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B1 > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What are the major metabolic roles of carbohydrates and their general chemical structure? Which carbohydrate is most common in a healthy human diet?

A

Energy source

[C(H20)]n

Classified according to number of monomers: monosaccharides, disaccharides, oligosaccharides and polysaccharides

Polysaccharides most common - complex carbohydrates that need to be broken down to be absorbed

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2
Q

Sucrose =

Lactose =

Maltose =

A

Glucose + Fructose = Sucrose

Galactose + Glucose= Lactose

Glucose + Glucose = Maltose

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3
Q

What are the important monosaccharides and how many C atoms do they contain?

A

Glucose, fructose and galactose - hexoses (6C)

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4
Q

What are 5 roles of lipids?

A

Fuels for cells (fatty acids/ketone bodies)
Energy storage (triglycerides)
Transport between tissues (cholesterol esters, triglycerides)
Structural components of cell membranes (phospholipids/cholesterol)
Chemical messengers (diglycerides)

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5
Q

What’s the structure of a steroid and why is cholesterol important?

A

4 ring like structures

Oestrogen, progesterone and testosterone are synthesised from cholesterol

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6
Q

What’re the major metabolic roles of amino acids?

A 
Building blocks of proteins:
Regulation - enzymes
Transport - Hb/plasma proteins
Protection - antibodies
Contraction - actin and myosin
Structure - keratin
Energy - proteins can be broken down when needed
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7
Q

Explain the roles of biological membranes and membrane transporter proteins in the regulation of metabolism

A

Membrane transporter proteins allow control of substances entering a cell - glucose cannot readily pass through membrane so relies on GLUT1-GLUT5 transmembrane proteins

GLUT1 - highest affinity so in brain and RBCSs
GLUT2 in pancreatic B-cells after food
GLUT4 - fat storage
SGLT1 & SGLT2 are co-transporters in intestine and kidney

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8
Q 
What tissues are these substrates essential for:
Glucose
Fatty acids
Ketones
Amino acids
A

Glucose - brain and RBCs

Fatty acids - all tissues but neurones

Ketones - synthesised in liver and used in other tissues, back up energy for brain

Amino acids - glutamine used in fast dividing cells (cancer, enterocytes)

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9
Q

Describe anaerobic ATP formation through glycolysis

A

Reactions in cytosol converting 1 glucose molecule into 4x ATP and 2x Pyruvates (3C molecule) and 2 NADH

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10
Q

Outline fatty acid oxidation

A

Fatty acids metabolised by B-oxidation where 2C atoms are removed from each end of the fatty acid chain to form acetyl-CoA, which enters the Krebs cycle

Reaction keeps happening, generating more acetyl Co-A molecules and shortening the fatty acid chain

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11
Q

Outline amino acid transamination, deamination and urea synthesis

A

Transamination: NH2 group transferred from amino acid to keto acid to make a different amino acid

Deamination: amino acid loses NH2 group to become a keto acid, NAD+ converted to NADH to generate ATP

Urea synthesis: in the liver, NH4 reacts with CO2 to form urea and H20

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12
Q

Outline the TCA cycle and its roles

A

Energy production: converts oxoloacetate (4C) into citrate (6C) generating 1 ATP molecule per cycle

Products:
2 CO2, 1 ATP, 1 FADH, 3 NADH + H+ (electron carriers)

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13
Q

Describe the electron transport chain and oxidative phosphorylation

A

Series of redox reactions on inner mitochondrial membrane - proton gradient to drive synthesis of ATP by chemiosmosis

NADH and FADH2 > NAD+ and FAD
e- move from higher energy level to lower, releasing energy which is used to pump further H+ ions out to establish electrochemical gradient

e- transferred to O2 to form H20

1 ATP synthesised from 3H+ flowing through ATP synthase (ADP + Pi -> ATP)

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14
Q

How are monosaccharides classified?

A

By how many C atoms they contain: triode, tetrose, pentose, hexose
Londer chain monosaccharides (pentoses, hexoses) form cyclic molecules

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15
Q

How are disaccharides formed?

A

By a reaction between 2 monosaccharides, producing water and a glycosidic bond

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16
Q

What are the 4 important poly/oligosaccharides?

A

Glycogen (branched polymer of glucose)
Starch (from diet in plant sources)
Dextrin (breakdown product of starch and glycogen)
Cellulose (in diet from plant sources but not digestible)

17
Q

Outline fatty acids

A

Hydrocarbon chains of various lengths: long chain>12C and very long chain if >22C

Can be saturated or unsaturated (double bond)

18
Q

What’s the molecular structure of triglycerides?

A

Glycerol + 3 fatty acid chains

19
Q

What’s the difference between cis and trans fatty acids?

A

Type of stereoisomerism around the double bond (in unsaturated fatty acids only)
Cis fatty acids (have a kink by the bond) pack less closely together = cause membranes to be more fluid

20
Q

What are modified lipids? What’s an important feature of them?

A

Phosphate group + fatty acid chain bound via glycerol or sphingosine
Amphiphatic = polar and non-polar ends for membrane structure

21
Q

How are ketone bodies formed? What’s their breakdown product?

A

Small 4C fatty acids formed by oxidation of fatty acids in the liver (during fasting)
Acetone is exhaled

22
Q

Why are ketone bodies dangerous in diabetes?

A

Excessive formation of ketone bodies in the liver cause blood levels to dangerously rise
Brain will use ketone bodies as an energy source
= diabetic ketoacidosis

23
Q

What type of metabolic processes use and produce ATP?

A

Anabolic uses ATP (energy stored in high-energy bond is released)
Catabolic processes produce ATP (energy from oxidation stored in bond)

24
Q

Outline the relevance of glucose and fatty acid interactions?

A

Fatty acids can be formed from glucose
Excess glucose stored as lipid/triglycerides in white adipose tissue, but this can only be metabolised as fatty acid

Spillover of triglyceride storage into ectopic tissues has pathological consequences (skeletal, cardiac muscle, liver)

25
Q

What are the 5 different passive glucose transporters and the 2 using facilitated transport?

A

GLUT1 - GLUT5 passive
GLUT5 specialised to transport Fructose in the intestine

SGLT1 - SGLT2 active (in kidney and co-transport Na+)

26
Q

What is glucose phosphorylated by once inside the cell?

A

Hexokinase

Tissues with low affinity GLUTs express low affinity Hexokinases (liver, pancreatic B-cells)

27
Q

What’s the Warburg effect?

A

Cancer cells use glucose anaerobically even when O2 present = use glucose at a very high rate

28
Q

How can Acetyl CoA be formed?

A

From pyruvate
From lipids (fatty acids undero B-oxidation to acetyl coA)
From amino acids

29
Q

What’re the effects of proton uncoupling?

A

H+ influx can be uncoupled from ATP synthase by UCP1

Dissipation of the proton gradient releases heat = non-shivering thermogenesis in brown adipose tissue

B1 (19 decks)

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