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Biology > 3. Digestion & Absorption > Flashcards

3. Digestion & Absorption Flashcards

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1
Q

Ingestion

A

Taking in food

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2
Q

Digestion

A

The breakdown of large insoluble molecules into small soluble molecules

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3
Q

Absorption

A

Movement of nutrients into cells

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4
Q

Assimilation

A

Using products of digestion to build new parts of the cell

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5
Q

Elimination/Egestion

A

Removing undigested food/material

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6
Q

Physical breakdown

A

Broken into smaller pieces by the teeth and tongue

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7
Q

Why is physical breakdown useful?

A

Increases surface area for action of enzymes

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8
Q

Where/how does physical breakdown continue after the mouth?

A

Continues by churning in the stomach

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9
Q

Chemical breakdown

A

Hydrolysis of large insoluble molecules into smaller soluble ones by enzymes, often in stages.

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10
Q

What 3 things does saliva contain?

A
  1. Water - dissolves soluble substances
  2. Mucus - lubrication
  3. Amylase - hydrolyses starch (which consists of amylose and amylopectin)
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11
Q

Does digestion take place in the oesophagus?

A

NONONO

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12
Q

What process moves food through the alimentary canal?

A

Peristalsis

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13
Q

What type of muscles are in the oesophagus?

A

Circular and longitudinal - they are an antagonistic pair (one relaxes while the other contracts)

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14
Q

What do the glands of the stomach secrete?

A

Gastric juice

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15
Q

What does gastric juice contain?

A 
Hydrochloric acid (pH 2) to kill bacteria
Some protease enzymes
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16
Q

What does the bolus become in the stomach?

A

Chyme

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17
Q

What is emptied into the duodenum?

A

Bile from the gall bladder and liver

Pancreatic enzymes

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18
Q

What does bile do?

A

Neutralise acidic contents from stomach

Emulsifies lipids

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19
Q

What happens in the large intestine?

A

Absorption of water

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20
Q

What does bacteria in the large intestine do?

A

Aid digestions & helps to synthesise vitamin K

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21
Q

Where is faeces stored?

A

Rectum

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22
Q

The process of removing faeces via the anus is called…

A

Egestion

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23
Q

Pancreatic juice containing pancreatic enzymes is released via…

A

the pancreatic duct

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24
Q

The pancreas synthesises three main types of digestive enzyme:

A
  1. Amylase
  2. Lipases
  3. Proteases
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25
Q

Polysaccharides and disaccharides are digested into monosaccharides by…

A

hydrolysis of the glycosidic bonds

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26
Q

Where are membrane-bound disaccharidases found, and what do they do?

A

The epithelial lining of the ileum

They hydrolyse the single glycosidic bond

27
Q

How is maltose hydrolysed?

A

Using maltase: glucose + glucose

28
Q

How is sucrose hydrolysed?

A

Using sucrase:

glucose + fructose

29
Q

How is lactose hydrolysed?

A

Using lactase:

glucose + galactose

30
Q

Why is it beneficial for enzymes to be attached to the membranes of the epithelium?

A
  1. Always be in contact: more efficient
  2. Don’t want to egest enzymes!
  3. Could be auto-digested if they come into contact with proteases
  4. Enzymes can be reused over and over again
31
Q

What does bile contain?

A

Bile salts and pigments (bilirubin)

32
Q

Bile salt molecules have…

A

A hydrophobic surface and a hydrophilic surface.

They are amphipathic!

33
Q

The hydrophobic end of the bile salt molecule…

A

interacts with the lipid

34
Q

The hydrophilic end of the bile salt molecule…

A

faces out and prevents lipids from coalescing

35
Q

What do bile salts do?

A

Divide the fat globule into smaller droplets (emulsification)

36
Q

Why is emulsification useful?

A

Increases the total surface area available for lipase activity

37
Q

Bile salts enter the ileum via the…

A

bile duct

38
Q

Bile salts emulsify lipids into…

A

micelles

39
Q

How do lipases digest lipids?

A

Hydrolyse the ester bond to form fatty acids and monoglycerides

40
Q

Endopeptidases

A

Hydrolyse the peptide bond between amino acids in the central region of the protein, forming peptide molecules

41
Q

Exopeptidases

A

Hydrolyse peptide bonds on the terminal amino acid of the peptides formed by endopeptidases

42
Q

Dipeptidases

A

Hydrolyse bond between two amino acids of dipeptide

43
Q

What is special about dipeptidases?

A

They are membrane-bound in the ileum

44
Q

What type of protease is found in the gastric juice in the stomach?

A

Endopeptidase

45
Q

What type of protease is found in the pancreas?

A

Endopeptidase AND exopeptidase

46
Q

What type of protease is found in the epithelium of the small intestine?

A

Dipeptidase

47
Q

Serosa

A

Outermost layer of the ileum. It is strong and protective.

48
Q

Muscularis

A

Right after the serosa: consists of inner (circular) and outer (longitudinal) muscles which perform peristalsis

49
Q

Sub-mucosa

A

Right after the muscularis: connective tissue between the mucosa and muscle

50
Q

Mucosa

A

Right after the sub-mucosa

Inner lining which includes villi

51
Q

Location of villi and microvilli

A

Circular folds in the mucosa contain villi.

Epithelial cells on each villus contain microvilli.

52
Q

Co-transport

A

Glucose & amino acids

53
Q

Facilitated diffusion

A

Monosaccharides

54
Q

Simple diffusion

A

Triglycerides

55
Q

Initially, absorption of monosaccharides and amino acids will be by…

A

facilitated diffusion

56
Q

What is the problem with only facilitated diffusion in absorption of monosaccharides and amino acids? What is the solution?

A

Diffusion can only result in equal concentrations either side of the intestinal epithelium.
Therefore active transport is involved in the uptake of these monomers.

57
Q

How is active transport of monosaccharides and amino acids carried out?

A

Via co-transport using sodium ions (review from previous topic)

58
Q

What happens following emulsification?

A

The bile salts remain associated with monoglycerides and fatty acids, forming micelles

59
Q

What happens when micelles come into contact with the epithelium of the ileum? What happens after that?

A

They break down, releasing monoglycerides and fatty acids.

Because they are non-polar molecules, they easily diffuse across the cell surface membrane into the epithelial cells.

60
Q

What happens to the monoglycerides and fatty acids once inside the epithelial cells?

A

They are transported to the smooth endoplasmic reticulum and reformed into triglycerides.

61
Q

What happens after triglycerides are reformed in the epithelium?

A

They associate with cholesterol and lipoproteins in the ER and Golgi to form chylomicrons

62
Q

What are chylomicrons?

A

Lipoprotein particles that consist of triglycerides, phospholipids, cholesterol and proteins that transport dietary lipids from the intestines to other locations in the body

63
Q

What happens right after chylomicron formation?

A

They enter the lacteal via exocytosis, and enter the blood circulation via the lymphatic system.

Enzymes in the endothelium of the blood vessels hydrolyse the triglycerides and they diffuse into cells.

Biology (42 decks)

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