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Secondary 3 Biology > nutrition in humans > Flashcards

nutrition in humans Flashcards

1
Q

what is the definition of nutrition?

A

process by which organisms obtain food and energy for growth, repair and maintenance of the body

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2
Q

what are the processes when food enters in your body?

A
  1. Ingestion
    - food is taken into the body
  2. digestion
    - large, complex, insoluble and indiffusible food molecules are broken down into smaller, simpler, soluble and diffusible food molecules
  3. absorption and assimilation
    - digested food molecules are absorbed into the cells
    - the food molecules are converted into new protoplasm or used to provide energy
  4. egestion
    - undigested food is removed from the body
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3
Q

what is physical digestion?

A
  • mechanical break up of good into smaller particles

- by: chewing, peristalsis, emulsification

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4
Q

what is chemical digestion?

A
  • break-down of large, insoluble molecules into smaller, soluble molecules that can be absorbed
  • hydrolytic reactions catalysed by digestive enzymes
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5
Q

what is chemical digestion?

A
  • break-down of large, insoluble molecules into smaller, soluble molecules that can be absorbed
  • hydrolytic reactions catalysed by digestive enzymes
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6
Q

how is the food physically digested in the mouth?

A

by chewing, teeth cut and grinds food into smaller pieces so as to increase surface area for salivary amylase to digest starch

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7
Q

how is the food chemically digested in the mouth?

A
  • salivary glands in mouth secretes saliva, which contains salivary amylase
  • starch –> (salivary amylase) –> maltose
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8
Q

what happens when tongue rolls food into boli?

A
  • food goes to buccal cavity
    pharynx (both food and air enter)
  • connects buccal cavity to oesophagus, larynx and trachea
    larynx (voice-box)
  • has a slit opening, glottis (hole_
  • when breathing, larynx moves downwards and glottis opens, allowing air to enter trachea and move into lungs
  • when swallowing, larynx moves upwards and epiglottis covers glottis, preventing food particlaes from entering trachea
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9
Q

describe the oesophagus?

A
  • narrow, muscular tube. Extend to stomach
  • walls made up of circular and longitunal muscles
  • peristalsis occurs
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10
Q

define peristalsis?

A

longitunal muscles and circular muscles contract and relax alternately to produce a rhythmic wave-like muscular contraction

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11
Q

describe the stomach?

A
  • gravity pushes food bolus into stomach
  • stomach is a thick, distensible muscular bag
  • stomach walls has numerous gastric pits
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12
Q

what happens when food is physically digested in the stomach?

A
  • peristalsis, mixes food with gastric juice and churns food into smaller pieces
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13
Q

what happens when food is chemically digested?

A
  • gastric glands secrete gastric juice
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14
Q

what is gastric juice?

A
  • dilute solution of hydrochloric acid, mucus and enzyme (pepsin. pH 2)
  • function of HCl
  • denatures salivary amylase
  • converts inactive pepsinogen into active pepsin (chemical digests protein into polypeptides)
  • provide acidic medium for action of pepsin
  • kills harmful microorganisms in food
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15
Q

describe the activation of pepsin?

A
  • enzyme pepsin is produced and released in the stomach as inactive pepsinogen
  • as bolus enters the stomach, gastric glands are stimulated to produce gastric juice containing hydrochloric acid which activates pepsinogen to active pepin
    pepsinogn (inactive) –> (activated by HCl) –> pepsin (active)
    proteins –> pepsin digests polypeptides
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16
Q

describe the small intestine?

A
  • consists of duodenum, jejunum and ileum
  • chyme enters duodenum and stimulates the release of:
  • pancreatic juice by pancreas
  • bile of gall bladder
  • intestinal juuice by small intestine
  • these alkaline fluids neutralise the acidic chyme
  • alkaline medium is needed for action of intestinal and pancreatic enzymes
17
Q

what is the function of the gall bladder?

A
  • release stored bile

- bile passes through bile duct into duodenum

18
Q

what is the function of bile?

A

emulsify fat into smaller fat globules so as to increase surface area to volume ratio for faster digestion by lipase into fatty acids and glycerol

19
Q

what is the function of the pancreas?

A
  • secrees pancreatic juice, which contains the enzymes: pancreatic amylase, pancreatic lipase and trypsin
  • fats –> (pancreatic lipase) –> fatty acids + glycerol
  • proteins –> (trypsin) –> polypeptides
  • starch –> (pancreatic amylase) –> maltose
20
Q

what is the function of intestinal glands?

A
  • secretes intestinal juice containing enzymes: maltase, sucrase, lactase, peptidases and intestinal lipase
  • digest food molecules
  • fats –> (intestinal lipase) –> fatty acids + glycerol
  • polypeptides –> (peptidases) –> amino acids
  • maltose –> (maltase) –> glucose
  • sucrose –> (sucrase) –> glucose + fructose
  • lactose –> (lactase) –> glucose + galactose
21
Q

how are carbohydrates digested?

A
  1. mouth
    - starch –> (salivary amylase) –> maltose
  2. small intestine
    - maltose –> (maltase) –> glucose
    - lactose –> (lactase) –> glucose + galactose
    - sucrose –> (sucrase) –> glucose + fructose
22
Q

how are proteins digested?

