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Eduqas A level Biology - Year 1 COPY > Component 3.3 - Human Digestive System > Flashcards

Component 3.3 - Human Digestive System Flashcards

1
Q

What is ingestion

A

Taking food into the body through the mouth

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2
Q

What is digestion

A

The break down of large insoluble molecules into soluble molecules that are small enough to be absorbed into the blood

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3
Q

What is mechanical digestion?

A

Cutting and crushing by teeth and muscle contractions of the gut wall, increases the surface area over which enzymes can act.

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4
Q

What is chemical digestion?

A

Digestion by the secretion if digestive enzymes. Bile and stomach acid contribute to chemical digestion.

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5
Q

What is absorption?

A

The passage of molecules and ions through the gut wall into the blood.

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6
Q

What is egestion?

A

The elimination of waste not made by the body, including food that cannot be digested

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7
Q

What’s the general function of the mouth?

A

Ingestion and digestion of starch

Tongue muscles push food into the pharynx

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8
Q

What is the general function of the oesophagus?

A

The carriage of food to the stomach

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9
Q

What is the general function of the stomach?

A

Digestion of protein

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10
Q

What is the general function of the duodenum?

A

Digestion of carbohydrates, fats and proteins.

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11
Q

What is the general function of the ileum?

A

Digestion of carbohydrates, fats and proteins. Absorption of digested food.

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12
Q

What is the general function of the colon?

A

Absorption of water

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13
Q

What is the general function of the rectum?

A

Storage of faeces

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14
Q

What is the structure of the gut wall from inside to out?

A

Mucosa, sub-mucosa, inner circular muscles, outer longitudinal muscles (muscularis) serosa

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15
Q

What is the function of the serosa?

A

It is a tough connective tissue which protects the gut wall. Serosa reduces friction with other abdominal organs.

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16
Q

What is the function of the layers of muscles?

A

The two layers of muscles are in different directions and they make waves of contractions, behind the ball of food circular muscles contract and longitudinal muscles relax, pushing the food along.

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17
Q

What is the function of the submucosa?

A

It is connective tissue containing blood and lymph vessels, which remove absorbed products of digestion, and nerves that co-ordinate peristalsis.

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18
Q

What is the function of the mucosa throughout the gut?

A

It lines the gut wall. It’s epithelium secretes mucus, lubricating food and preventing autodigestion of gut wall

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19
Q

How do some functions of the mucosa differ throughout the gut?

A

In some regions of the gut, it secretes digestive juices and in others, it absorbs digested food.

20
Q

How are carbohydrates broken down and what are they broken down into?

A

Salivary amylase hydrolyses starch to the disaccharide maltose and Maltase digests maltose into the monosaccharide, alpha glucose.

Sucrase digests sucrose

Lactase digests lactose.

21
Q

What is the general name for carbohydrate-digesting enzymes?

A

Carbohydrase

22
Q

How are proteins broken down and what are they broken down into?

A

1) Endopeptidases hydrolyse non-terminal peptide bonds within the protein molecule to form peptides
2) Then exopeptidases hydrolyse the terminal peptide bonds at the end of these shorter polypeptides.

23
Q

What are the general names for protein-digesting enzymes?

A

Protease and peptidases

24
Q

How are fats broken down and what are they broken down into?

A

They are digested to fatty acids and glycerol by one enzyme, lipase.

25
Q

Describe mechanical digestion in the mouth

A

Food is mixed with saliva and chewed with teeth. This increases foods surface area giving enzymes a large surface area to act upon

26
Q

What does saliva contain?

A

1) Amylase which begins the digestion of starch to maltose
2) HCO3(-) and CO3(2-), so the PH in the mouth is slightly alkaline, the optimum for amylase
3) Mucus lubricating the foods passage down the oesophagus

27
Q

How do the stomach walls help with digestion?

A

They contract rhythmically and mix the food with gastric juice secretes by glands in the stomach wall.

28
Q

What is the function of hydrochloric acid in the stomach and where is it secreted from?

A

It lowers the PH of the stomach contents to about PH2, the optimum PH for the enzymes and kills most bacteria in food.

29
Q

What is the function of mucus in the stomach and where is it secreted from?

A

It forms a lining which protects the stomach wall from the enzymes and lubricates the food.

30
Q

Describe what enzymes are in the stomach and where they are secreted from

A

Pepsinogen, an inactive enzyme, is secreted and activated by H+ ions to pepsin, an endopeptidase which hydrolyses protein to polypeptides.

Secreted from gastric glands

31
Q

Where is bile made and stored and how does it get into the duodenum?

A

It is made in the liver, stored in the gall bladder and passes through the bile duct into the duodenum.

32
Q

What is the function of bile?

A

1) Bile contains bile salts. They emulsify lipids in foods breaking up large globules, which increases surface area. Makes lipase digestion more efficient.
2) Bike is alkaline and neutralises the acid in the food coming from the stomach. Provides a suitable PH for the enzymes in the small intestine.

33
Q

Where is pancreatic juice secreted from and how does it enter the duodenum?

A

It is secreted by islet cells, which are exocrine glands and enters the duodenum through the pancreatic duct.

34
Q

What enzymes are in pancreatic juice?

A

Endopeptidases, amylase, lipase and trypsinogen, an inactive enzyme which is converted into the protease enzyme trypsin by enterokinase which is also in pancreatic juice.

35
Q

What happens to food coming from the stomach?

A

It is lubricated by mucus and alkaline secretions neutralise stomach acid and provide suitable conditions for pancreatic enzymes

36
Q

What protein digesting enzymes are associated with the epithelial cells at the tips of villi?

A

Endopeptidases and exopeptidases are secreted by epithelial villus cells into the gut lumen and continue digestion of polypeptides.

Dipeptides are digested into amino acids by enzymes on the cell membranes of epithelial cells.

37
Q

What carbohydrates are associated with the epithelial cells at the tips of villi?

A

1) Disaccharides are absorbed into epithelial cells of villi
2) Carbohydrases here digest them into monosaccharides.

This is the final stage of carbohydrates digestion.

38
Q

How is the ileum adapted for absorption?

A

It is very long - large amount of time for products to be absorbed

Lining is folded, on surface of folds are villi which have projections called microvilli - produce a very large surface area for absorption.

39
Q

Why are some of the enzymes secreted as inactive?

A

So they do not digest the cells in which they are synthesised.

40
Q

How do amino acids get into the blood?

A

They are absorbed into the epithelial cells by active transport and, as individual amino acids they pass into the capillaries by facilitated diffusion.

41
Q

Describe how glucose gets into the blood

A

It passes into the epithelial cells by co transport with sodium or and glucose enters the capillaries by facilitated diffusion but sodium enters by active transport.

42
Q

How do fatty acids and glycerol get into the blood?

A

They diffuse into the epithelial cells, reassembled into triglycerides and then they pass into the lacteals. They are then carried by the lymphatic system to the blood

43
Q

How do water-soluble vitamins and fat soluble vitamins get into the blood?

A

Water and fat soluble vitamins diffuse into the epithelial cells and then water soluble vitamins diffuse into the capillary but fat soluble vitamins diffuse into the lacteal.

44
Q

How is water absorbed into the blood?

A

It is absorbed into epithelial cells by osmosis and into the blood by osmosis.

45
Q

How is the mucosa in the small intestine different than in the large intestine?

A

It has larger villi

46
Q

Where are glucose and amino acids transported after absorption?

A

To the liver via the hepatic portal vein

47
Q

What is the function of the anus?

A

Opening at the lower end of the digestive tract that controls the expulsion of faeces

Eduqas A level Biology - Year 1 COPY (53 decks)

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