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MBBCh 2- PHSL2004A > 6. Energy Metabolism > Flashcards

6. Energy Metabolism Flashcards

1
Q

Excess energy intake
results in OBESITY which
causes _______
derangements, e.g.
insulin resistance,
hyperlipidaemias &
metabolic diseases, for
example metabolic
syndrome and type II
diabetes mellitus

A

metabolic

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2
Q

Protein-energy malnutrition:

A

PEM results from severe deficiency of dietary intake of energy and protein.

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3
Q

Kwashiorkor:

A

Severe deficiency of dietary protein. Signs – thinning & hair loss, “pot bell”, oedema & generalised body swelling, flaky rash, skin depigmentation, loss of
muscle mass, stunting, diarrhoea.

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4
Q

Cachexia in cancer patients:

A

Complex metabolic syndrome associated with / characterised by loss of muscle with or without
loss of fat mass.

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5
Q

Anorexia:

A

An eating disorder characterised by abnormally low body weight, fear to gain body weight & strong desire to be thin resulting in food intake restriction. Also
called anorexia nervosa.

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6
Q

Physical Inactivity: (3)

A
  • excess energy converted to fat
  • fat deposited around the waist area & in and around key organs
  • obesity sets in leading to metabolic ill-healt
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7
Q

Exercise/Physical Activity: (3)

A
  • burns off excess energy
  • prevent development of obesity
  • improves health
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8
Q

a. energy necessary to support ________ reactions that maintain homeostasis
b. substances/substrates necessary for:
* building & _______ the body
* specific bodily functions

A

biochemical
maintaining

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9
Q

Macronutrients/energy sources: (3)

A
  • carbohydrates
  • fats
  • proteins (important only in starvation)
    NB: macronutrients are the fuel molecules are oxidised to generate AT
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10
Q

Micronutrients – essential: (2)

A
  • vitamins – fat soluble and water soluble
  • minerals
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11
Q

Energy is measured in units of HEAT
* 1 small calorie (cal) = ____ _____ required to increase the temperature of 1g of water by 1°C
* 1 joule = energy used when a force of 1N moves a mass through 1m
o 1 cal = 4.184 J 1 joule = 0.24 cal
Point to note:
In nutrition 1 LARGE calorie (Cal) = 1000 cal or 1 kcal = 4.2 kJ is used as a measure of _____

A

heat energy
energy

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12
Q

Bomb calorimetry used – gives GROSS (POTENTIAL) ENERGY value
Nutrient _____ Energy Values
* carbohydrates: 17 kJ/g
* fats: 38.9kJ/g
* proteins: 22.5 kJ/g
Actual ________ Energy Values
* carbohydrates: 17 kJ/g
* fats: 37 kJ/g
* proteins: 17kJ/g
* alcohol: 29 kJ/g

A

Gross
Physiological

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13
Q
  • A ______ diet – ENERGY must come from
    CARBOHYDRATES, PROTEINS & FATS
  • ENERGY should mostly be gained from FRUIT,
    VEGETABLES & UNPROCESSED CEREALS to ensure
    enough adequate supply of __________
  • Recommended adult energy intake = approx. 10 000
    kJ/day (or 2 400 Cal/day)
A

balanced
MICRONUTRIENTS

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14
Q

a. Direct calorimetry:
b. Indirect calorimetry:

A

measures heat generated to measure heat expenditure
relates energy expenditure to O2 consumption

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15
Q

The respiratory quotient (RQ) is the RATIO of the VOLUME OF CARBON DIOXIDE EVOLVED to that of OXYGEN CONSUMED by an organism,
tissue, or cell in a given time

Respiratory quotient =

A
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16
Q

For the aerobic oxidation of only glucose for energy:

For the oxidation of fatty acids for energy (palmitic acid as an example):

A
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17
Q

The respiratory quotient of a balanced diet is ~ 0.82

For the RQ = 0.82, energy expenditure = 20.2 kJ/l of O2 consumed

Therefore estimated energy _______ (kJ) = VO2 (l) × 20.2 kJ/l

Average energy expenditure is ~ 10 000kJ/day which equates to 500L of O2 per day
* basal metabolism – _______
* thermogenesis – ______
* external work/physical activity – 10-20%
NB: The energy expenditure of an individual depends mostly on exercise levels

A

expended
60-70%
10-20%

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18
Q

Basal metabolic rate (BMR): (2)

A

energy expenditure required to maintain body functions at complete rest
* Energy spent in maintenance of normal physiological functions
* measured following 12 hrs fasting & at comfortable temperatures

