State units used to measure energy content of food
Define the term respiration
Name the food molecule which is the main source of
energy in cells
Describe how respiration is controlled
Describe what happens to the chemical energy in
food during respiration
Respiration is a chemical process in which energy is released from food molecules in cells. During respiration glucose is broken down in a series of reactions controlled by enzymes. The main food molecule used in cells is glucose. G
during respiration is not used directly by the cell
G respiration glucose energy Energy stored by forming ATP
An enzyme joins an inorganic phosphate group (Pi) onto an A D P molecule to form an A T P molecule. A T P: contains a high level of chemical energy + Pi + energy Adenosine Pi Pi A D P Enzyme Adenosine Pi Pi Pi
You have to move muscles and need that stored energy. How is it released…? Enzyme + + Adenosine Pi Pi Pi Energy A D P Released for all cell activities Adenosine Pi Pi Pi A T P
This forms a continuous cycle of ATP-ADP-ATP… Storing and releasing energy when needed G glucose respiration A D P + Pi A T P Used in cell activities e.g muscle contraction
Anaero bic respiration is the breakdown of glucose in cells without oxygen. This could happen in animal cells if not enough oxygen is getting to muscles during heavy exercise. Cells would have to change from: aer obic respiration to anaer obic respiration
As with aerobic respiration this happens in 2 stages: 1. Glycolysis (exactly the same as aerobic respiration) 2. Breakdown of pyruvic acid (but without oxygen) Pyruvic acid NO oxygen Enzyme controlled reactions Lactic Acid
Overall A T P production during anaer obic respiration in animals : G Glucose Pyruvic acid 2 A D P + 2 Pi 2 A T P (No oxygen) Lactic Acid No A T P molecules formed! Total = 2 ATP molecules/ glucose
Describe an experiment used to investigate anaerobic respiration in yeast.
Compare aerobic respiration with anaerobic respiration in both animals and plants. Use: glycolysis, ATP yields, and overall products.
Just as in animals, glucose is only partially broken down in the absence of oxygen. Anaerobic conditions can occur when root cells of plants grow in muddy soil or there has been floods. Yeast cells are deprived of oxygen when used in brewing and bread-making.
As with anaerobic respiration in animals this happens in 2 stages: 1. Glycolysis (exactly the same as aerobic respiration) 2. Breakdown of pyruvic acid (but without oxygen) Pyruvic acid NO oxygen Enzyme controlled reactions Ethanol + Carbon dioxide (lost- reaction irreversible)
Overall A T P production during anaer obic respiration in plants and yeasts : Total = 2 ATP molecules/ glucose G Glucose Pyruvic acid 2 A D P + 2 Pi 2 A T P (No oxygen) Ethanol + CO2 No A T P molecules formed!
State which type of respiration takes place in yeast
under different conditions.
Name the food source in yeast and the products of
respiration under these different conditions.
Explain why yeast is used in bread making.
Explain why yeast is used in beer making.
Explain why germinated barley is used in beer
Explain why there is a limit to the concentration of
alcohol produced during anaerobic respiration.
Yeast - Unicellular fungus - Cell is dividing - Ferment sugars (used in brewing and bread making) These circles are formed when the cell divides. The new cell ‘ buds off’ and leaves a scar.
During ae robic respiration, yeast uses up glucose and oxygen and produces carbon dioxide and water. As oxygen is used up the yeast changes over to anae robic respiration and converts glucose to carbon dioxide and ethanol (alcohol).