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Biology 🦠 > Chapter 5: Nutrition in Humans > Flashcards

Chapter 5: Nutrition in Humans Flashcards

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1
Q

Nutrition

A
  • the process by which organisms obtain food and energy for growth, repair and maintenance of the body
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2
Q

Feeding/ingestion

A
  • food is taken into the body
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3
Q

Digestion

A

large food molecules are broken down into smaller, soluble molecules that can be absorbed into the body cells

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4
Q

Absorption

A

Nutrients move from the small intestine into the bloodstream

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5
Q

Assimilation

A

the process whereby some of the absorbed nutrients are converted into new cytoplasm or used to provide energy

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6
Q

Egestion

A

Undigested matter is removed from body

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7
Q

Mouth/Buccal Cavity

A
  • food enters the body through the mouth, which leads to the buccal cavity
  • teeth breaks large pieces of food into smaller pieces to increase surface area of food so that enzymes can act on it more efficiently
  • tongue rolls food into boli (singular is bolus) and pushes them to the back of buccal cavity for swallowing
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8
Q

Salivary Glands

A
  • secretes saliva that contains amylase which digests starch into maltose and mucus which softens food
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9
Q

Pharynx

A
  • connects the buccal cavity to oesophagus and larynx (voice box)
  • leads to trachea
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10
Q

Oesophagus

A
  • muscular tubing connecting mouth cavity and stomach
  • consista of circular muscles inside and longitudinal muscles outside
  • both sets of muscles produce long, slow contractions which move food along the gut via peristalsis
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11
Q

Stomach

A
  • muscular bag which churns the food for up to 4 hours
  • secretes gastric juices which contains enzyme pepsin for digesting proteins into polypeptide, enzyme renin to clot protein in milk & hydrochloric acid to provide correct pH for enzyme to work and to kill potentially harmful bacteria
  • forms chyme by passing through a ring of muscles called pyloric sphincter, which relaxes to allow the food to enter the duodenum
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12
Q

Duodenum

A
  • about 30cm long
  • receives bile by liver via bile duct
  • receives pancreatic juice from pancreas, through the pancreatic duct
  • releases a digestive juice from its walls. the intestinal juices contain enzymes for digestion
  • contents of bile, pancreatic juice and intestinal juices are all alkali in nature, causing pH of duodenum and small intestine to be alkaline
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13
Q

Ileum

A
  • 6m long
  • carries out most of the digestive processes and all digestion ends here
  • linings of walls of small intestine contains glands that secretes digestive enzymes
  • enzymes from intestinal and pancreatic juices digests the food
  • absorption of digested food occurs here
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14
Q

Large intestine

A
  • shorter but border than small intestine
  • about 1.4 meters long
  • consists of the colon, rectum and anus
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15
Q

Colon

A
  • absorbs 90% of remaining water and mineral salts from undigested food material
  • for more effective absorption, its walls are folded to increase its surface area.
  • infections of colon leads to diarrhoea
  • food is moved steadily along duodenum, ileum and colon by peristalsis
  • indigestible fibre forms the bulk against which the muscles of the intestines can push
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16
Q

Rectum

A
  • muscular chambre where undigested food (faeces) is held and moulded before being pushed out through the anus during egestion
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17
Q

Anus

A
  • exit to the alimentary canal
  • closed by a ring of muscle which is relaxed during egestion or defaecation
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18
Q

Liver

A
  • largest gland in the body
  • liver cells produce and secrete bile
  • bile is a greenish-yellow alkaline liquid containing bile salts which is used to neutralise acidic chyme from stomach and emulsify fats to speed up digestion of fats
  • bile is stored temporarily in gall bladder before it is passed into the duodenum
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19
Q

Pancreas

A
  • lies between the stomach and duodenum
  • connected to the duodenum by pancreatic duct
  • secretes insulin and glucagon, which plays an important role in maintaining blood glucose concentration
  • produces pancreatic juices, which passes to the duodenum to help in digestion
  • contains amylase to digest starch to maltase
  • contains trypsin for digesting proteins into polypeptides
  • contains lipase for digesting fats into fatty acids and glycerol
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20
Q

Peristalsis

A
  • rhythmic, wave-like muscular contractions in the walls of the alimentary canal
  • enables contents of the alimentary canal to the well mixed with digestive enzymes
  • move and propels food along the gut
  • is a form of churning in the stomach (physical digestion)
  • longitudinal muscles outside and circular muscles inside, they are antagonistic muscles
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21
Q

How Peristalsis works

A
  • when the circular muscles contract and longitudinal muscles relax, the lumen is constricted and decreases in size 👉 food is pushed forwards
  • when the circular muscles relax and longitudinal muscles contract, they shorten and widen the lumen 👉 allow food to enter
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22
Q

Physical digestion

A
  • increases the surface area-to-volume ratio of the ingested food so that the digestive enzymes can act on the food more effectively
23
Q