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19
Q

Factors Affecting BM: (5)

A
  • sex
  • age
  • body composition
  • health status
  • physiological status e.g. pregnant, lactatin
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20
Q

Tissue Energy Expenditure as Total of BMR:

A
  • sex
  • age
  • body composition
  • health status
  • physiological status e.g. pregnant, lactating
  • brain function ~20%
  • liver ~25%
  • muscle ~25%
  • heart ~9%
  • kidney ~8%
  • adipose ~4%
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21
Q

Thermogenesis:

A

: heat production in the body by physiological actions/metabolic processes

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22
Q

Types of Thermogenesis: (5)

A
  • thermic effect of food (specific dynamic action of food/heat increment)
  • cold and heat-induced thermogenesis
  • “substance-induced” thermogenesis
  • psychological thermogenesis
  • muscle shiverin
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23
Q

Point to note: (3)

A
  • Physical activity level (PAL) is the most variable part of total energy expenditure
  • PAL is expressed as a multiple of BMR
  • A PAL of 1.4 for minimal activity (sedentary) & up to 7 for climbing steps or playing sports12
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24
Q

The Concept of Free Energy
* Free energy (G) =

A

TOTAL ENERGY in a MOLECULE (mostly harnessed in bonds of the molecule)
* G changes when one molecule is converted to another

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25
Q

The change in free energy is ___.

A

ΔG

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26
Q

If ΔG is –Ve then,
If ΔG is +Ve then,

A
27
Q

Energy metabolism:

A

series of oxidation reactions that in total are EXERGONIC & release electrons that are used to drive ATP
synthesis

28
Q

BUT, not all the reactions in the pathway are exergonic: In metabolism many reactions are endergonic, for example:

A
29
Q

Reaction(s) and Notes:
Energy Change:

A
30
Q
  • The reaction is fully reversible; _____ _______ is used to ‘store’ ATP in skeletal and cardiac muscle and brain
  • The reaction is catalysed by creatine kinase (CK or CPK) & there are three different _______ of creatine kinase CK-MM in skeletal muscle, CK-MB in cardiac muscle and CK-BB in nervous tissue
  • Creatine is broken down to ________ and excreted in the urine
A

creatine phosphate
isoenzymes
creatinine

31
Q

What is the full diagram of energy metabolism?

A
32
Q

What is the Krebs cycle? (2)

A
33
Q

In addition to producing reduced co-enzymes, GTP and CO2, the Krebs cycle provides metabolic intermediates for the synthesis of: (3)

A
  • amino acids and glucose
  • fatty acids and haem
  • neurotransmitter
34
Q

Cycle Reactions and Enzymes: (3)

A
  • 8 enzymes catalysed reactions
  • Reacts 3 and 4 are OXIDATIVE DECARBOXYLATIONS
  • 2 acetyl group carbon are oxidised (‘blown off”) as CO2
35
Q

Cycle Products: (3)

A
  • four pairs of electrons are removed
    o 3 ×NADH & 1 × FADH2
  • one molecule of GTP produced – equivalent to 1 × ATP
  • net energy production per turn of the cycle = 12 ATP
36
Q

REGULATION OF THE KREBS CYCLE: (2)

A
  • Cycle Stimulators
  • Cycle Inhibitors
37
Q

Cycle Stimulators: (2)

A
  • Adenosine diphosphate (ADP)
  • Calcium ions (Ca2+)
38
Q

Cycle Inhibitors: (4)

A
  • Adenosine triphosphate (ATP)
  • Reduced NAD (NADH)
  • Guanine triphosphate (GTP)
  • Succinyl-CoA
39
Q

Points to Note:
* availability of NAD+ and FAD+ - these coenzymes are required for the cycle to occur
* increased ATP inhibits the enzymes of the cycle
* increased ADP stimulates the enzymes of the cycle
* ISOCITRATE DEHYDROGENASE, which cataylses conversion of citrate to __________, is the RATE LIMITING ENZYME

A

coenzymes
α-ketoglutarate

40
Q

REPLENISHING THE KREBS (TCA) CYCLE:

The Krebs/TCA cycle is replenished from a variety of substrates whose _______ enter it at different points

A

metabolites

41
Q

Points to Note:
* Oxaloacetate is produced from pyruvate derived from alanine by ALT during __________, or from glucose during glycolysis
* Oxaloacetate is produced from the amino acid, aspartate (by aspartate transaminase, AST) during protein catabolism
* _________ is produced from the amino acid, glutamate (by transaminases) during protein catabolism
* _____-_____ is produced from catabolism of amino acids and fatty acids (with odd numbers of carbon atoms)
* _________ is produced from catabolism of amino acids

