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BIOC192 > 23 > Flashcards

23 Flashcards

1
Q

What are the main macronutrients contributing to energy production in the body

A

Carbohydrate, protein and fat

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2
Q

Why are (to a lesser extent) nucueic acidds important?

A
  • protein and nucleic acid components supply body with nitrogen which is important for the biosynthesis of various nitrogen compounds that we need for cellular function
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3
Q

Why are larger compounds broken down

A

To be absorbed by the body

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4
Q

Main food components and what they’re broken into

A
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5
Q

After macronutrients are consumes in the diet, where do they pass through?

A

The GI tract

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6
Q

These smalle dmolecules are used to

A

Make ATP

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7
Q

Saliva at what ph contains what to start what?

A

S aliva (neutral pH) contains mucous and amylase which starts the digestion of carbohydrates

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8
Q

Function of stomach - what does it do and what dies it produce

A

Storage and mixing of food with gastric juices, producing the ‘chyme’ that is slowly released into intestine

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9
Q

Things that are secreted into the stomach (by the stomach?)

A

„secretes acid (0.1 M HCl) =
denaturing

„secretes pepsinogen -> pepsin secrete
= protein digestion (protease)

„secretes mucous layer (protective)

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10
Q

PH of pancreas

A

„ slightly alkaline – around pH 7

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11
Q

Function of pancrease

A

„secretes most of the digestive enzymes including amylase, lipase and several proteases

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12
Q

Function of liver

A

„synthesis of bile salts/acids (stored in gall bladder) important for fat digestion

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13
Q

Function of small intestine

A

„final phase of digestion and absorption

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14
Q

Two main phases of digestion

A
  1. Hydrolysis of bonds connecting monomer units in
    food macromolecules

Carbohydrate: Glycosidic bonds – starch -> disaccharides
Proteins: Peptide bonds
Fat: Triacylglycerol ester bonds
(This breakdown depends on how fast it can be absorbed into the body)

  1. Absorption of hydrolysis products from gastrointestinal
    tract into body
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15
Q

Digestions of dietary carbohydrates - what percent of energy does it provide - what are some examples

A

Provides 40-50% of energy intake

Starch (ie. α-amylose, amylopectin)
Simple sugars ie. sucrose, lactose, fructose, glucose (diglucose)
Fibre – such as cellulose (undigestible by most mammals) (don’t have the enzyme to hydrolyse that polymer bond)

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16
Q

Main component of plant starch

A

Amylopectin

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17
Q

Amylopectin is the main component of…

A

…plant starch

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18
Q

Amylopectin is a polymer up to ____ _____ Union s

A

1 million glucose units

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19
Q

Structure of amylopectin

A
  • each bond needs a specific enzyme to be hydrolysed
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20
Q

Maltose is present in…

A

…honey

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21
Q

Structure of maltose - what kid of polymer..

A

Disaccharide

22
Q

C ellobiose and lactose are ________ of one another

A

stereoisomers

23
Q

stereoisomers - how Cellobiose and lactose are stereoisomers of one another - what does this mean?

A

Cellobiose is a repeating disaccharide unit in cellulose
- Mammals do not have an enzyme that can hydrolyse the b(1->4) glycosidic bonds in cellulose

Lactose is present in milk
- Some people do not have the lactase enzyme and are unable to hydrolyse lactose

24
Q

How do stereoisomers arise

A

The functional groups in monosaccharides can be in either of two orientations

There is a convention of numbering the carbon atoms

(- any functional groups - like hydroxyl groups can either be pointing out of the carbon or out the other side of the plane of the ring - this influences overall structure (although it has the same chemical make up as another stereoisomer group)

25
Q

What is sucrose made of

A

Fructose and glucose

26
Q

Sucrose is hydrolysed to form

A

Glucose and fructose

27
Q

Consumption of ‘high fructose corn syrup’ is increasing - why

A

Enzyme hydrolysis of ‘corn starch’ to glucose and isomerization to fructose

  • easier then other ways of sweetenening?
28
Q
A
29
Q

Starch from plants consists mainly of:

A
  • Amylose (a linear polymer of a(1->4) linked glucose units)
  • Amylopectin (a branched polymer of a(1->4) and a(1->6) linked
    glucose units)
30
Q

H ydrolysis of glycogen

A

Glycogen has a similar branched structure to amylopectin

Glycogen can be present in consumed foods such as liver and muscle

Glycogen is synthesized in animals from glucose and stored in liver and muscle, and then broken down to glucose when required by the body

The breakdown of glycogen stored in liver and muscle cells to glucose requires a ‘debranching enzyme’ (will be discussed further in Prof. Julian Eaton-Rye’s lectures)

