23 - Anabolism and regulation of metabolism

Question 1

Macromolecule

Answer 1

a very large molecule important to biophysical processes (e.g. protein or nucleic acid)

Question 2

Gluconeogenesis

Answer 2

generation of glucose from non-carbohydrate carbon substrates (esp. pyruvate and lactate)

Question 3

Amphibolic

Answer 3

biochemical pathway that involves both catabolism and anabolism

Question 4

Central metabolic pathways

Answer 4

pathways that generate the 12 precursor
metabolites. Includes the glycolytic pathways (i.e. Embden-Meyerhof, Entner-Doudoroff, pentose phosphate) and the TCA cycle

Question 5

Metabolic channeling

Answer 5

regulation of metabolic pathway activity by localising metabolites and enzymes to specific parts of a cell

Question 6

Allosteric

Answer 6

regulation of an enzyme by binding an effector molecule (allosteric effector) at a site other than the enzyme’s active site

Question 7

Feedback inhibition

Answer 7

enzyme inhibition by the end products of a pathway

Question 8

Level of organisation

Answer 8

Inorganic molecules + carbon source –> precursor metabolites –> Monomers or building blocks –> macromoleucles –> supramolecular systems –> organelles –> cells

Question 9

Macromolecule examples

Answer 9

Nucleic acids, proteins, polysaccharides, lipids

Question 10

Anabolism

Answer 10

Synthesis of complex molecules from simple ones.

Question 11

Turnover

Answer 11

non-growing cells degrade and replace (resynthesise) cellular constituents, requiring ATP

Question 12

first 3 principles governing biosynthesis

Answer 12

1. Macromolecules are synthesised from a limited number of simple structural units (monomers)
2. Many enzymes are used for both catabolism and anabolic processes
3. Some enzymes function in only one direction in amphibolic pathways

Question 13

last 3 principles governing biosynthesis

Answer 13

4. Anabolism consumes energy (endogonic)
5. Anabolic and catabolic reactions can be physically separated
6. Anabolic and catabolic reactions use different cofactors

Question 14

12 precursor metabolites

Answer 14

building blocks of all molecules in cells.

they make up the majority of the intermediates of glycolsis and TCA cycle

termed the central metabolic

Question 15

Macromolecules are synthesized from a limited number of simple structural units (monomers)

Answer 15

Saves genetic storage capacity, biosynthetic raw material, and energy

Question 16

Many enzymes are used for both catalytic and
anabolic processes

Answer 16

Most enzymes involved in the glycolysis pathway that produces ATP from glucose are also involved in the gluconeogenesis. Saves materials and energy.

Question 17

Some enzymes function in only one direction in amphibolic pathways

Answer 17

enables independent regulation of catabolism and anabolism by regulating the activity of pathway-specific enzymes

Question 18

Anabolic and catabolic reactions can be physically separated

Answer 18

Biosynthesis and catabolic functions are
located in separate organelles (e.g. mitochondria, lysosomes, ER).

Allows some pathways to operate simultaneously but independently

Question 19

Which cofactors do anabolic and catabolic pathways use

Answer 19

• Catabolism produces NADH (acts as an electron acceptor)
• Anabolism uses NADPH as an electron donor

Question 20

What does NADPH stand for

Answer 20

nicotinamide adenine dinucleotide phosphate

Question 21

name 3 Precursor metabolites

Answer 21

Glucose - 6, Ribose - 5, Pyruvate

Question 22

What is regulation of metabolism important for

Answer 22

1. Efficiency (conservation of energy and materials) e.g. no synthesis of enzymes for which no substrate is available or no synthesis of enzymes to produce end products already in abundance
2. Maintenance of metabolic balance in response to external changes

Question 23

3 major ways of metabolism regulation

Answer 23

1. Metabolic channelling
2. Regulation of gene expression
3. Posttranslational regulation of enzyme activity

Question 24

Metabolic channelling

Answer 24

• metabolic channeling is the physical separation of metabolic pathways in the cell
• compartmentalisation
• common way organisms separate and regulate pathways

-enables better control as key metabolites can be restricted or enhanced to affect the efficeint functioning of the pathway

Question 25

Advantages of metabolic channelling*

Answer 25

• Facilitates separate operation and regulation of similar pathways
• Enables enhanced pathway control by regulation of delivery of key metabolites to the various compartments.

Question 26

Regulation of gene expression

Answer 26

• Controls the synthesis of a particular enzyme
• Relatively slow, but conserves energy and the use of cellular materials
• Can occur at transcription or translation

Question 27

Posttranslational regulation of enzyme activity

Answer 27

• Following synthesis of the enzyme
• Involves direct stimulation or inhibition of the activity of critical enzymes

Question 28

Three important mechanisms of Posttranslational regulation of enzyme activity

Answer 28

1. Allosteric regulation
2. Covalent modification of enzymes
3. Feedback inhibition

Question 29

Allosteric regulation

Answer 29

Allosteric effector binds non-covalently at regulatory site changing the shape of the enzyme and alters activity of the catalytic site.

Can be:
- Positive effector increases enzyme activity
- Negative effector inhibits the enzyme

Question 30

Covalent modification of enzymes

Answer 30

• Covalent bonding of a chemical group to the
  enzyme affects its activity
• Allows more sophisticated control (Regulation of the enzymes that catalyse the covalent modification adds a second level of control)

Question 31

Feedback (end product) inhibition

Answer 31

• End products inhibit one or more critical enzymes in a pathway
• Each end product regulates its own branch of a branching pathway
• involves the “pacemaker” enzyme which
  catalyses the slowest rate-limiting reaction