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Biology > Nutrition in humans > Flashcards

Nutrition in humans Flashcards

1
Q

In humans, what does nutrition consist of?

A
  • feeding
  • digestion
  • absorption
  • assimilation
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2
Q

What are the parts in the human digestive system?

A
  • Mouth
  • buccal cavity (teeth, tongue)
  • pharynx
  • oesophagus
  • stomach
  • small intestine (duodenum, jejunum, ileum)
  • large intestine/colon
  • rectum
  • anus
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3
Q

What are the associated glands in the human digestive system?

A
  • salivary glands
  • liver
  • gall bladder
  • pancreas
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4
Q

What does the teeth do?

A
  • it performs mechanical digestion
  • it breaks up food into smaller pieces (mastication)
  • increases surface area to volume ratio for salivary amylase to work on
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5
Q

What does the tongue do?

A
  • rolls food up into bolus for easier swallowing
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6
Q

What does the pharynx do?

A
  • it is a common passageway for respiration and digestion
  • food and air had to enter the pharynx to enter the oseophagus or trachea
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7
Q

What does the oseophagus do?

A
  • it is a long muscular tube that transports food from the pharynx to the stomach through peristalsis
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8
Q

What does peristalsis do?

A
  • wave-like contractions
  • along the walls oesophagus
  • circular and longitudinal muscles work antagonistically
  • circular muscles contract, longitudinal muscles relax → oesophagus constricts, narrower and longer → food is pushed forward
  • circular muscles relax, longitudinal muscles contract → oesophagus dilates, oesophagus widens and shortens → food is pushed through
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9
Q

What does the stomach do?

A
  • gastric glands in the stomach are stimulated by the presence of food and secrete gastric juices into the stomach cavity
  • peristalsis churns the food and mixes it well with gastric juices
  • food remains in the stomach for 3 to 4 hrs
  • the partly digested food is liquefied, forming chyme
  • chyme passes in small amounts into the duodenum when the pyloric sphincter relaxes and opens
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10
Q

What does gastric juice contain?

A
  • dilute solution of hydrochloric acid and pepsin
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11
Q

What does dilute hydrochloric acid do?

A
  • stops the action of salivary amylase by denaturing it
  • changes the inactive form of pepsinogen, in the gastric juice into active pepsin
  • provides a slightly acidic medium suitable for the action of pepsin
  • kills potentially harmful microorganisms in food
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12
Q

How to proteins get digested into polypeptides?

A
  • protease (pepsin) digests it
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13
Q

What happens when chyme enters the small intestine?

A
  • it stimulates the pancreas to secrete pancreatic juice
  • it stimulates the gall bladder to release bile
  • it stimulates the epithelial cells in the small intestine to produce maltase, peptidase and lipase
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14
Q

What does pancreatic juice contain?

A
  • the enzymes pancreatic amylase, pancreatic protease (trypsin) and pancreatic lipase
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15
Q

How does the pancreatic juice enter the duodenum?

A
  • pancreatic juice passes through the pancreatic duct into the duodenum
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16
Q

What does bile contain?

A
  • bile does not contain enzymes
  • bile salts
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17
Q

What do bile salts do?

A
  • speeds up the digestion of fats
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18
Q

How does bile enter the duodenum?

A
  • bile passes through the bile duct into the duodenum
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19
Q

What do pancreatic juice, intestinal juice and bile do to food?

A
  • all three fluids are alkaline
  • they neutralise acidic chyme
  • provide a suitable alkaline medium for the action of pancreatic and intestinal enzymes
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20
Q

What is starch digested by?

A
  • amylases
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21
Q

Where does starch digestion occur?

A
  • mouth
  • small intestine
    (no starch digestion in the stomach)
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22
Q

How much starch is digested in the mouth?

A
  • only a little as food does not remain in the mouth for long
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23
Q

What starch digestion occurs in the small intestine using what enzymes?

A
  • starch is digested by pancreatic amylase to form maltose
  • maltose is digested by maltase to form glucose
  • lactose is digested by lactase to form glucose and galactose
  • sucrose is digested by sucrase to form glucose and fructose
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24
Q

What happens after carbohydrate digestion?

A
  • the end product is simple sugars
  • they can be absorbed into the bloodstream
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25
Q

What are proteins digested by?

A
  • proteases
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26
Q

Where does protein digestion take place?

A
  • stomach
  • small intestine
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27
Q

What is the process of protein digestion in the small intestine?

A
  • undigested proteins which enter the small intestine are digested into polypeptides by trypsin
  • polypeptides are digested by peptidases into amino acids
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28
Q

What is the end product of protein digestion?

A
  • amino acids
29
Q

What do bile salts do?

A
  • emulsify fats
30
Q

What does emulsifying fats do?

A
  • lowers surface tension of fats (reduces attractive forces between fat molecules)
  • fats break into tiny fat droplets suspended in water (only physical break up)
  • this forms an emulsion
31
Q

What does emulsification do to speed up digestion by lipases?

