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semester 1 > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What are carbohydrates

A

Highly oxidisable
Store potential energy
Major energy source

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2
Q

What are the monosaccharides

A

Glucose
Galactose
Fructose

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3
Q

What are disaccharides

A

Formed from monomers
Linked by glycosidic bonds

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4
Q

What are the three important Disaccharides

A

Maltose
Lactose
Sucrose

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5
Q

What is maltose

A

Breakdown product of starch

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6
Q

Between maltose, lactose, sucrose, which are reducing sugars

A

Maltose and lactose

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7
Q

What is the structure of Lactose

A

Galactose + glucose combined with glycosidic bond

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8
Q

What % of our diet carbs is sucrose

A

25%

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9
Q

What are polysaccharides

A

Polymers of medium-high molecular weight

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10
Q

What are the types of polysaccharides

A

Homopolysaccharides - Single monomer
Heteropolysaccharides - Two or more monomers

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11
Q

What are the two types of starch

A

Amylose - 20-25%, D-glucose residues
Amylopectin - 75-80%, Glycosidic bonds

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12
Q

What is glycogen and where is it found

A

Polymer of glucose
90% in:
Liver - replenishes glucose
Skeletal muscle - Produces ATP

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13
Q

What is used to digest carbs in the mouth

A

Salivary amylase hydrolyses starch

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14
Q

What digests starch in the stomach

A

No digestion

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15
Q

What digests starch in the duodenum

A

Pancreatic amylase

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16
Q

What are the final digestions in the Jejunum

A

Isomaltase - Hydrolyses a1-6 bonds
Glucoamylase- removes glc sequentially
Sucrase -> sucrose
Lactase ->Lactose

17
Q

How is glucose and galactose absorbed

A

Na+ pump maintains low Na+ content
Allows glucose to be moved into cells
Works when glucose moves against cg

18
Q

How is fructose absorbed

A

Bind to channel protein GLUT5
Moves down its cg

19
Q

Can Cellulose and Hemicellulose be digested

A

Nope

20
Q

What happens after glucose is absorbed

A

Glc diffuses through intestinal cells->blood->liver
Phosphorylated->G-6-P by hepatocytes
G-6-P can’t diffuse out of cell as GLUT transporters no longer recognise it.

21
Q

What are the enzymes for glucose

A

Glucokinase- liver
Hexokinase- skeletal muscle

22
Q

What is Vmax and Km

A

High number = efficient enzyme
Low Km = high affinity for substrate

23
Q

What is the Km andVmax for hexo/glucokinase

A

When blood glc normal - liver doesnt grab all glc
Blood glc high - Liver grabs Glc
High glckinase Vmax - phosphorylates Glc quickly
Hexokinase low Km - tissues grab Glc at low Glc
Hexokinase low Vmax - tissues easily satisfied

24
Q

What does hexokinase and glucokinase convert glucose to

A

Glucose 6 phosphate

25
Q

Where is glycogen converted

A

In liver: glycogen->G6P->Glc in blood
In skeletal muscle: Glycogen->G6P->lactate and ATP via glycolysis

26
Q

What are steps of synthesis of glycogen

A

Glycogenin binds Glc from UDP-glc to form 8 glc residues
Glycogen synthase extends the chain
Chains then broken by glycogen-branching enzyme
Re-attached via (a1-6) bonds

27
Q

What are the steps of glycogen degradation?

A

Glc monomers removed one by one
Glc removed by de-branching enzyme
Transferase activity of de-branching enzyme removes 3 Glc at a time
Attaches them to nearest nonreducing end via (a1→4bond)
Glucosidase removes final Glc by breaking(a1→6) linkage
Leaves unbranched chain

28
Q

What are the two glycolysis phases

A

Preparatory phase: 1 Glc passes through
2 molecules of G3P produced
Payoff phase: For each Glc 2ATP used in prep phase
4ATP gained in payoff phase

29
Q

What are the irreversable steps of glycolysis

A

Step 1. Phosphorylation of glucose
Glc -> G6P, catalysed by hexokinase
Uses 1ATP
Step 3. Phosphorylation of F6P -> F1,6-bisP catalysed phosphofructokinase-1
1ATP used
Step 10. Transfer of P from PEP to ADP
Catalysed - pyruvate kinase
2ATP produced

30
Q

What are the three substances pyruvate can be converted to

A

Lactate
Acteyl COA
Ethanol

31
Q

What is the Cori cycle

A

ATP produced via substrate level phosphorylation
Produced lactate
Lactate converted to Glc via gluconeogenesis

32
Q

What is the function of gluconeogenesis

A

4 reactions that sidestep the 3 irreversable glycolysis reactions

33
Q

What are the A and B gluconeogenesis reactions

A

Pyruvate->Oxaloacetate->malate->Oxaloacetate->PEP
Takes place in mitochondria

34
Q

What happens in reaction C

A

Fructose1,6-bisP->F6P
Fructose 1,6 bisphosphatase catalyses this

semester 1 (65 decks)

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