Chapter 5: Nutrition in humans! 🍣🍡

Question 1

What is the process of nutrition?

Answer 1

• Nutrition is the process by which organisms obtain food and energy for the growth, repair, and maintenance of the body and it consists of 5 processes.

Question 2

What are the 5 processes of nutrition?

Answer 2

1. Feeding/ingestion:
   - Food is taken into the body usually through the mouth (food intake).
2. Digestion:
   - Food molecules are broken down into simple molecules that can be absorbed by the alimentary canal.
3. Absorption:
   - Digested food is absorbed by the small intestine.
4. Assimilation:
   - Absorbed nutrients are converted into new cell components or used by the cell to provide energy.
5. Egestion:
   - Undigested food is removed as faeces (poop).

Question 3

What are some examples of poop?

Answer 3

• Faeces can be hard or soft.
• Hard faeces: Constipation and slow bowel movements.
• Soft faeces: Diarrhoea and watery, which can be caused by dieting and the endocrine system when hormones are released during menstruation.
• Prostaglandins: They begin to relax the smooth muscle tissues inside your uterus to help it shed its lining and it affects your bowels in your large intestine, resulting in diarrhoea and more faeces produced.

Question 4

What is digestion?

Answer 4

• Digestion is the process by which big and complex food molecules are broken down into smaller and simpler soluble molecules that the body can absorb.

Question 5

What are the 2 types of digestion that takes place in the human digestive system?

Answer 5

• The digestive system carries out CHEMICAL and PHYSICAL digestion.

Question 6

What is physical digestion?

Answer 6

• Physical digestion is the mechanical break-up of food into smaller pieces, which in turn increases the amount of surface area with enzymes and acid so that digestive enzymes can act on them more efficiently.
  -The chewing action of the teeth and the tongue breaks down the food molecules into smaller pieces.
• The churning action brought about by the contraction and relaxation of stomach muscles breaks up the pieces of food and mixes them up with digestive juice.
• e.g. Gastric juice and hydrochloric acid.

Question 7

What is the emulsification of the breaking up of fats into tiny droplets by bile and how does it aid in the digestion of fats and fat globules?

Answer 7

• The emulsification of breaking up fats into tiny fat droplets by bile which is produced by the liver and is stored in the gall bladder increases the surface area-to-volume ratio.
• This speeds up fat digestion by lipases.

Question 8

What is bile?

Answer 8

• Bile is an alkaline, greenish-yellow liquid that does not contain any enzymes.

Question 9

What is chemical digestion?

Answer 9

• Chemical digestion is the breakdown of food into simpler and soluble molecules that are small enough to be absorbed by the body.
• It is carried out by the digestive enzymes.

Question 10

What is the alimentary canal and what are the related organs?

Answer 10

• The human digestive canal consists of the alimentary canal (gut), and the related organs such as the liver, gall bladder, and pancreas.
• The liver is the largest gland in the body, and it is located below the diaphragm.

Question 11

What is the mouth and what are its functions?

Answer 11

-The mouth ingests (takes in) food.
- Salivary glands secrete saliva.
- Teeth break up large pieces of food into smaller pieces by chewing.
- Tongue mixes the food with saliva and rolls the food in BOLI (a small mass of food that reduces friction to make the BOLI travel down the gullet more quickly and easily.

Question 12

What is the pharynx and what are its functions?

Answer 12

• The pharynx joins the mouth to the oesophagus, larynx (voice box), and trachea (windpipe).
• Prevents food or drink from entering the trachea during swallowing by a flap-like tissue called epiglottis.

Question 13

What is the oesophagus and what are its functions?

Answer 13

• The oesophagus joins the pharynx to the stomach, allowing the boli to travel down to the stomach.
• Pushes food towards the stomach by wave-like contractions of its walls.

Question 14

What is peristalsis?

Answer 14

• Peristalsis is the rhythmic contraction and relaxation of the muscles in the alimentary canal that occurs from the oesophagus to the rectum.

Question 15

What is the stomach and what are its functions?

Answer 15

• A stomach is a distensible bag with thick and muscular walls.
• Breaks large pieces of food into smaller pieces by muscular contractions of its walls.
• Glands secrete gastric juice containing enzymes to digest proteins.
• Forms cyme, which is the mixture of enzymes and food in the stomach.

Question 16

What is the small intestine and what are its functions?

Answer 16

• the small intestine consists of the duodenum and ileum, where digestion is completed.
• Receives pancreatic juice and bile via the pancreatic duct and bile duct respectively.
• Secretes intestinal juice which contains maltase, peptidases, and lipase.
• Absorbs water and nutrients from food.

Question 17

What is the large intestine and what are its functions?

Answer 17

• the large intestine consists of the colon, the rectum, and the anus.
• Colons absorb water and mineral salts from undigested food.
• Faeces is stored in the rectum temporarily and expelled through the anus when the rectum contracts.