Chemical digestion

A
  • breaking down of large molecules into smaller soluble molecules that can be absorbed
24
Q

Processes that take place in the mouth

A
  1. Food in mouth stimulates salivary glands to secrete saliva
  2. Saliva is mixed with food to soften it
  3. Saliva contains salivary amylases which digests starch to maltase
  4. optimum pH of salivary amylase is 7
  5. chewing breaks up food into smaller pieces to increase surface area-to-volume ratio for salivary amylase to work on
  6. Tongue rolls food into small slippery round masses or boli
  7. Boli are swallowed and passes down into oesophagus via pharynx
  8. Peristalsis in walls of oesophagus pushes each bolus of food down into stomach
25
Q

Processes that take place in stomach

A
  1. Presence of food stimulates gastric glands to secrete gastric juices into stomach cavity
  2. Peristalsis in stomach churns and breaks up food and mixes food well with gastric juices
  3. Gastric juices contain HCL, mucus and enzyme pepsin
  4. pepsin digests proteins into polypeptides
  5. mucus layer protects stomach wall from being digested by pepsin as well as moistens food to allow easy movement within stomach
  6. Food remains in stomach for 3 to 4 hours and partially digested food becomes chyme
  7. Chyme passes in small amounts into duodenum when pyloric sphincter relaxes and opens
26
Q

Use of HCL in stomach

A
  1. stops action of salivary amylase by denaturing it
  2. provides a low pH environment within stomach, about pH of 2, which is optimum pH for protease to digests proteins
  3. kills certain potential harmful microorganisms in food
27
Q

Processes in small intestine

A
  1. when chyme enters the duodenum, it stimulates the pancreas to secrete pancreatic juices, gall bladder to release bile and epithelia cells in small intestine to produce enzymes maltase, protease and lipase
  2. food now comes into contact with pancreatic juices, bile and intestinal juices which are all alkali
  3. they neutralise acidic chyme and provide suitable alkaline medium (pH8) for the action of pancreatic and intestinal enzymes
28
Q

Carbohydrate digestion

A
  • digested by carbohydrases
  • begins in mouth. salivary amylase in mouth digests starch in maltose. Only a little starch can be digested because food does not remain long in the mouth
  • no digestion of carbohydrates occurs in stomach as there are no carbohydrases there
  • when carbohydrates enter small intestine, they are digested into simple sugars
29
Q

Protein digestion

A
  • digested by proteases
  • some digestion begin in stomach, where protease in stomach digests proteins into polypeptides
  • undigested proteins that enter small intestine are digested by intestinal protease into polypeptides
  • polypeptides are further digested into amino acids by intestinal protease
30
Q

Fat digestion

A
  • bile is released in duodenum
  • bile salts emulsify fats (physical digestion)
  • emulsification is the breaking up of fats into tiny fate droplets to lower the surface tension of fats 👉 reduce the attractive forces between the fate molecules
  • causes fats to break into tiny fate droplets suspended in water, forming an emulsion
  • this increases surface area-to-volume ratio of fats, speeding up digestion by lipases
31
Q

What is absorption

A
  • the process whereby digested food substances are absorbed into the body cells
32
Q

How is the small intestine adapted for absorption

A
  • small intestine is long
  • inner surface of ileum is folded extensively and has numerous minute finger-like projections called villi
  • the epithelium is only 1 cell thick
  • each villus has many blood capillaries and a lacteal
  • epithelial cells contains many mitochondria to provide energy for active transport of nutrients into the villi
33
Q

Why is the small intestine long?

A
  • so that there is longer/sufficient time for absorption
  • allows more digested food substances to be absorbed by the walls of the small intestine
34
Q

Why is the inner surface of the ileum folded extensively and have numerous villi?

A
  • to increase the surface area for more efficient absorption
  • allows food to be absorbed faster
35
Q

Why is the epithelium only 1 cell thick

A
  • shorter diffusion distance
  • quicker absorption since rate of diffusion increases
36
Q

Why each villus has many blood capillaries and 1 lacteal

A
  • digested food are quickly absorbed and carried away
  • continued transport of digested food substances maintains the concentration gradient for the efficient absorption of digested food substances
37
Q

How does absorption take place in the small intestine

A
  • glucose and amino acids are absorbed by diffusion into the blood capillaries of the villi
  • glucose and amino acids are also absorbed by active transport when there is a lower concentration of food substances in lumen of small intestine than in blood capillaries
  • glycerol and fatty acids diffuse into the epithelium where they combine to form minute fat globules that enter the lumen
38
Q

What happens to undigested and unabsorbed matter

A
  • they are stored in the rectum temporarily
  • discharged as faeces through anus
  • removal of undigested matter from the body is called egestion/defecation
39
Q

