B3b

Question 1

What are some examples of proteins?

Answer 1

Collagen, insulin and haemoglobin

Question 2

What are proteins made of?

Answer 2

Long chains of amino acids.

Question 3

What are some functions of proteins?

Answer 3

Structural Proteins - are physically strong. E.g. collagen is a structural protein that strengthens connective tissues.
Hormones - used to carry messages around the body. E.g. insulin is a hormone released into the blood by the pancreas to regulate the blood sugar level.
Carrier Molecules - used to transport smaller molecules. E.g. haemoglobin binds to oxygen molecules and transports them around the body.
Enzymes - control cell reactions. As a biological catalyst, they reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body. Every different biological reaction has its own enzyme designed especially for it.

Question 4

What does each protein have and what does it result in?

Answer 4

Its own number and sequence of amino acids, which results in differently shaped molecules, which have different functions.

Question 5

What are enzymes?

Answer 5

Proteins.
Work best at a particular temperature - each enzyme has its own optimum temperature when the reaction goes fastest.
Enzymes act as biological catalysts - a catalyst is a substance that speeds up a reaction, without being changed or used up in the reaction itself.

Question 6

What do the active sites in enzymes do?

Answer 6

An active site is the part where it joins on to the substrate to catalyse the reaction. The substrate is the chemical changed in the reaction and chemical reactions usually involve things being split apart or joined together.

Question 7

What are some examples of chemical reactions in living cells that are catalysed in enzymes?

Answer 7

Respiration, photosynthesis and protein synthesis.

Question 8

Why do enzymes have a high specificity for their substrate?

Answer 8

Enzymes are really picky - they usually only work with one substrate.

Question 9

What is the lock and key mechanism?

Answer 9

For enzymes to work, the substrate has to fit into the active site. If the substrate’s shape doesn’t match the active site’s shape, then the reaction won’t be catalysed . This is called the lock and key mechanism, because the substrate fits into the enzyme just like a key into a lock.

Question 10

How will changing temperature and pH, away from the optimum, change the rate of reaction of an enzyme catalysed reaction?

Answer 10

If it gets too hot, some of the bonds holding the enzyme together will break. This makes the enzyme lose its shape - it’s active site doesn’t fit the shape of the substrate any more. This means it can’t catalyse the reaction and the reaction stops - the enzyme can’t function. The enzyme is now said to be denatured. Its change in shape is irreversible.
Low temperatures lower the collision rate so their is a slower reaction.
If the pH is too high or low, it interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.

Question 11

Where is the optimum temperature and pH?

Answer 11

Each enzyme has its own optimum temperature when the reaction goes fastest. This is the temperature just before it gets too hot and starts to denature.
All enzymes have an optimum pH that they work best at. It’s often neutral pH 7, but not always.

Question 12

How do you calculate the Q10 value for a reaction?

Answer 12

Q10 = rate at higher temperature/rate at lower temperature

It is for when the temperature is raised by 10 degrees C. e.g. using the rate between 30 and 40 degrees C.

Question 13

How do you interpret the Q10 value?

Answer 13

The q10 value for a reaction shows how much the rate changes when the temperature is raised by 10 degrees C.
A Q10 value of 2 means that the rate doubles when the temperature is raised by 10 degrees C. A Q10 value of 3 would mean that the rate trebles.

Question 14

What will different cells and different organisms produce?

Answer 14

Different proteins.

Question 15

What are gene mutations?

Answer 15

Changes to genes.

Question 16

What may gene mutations lead to?

Answer 16

The production of different proteins.

Question 17

When do mutations occur?

Answer 17

Mutations can happen spontaneously - when a chromosome doesn’t quite copy itself. However, the chance of a mutation is increased if you’re exposed to:
Ionising radiation - including x-rays and ultraviolet lights, together with radiation from radioactive substances. For each of these examples, the greater the does of radiation, the greater the chance of mutation.
Certain chemicals which are known to cause mutations (mutagens). If the mutations produce cancer then the chemicals are often called carcinogens. Cigarette smoke contains chemical mutagens.

Question 18

How can mutations be harmful?

Answer 18

Producing the wrong protein or no protein at all can be harmful. If a mutation occurs in reproductive cells, then the offspring might develop abnormally or die at an early stage of their development.

Question 19

Sometimes mutations can be beneficial or have no effect, how?

Answer 19

Occasionally a different protein may be produced after a mutation that actually benefits the organism - the new protein is an improvement on the one it was supposed to be. This gives the organism a survival advantage over the rest of the population which passes its mutated DNA to its offspring, so it comes more common. Some mutations aren’t harmful or helpful, they don’t change the protein being coded for, so they have no effect on the organism.

Question 20

What do genes switched on determine?

Answer 20

The functions of a cell

Question 21

How do changes to genes, alter or prevent, the production of the protein which is normally made?

Answer 21

If a mutation occurs within a gene, it could stop the production of the protein the gene normally codes for - or it might mean a different protein is produced instead.