an acetyl group or to one of the larger carbon compounds of the glycolytic pathway or the Krebs cycle so that it can be processed at this stage of the central pathway. The amino groups, if not neutralised, are eventually excreted as urea or other nitrogen-containing wastes.

Outline fermentation to 2-hydroxypropanoate (lactate) and to ethanol and the circumstances in which they occur in cells

• Fermentation-a type of anaerobic pathway. In the absence of oxygen, pyruvic acid can be converted to ethanol or to one of several different organic acids, of which lactic acid is the most common. Yeast cells, for example, present as a "bloom" on the skin of grapes can grow either with or without oxygen. When the sugar-filled juices are extracted and stored under anaerobic conditions, the yeast cells turn the fruit juice to wine by converting glucose into ethanol. When the sugar is exhausted, the yeast cells cease to function; at this point alcohol concentration is between 12 and 17 percent. Anaerobic respiration yields only 5% of the amount of ATP's than in aerobic respiration. In some organisms, lactic acid is formed from pyruvic acid. Pyruvic acid is usually converted to lactate in the absence of oxygen with no loss of carbon dioxide so the reaction is irreversible.

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