A

gluconeogenesis
α-ketoglutarate
Succinyl-CoA
Fumarate

42
Q

METABOLISM OF α-KETOGLUTARATE & PYRUVATE: SIMILARITIES (4)

A

Points to note:
* The metabolism of pyruvate to acetyl-CoA and α-ketoglutarate is catalysed by dehydrogenases
* both enzymes catalyse oxidative decarboxylation reactions
* both enzymes require thiamine as a co-enzyme
* therefore both enzymes are affected by thiamine deficiency

43
Q

Thiamine deficiency –wet & dry _______

A

beriberi

44
Q

Riboflavin deficiency:

A

marasmic child and older boy with angular stomatitis, a
sign of riboflavin deficiency (Source: Dr Roger Whitehead

45
Q

ELECTRON TRANSPORT CHAIN & OXIDATIVE PHOSPHORYLATION: AN INTRODUCTORY OVERVIEW
The chain operates like a conveyor belt system and is dependent on the availability of O2. Oxygen is the terminal electron acceptor. Therefore any condition that impact the _____ _____ ______ and or the supply of oxygen impacts the ETC.

A

basal metabolic rate

46
Q

Conditions and Factors that May Affect the Electron Transport Chain:

Hyperthyroidism-

A
47
Q

Conditions and Factors that May Affect the Electron Transport Chain:

Hypothyroidism-

A
48
Q

Conditions and Factors that May Affect the Electron Transport Chain:

Emphysema-

A
49
Q

Conditions and Factors that May Affect the Electron Transport Chain:

Hypoxia-

A
50
Q

Outer membrane:

A

Small molecules can pass freely through the outer membrane. This outer portion includes proteins called porins, which form channels that allow proteins to cross. The outer membrane also hosts a number of enzymes with a wide variety of functions.

51
Q

Intermembrane space:

A

This is the area between the inner and outer membranes.

52
Q

Inner membrane:

A

This membrane holds proteins that have several roles. Because there are no porins in the inner membrane, it is impermeable to most molecules. Molecules can only cross the inner membrane in special membrane transporters. The inner membrane is where most
ATP is created.

53
Q

Cristae:

A

These are the folds of the inner membrane; increase the surface area of the membrane, therefore increasing the space available for chemical reactions

54
Q

Matrix:

A

This is the space within the inner membrane. Containing hundreds of enzymes, it is important in the production of ATP. Mitochondrial DNA is housed here.

55
Q

Points to note:
* the outer membrane is ________
* the inner membrane is impermeable to H+ but is permeable to O2, H2O& CO2
* the matrix contains the enzymes for the Krebs/TCA cycle and ____ _______
* enzymes of the electron transport chain are embedded within the inner membrane
* the inter-membrane space is important in _____ synthesis

A

permeable
FA oxidation
ATP

56
Q

ORGANISATION OF THE ELECTRON TRANSPORT CHAIN: AN OVERVIEW

A
57
Q

THE ELECTRON TRANSPORT CHAIN: OXIDATION OF NADH + H+

A
58
Q

THE ELECTRON TRANSPORT CHAIN: OXIDATION OF FADH2

A
59
Q

THE ELECTRON TRANSPORT CHAIN AND ATP SYNTHESIS/OXIDATIVE PHOSPHORYLATION:

A
60
Q

THE ELECTRON TRANSPORT CHAIN: PHYSIOLOGICAL UNCOUPLING
_______ adipose tissue (BAT), through the activity of uncoupling protein-1 (UCP-1), is responsible for non-shivering _______, a major component of facultative thermogenesis in human neonates. The UCP de-links (uncouples) substrate _______ to ATP production resulting instead in HEAT production

A

Brown
thermogenesis
oxidation

61
Q

What is chemical induced uncoupling in the electron transport chain?

A
62
Q

THE ELECTRON TRANSPORT CHAIN: INHIBITORS OF OXIDATIVE PHOSPHORYLATION

There are ETC “complex-specific” inhibitors. However _______ (lack of oxygen) inhibits the entire electron transport ch

A

hypoxia

63
Q

What are the inhibitors involved? (3)

A
  • Complex I inhibitors - amobarbitol (a barbiturate) and retonone
  • Complex IV inhibitors - carbon monoxide and cyanide
  • Hypoxia –inhibits the entire electron transport chai

MBBCh 2- PHSL2004A (19 decks)

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