A
  • increases the surface area to volume ratio of fats
32
Q

What are the emulsified fats digested by?

A
  • lipase (pancreatic and intestinal lipases)
33
Q

What does lipase digest emulsified fats into?

A
  • glycerol
  • fatty acids
34
Q

What are the end products of fat digestion?

A
  • glycerol
  • fatty acids
35
Q

What is absorption?

A
  • the process in which digested food substances are absorbed into body cells
36
Q

What is the process of absorption?

A
  • products of digestion (simple sugars, glycerol, fatty acids and amino acids) are absorbed throughout the small intestine (especially the ileum)
  • absorbed nutrients pass from the small intestine into the bloodstream
  • water and mineral salts are absorbed by the small intestine and colon
37
Q

Other than nutrients, what else does the small intestine absorb?

A
  • most of the water that enters the alimentary canal
38
Q

Where is undigested and unabsorbed matter stored?

A
  • in the rectum
  • before it is discharged as faeces through the anus
39
Q

What is the removal of undigested and unabsorbed matter from the body called?

A
  • egestion/defecation
40
Q

What is assimilation?

A
  • assimilation is a process in which some of the absorbed food substances are converted into new protoplasm or used to provide energy
41
Q

What happens to the blood in the villi after absorption?

A
  • it is now rich in nutrients
42
Q

What do blood capillaries do to transport nutrients to the liver?

A
  • they unite to form a large vein
  • known as the hepatic portal vein
43
Q

What happens to the absorbed sugar in the liver?

A
  • converted to glycogen and stored
44
Q

How does glucose help in the vital activities of cells?

A
  • glucose is assimilated and oxidised during tissue respiration
  • release energy for the vital activities of cells
45
Q

What happens to excess glucose?

A
  • excess glucose is returned to the liver and stored as glycogen
  • a hormone called insulin, produced by the islets of langerhans in the pancreas stimulates liver cells to convert excess glucose to glycogen
46
Q

What does the liver do when the body needs energy?

A
  • the liver converts stored glycogen back into glucose (using glucagon secreted by the islets of langerhans in the pancreas)
  • which is then transported by the blood to the cells
47
Q

What are amino acids used for?

A
  • amino acids which enter the cells are converted to new protoplasm used for growth and repair of worn out parts of the body
  • used to form enzymes and hormones
48
Q

What happens to excess amino acids?

A
  • deaminated in the liver
  • converted to urea
49
Q

What are fats absorbed into?

A
  • lymphatic capillaries
50
Q

How are fats discharged into the bloodstream?

A
  • lymphatic capillaries join to form a larger lymphatic vessel
  • they discharge fats into the bloodstream
51
Q

In normal conditions, when there is a sufficient supply of glucose, what are fats used for?

A
  • fats not broken down
  • building protoplasm
52
Q

What are fats used for when glucose is in short supply?

A
  • fats are broken down
  • this is to provide energy needed by the body
53
Q

What does the liver secrete?

A
  • bile
54
Q

Where is the substance secreted by the liver stored?

A
  • gall bladder
55
Q

What does the liver do to haemoglobin in red blood cells?

A
  • breaks them down
  • stores the iron released
56
Q

What is formed from the breakdown of haemoglobin?

A
  • bile pigment
57
Q

What does the liver synthesize?

A
  • proteins found in blood plasma
  • from amino acids in diet
58
Q

What are some plasma proteins?

A
  • prothrombin
  • fibrinogen
59
Q

What is detoxification?

A
  • a process in which harmful substances are converted to harmless substances
60
Q

Where is alcohol broken down?

A
  • liver
61
Q

What do liver cells contain that break alcohol down?

A
  • alcohol dehydrogenase
62
Q

What is alcohol broken down into?

A
  • acetaldehyde
63
Q

What can acetaldehyde be broken down into to do what?

A
  • compounds
  • that can be used in respiration to provide energy for cell activities
64
Q

What are the harmful effects of excessive alcohol consumption on the digestive system?

A
  • gastric ulcer (due to excess stomach acid being secreted due to the alcohol stimulating it)
  • cirrhosis of the liver (in which liver cells are destroyed and replaced with fibrous tissue, causing the liver be less able to function)
  • liver failure
  • death
65
Q

What are the harmful effects of alcohol on the nervous system?

A
  • depressant
  • reducing self-control
  • increased reaction time
66
Q

How is alcohol a depressant?

A
  • it slows down brain function
  • effects may vary person to person
67
Q

How does alcohol reduce self-control?

A
  • a person become carefree as alcohol takes away inhibitions
  • they might have social/personal liberties which they may regret
68
Q

How does alcohol increase reaction time?

A
  • as a person drinks more alcohol
  • observable effects of intoxification:
  • slurred speech
  • blurred vision and poor muscle coordination
  • judgement deteriorates (underestimating speed)
  • they may drive faster, with less caution
69
Q

What are some social implications of excessive alcohol consumption?

A
  • neglect work and family
  • exhibits violent behaviour (especially towards family)
  • commit more crimes (compared to sober people)

Biology (8 decks)

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