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Digestion and Renal Sciences > Digestion and absorption of carbohydrates and proteins > Flashcards

Digestion and absorption of carbohydrates and proteins Flashcards

1
Q

What are monosaccharides?

A

Dietary carbohydrates

Monomers

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2
Q

What are oligosaccharides?

A

Dietary carbohydrates

Short polymers

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3
Q

What are polysaccharides?

A

Dietary carbohydrates

Long polymers

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4
Q

Which dietary carbohydrates can be directly absorbed by the small intestine?

A

Monosaccharides

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5
Q

What are the two categories of polymers?

A

Digestible

Non digestible

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6
Q

What is dietary fibre?

A

Both soluble and insoluble forms of fibre

Found in fruits, vegetables and cereals

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7
Q

Describe insoluble fibre

A

Non water soluble
Not easily fermented
Cellulose and hemicellulose
Aids the digestive system and eases elimination

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8
Q

Describe soluble fibre

A

Water soluble
Pectins, gums, mucilage
Easily digested by bacteria in the colon

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9
Q

What forms 45-60% of dietary carbohydrate?

A

Starch

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10
Q

Describe starch

A

Starch is a carbohydrate primarily found in plants
Polysaccharide
Consists of amylose and amylopectin

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11
Q

Describe amylose

A

Straight chain glucose polymer

Connected by alpha-1,4 linkages

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12
Q

Describe amylopectin

A

Branched glucose polymer

Alpha-1,4 and alpha-1,6 linkages

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13
Q

What is glycogen?

A

The “animal starch”

Structure like amylopectin but even more highly branched

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14
Q

What makes up 30-40% of dietary carbohydrate?

A

Disaccharides
Sucrose
Lactose

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15
Q

What makes up 5-10% of dietary carbohydrate?

A

Monosaccharides
Glucose
Fructose

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16
Q

Where does sucrose come from?

A

Sugar cane

Sugar beets

17
Q

Where does lactose come from?

A

Milk

18
Q

Are disaccharides directly absorbed by the small intestine?

A

No

19
Q

What are the two steps to digesting dietary carbohydrates?

A

Intraluminal hydrolysis

Membrane digestion

20
Q

Which enzymes are involved in luminal digestion?

A

Salivary amylase and pancreatic amylase

21
Q

What inactivates salivary amylase?

A

Gastric acid

22
Q

What induces pancreatic amylase?

A

CCK

23
Q

Describe amylase

A

An endoenzyme

Hydrolyses internal alpha-1,4 linkages

24
Q

What are the products of starch hydrolysis by amylase?

A

Maltose
Maltotriose
Alpha-limit dextrins

25
Q

How many oligosaccharidases are there in the human brush border?

A

3

26
Q

Name the 3 oligosaccharidases

A

Lactase
Maltase
Sucrase-isomaltase

27
Q

What is the substrate of lactase and what are the products?

A

Lactose

Glucose and galactose

28
Q

What is the substrate of maltase and what are the products?

A

Alpha-1,4 linkages in straight chains

Produces glucose

29
Q

What enzymes cleave alpha-1,4 linkages?

A

Maltase
Sucrase
Isomaltase

30
Q

What is the substrate and products of sucrase?

A

Sucrose

Glucose and fructose

31
Q

What is the substrate and products of isomaltase?

A

The only enzyme that can split the alpha-1,6 linkages of alpha limit dextrins

32
Q

Where is the highest concentration of oligosaccharides?

A

Proximal jejunum

33
Q

What are the two stages to absorption of glucose, galactose and fructose?

A

Uptake across the apical membrane

Exit across the basolateral membrane

34
Q

What is responsible for the uptake of glucose and galactose?

A

Na/glucose transporter SGLT1
Active transport
Energy from Na+ gradient

35
Q

What is responsible for the uptake of fructose?

A

GLUT5

Facilitated diffusion

36
Q

What is responsible for the exit of monosaccharides across the basolateral membrane?

A

GLUT2

37
Q

What are the symptoms of lactase deficiency?

A

Diarrhoea and cramps
High hydrogen breath levels
Lactose is metabolised by colonic bacteria

38
Q

How are proteins absorbed?

A

Digested into constituent oligopeptides and amino acids

39
Q

Where is protein sourced from?

A

50% diet

50% endogenous

Digestion and Renal Sciences (27 decks)

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