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biology paper 1 > digestion and absorption (+enzymes) > Flashcards

digestion and absorption (+enzymes) Flashcards

Organisms exchange substances with their environment

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1
Q

define digestion

A

Large (insoluble) biological molecules hydrolysed to smaller (soluble) molecules
that are small enough be absorbed across cell membranes into blood

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2
Q

what is the role of salivary glands in the digestive system?

A

release salivary amylase enzymes

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3
Q

what is the role of the stomach in the digestive system?

A

produces HCL and protease enzymes. Also physically churns food

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4
Q

what is the role of the teeth?

A

physically break food into smaller pieces and increase its surface area

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5
Q

what is the role of the oesophagus?

A

carries food from the mouth to the stomach

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6
Q

what is the role of the liver?

A

produces bile

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7
Q

what is the role of pancreas?

A

Releases pancreatic juice onto food, as it exits the stomach, which contains proteases, lipases and carbohydrases.

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8
Q

what is the role of gall blander?

A

stores/release bile into ileum

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9
Q

what is the role of ileum?

A

Produces enzymes to digest food and absorbs products of food digestion into the blood

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10
Q

what is the role of the large intestine?

A

absorbs water

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11
Q

what are the 2 stages of digestion in a human?

A

-Physical breakdown by teeth or stomach churning
-Chemical digestion by enzymes

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12
Q

what are the carbohydrase enzymes?

A

-Salivary Amylase +
Pancreatic Amylase (substrate: starch)
-Maltase (substrate: maltose)
-Sucrase (substrate: sucrose)
-Lactase (substrate: lactose)

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13
Q

Give some examples of proteases involved in digestion

A

-Endopeptidase (substrate: protein)
-Exopeptidase(substrate: protein)
-Dipeptidase (substrate: dipeptides)

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14
Q

what are the mebranes bound enzymes?

A

-maltase
-sucrose
-lactase
-dipeptidases

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15
Q

what is the function of salivary amylase and pancreatic amylase

A
  • makes maltose
  • in salivary glands, pancreas
    -acts in the mouth, ileum
    -alpha 1,4 and beta 1,6 glycosidic bonds are broken
    -the pancreatic amylase hydrolyse starch in the ileum that was not broken down in the mouth.
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16
Q

what is the function of moltase?

A

-To break down maltose into 2 α-glucose molecules
-made in the ileum lining (stuck at the lining so it can be reused, if not it would be replenished which takes up a lot of energy)
-acts on the ileum
-a 1,4 glycosidic bonds are broken

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17
Q

what is the function of sucrase?

A

-breaks down sucrose into a-glucose and fructose
-made in the ileum lining
-acts in the ileum

18
Q

what is the function of lactase?

A

-hydrolyse lactose into a-glucose and galactose
-made in the ileum lining
-acts in the ileum

19
Q

what is the function of endopeptidase?

A

-To hydrolyse the central peptide bonds in a large protein molecule to give smaller peptide molecules.
-made in the stomach and pancreas
-acts in the stomach and ileum
-peptide bonds are broken

20
Q

what is the function of exopeptidase?

A

-To hydrolyse the peptide bonds at the ends of peptide molecules, which releases amino acids and dipeptides
-made in the stomach and pancreas
-acts in the ileum and stomach
-peptide bonds broken

21
Q

What is the function of dipeptidases?

A

-hydrolyse dipeptides into amino acids
-made in the ileum lining
-acts in the ileum
-peptide bonds broken

22
Q

what is the function of lipase ?

A

-hydrolysis of ester bonds in a lipid molecule to form 2 fatty acids and a monoglyceride
-made in the ileum lining
-acts in the ileum

23
Q

What is meant by egestion?

A

The removal of faeces via the anus

24
Q

What is the function of bile salts?

A

To emulsify large lipid molecules into smaller lipid micelles. To increase the surface area that lipase can act on.

25
Q

How does physical breakdown aid digestion?

A

-Creates a larger surface area for enzymes to act on.
-Makes food easier to ingest (swallow).

26
Q

Starch is not digested when food enters the stomach. Why?

A

The salivary amylase enzymes are denatured by the hydrochloric acid in the stomach.

27
Q

What is a membrane-bound disaccharidase?

A

An enzyme that is part of the epithelial cell surface membranes of the ileum. They break down disaccharides.

28
Q

What is a gland?

A

An organ in the body that secretes substances such as enzymes or hormones.

