5 — nutrition in human

Question 1

Nutrition definition

Answer 1

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

Question 2

Digestion

Answer 2

Definition: process where large, insoluble, complex food molecules are broken down into smaller, simpler, soluble molecules that can diffuse across cell membranes for absorption into body cells, either thru physical or chemical process.

Definition of physical digestion:
The mechanical break up of food into smaller parts to increase surface area to volume ratio to speed up enzyme action

Definition of chemical digestion:
Process whereby enzymes digest large, insoluble, complex food molecules into smaller, soluble, simple molecules that can be absorbed into body cell.s

Digestion can be a physical process, which involves the mechanical breakdown of large food pieces into smaller pieces by chewing, peristalsis and emulsification. This increases the food molecules’ surface area to volume ratio for faster chemical digestion. [1]

Digestion can be a chemical process, which involves the breaking of bonds in molecules, where food molecules are digested by enzymes into its corresponding products. [1]

Question 3

Absorption

Answer 3

Process where digested substances such as glucose and amino acids will be absorbed and taken into the bloodstream thru wall of ileum of small intestine into the bloodstream and into the body cells via active transport n diffusion. (not equal to diffusion)

Question 4

Assimilation

Answer 4

Process where some of the digested food substances are absorbed into cells n tissues to be converted into new protoplasm or used to release energy

Question 5

Egestion/defecation:

Answer 5

undigested matter is removed from the body

Question 6

Deamination

Answer 6

Amino groups removed from amino acids n converted to urea

Question 7

Peristalsis

Answer 7

rhythmic, wave-like muscular contractions in wall of alimentary canal where the circular and longitudinal muscles contract n relax alternately.

Question 8

Antagonistic muscles:

Answer 8

a pair of muscles whose movements oppose each other

Question 9

Detoxification

Answer 9

The process where harmful substances r converted into harmless substances

Question 10

Mouth & buccal cavity’s function, secretion and digestion

Answer 10

Teeth:
- Breaks up large pieces of food into small round bolus (boli: plural) to increase SA:V of food for enzymes to digest it more efficiently

Salivary glands:(3 pairs)
- Secrete saliva into mouth to be mixed with food by tongue
- Saliva contains mucin which softens the food
- Salivary amylase digests starch to maltose

Tongue:
- Mixes food with saliva
- Rolls food into a bolus to back of mouth to be swallowed

Secretion of saliva, digestion of Carbohydrates:
Starch -(salivary amylase)-> maltose

Question 11

Oesophagus function, secretion and digestion

Answer 11

Peristalsis occurs, helps movement of food along gut + enables food to mix w digestive juices.

• The inner circular muscles contract, outer longitudinal muscles relax. Wall constricts. Gut is narrower n longer n food is pushed forward.
• Longitudinal muscles contracts n circular muscles relax, gut dilates, walls widens n shortens, thus widens lumen to allow food to enter.

No secretion, digestion of starch by salivary amylase continues

Question 12

Stomach function, secretion and digestion

Answer 12

• Bolus enters stomach -> stimulates release of gastric juice by gastric glands -> HCl activates (inactive state of pepsin in stomach; protease) pepsinogen to active pepsin -> digests proteins
• Peristalsis in walls of stomach churns + break up food & mixes food with gastric juice
• Inactive pepsinogen only activates with HCl in cavity to prevent self-digestion of gland cells

Secretion:
Gastric glands in stomach secrete gastric juice: dilute solution of hydrochloric acid (HCl) + pepsin + mucus;

the HCl:
- denatures salivary amylase
- Converts inactive pepsinogen into pepsin
- Prov an acidic medium for action of pepsin
- Kills harmful microorganisms in food
- Pepsin breaks down protein -> short polypeptides

Mucus:
- Prevents contact betw HCl & pepsin with stomach lining
- Moistens food -> easy movement of food

Digestion of Proteins —(Pepsinogen activated to Pepsin by HCl in gastric juice) —> polypeptides

Question 13

Gall bladder function (not part of digestive system)

Answer 13

• Temporarily stores bile produced from liver

Question 14

Pancreas function, secretion and digestion (not part of digestive system)

Answer 14

Produce + secretes:
- pancreatic juice
- Hormones
- Insulin
- Glucagon

Pancreas secretes pancreatic juice containing digestive enzymes: pancreatic trypsin, lipase and amylase

Question 15

If duodenum in SI is blocked

Answer 15

• Carbohydrates & protein digestion not affected
• Bile cannot enter duodenum from gall bladder -> no bile present to emulsify fat into smaller fat globules -> smaller SAtV ratio for lipase to act on -> slower digestion of fats by lipase

