Lecture 10 --energy nutrition: metabolism of CHO & Fats

Question 1

Carbohydrates (‘describe the molecules from which we derive energy’)

Answer 1

Formula: CH2O

Only MONOSACCHARIDES are absorbed

Question 2

Proteins (‘describe the molecules from which we derive energy’)

Answer 2

Chains of amino acids joined by peptide bonds

Question 3

Fats (‘describe the molecules from which we derive energy’)

Answer 3

Formula: CH3–(CH2)n–COOH

We mostly consume Triglycerides

Can be SATURATED or UNSATURATED

Question 4

How much energy is in carbohydrates?

Answer 4

4 kcal/g

Question 5

What are SATURATED FATS?

Answer 5

Have only linear, single bonds

Question 6

What are UNSATURATED FATS?

Answer 6

have CIS DOUBLE BONDS (which give them ‘kinky chains’)

Question 7

What form of Fatty Acid is easiest to metabolise? Why?

Answer 7

Saturated FA are easier to metabolise

Unsaturated FA have CIS DOUBLE BONDS which gives them ‘kinky chains’ that are hard to metabolise

Question 8

What is the purpose of enzymes in Unsaturated FA metabolism?

Answer 8

To convert the CIS double bonds to TRANS double bonds

Question 9

What are the enzymes involved in unsaturated FA metabolism?

Answer 9

(1) Enoyl CoA isomerase

(2) 2,4 Dienoyl CoA reductase

Question 10

(‘Outline hepatic processing’) What are the 3 processes involved in hepatic processing?

Answer 10

(1) Glycogenesis
(2) Glycogenolysis
(3) Gluconeogenesis

Question 11

What is GLYCOGENESIS

Answer 11

Conversion of glucose –> glycogen for storage

Question 12

What is GLYCOGENOLYSIS

Answer 12

Breakdown of glycogen to glucose-6-phosphate

Question 13

What is GLUCONEOGENESIS

Answer 13

Synthesis of glucose from Fats and Amino Acids (Alanine & Lactate)

Question 14

What are the main Amino Acids used in gluconeogenesis?

Answer 14

Alanine

Lactate

Question 15

What % of the liver = glycogen?

Answer 15

7-10% of weight of liver = glycogen

Question 16

What are the processes:

Glycogen –PROCESS?–> glucose-1-P
Glucose-1P–PROCESS?–>Glycogen?
Pyruvate–PROCESS?—>Glucose-6-P?

Answer 16

(1) Glycogenolysis
(2) Glycogenesis
(3) Gluconeogenesis

Question 17

What enzyme enables glycogen to be converted back to glucose in the liver?

Answer 17

Glucose-6-Phosphatase

Question 18

How are fats metabolised?

Answer 18

(1) Emulsified with bile salts
(2) Incorporated into BILE SALT MICELLES
(3) Packaged into CHYLOMICRONS in enteric cells
(4) LIPOLYSIS: lyses lipids, cleaving the FAs from the glycerol backbone

Question 19

Outline the process of GLYCOLYSIS

Answer 19

> ANAEROBIC process

In a nutshell: GLUCOSE LYSIS (6 carbons),

> Consumes: -1 glucose, -2 ATP
Produces: +4 ATP, +2 NADH, +2 pyruvate
NET +2ATP, +2NADH, +2 pyruvate (3 carbons each)

Question 20

Outline the process of the CITRIC ACID CYCLE

Answer 20

> AEROBIC PROCESS

Pyruvate (3C) –> Acetyl CoA (2C) =>Citrate ==FED INTO==> CITRIC ACID CYCLE

Produces: 10 NADH (per glucose)

The 2 carbons from Acetyl CoA are released throughout the CAC and used to drive the oxidation of NADH & FADH

Question 21

What is the use of the 2 carbons from acetyl CoA in the citric Acid Cycle?

Answer 21

They are used released and used to drive the oxidation of NADH & FADH

Question 22

Outline the process of OXIDATIVE PHOSPHORYLATION (electron transport chain)

Answer 22

> AEROBIC PROCESS

(1) NADH–reduced–> NAD+ & H+
(2) Pump H+ across the mitochondrial membrane –> inter membrane space
(3) = High [proton] = protons travel down [gradient] across inner mitochondrial membrane through ATP SYNTHASE
(4) The energy derived from protons travelling down their [gradient] is used to phosphorylate ADP–>ATP

Question 23

What role do NADH & FADH produced in glycolysis & the citric acid cycle play in the production of ATP?

Answer 23

In the electron transport chain (ETC) NADH is REDUCED and used to drive oxidative phosphorylation of ADP–> ATP

Question 24

How many ATP are produced per NADH in the ETC?

Answer 24

3 ATP

Question 25

How many NADH are derived from EACH glucose molecule and enter the electron transport chain?

Answer 25

1 glucose =

(1) GLYCOLYSIS: +2 NADH
(2) CITRIC ACID CYCLE: +10 NADH

Net: + 12 NADH

Question 26

What is the overall reaction with each step of glucose metabolism? (briefly summarise each step)

Answer 26

(1) Glycolysis:
Glucose–lysis–> 2 pyruvate + 2 ATP + 2NADH (net)

(2) The Citric Acid Cycle:
Pyruvate –> Acetyl CoA –> Citrate–> +10 NADH

(3) The electron transport chain:
12 NADH –>reduced and used to drive phosphorylation of ADP–>ATP –> x3ATP per NADH = net 36 ATP

NET OF STEPS 1–>3
38 ATP

Question 27

What is LIPOLYSIS

Answer 27

Cleave free fatty acids from the glycerol backbone

Enzymes = LIPASES

Question 28

What is B-oxidation?

Answer 28

Break down of free fatty acids (FFAs) to ACETYL CoA

For each ‘round’ of B-oxidation 2 carbons are cleaved from the FA chain (2 carbons => acetyl CoA)

Question 29

Excess Acetyl CoA from _______ is converted to _______

Answer 29

excess acetyl CoA from B-OXIDATION is converted to KETONE BODIES

Question 30

Describe the roles of energy carrying intermediates in energy metabolism

Answer 30

> Chemical energy is used to drive reactions, it needs to be stored so it can be drawn upon later.
Chemical energy is stored in HIGH ENERGY INTERMEDIATES (FADH & NAD)
FADH/NADH –OXIDISED–> FADH2 & NADH
These high energy intermediates can EASILY BE REDUCED and .: donate energy later on