Question 18

What is the liver and what are its functions? (related organs but not the main ones)

Answer 18

• The liver secretes bile, which is stored in the gall bladder, via the bile duct (connects liver and gall bladder) into the duodenum to aid in fat digestion.

Question 19

What is the pancreas and what are its functions? (related organs but not the main ones)

Answer 19

• The pancreas secretes pancreatic juice, which contains digestive enzymes such as amylase, lipase, and protease.
• Secretes the hormone insulin that helps to control the blood sugar level in the blood (level of sugar in the blood).

Question 20

What is one of the advantages of peristalsis moving food along the gut?

Answer 20

• Peristalsis moves food along the gut and allows it to be mixed with digestive juices.

Question 21

What are the 2 ANTAGONISTIC muscles that help to carry out muscle contractions?

Answer 21

• This muscle contraction is carried out by 2 sets of antagonistic muscles:
  1. Circular muscles:
• Are located next to the lumen.
  2. Longitudinal muscles:
• Are located on the outer parts of the organ.

Question 22

What happens when the circular muscles contract?

Answer 22

• When the circular muscles contract, the longitudinal muscles (muscles located outside the organ, thus covering it) relax.

Question 23

What happens when a bolus (ball of food) tries to enter the oesopahgus and travels through it?

Answer 23

• The alimentary canal is divided into sections.
• When a section constricts, the food bolus is squeezed through to the following section ahead of it which dilates and allows the bolus to enter.

Question 24

How are the end-products of digestion and water absorbed?

Answer 24

• The end-products of digestion and water are absorbed throughout the length of the small intestine, especially in the ileum.
• Glucose and amino acids are absorbed by diffusion and active transport.
• Fatty acids and glycerol are absorbed by diffusion into the epithelium and they combine into fat globules to enter lacteals (the lymphatic vessels of the small intestine which absorb digested fats).

Question 25

why are the inner walls of the small intestine highly folded?

Answer 25

• This is to aid in absorption and to allow for easier absorption, thus the inner walls of the small intestine are highly folded and are lined with villi (small folds in the small intestine).

Question 26

What is a villi?

Answer 26

• Small folds and finger-like projections that are found mostly in the ileum of the small intestine which increases the surface area for the digestion of food substances and absorption of nutrients.

Question 27

What is the advantage of having villi in the absorption of nutrients in the small intestine?

Answer 27

-The villi can increase the amount of surface area for the digestion of food and the absorption of nutrients, glucose, and amino acids, which are then transported away by blood capillaries.
-This makes the process more efficient and quicker, leading to easier and faster digestion.

Question 28

Where are lacteals and lymphatic capillaries found?

Answer 28

• Lacteals or lymphatic capillaries are found within the villi, transporting absorbed fats away to other parts of the body.

Question 29

Why does the epithelial cells have so many mitochondria in them?

Answer 29

• The epithelial cells have a lot of mitochondria to provide energy for active transport of nutrients.

Question 30

What are the adaptations of the small intestine for absorption?

Answer 30

1. To increase the surface area-to-volume-ratio:
   - Relatively long organs.
   - E.g. villi; folds of the small intestine to increase surface area for digestion of food and the absorption of nutrients.
   - Folded inner surface
   - The presence of numerous villi.
   - The presence of microvilli (smaller villi) on each villi.
2. To increase diffusion rate:
   - One-cell thick wall of villus for the rapid movement of nutrients.
   - One-cell thick wall of blood capillary for the rapid entry of nutrients.
   - Steep concentration gradients of the nutrients, which is maintained by the continuous and rapid transport of digested food away by the lacteals and blood capillaries.

Question 31

Where is water, mineral salts and vitamins absorbed at?

Answer 31

• Water, mineral salts and vitamins are absorbed by the large intestine.

Question 32

What is the process of defecation?

Answer 32

• Defecation is a process whereby undigested and unabsorbed matter is temporarily stored in the rectum before being egested or expelled (passed out) as faeces through the anus.

Question 33

Where are sugars, amino acids and fatty acids and glycerol absorbed in?

Answer 33

• All digested food substances such as sugars, amino acids, fatty acids, and glycerol are absorbed in the small intestine.

Question 34

How is the hepatic portal vein formed?

Answer 34

• Glucose and amino acids are absorbed by diffusion and active transport into blood capillaries which joins to form small veins and unite to form the hepatic portal vein.

Question 35

What is the hepatic portal vein?

Answer 35

• The hepatic portal vein is a dedicated vessel from the small intestine to the liver, which helps to transport nutrients to the liver.

Question 36

What is the medium and substance that absorbs fatty acids and glycerol?

Answer 36

• Fatty acids and glycerol are absorbed by lacteals which combine to form lymphatic vessels.

Question 37

What happens after the lymphatic vessels eventually empty into the bloodstream/

Answer 37

• The lymphatic vessels eventually empty into the bloodstream and fats are transported to all parts of the body, especially the liver.