31
Q

Glycogen has a similar branched structure to

A

Amylopectin

32
Q

Glycogen can be present in consumed food such as…

A

… liver and muscle

33
Q

Glycogen is ____ in animals from _____ and stored in ___ and _____, and then broken down to glucose when required by the body

A

synthesized

glucose

liver

muscle

34
Q

The breakdown of glycogen stored in liver and muscle cells to glucose requires a_______

A

‘debranching enzyme’

35
Q

Hydrolysis of starch - digestion of starch

A

(Sequential hydrolysis process)
The enzyme amylase hydrolyses a(1->4) glycosidic bonds

Repeated internal attack yielding smaller and smaller oligosaccharides producing maltose/isomaltose disaccharides as end products

36
Q

Final digestion at ‘Brush Border’ after amylase digestion, what happens - what enzymes do what cells secrete ? What happens after?

A

Intestinal epithelial cells secrete …

Maltase/isomaltase
Maltose/isomaltose ——-> 2 glucose

Sucrase
Sucrose ———> fructose + glucose

Lactase
Lactose ———> galactose + glucose

The monosaccharides are now absorbed into the body

37
Q

Isomaltose and maltose

A
  • different isomers = different enzymes
38
Q

Overview of dietary carbohydrate processing in the gastrointestinal tract

A
39
Q

Lactose interlace - how it occurs - what is causes - how to fix it

A

L actase enzyme deficiency (genetic basis)

Causes bloating, flatulence and diarrhoea due to fermentation of lactose by intestinal bacteria

Need to avoid lactose in diet

40
Q

Digestion of dietary protein - what this supplies to the body

A

Supplies amino acids to make body proteins

Supplies essential amino acids

Source of nitrogen for purines, pyrimidines, haem

Carbon skeletons can be used as fuel (N converted to urea and excreted in urine)

41
Q

Essential amino acids

A

Leucine Isoleucine
Lysine Methionine
Threonine Phenylalanine
Tryptophan Valine

(Non-essential are the amino acids we have evolved to have enzymes to break down/synthsystie/ interconvert )

Could be obtained form plant or animal sources

42
Q

Kwashiorkor - what is it caused by, what does it result in - what is low in the blood and what does that affect

A

‘Kwashiorkor’ is the result of a deficiency of dietary protein which causes an osmotic imbalance in the gastrointestinal system, causing the abdomen to swell (oedema) due to retention of water

In addition, the level of albumin in the blood is low affecting colloidal osmotic (oncotic) pressure, and also transport of molecules, eg hormones and drugs

43
Q

How are proteases activated ?

A

by cleavage of peptides from their structure

44
Q

All proteases secreted as

A

All proteases secreted as inactive forms (zymogens or proenzymes)
- this minimises unwanted hydrolysis of body structure

45
Q

Protein digestion

A

Involves hydrolysis of specific peptide bonds
Performed by several different proteases
All proteases secreted as inactive forms (zymogens or proenzymes)
All proteases activated by cleavage of peptides from their structure

46
Q

Protease specificity is determined by

A

adjacent amino acid side chains in protein substrate

47
Q

Examples of amino acid side chains that determine a specific protease specificity

A

Pepsin = aromatic - ie Phe, Tyr
Trypsin = positively charged - ie Lys, Arg
Chymotrypsin = aromatic - ie Phe, Tyr

Whether bond is hydrolysed or not depends on the amino acid side chain

48
Q

Two stages of protein digestion

A

Endopeptidases attack peptide bonds within the protein (peptide) polymer
- Examples: pepsin, trypsin, chymotrypsin

Exopeptidases attack peptide bonds at the end of protein (peptide) polymer
- Two types:
- Aminopeptidase
- Carboxypeptidase

49
Q

Endopeptidases vs Exopeptidase in protein digestion

A

Endopeptidases attack peptide bonds within the protein (peptide) polymer

Exopeptidases attack peptide bonds at the end of protein (peptide) polymer

50
Q

How is Pepsinogen activated to pepsin

A

Pepsinogen, the inactive zymogen (proenzyme) is activated to pepsin following exposure of pepsinogen to HCl in the stomach

In the stomach acidic environment, part of the pepsinogen protein unfolds, which activates the pepsin protease and results in hydrolysis of part of the pepsinogen protein sequence to generate stably activated pepsin protease

  • activated pepsin can also directly activate inactive pepsin (causes it to refold and become active)
51
Q

Protein digestion – sequential hydrolysis by proteases
DIAGRAMS

A
52
Q

Enterokinase flow on effects on proteases from pancreas - how appropriate proteases are activated at an appropriate time to carry out their function

A

Membrane bound in the intestine lumen
- able to hydrolyse part of the trypsinogen protein molecule activating it to active trypsin protease
- active trypsin can active chymotrypsinogen to chymotrypsin
- trypsin can also hydrolyse part of procarboxypeptidase to activate it

BIOC192 (38 decks)

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