respiration 1 Y3 bio 2026

Define cellular respiration

Cellular respiration involves a series of catabolic reactions in living cells that break down nutrients to release energy

Uses of energy in the body (5 categories)

1. Anabolic reactions like synthesis of: —new protoplasm for growth and repair of cell

   —proteins from amino acids —Lipids for incorporation into cell membranes

2. Active transport, movement of substances across concentration gradient across cell membrane like absorption of food substances into small intestine

3. Muscular contractions like breathing, heartbeat, shivering

4. Cell division

5. Generation and transmission of electrical nerve impulses

Define anabolic and catabolic reactions

Anabolic reactions synthesize complex molecule from simpler molecules, requiring energy

Catabolic reactions break down complex molecules into simpler molecules, releasing energy

Chemical equation for aerobic respiration and define aerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O, Large amount of energy released

Breakdown of glucose using oxygen to release a large amount of energy, taking place in cytoplasm AND mitochondria Carbon dioxide and water are released as waste products

How test for carbon dioxide SEMI-QUANTITATIVELY

Bicarbonate(hydrogen carbonate) indicator can be used to test for carbon dioxide, semi-quantitatively, turning from yellow to red to purple with increasing pH/CO2 conc

Structure of mitochondrion and why it’s like this

mitochondrionhas a double membrane, with an outer smooth mitochondrial membrane and an inner mitochondrial membrane that is highly in- folded to form cristae, increasing surface area to contain more enzymes involved in ATP synthesis on the membrane

Chemical of anaerobic respiration and define anaerobic respiration

C6H12O6 → 2C3H6O3, small amount of energy released

Breakdown of glucose WITHOUT OXYGEN to release A SMALL AMOUNT OF ENERGY (2 ATP molecules), incomplete oxidation of glucose, takes place ONLY IN CYTOPLASM of a cell

Why do humans carry out anaerobic respiration

During high intensity physical exercise, muscle cells require a lot of energy in a short amount of time. Even with increased heart rate and breathing, INSUFFICIENT OXYGEN is transported to the muscles, rate of aerobic respiration IS NOT ABLE FO KEEP UP WITH THE ENERGY REQUIREMENTS of the muscle cells to contract at a fast rate. Hence, muscle cells also carry out anaerobic respiration to release extra energy for A LIMITED TIME.

Effect of lactic acid

Lactic acid produced during anaerobic respiration builds up in skeletal muscles, may lead to lactic acidosis(low pH in blood&tissue fluid), affecting enzyme activity

What happens to lactic acid acid after being produced?

Lactic acid is transported in blood plasma to liver. Some lactic acid is oxidised and then goes through the aerobic respiration pathway to form carbon dioxide and water. Most lactic acid is converted back to glucose and stored as glycogen

What’s oxygen debt and how long is it

After strenuous exercise, a person’s heart rate and breathing rate do not return to normal straight away as oxygen is required to remove the lactic acid and replenish the body’s oxygen reserves. Oxygen debt is the amount of oxygen required to remove lactic acid, lasting up to 38 hours

what are yeast

yeast are single cell fungi. They are facultative anaerobes i.e. they usually carry out aerobic respiration and only switch to anaerobic respiration when the environment has little or no oxygen

Chemical eqn of the anaerobic respiration in yeast. Give another name for this. what is this process used for? What is the long term outcome of this process

C6H12O6 → 2C2H5OH + CO2, small amount of energy released. This process is also known as ALCOHOL FERMENTATION IN YEAST, used by humans in making wine and bread. As yeast cannot metabolise ethanol, ethanol will build up to toxic levels if anaerobic respiration continues, eventually killing the yeast cells.