A
  1. stomach
    - protein –> (pepsin) –> polypeptide
  2. small intestine
    - protein –> (trypsin) (trysinogen) –> polypeptides –> (peptidase) –> amino acids
23
Q

how are fats digested?

A
  1. small intestine
    - large fat globules –> (bile) –> small fat globules –> (intestinal lipase) (pancreatic lipase) –> fatty acids and glycerol
24
Q

how is absorption done?

A
  • small intestine is the site of absorption of the final products of digestion
  • ileum is the main region of absorption
25
Q

how is the small intestine adapted?

A
  1. small intestine is long to provide sufficient time for absorption of digested food susbtances via diffusion and active transport from lumen of small intestine
  2. inner surface of small intestine has numerous folds, and folds have numerous villi to increase the surface area to volume ratio for faster absorption of digested food substances via diffusion and active transport from lumen of the small intestine
26
Q

how the small intestine + villus is adapted?

A

villi/villus are minute finger like projections on the folds of the small intestine

  1. presence of microvilli on the epithelial cells to further increase surface area for faster absorption of giested food substances to take place via diffusion and active transport
  2. epithelium is one cell thick to provide shorter distance for absorption of digested food materials via diffusion and active transport
  3. richly supplied with blood capillaries and lacteal. Blood capillaries transport sugar and amino acids to te body. Lacteal transport fats to body. This continual transport of digested food susbtances maintains the steep concentration graient for absorption of digested food susbtances to take place
27
Q

what are the factors affecting rate of absorption?

A
  1. surface area
  2. thickness of separating membrane
  3. concentration gradient
28
Q

how are nutrients absorbed into villi?

A
  1. by diffusion
    - if concentration of glucose and amino acids are higher in the lumen as compared to villi,
    - glucose and amino acids will be absorbed into the blood capillaries by diffusion
    - fatty acids and glycerol diffuse into the epithelium, and combine to form small fat globules which enter lymphatic capillary (lacteal)
  2. by active transport
    - if concentration of glucose and amino acids are lower in the lumen as compared to villi,
    - glucose and amino acids will be absorbed into the blood capillaries by active transport
29
Q

what happens to the undigested food?

A
  • enters large intestine
  • stored temporarily in rectum and discharged as faeces through anus
  • discharging of faeces: egestion
30
Q

what are the functions of the hepatic portal vein?

A
  • blood capillaries that supply small intestine unite to form hepatic portal vein
  • it transports glucose and amino acids to the liver
31
Q

what happens to the absorbed glucose?

A
  • hepatic portal vein transports glucose to liver
    in liver:
  • most glucose is converted to glycogen and stored
  • the rest of the glucose are transported by hepatic portal vein to different parts of the body
    glucose + O2–> CO2 + H2O + energy
32
Q

what happens to absorbed amino acids?

A

in liver:
- amino acids are transported by hepatic portal vein to different parts of body
- excess amino acids are converted to urea by deamination
- amino acids used for:
1. growth and repair in cells
2. form enzymes and hormones
H2H –> (deamination) –> amino group –> ammonia –> urea

33
Q

what are the 5 functions of the liver?

A
  1. production of bile
  2. regulation of blood glucose
  3. concentration protein synthesis
  4. storage of iron
  5. detoxification
34
Q

describe production of bile?

A

bile emulsifies large fat globules into smaller fat glbules so as to increase surface area to volume ratio for faster digestion by lipase

35
Q

describ regulation of blood glucose concentration?

A
  • liver keeps blood glucose concentration constant at about 70-90 mg/100cm3 of blood
  • if blood glucose concentration is higher than norma
  • islets of Langerhans in pancreas will be stimulated to release more insulin
  • insulin stimulates liver to convert excess glucose into glycogen for storage in the liver &muscles
  • blood glucose level decreases back to the norm
  • if blood glucose concentration is lower than normal
  • islets of Langerhans in the pancreas will be stimulated to release more glucagon
  • glucagon stimulates liver to convert stored glycogen into glucose, which is released into the bloodstream
  • blood glucose level increases back to the norm
36
Q

describe protein synthesis?

A
  • liver uses amino acids to synthesize proteins such as prothrombin and fibrinogen which are essential for clotting of blood
  • amino group of amino acids are removed (deamination) and converted to urea in liver
  • carbon residues of amino acids from deamination are onverted to glucose in the liver
37
Q

describe storage of iron?

A
  • red blood cells have a lifespan of about three months
  • when red blood cells are worn out, they are destroyed in the spleen. Their haemoglobin will be sent to liver and be recycled
  • breakdown of haemoglobin produces iron and bile
  • iron will be stored in liver –> and be used to synthesize new red blood cells
38
Q

describe detoxification?

A
  • process of converting harmful substances into harmless products
  • in the liver, alcohol dehydrogenase is present
  • the enzyme will convert alcohol to acetaldehyde which can be broken down further to form acetate that can be used for cellular respiration
    alcohol –> acetaldehyde –> acetate for cellular respiration –> energy
39
Q

what are the harmful effects of alcohol?

A
  1. short term
    - reduced self- controk
    - slows down some brain functions
    - slower reaction rate
    - longer reaction time
  2. long term
    - may lead to addiction
    - liver cirrhosis –> liver failure –> death
    - alcohol stimulates acid secretion in the stomach which increases the risk of gastric ulcers

Secondary 3 Biology (13 decks)

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