Question 38

What is the assimilation?

Answer 38

• Assimilation is the process in which nutrients are absorbed and converted into a new cytoplasm or used to provide energy.

Question 39

How is glucose used in the body?

Answer 39

• Glucose is taken into the cells and is broken down during respiration to release energy.
• Excess glucose returns to the liver and is stored as glycogen.
• BUT eventually glycogen is converted back into glucose when energy is needed.

Question 40

How are amino acids used in the body?

Answer 40

• Amino acids enter cells and are converted into a new cytoplasm that is used for (cell) growth, and the repair of worn-out body parts.
• Is used to form enzymes and hormones.
• The excess amino acids are deaminated (the removal of an amino group from an amino acid or other compound) in the liver.

Question 41

How are fats used in the body?

Answer 41

• Fats are used to build protoplasm when there is sufficient glucose.
• it is broken down to provide energy when glucose is insufficient.
• Excess fats are stored in ADIPOSE tissues under the skin or around the heart and kidneys.

Question 42

What is an ADIPOSE tissue?

Answer 42

• An adipose tissue is a connective tissue that extends throughout your body.
• It is found under your skin, between your internal organs, and in the inner cavities of bones.
• It is primarily composed of fat cells that store energy in the form of TRIGLYCERIDES.

Question 43

What are the roles and functions of the liver?

Answer 43

• The liver has roles in regulating blood glucose levels, fat digestion, the deamination of amino acids, breaking down of hormones, and detoxification.

Question 44

What are the hormones insulin and glucagon?

Answer 44

• Insulin and glucagon are hormones that are produced and secreted by the islets of Langerhans in the pancreas in the pancreas.
• These hormones act on liver cells to regulate blood glucose concentration.

Question 45

What are the actions of insulin and glucagon on the liver in the regulation of blood glucose concentration?

Answer 45

1. Stimulus: High blood glucose concentration
   Hormone: Insulin
   Overall effects:
   - Acts on liver cells to convert excess glucose to glycogen for storage.
   - returns blood glucose to a normal level.
2. Stimulus: Low blood glucose concentration
   Hormone: Glucagon
   Overall effects:
   - Acts on liver cells to convert glycogen to glucose for energy.
   - Returns blood glucose to a normal level.

Question 46

How does the liver help in fat digestion and where is bile stored at?

Answer 46

• The liver helps in fat digestion by secreting bile.
• Bile is temporarily stored in the gall bladder.

Question 47

What is the acid/enzyme that the liver removes?

Answer 47

• The liver removes the excess amino acids.
• The amino group (NH2) in an amino acid is removed and is then converted first to ammonia, and subsequently to urea for excretion by the kidneys. (DEAMINATION)
• The remains of the deaminated amino acids are converted into first glucose and subsequently to glycogen for storage.

Question 48

What is deamination?

Answer 48

• Deamination is the process when the amino group (NH2), in an amino acid, is removed and converted first to ammonia, and subsequently to urea for excretion by the kidneys.

Question 49

Where are the hormones brought to after they have exerted their effects?

Answer 49

• Hormones, which are largely protein in nature, are brought to the liver to be broken down after they have exerted their effects.

Question 50

What is detoxification?

Answer 50

• Detoxification is the process whereby the liver cells carry out and it is where harmful substances are converted to harmless ones.

Question 51

What is alcohol dehydrogenase and what (substance) does it break down?

Answer 51

• The liver contains an enzyme called alcohol dehydrogenase and it breaks down alcohol to acetaldehyde.
• Acetaldehyde is then broken down into compounds, which can be used in respiration to provide energy.

Question 52

What are the effects of alcohol consumption in the digestive system?

Answer 52

Organ: Stomach
Effects: Increases acidic secretions, which increases the risk of stomach ulcers.
Organ: Liver
Effects:
- Prolonged abuse causes liver cirrhosis, where liver cells are destroyed, and replaced by fibrous tissue.
-Liver cirrhosis can lead to bleeding in the liver, liver failures and death.

Question 53

What are the effects of alcohol consumption in the nervous system?

Answer 53

Organ: Brain
Effects:
- It slows down brain functions and decreases reaction time which reduces a person’s responsiveness.
- Reduces self-control and inhibition, making a person more carefree and it may result in a person taking unwarranted personal and social liberties.
- Other effects of intoxification include slurred speech, blurred vision, and poor muscle coordination.
-Effect of long-term alcohol consumption is “wet brain”, which is dementia caused by brain damage, and shrinkage of the brain volume and it is especially in the region to do with memory and reasoning.
- Heavy consumption during pregnancy may interfere with the development of the fetus’ brain.

Question 54

What is the effect of the frequent excessive use of alcohol?

Answer 54

• Frequent excessive use of alcohol may have a detrimental social impact.
• Family responsibilities may be neglected by individuals.
  Violent behaviour may be targeted at family members.
• The likelihood of individuals performing criminal activities may increase.