Question 16

SI secretion

Answer 16

• Epithelial cells in SI produce + secretes intestinal juice containing enzymes:
  
  • Maltase
  • Sucrose
  • Lactase
  • Peptidases
  • Intestinal lipase
  • Enterokinase
• Secretes pancreatic juice by pancreas (enters duodenum from pancreatic duct) + bile from liver (stored in gall bladder->passes thru bile duct) + intestinal juice by intestinal glands

Question 17

SI digestion

Answer 17

Carbohydrates:
(End products: simple sugars: glucose, fructose, galactose)
- Starch -(pancreatic amylase)-> maltose -(maltase)-> glucose
- Lactose -(lactase)-> glucose + galactose
- Sucrose -(sucrase)-> glucose + fructose

Proteins:
- Proteins —[trypsinogen -(enterokinase in intestinal juice)-> trypsin] —> polypeptides— (peptidases)-> amino acids

Fats:
- Large fat globules —(bile salts)-> small fat globules —(intestinal & pancreatic lipase)-> fatty acids + glycero

Question 18

Gall bladder blocked

Answer 18

Crystallisation of bile components causes gallstones to form in gallbladder, causing blockage.

Gall bladder blocked
- Pancreatic juice cannot enter duodenum from pancreas -> reduced digestion of starch, lipids + proteins
- Bile cannot enter duodenum from gall bladder -> no bile present to emulsify fat to smaller fat globules -> smaller SAtV ratio for lipase to act on -> slower digestion of fats by lipase

Question 19

Gastric bypass surgery:

Answer 19

weight loss surgery by restricting amt of food stomach holds + changing gut hormones -> feel full longer, suppress appetite -> reversal of obesity-caused metabolic syndrome

Question 20

Describe the digestion and absorption processes of x in mammals. [6] (formula)

Answer 20

• Physical digestion of x begin at the mouth, via chewing, to increase the surface area to volume ratio for faster chemical digestion of proteins in the stomach by [enzyme]. [1]
• [enzyme] in the [mouth/stomach], (with the aid of hydrochloric acid which provides an acidic pH in the stomach), will chemically digest x into [y]. [1]
• Pancreatic/ intestinal [enzyme] found in SI will chemically digest the remaining x into [y] in the duodenum IN ALKALINE CONDITION. [1]
• [enzyme], produced by the small intestine, will chemically digest the [y] into [product] in the small intestine IN ALKALINE CONDITIONS. [1]
• The [product] will be absorbed into the villi epithelial cells and into the bloodstream.[1]
• By active transport and diffusion. [1]

Question 21

Describe the role of bile in digestion process. [3]

Answer 21

• Bile is involved in the physical digestion of fat molecules. [1]
• Bile salts in bile emulsify large fat globules into smaller fat droplets. [1]
• This will increase the fat molecules’ surface area to volume ratio for faster chemical digestion by pancreatic and intestinal lipase into glycerol and fatty acids. [1]

Question 22

CAQ: Y amt of fat doesn’t decrease immediately aft entering duodenum

Answer 22

• Time is needed for bile to emulsify larger fat globules into smaller fat globules to increase SAtVR for faster digestion by lipase to digest fats into fatty acids + glycerol.
• Lipase needs an alkaline env to digest fats. Chyme needs to be neutralise b4 lipase can act on it.

Question 23

Absorption of nutrients at SI

Answer 23

• Glucose & amino acids diffuse/absorbed by active transport into blood capillaries
• Glycerol & fatty acids diffuse into epithelium, combine to form minute fat globules n enter lymphatic capillary

Question 24

Adaptations of SI for efficient absorption

Answer 24

SI: 1. Presence of numerous villi (s: villus) on epithelium cells to increase SAtV ratio -> faster absorption of digested nutrients

Villi: 2. Presence of microvilli on epithelial cells -> further ^SA:V -> faster absorption rate of digested nutrients

Villi: 3. Each villus has a one cell thick epithelial wall -> Prov shorter diffusion distance for faster absorption of digested food substances into the bloodstream

Villi: 4. Each villus is rich in blood capillaries (BC) and lacteal present
- BC: to absorb glucose n AA n transport them away
- Lacteal/ lymphatic capillary absorb n transport fats to body
- To help transport absorbed glucose + amino acids + fats quickly -> maintain steep conc gradient for diffusion & active transport
- Diffusion + AT: Glucose & amino acids into blood capillaries (AT when: lower conc in lumen of SI than in BC)
- Diffusion: glycerol & fatty acids into epithelium, combine to form minute fat globules that enter lacteals

Villi: 5. Epithelial cells contain many mitochondria. -> Prov energy for active transport of nutrients into villi

Villi 6: continuous blood flow to maintain a steep concentration gradient → for faster absorption of digested nutrients into the blood capillaries by diffusion.