How glucose and amino acids transported in body

A
  • after absorption, blood in villi is now rich with nutrients
  • blood capillaries unite to form larger blood vessels
  • which in turn unite to form a large vein, the hepatic portal vein
  • hepatic portal vein transports nutrients from the small intestine to the liver
  • in the liver, most of absorbed sugars are converted into glycogen & stored
  • some glucose transported by blood leaves the liver and distributes around the body
40
Q

How glucose and amino acids are utilised

A
  • all cells use glucose as a source of energy
  • glucose is assimilated and then broken down during tissue respiration to release energy for vital activities within cell
  • excess glucose is returned to liver and stored as glycogen
  • glycogen is converted back to glucose when there is a decrease in blood glucose concentration
  • amino acids that enter the cells are converted into new cytoplasm that is used for growth and repair of worn-out parts of the body
  • amino acids are also used to form enzymes and hormones
  • excess amino acids are deaminated in the liver
41
Q

How are fats transported

A
  • fats are absorbed into the lymphatic capillaries
  • lymphatic capillaries join to form larger lymphatic vessels, which discharge fats into the blood stream
  • blood carries fats to all parts of the body, especially the liver where fats are converted into forms that can either be broken down or stored
42
Q

How are fats utilised

A
  • under normal circumstances, when there is a sufficient supply of glucose, fats are not broken down. Instead, they are used to build protoplasm
  • when glucose is in short supply, fats are broken down to provide energy needed for the vital activities of the body
  • excess fats are stored in special tissue called adipose tissue, which can be found beneath the skin and around the heart and kidneys
  • adipose tissues protect these organs by acting as shock absorbers
43
Q

Functions of liver

A
  1. Production of bile
  2. Deamination of amino acids
  3. Regulation of blood glucose concentration
  4. Break down of hormones are they have served their purpose
  5. Detoxification
44
Q

Deamination of amino acids

A
  • excess amino acids are transported to the liver
  • deamination is the process of removing amino groups from amino acid to convert it to urea
  • urea is removes from body in urine
  • remains of deaminated amino acid are converted into glucose in liver
  • any excess glucose formed this way is converted into glycogen
45
Q

Regulation of blood glucose concentration

A
  • keeps blood glucose concentration constant especially after a meal/ during fasting
  • when blood glucose concentration is high, Islets of Langerhans in pancreas secrete insulin so that cells in liver convert excess glucose into glycogen that is stored in liver, decreasing blood glucose levels
  • when blood glucose concentration is low, Islets of Langerhans in pancreas secrete insulin so that cells in liver convert stored glycogen into glucose to be released into blood stream, increasing blood sugar concentration
46
Q

Detoxification

A
  • harmful substances may be absorbed into the blood from the gut
  • these substances are made harmless by the liver cells
  • the process of converting harmful substances into harmless one is known as detoxification
  • alcohol is a harmful substance
47
Q

Effects of alcohol on digestive system

A
  • alcohol stimulates acid secretion in stomach
  • excess stomach acid increases risk of gastric ulcers
  • prolonged alcohol abuse leads to cirrhosis of liver
  • cirrhosis is a disease in which liver cells are destroyed and replaced with fibrous tissue, making the liver less able to function. Patients with alcoholic cirrhosis may suffer haemorrhage (heavy bleeding) in the liver
  • this leads to liver failure and even death
48
Q

Effects of alcohol on nervous system

A
  1. Depressant
  2. Reduced self-control
  3. Effects reaction time
  4. Long term alcohol consumption on brain
  5. Shrinkage of brain volume
49
Q

Alcohol as depressant

A
  • slows down some brain function
  • can vary from one person to another
50
Q

Alcohol reducing self-control

A
  • under influence of alcohol, a person becomes carefree as alcohol takes away self-control (gurl)
  • with their self-control reduced, they may do things that they may regret after the effects of alcohol have worn off
51
Q

Alcohol affecting reaction time

A
  • as person drinks more alcohol, more observable effects of intoxication occurs
  • blurred vision and poor muscular coordination causes him to walk unsteadily
  • judgement deteriorates & he tends to underestimate speed
52
Q

Long-term effect of alcohol consumption on brain

A
  1. “Wet-brain”: Types of dementia caused by brain damage since alcohol interferes with absorption of vitamin B1, which is essential part of enzyme needed to break down sugar to release energy for brain activities
  2. Shrinkage of brain volume, especially regions associated with memory and reasoning
  3. can interfere with development of fetus brain during pregnancy, which may lead to lifelong physical, mental and behavioural problems
53
Q

Social implications of alcohol consumption

A
  • when sb drinks too much alcohol, they become addicted
  • they are unable to stop until they are drunk
  • their body becomes dependant on alcohol and he becomes an alcoholic
  • they tends to neglect their work & family
  • they also exhibit violent behaviour, especially towards family members and have higher tendency to commit crimes

Biology 🦠 (18 decks)

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