Unit 2 Topic 1

Question 1

What is metabolism?

Answer 1

metabolism is the term used to describe the enormous number of integrated and complex biochemical reactions that occur in any organism

Question 2

What is a catabolic reaction?

Answer 2

a catabolic reaction releases energy through the breakdown of a large molecule into smaller units

Question 3

Catabolic = ??

Answer 3

BREAKDOWN

Question 4

What is an anabolic reaction?

Answer 4

an anabolic reaction uses energy to build small molecules into larger ones, such as the synthesis of a protein from amino acids

Question 5

Anabolic = ??

Answer 5

BUILD UP

Question 6

What does the plasma membrane do?

Answer 6

the plasma membrane separates the cell from its immediate environment

Question 7

Give details of the plasma membrane

Answer 7

approximately 8nm wide
selectively permeable
it’s unique structure determines both its function and physical characteristics

Question 8

What are channel (pore) proteins?

Answer 8

these proteins allow specific molecules and ions to pass through the membrane, for example, a protein channel found in the plasma membrane allows chloride ions (Cl-) to cross the membrane

Question 9

What are carrier (pump) proteins?

Answer 9

carrier proteins bind to specific molecules or ions temporarily, enabling them to cross the membrane. this involves a change to the confirmation of the carrier protein, which may require energy provided by ATP

Question 10

What are enzymes in the membrane structure?

Answer 10

some proteins in the membrane catalyse a specific reaction. some receptor proteins have enzymatic activity, in which the cytoplasmic portion of the protein catalyses a reaction in response to binding by a ligand

Question 11

What are structural support proteins?

Answer 11

some membrane proteins are linked to the cytoskeleton and helo to maintain the shape of the cell

Question 12

What is a metabolite?

Answer 12

the intermediates and products of metabolic reactions that take place in organisms

Question 13

What is a metabolic pathway?

Answer 13

a metabolic pathway is a sequence of reactions that is controlled by enzymes that change one metabolite to another

Question 14

How many problems occur in metabolic pathways?

Answer 14

if the enzymes are not synthesised correctly, due to mutations in the genes that code for them. the next reaction is then unable to occur and the intermediate metabolite builds up in the system

Question 15

How are metabolic pathways controlled?

Answer 15

metabolic pathways are controlled by altering the presence and/or activity of key enzymes within the pathway. the regulation is brought about by signalling molecules from within the cell or from other cells

Question 16

Give properties of enzymes

Answer 16

enzymes are 3D biological catalysts comprising of globular protein molecules that are only produced in living organisms. they possess a small region called the active site where the substrate binds and the reaction occurs, and are specific in the reactions that they catalyse

Question 17

What is an active site?

Answer 17

the region of an enzyme molecule where the enzyme acts on the substrate

Question 18

What is an induced fit model?

Answer 18

a model of an enzyme-substrate reaction that causes a conformational change in the active site of the enzyme that allows the substrate to fit perfectly

Question 19

What does enzyme activity conform to?

Answer 19

the induced fit model

Question 20

What happens during the induced fit model?

Answer 20

the substrate molecule induces a slight change in the shape of the active site to allow the substrate molecule to fit perfectly

Question 21

What happens to the affinity of the products after the reaction is complete?

Answer 21

the products have a low affinity for the active site and are released: the active site resumes its normal shape and the enzyme is free to attach to more substrate molecules

Question 22

What affects the activity of enzymes?

Answer 22

factors such as pH and temperature

Question 23

What else (apart from temp and pH) affects the rate of an enzyme-catalysed reaction

Answer 23

the concentration of the enzyme
the concentration of the substrate

Question 24

Since enzymes are catalysts they _____

Answer 24

are required only in relatively small amounts
remain unchanged at the end of the reaction

Question 25

What is activation energy?

Answer 25

the minimum energy required by reactants to allow reaction to occur

Question 26

What happens to the activation energy of no catalyst is present?

Answer 26

the energy required to cause a chemical reaction is quite large and the speed of the reaction is extremely slow

Question 27

What does a catalyst do?

Answer 27

lower the activation energy

Question 28

How can regulation of enzyme activity be achieved?

Answer 28

•control of the number of enzyme molecules actually present in the cell- this is generally achieved at the level of gene expression
•compartmentalisation, for example the enzymes required for the citric acid cycle and the electron transfer chain are contained in the mitochondria
•change of enzyme shape- by far the most effective way of regulating an enzyme is to change its shape and therefore enzyme efficiency: a change in shape may either reduce or enhance enzyme activity, depending on the precise events taking place

Question 29

What are competitive inhibitors?

Answer 29

competitive inhibition of enzyme activity occurs when an inhibitor, resembling the structure of the substrate, binds to the active site of the enzyme and blocks the binding of the substrate

Question 30

Where do competitive inhibitors bind?

Answer 30

the active site

Question 31

How can competitive inhibition be reversed?

Answer 31

by increasing the concentration of the correct substrate in the reaction

Question 32

Where do non-competitive inhibitors bind?

Answer 32

away from the active site

Question 33

What do non-competitive inhibitors do?

Answer 33

change the shape of the active site

Question 34

Can non-competitive inhibition be reversed by increasing substrate concentration?

Answer 34

no

Question 35

What is feedback inhibition?

Answer 35

the regulation of enzyme activity where the first enzyme of a metabolic pathway is inhibited by the reversible binding of the final product of the pathway

Question 36

When does feedback inhibition occur?

Answer 36

feedback inhibition occurs when the end-product in the metabolic pathway reaches a critical condition