SI: 7. Length of SI is abt 6m -> Increases time for more efficient absorption of digested food substances

Question 25

Explain how the villus is adapted in absorption of digested nutrients in mammals. [4]

Answer 25

A. Villi r finger-like projections in SI that increase SAtV ratio for faster absorption

Purpose of microvilli in SI [2]:

Microvilli increases surface area to volume ratio of villi of the small intestine; [1]
To increase rate of absorption of digested food molecules into the blood stream/ lacteal of the villi; [1]

1. Each villus has a one-cell-thick epithelial wall → to provide a shorter distance for faster absorption of digested nutrients. [1]
2. Presence of numerous microvilli on the epithelial cells of the villus → to increase its surface area to volume ratio for faster absorption of digested nutrients. [1]
3. Each villus has a lacteal → for the absorption and transport of fat molecules. [1]
4. Each villus is rich in blood capillaries → for faster absorption of glucose and amino acids. [1]
5. There is a continuous blood flow to maintain a steep concentration gradient → for faster absorption of digested nutrients into the blood capillaries by diffusion. [1]

Question 26

Desc how fat globules enter villus

Answer 26

Fatty acids & glycerol enter by diffusion across epithelium where they combine to form tiny fat globules b4 entering lacteal.

Question 27

Factors affecting absorption rate in villus

Answer 27

• Total surface area of villi
• Thickness of epithelium
• Steepness of concentration gradient

Question 28

Impact of reduced villi and diet accommodation to medical condition

Answer 28

• Reduced villi decrease SAtV ratio in absorption of digested nutrients like glucose, amino acids, fat globules formed from fatty acids and glycerol.
• Absorption of digested nutrients is slower compared to normal.
• Patient suffer from malnutrition

Question 29

Why prolonged gastric problems like excess acid production will lead to weight loss

Answer 29

• Excess acid in chyme gg to SI will change SI pH to non-optimum pH in SI
• Pancreatic and intestinal digestive enzymes will denature
• Reduced digestion n absorption of nutrients leading to weight loss

Question 30

State dietary adjustments for XX health problems

Answer 30

• Eat smaller but frequent meals to reduce stomach workload for digestion
• Avoid alcohol consumption to reduce inflammation of stomach lining (depends on qs)
• Ingestion of digestive enzymes supplement with each meal to aid in digestion of nutrients in stomach and SI (depends on qs)

Question 31

Hepatic portal vein function

Answer 31

• Transports absorbed glucose to liver -> most of glucose r excess -> [insulin produced by pancreas stimulates] liver to convert excess glucose to glycogen n stored; glucose transported by hepatic vein to diff parts of body
• Transports absorbed amino acids to liver -> excess amino acids converted to urea (found in urine produced by kidney) by deamination in liver -> transported by hepatic vein to diff parts of body

Question 32

Function of fats

Answer 32

• IF ENOUGH GLUCOSE: fats not broken down n used to build protoplasm like cell membranes
• IF GLUCOSE IN SHORT SUPPLY: fats broken down to prov energy needed for vital activities in body
• Excess fat stored in adipose tissues beneath skin n around heart & kidneys
  
  • Adipose tissues protect organs by acting as shock absorbers

Question 33

Describe the functions of the liver

Answer 33

CARBS METABOLISM:
A. The liver helps to regulate the blood glucose concentration in the blood plasma with the aid of insulin and glucagon. [1]

• If the blood glucose concentration is higher than the norm, the islets of Langerhans in the pancreas will be stimulated to release more insulin. [1] This stimulates the liver to convert excess glucose into glycogen for storage in liver and muscles. [1] Hence, blood glucose level decreases and returns back to the norm. [1]
• If the blood glucose concentration is lower than the norm, the islets of Langerhans in the pancreas will be stimulated to release more glucagon. [1] This stimulates the liver to convert stored glycogen into glucose, which is released into the bloodstream. [1] Hence, blood glucose level increases and returns back to the norm. [1]

Excess glucose can be converted to fats in the liver. [1]

B. Deamination of amino acids into urea by the removal of amino group. [1]
- amino acids used to synthesise plasma proteins such as prothrombin and fibrinogen in liver that is essential for blood clotting [1]
- excess amino acids undergo deamination in liver [1]
- Amino group of amino acids are removed n converted to urea in liver and excreted in kidneys. [1]
- Carbon residues of amino acids from deamination r converted to glucose in the liver. Excess glucose will be converted and stored as glycogen in the liver. [1]