29
Q

Describe the digestion of starch in mammals

A

● Amylase (produced by salivary glands / pancreas) hydrolyses starch to maltose
● Membrane-bound maltase (attached to cells lining ileum) hydrolyses maltose to glucose
● Hydrolysis of glycosidic bond

30
Q

Describe the digestion of lipids in mammals, including action of bile salts

A

● Bile salts (produced by liver) emulsify lipids causing them to form smaller lipid droplets
● This increases surface area of lipids for increased / faster lipase activity
● Lipase (made in pancreas) hydrolyses lipids (eg. triglycerides) → monoglycerides + fatty acids
● Hydrolysis of ester bond

31
Q

Describe the digestion of proteins by a mammal

A

● Endopeptidases - hydrolyse internal (peptide) bonds
within a polypeptide → smaller peptides
○ So more ends / surface area for exopeptidases
● Exopeptidases - hydrolyse terminal (peptide) bonds at
ends of polypeptide → single amino acids
● Membrane-bound dipeptidases - hydrolyse (peptide)
bond between a dipeptide → 2 amino acids
● Hydrolysis of peptide bond

32
Q

Suggest why membrane-bound enzymes are important in digestion

A

● Membrane-bound enzymes are located on cell membranes of epithelial cells lining ileum
● (By hydrolysing molecules at the site of absorption they) maintain concentration gradients for absorption

33
Q

what are micelles?

A

smaller emulsified lipid droplets associated with bile salts which creates a larger surface area for faster lipase action

34
Q

what are the advantages of micelle formation?

A
  1. droplets increase surface area (for lipase/enzyme action)
  2. so faster hydrolysis/digestion of triglycerides/lipids
    3.micelles carry fatty acids and glycerol through membrane to internal epithelial cell
35
Q

exo and edopeptidases are required for protein hydrolysis - name another enzyme needed to complete protein hydrolysis

A

dipeptidases

36
Q

Why does the action of exo and endopeptidases result in more efficient hydrolysis?

A

endopeptidases create more ends or increase in surface area (for exopeptidases);

37
Q

Describe the action of membrane dipeptidases

A

-Hydrolyse peptide bond to release amino acids
(dipeptides cannot cross the cell membrane)

38
Q

Describe the pathway for absorption of products of digestion in mammals

A

Lumen (inside) of ileum → cells lining ileum (part of small intestine) → blood

39
Q

Describe the absorption of monosaccharides in mammals

A
  1. sodium removed from epithelial cell by active transport via sodium potassium carrier protein
  2. into the blood
  3. maintaining a low concentration of sodium in the cell
  4. glucose moves into the sodium
  5. via a co-transporter carrier protein
    6.glucose moves into the blood
  6. by facilitated diffusion
40
Q

Describe the absorption of amino acids in mammals

A
  1. sodium removed from epithelial cell by active transport via sodium potassium carrier protein
  2. into the blood
  3. maintaining a low concentration of sodium in the cell
  4. amino acid moves into the sodium
  5. via a co-transporter carrier protein
  6. amino caid moves into the blood
  7. by facilitated diffusion
41
Q

Describe the absorption of lipids by a mammal, including the role of micelles

A

● Bile salts combine with monoglycerides and fatty acids to form micelles
○ Micelles make monoglycerides and fatty acids (more) soluble in water
○ Micelles carry fatty acids and monoglycerides to cells lining the ileum, where they break down to
release them
○ This maintains a high concentration of fatty acids and monoglycerides near cells lining the ileum
● Monoglycerides / fatty acids are absorbed (into epithelial cell) by diffusion (as they’re lipid soluble)
● Triglycerides reformed in (epithelial) cells and aggregate into globules
● Globules coated with proteins forming chylomicrons which are then packaged into vesicles
● Vesicles move to cell membrane and fuse with it, releasing chylomicrons via exocytosis
○ Chylomicrons enter lymphatic vessels and eventually return to blood circulation

42
Q

describe the structures of capillaries and how it aids function

A
  1. walls are folded into villi- increase the S.A for faster absorption
  2. walls are 1 cell thick- short diffusion distance so faster absorption
  3. epithelial cells have microvilli - increase in S.A for faster absorption
  4. many capillaries- rich blood supply maintains diffusion gradient
  5. muscle in villi- main diffusion gradient by moving contents of lumen

biology paper 1 (7 decks)

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