Human Metabolism: Outcome 2

Front 1

What are metabolic pathways?

Back 1

A series of interconnected biochemical reactions which convert a substrate into a product through a step wise process each catalysed by an enzyme

Front 2

Using a diagram, describe anabolic and catabolic pathways, explaining clearly how they are linked.

Back 2

Anabolic synthesizes large complex molecules from small simple ones. Requires ATP.

Catabolic breakdown later complex molecules into smaller simpler molecules. Releases ATP.

Front 3

Define an amphibolic pathway and give an example

Back 3

A pathway which can either be catabolic or anabolic depending on either the availability of energy or indeed the need for energy.

Ex. TCA cycle

Front 4

What is the function of key junction points?

Back 4

To allow metabolites to enter into alternative pathways when required.

Front 5

Give 3 key junctions, their 3 sources of molecules and their 3 fates.

Back 5

Glucose-6-phosphate - glucose in glycolysis, pyruvate, glycogen - pyruvate, glycogen, ribose-5-phosphate

Pyruvate - glucose-6-phosphate, alanine, lactate - lactate, transamination to alanine, carboxylation to oxaloacetate

Acetyl CoA - glycolysis, beta oxidation of fatty acids, ketogenic amino acids - CO2 by TCA cycle, fatty acid synthesis, ketogenesis

Front 6

How can metabolic pathways be regulated by the presence of compartments?

Back 6

Because the fates of certain molecules depends on where they are located within the cell e.g. if they are in the cystol or the mitochondria.

Front 7

Give an example of regulation by compartments.

Back 7

Fatty acids are transported into the mitochondria for oxidation only when energy is required.

Fatty acids remaining in the cystol are esterified or exposed.

Front 8

3 advantages of a multienzyme complex.

Back 8

Concentration of reactions in one location

Protection of intermediates

Increased catalytic efficiency

Prevention of unwanted side effects

Front 9

Give an example of reciprocal regulation of the glycolytic pathway

Back 9

Glycolysis - glucose to pyruvate

Gluconeogenesis - pyruvate to glucose

Front 10

Name the components of ATP

Back 10

Adenine organic base, ribose sugar, three inorganic phosphates.

Front 11

Participation of ADP in muscle cells by the enzyme creatine kinase can provide a useful boost to the supply of ATP.

Describe in words this chemical equation and state why it has so useful.

What is this process an example of?

Back 11

Phosphocreatine + ADP -> creatine + ATP

Useful at times when demand is high, such as during intense exercise

Substrate level phosphorylation

Front 12

What chemical process does the enzyme adenylate kinase catalyse?

Back 12

Catalyses the reversible transfer of phosphate group from one ADP molecule to another to generate ATP and form AMP

Front 13

Epinephrine (adrenaline) cannot pass through the phospholipid bilayer of the cell membrane and therefore must exert it's effect through a signal transition cascade.

Describe the role of G proteins in this process

Back 13

Epinephrine binds to a GPCR (G protein couples receptor) located in the plasma membrane.

GTP replaced GDP on the G protein- it becomes active

The G protein activates the effector- adenylyl cyclase

Front 14

Name second messenger produced in G protein process

Back 14

cAMP

Front 15

The second messenger diffused through the cytoplasm and activates other enzymes called kinases, the first being protein kinase A.

What is the function PDF kinases?

Back 15

Kinases are class of enzymes that phosphorylate other proteins and so alter their activity.

Front 16

What is the end effect of epinephrine in the cells of skeletal muscle?

Back 16

The activation of glycogen phosphorylase enzyme which breaks down glycogen into glucose ( provides energy for the fight or flight response)

Front 17

In a "fed state", insulin is released by the beta cells in the Islets of Langerhans.

Describe two effect of this increased insulin on skeletal muscle tissue.

Back 17

Increase in GLUT4 transported in the plasma membrane.

Increased glucose uptake into cells

Front 18

What is the effect of insulin on liver cells?

Which enzyme is involved in this process?

Back 18

Conversion of glucose into glucose-6-phosphate and then into glycogen

Glycogen synthase

Front 19

Using a diagram, describe the homeostatic process involved when glucose levels increase and also fall

Back 19

G

Front 20

What is the reaction catalysed by glycogen phosphorylase?

How is the enzyme regulated?

Back 20

Glycogen phosphorylase activity is controlled by reversible phosphorylation and dephosphorylation

Glycogen phosphorylase removes glucose units from glycogen

Front 21

Activity of some enzymes is altered as a result of binding of a molecule - an allosteric regulator or effector - to the enzyme at a site other than active site

Using a diagram, explain how downstream metabolites in a pathway can alter enzyme activity.

Back 21

A -|-> B --> C --> D --> E -->F

^ |

|_______________________|

F is a negative allosteric effector of the enzyme covering A to B

Molecule F binds to the regulator site

The affinity of the active site for molecule A is diminished.

Front 22

Name a positive modulator of the glycolytic enzyme phosphofructokinase.

Back 22

ADP

Front 23

Why is the pyruvate dehydrogenase complex a major regulatory point for metabolism in cellular respiration?

Back 23

It is the lining reaction between glycolysis and the citric acid cycle

Front 24

Where is the pyruvate dehydrogenase complex located?

Back 24

The mitochondrial matrix

Front 25

Reducing power in the form of either NADH or FADH2, is generated at which of the following metabolic stages?

Back 25

Glycolysis

The pyruvate dehydrogenase complex

The citric acid cycle

Front 26

Which membrane transporter protein is responsible for translocating pyruvate across inner mitochondrial membrane?

Back 26

Pyruvate translocase

Front 27

Name the three enzymes that comprise the large multi-enzyme complex PDC.

Back 27

E1 - pyruvate dehydrogenase

E2 - dihydrolipoyl transacetylase

E3 - dihydrolipoyl dehydrogenase

Front 28

Which overall reaction does the PDC catalyse?

Back 28

Pyruvate to Acetyl coA and carbon dioxide

Front 29

The pyruvate to Acetyl CoA and CO2 can be broken down into three chemical transformations, requiring all three enzymes in the complex. Name them.

Back 29

Decarboxylation

Oxidation of carbonyl group to carboxyl group

Activation by linkage to CoA through a thioester bond

Front 30

The PDC channels substrates from over enzyme to another. how is the 2-carbon metabolic substrate kept attached to the substrate?

Back 30

By the prosthetic groups

Front 31

What two mechanisms control the PDC?

Back 31

Product injunction by NADH and Acetyl CoA

Covalent modification by phosphorylation of the E1 subunit

Front 32

Using a diagram, highlight the possible source and fate of the following molecules: Glucose-6-phosphate, pyruvate and Acetyl CoA.

Back 32

Front 33

The production of ATP in the cristae of the mitochondria using the process of chemiosmosis is called oxidative phosphorylation because of the involvement of oxygen in the process. Briefly describe this process.

Back 33

NADH and FADH2 carry H and higher energy electrons to the ETC located in the cristae of the mitochondria.

H+ are pumped into the intermembrane space - creating a H+ gradient

High energy electrons are passed along protein carried complex

H+ ions pass through ATP synthase generations ATP from ADP+Pi

High energy electrons, H+ ions and oxygen combine to form water

Front 34

Give two examples of substrate level phosphorylation seen glycolysis.

Back 34

Conversion of 1,3-bisphosphateglycerate to 3-phosphoglycerate

Conversion of phosphoenolpyruvate to pyruvate

Front 35

Give two examples of substrate level phosphorylation seen glycolysis.

Back 35

Conversion of 1,3-bisphosphateglycerate to 3-phosphoglycerate

Conversion of phosphoenolpyruvate to pyruvate