C. Produces bile, which emulsifies large fat globules into smaller fat droplets for subsequent faster chemical digestion of fat molecules into fatty acids and glycerol by lipase. [1]

D. Detoxification of harmful substances such as alcohol, to less harmful or harmless substances. [1]
- Harmful substances like alcohol broken down by liver to make harmless, as it can cus dmg to digestive system + slow down brain functions
- Liver cells contains an enzyme which breaks down alcohol to compounds that can be used in respiration, prov energy for cell activities

E. Breakdown of hormones [1]

F. Iron storage from breakdown of haemoglobin; [1]

G. Synthesis of plasma proteins such as fibrinogen [1]

Question 34

Describe the long term and short term effect of excessive alcohol consumption on the human body. [6]

Answer 34

Short term
- Slows down brain functions such as blurred vision, poor muscular coordination, poor judgement and longer reaction time [1]
- Reduced self-control [1]

Long term - any 3 of the following 4 points:
- Liver cirrhosis [1]
- Alcohol addiction which leads to withdrawal symptoms [1]
- Increases the risk of gastric ulcers as alcohol stimulates acid secretion in the stomach, affecting the digestive system [1]
- Wet brain
- Shrinkage of brain volume
- Heavy consumption of alcohol during pregnancy may interfere with the development of the foetus’ brain -> may lead to lifelong physical, mental and behavioural problems.

Impact of alcohol to human digestive system:
- LT(long term): Alcohol stimulates acid secretion in stomach -> excess stomach acid increase risk of gastric ulcers
- LT: Alcoholic cirrhosis caused by too much alcohol may lead to haemorrhage in liver, liver failure n death

Impacts of alcohol on nervous system:
- ST(short term): Alcohol is a depressant and slows down some brain functions. Its effects vary from 1 person to another.
- ST: Reduced self control. Ppl r carefree n may do things they regret aft effects of alcohol worn off.
- Reduces reaction spd, Longer reaction time; Slurred speech, blurred vision + poor muscular coordination. Judgement deteriorates, tend to underestimate speed -> May drive faster with less caution, reactions r slower. Higher tendency for drunk drivers to involve in traffic accidents.

Social implications:
Alcoholics may,
- end up neglecting their work and families.
- exhibit violent behaviour, especially towards family members.
- be at a higher risk of committing crimes.

Question 35

Suggest how gallstones may affect the digestion of fats [3]

Answer 35

Gallstones may block the bile duct, preventing bile from entering the duodenum.
Lack of bile released from the gall bladder into the duodenum [1];
no emulsification of fats to small fat globules/droplets, lesser surface area for digestion of fats by lipase [1], hence there will be slower rate of fat digestion. [1].

Question 36

Gluten can affect the SI causing villi to decrease in size and number. Suggest and explain what effect this would have on the functioning of alimentary canal. [3]

Answer 36

Surface area to volume ratio of the villi will decrease and this reduces the rate of absorption of digested food molecules. [1]
Due to a decrease in the number of villi, lesser glucose and amino acid molecules will be absorbed into the blood stream. [1]
Lesser fats will be absorbed into the lacteals.[1]

Question 37

Suggest a reason for the reduction in number of cases of serious liver diseases over the years [1]

Answer 37

Many people had greater awareness and were educated on the harmfulness of excessive consumption of alcohol on the liver, resulting in reduction in alcohol consumption. [1]/
Higher cost of alcohol due to alcohol tax which results in reduction in alcohol consumption [1]/ Better medical treatment hence people do not get serious condition [1]

Question 38

Describe the roles of enzymes in human digestion. [5]

Answer 38

Enzymes are involved in chemical digestion in the body where large molecules are digested to smaller molecules; [1]
In the mouth, starch is digested by salivary amylase in saliva, produced by salivary glands, to maltose and the optimum pH of salivary amylase is pH 7; [1]
In the stomach, protein is digested by pepsin, produced by gastric glands, in the gastric juice, to polypeptides and the optimum pH of
pepsin is pH 2; [1]
In the duodenum, pancreatic juice produced by pancreas contains pancreatic lipase, pancreatic amylase and trypsin. Pancreatic lipase digests emulsified fats to fatty acids and glycerol/ Pancreatic amylase digests starch to maltose/ Trypsin digests proteins to polypeptides; [1]
In the small intestine, intestinal juice produced by intestinal glands contains intestinal lipase, maltase and peptidase. Maltase digests maltose to glucose/ Peptidase (erepsin)
digests polypeptides to amino acids/ Intestinal lipase digests emulsified fats to fatty acids and glycerol; [1]

Question 39

State the type of enzyme that breaks down proteins. [1]

Answer 39

Protease