Respiration and Metabolism

Question 1

What is respiration?

Answer 1

Respiration is the process of transferring energy from glucose, which goes on in every cell.

All living things respire. It involves many reactions which are important because respiration transfers the energy that the cell needs to do most things.

Question 2

Is respiration exothermic or endothermic? Why?

Answer 2

Exothermic - it transfers energy to the environment.

Question 3

Give three examples of how organisms use the energy transferred by respiration?

Answer 3

1. To build up larger molecules from smaller ones (like proteins from amino acids)
2. In animals, it’s used to allow the muscles to contract (so they can move about).
3. In mammals and birds, the energy is used to keep their body temperature steady in colder surroundings. (Mammals and birds keep their bodies constantly warm).

Question 4

Give examples of reactions where large molecules are made from smaller ones?

Answer 4

1. Lots of small glucose molecules are joined together in reactions to form starch (storage molecule in plant cells), glycogen (storage molecule in animal cells) and cellulose.
2. Lipid molecules are each made from one molecule of glycerol and three fatty acids.
3. Glucose is combined with nitrate ions to make amino acids, which are then made into proteins.

Question 5

Give examples of reactions where larger molecules are broken down into small ones?

Answer 5

1. Glucose is broken down in respiration. Respiration transfers energy to power all the reactions in the body that make molecules.
2. Excess protein is broken down in a reaction to produce urea. Urea is then excreted in urine.

Question 6

What is metabolism?

Answer 6

The sum of all of the reactions that happen in a cell or the body.