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GCSE Biology > Digestion > Flashcards

Digestion Flashcards

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1
Q

What is digestion?

A
  • Digestion is the breakdown of large molecules into smaller, soluble molecules that can be absorbed into the body.
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2
Q

What is chemical digestion?

A
  • Digestion of food using enzymes to speed it up
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3
Q

What is mechanical digestion?

A
  • The physical breakdown of food.
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4
Q

How does chewing and cutting pieces of food in the mouth aid digestion?

A
  • It cuts the food into smaller pieces and this increases their surface area.
  • This measn that enzymes can act on the food more quickly.
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5
Q

What two layers of muscles can be found in the walls of the intestine?

A
  • Circular muscle layer, which has fibres running in rings around the gut
  • Longitudinal muscle layers, which has fibres running down the length of the gut
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6
Q

How do these two muscles push the food along?

A
  • When the circular muscles contract and the longitudinal muscles realx, the gut is made narrower. Whent he opposite happens, the gut becomme wider.
  • Waves of muscle contraction like this pass along the gut, pushing the food along
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7
Q

How does saliva enter the mouth?

A
  • The presence of food in the mouth triggers a nervous reflex that causes the salivary glands to deliver saliva through ducts to the mouth.
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8
Q

What does the chemical mucin, found in saliva, help in the mouth?

A
  • It protects the lining of the mouth from abrasion and lubricates food for easier swallowing.
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9
Q

What does the enzyme lysozome do?

A
  • Kills many of the bacteria that enter the mouth with food.
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10
Q

What happens we swallow in the oesophagus?

A
  • The top of the windpipe moves up so that its opening is blocked by a flap of tissue, the epiglottis.
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11
Q

How does the oesophagus conduct food from the pharynx down to the stomach?

A
  • By perisaltis
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12
Q

How does peristaltsis work?

A
  • Muscles in the wall of the oesophagus contract behind the bolus and relax in front, so that the bolus is squeezed along.
  • The act of swallowing begins voluntarily, but then the involuntary waves of contraction by smooth muscles in the rest of the oesophagus take over.
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13
Q

Where does food boli enter the stomach from?

A
  • From the oesophagus via the cardiac sphincter muscle
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14
Q

What digestive fluid does the stomach secrete?

A
  • Gastric juice
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15
Q

How does the stomach mix this secretion with the food?

A
  • By the churning action of the muscles in the stomach wall.
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16
Q

What does gastric juice contain?

A
  • High concentration of hydrochloric acid
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17
Q

What is the pH of gastric juice?

A
  • 2
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18
Q

What does the hydrochloric acid in the gastric juice do?

A
  • The acid kills most bacteria that are swallowed with food.
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19
Q

Why is the lining of the stomach covered in mucus?

A
  • To prevent the acid causing damage to the stomach lining itself
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20
Q

What does pepsin break down and where is it found in the stomach?

A
  • Proteins
  • Found also in the gastric juice
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21
Q

How does pepsin break down proteins?

A
  • Pepsin breaks the bonds adjacent to specific amino acids, cleaving proteins into smaller polypeptides.
22
Q

How does the low pH of the gastric juice help in the digestion of proteins in the stomach?

A
  • It denatures (unfolds) the proteins in food, increasing exposure of their bonds to pepsin.
23
Q

After mixing and enzyme action what is the food in the stomach turned into?

A
  • Chyme
24
Q

Why is the stomach closed at both ends most of the time?

A
  • To prevent the backflow of acid chyme from the stomach into the lower end of the oesophagus, which can cause heartburn
25
Q

What is at the opening from the stomach to the small intestine and how does it help?

A
  • The pyloric sphincter, which helps regulate the passage of chyme into the intestine, one squirt at a time.
26
Q

What occurs in the small intestine?

A
  • Most of the enzymatic hydrolysis of food macromolecules and most of the absorption of nutrients into the blood occur in the small intestine.
27
Q

What is bile and where is it stored and how does it get from where it is stored to the food?

A
  • Green liquid
  • Stored in the gall blader in the liver
  • Passes down the bile duct on to the food
28
Q

How does bile help in the breakdown of food?

A
  • Bile act as emulsifier that break large lipid droplets up into smaller ones like a detergent and increase their surface area for the action of lipase.
29
Q

What else does bile contain that neutralsies the stomacha acid in the food?

A
  • Bicarbonate ions which are alkaline
30
Q

What happens in the ileum?

A
  • Here the small nutrient molecules released by mechanical and chemical digestion are absorbed into the bloodstream.
31
Q

How do nutrients in the lumen enter the body?

A
  • They have to cross the lining of the digestive tract
32
Q

How is the ileum highly adapted to absorb the digested food?

A
  • Lining of ileum hs a very large surface area, which means it can quickly and efficiently absorb the soluble products of digestion into the blood.
33
Q

What helps to give the ileum a large surface area?

A
  • The length of the intestine
  • Folds in its lining
  • Villi
34
Q

How do villi help in the absorption of food in the ileum?

A
  • There a millions of villi so the total area of the lining is thought to be 300m2.
  • This provides a mssive area in cntact with the digested tract.
  • Also, villi have microvilli which increae the surface area for absorption even more.
35
Q

How does the digested food enter the villi?

A
  • Through a newtork of blood capillaries
36
Q

How does gylcerol and fatty acids enter the villi?

A
  • Enter a tube in the middle of villus, called lacteal.
37
Q

What do the lacteal form part of?

A
  • The lymphatic system
38
Q

Where do the blood vessels from the ileum join up to?

A
  • Hepatic portal vein
39
Q

Where does the hepatic portal vein lead to and why is this.

A
  • To the liver
  • This ensures that the liver has first access to amino acids and sugars absorbed after a meal is digested.
40
Q

Where does the blood go from the liver?

A
  • From the liver, blood travels to the heart, which pumps the blood and the nutrients it contains to all parts of the body.
41
Q

What is assimilation?

A
  • The process by which the digested fod molceules are distributed around the body by the blood system.
42
Q

What is the function of the colon?

A
  • To absorb the mremaining water from the contents, and leaving faeces.
43
Q

Where is faeces stored and expelled from the body?

A
  • Stored in the rectum
  • Expelled through the anus
44
Q

What enzyme are carbohydrates broken down by?

A
  • Carbohydrase
45
Q

What does amaylse break down and where is the source of it?

A
  • Starch into maltose
  • From salivary glands
46
Q

What does maltase break down and where is the source of it?

A
  • Maltose into glucose
  • Source is wall of small intestine
47
Q

What enzme are proeins digested by?

A
  • Proteases
48
Q

What does pepsin break down and where is the source of it?

A
  • Proteins into peptides (short chains of amino acids)
  • Stomach wall
49
Q

What does trypsin break down and where is the source of it?

A
  • Proteins to peptides
  • Source in pancreas
50
Q

What does peptidases break down and where is the source of it?

A
  • Peptides to amino acids
  • Source in wall of small intestine
51
Q

What enzyme breaks down lipids?

A
  • Lipase
52
Q

What does lipase break down and where is the source of it?

A
  • Lipids to glycerol and fatty acids
  • Source in pancreas

GCSE Biology (9 decks)

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