Nutrition & Transport in Humans

Question 1

Define peristalsis

Answer 1

Rhythmic, wave-like contractions that enable food to be mixed with digestive juices & travel along the gut.

Question 2

Functions of hydrochloric acid secreted in the stomach

Answer 2

• Denatures salivary amylase
• Convert pepsinogen to active pepsin (enzyme)
• Provide acidic medium for action of pepsin
• Kill microorganisms in food

Question 3

What does pancreatic juice contain?

Answer 3

• pancreatic amylase
• pancreatic lipase
• trypsinogen (inactive form), active: trypsin

Question 4

What does intestinal juice contain?

Answer 4

• maltase
• peptidases
• intestinal lipase
• lactase
• sucrase

Question 5

Adaptations of small intestine that helps with absorption

Answer 5

1. Large surface area, thin separating membrane & steep concentration gradient - Make absorption efficient
2. Folds, villi and microvilli in the walls of the small intestine - increase the SA:V ratio for the absorption of nutrients
3. Long - Absorption to take place over long period of time
4. In each villus, there is a lacteal or lymphatic capillary - transport fats, surrounded by blood capillaries - transport sugars and amino acids, away from the intestine

Question 6

Explain how a villus is adapted to carry out its function

Answer 6

1. epithelial cells of the villus have microvilli - increase surface area to volume ratio, thus, increasing the rate of absorption of digested food substances
2. the villus has thin wall/membrane/ one cell thick epithelium - to decrease distance travelled by digested food substance during diffusion or active transport.
3. presence of lacteal/lymphatic capillary surrounded by blood capillaries in each villus (lacteal transports fats, blood capillaries transport sugars and amino acids away from the intestine) - continual transport of digested food substances maintains the concentration gradient for the absorption of digested food substances

Question 7

Carbohydrate digestion in SI

Answer 7

• Pancreatic amylase : starch → maltose
• Maltase : maltose → glucose
• Lactase : lactose → galactose + glucose
• Sucrase : sucrose → fructose + glucose

Question 8

Protein digestion in SI

Answer 8

• Trypsin : protein → polypeptides
• Peptidases : polypeptides → amino acids

Question 9

How are fats digested in the small intestine?

Answer 9

• Bile salts emulsify fats. Bile salts reduce attractive forces b/w fat molecules - lower surface tensions of fats, Increase SA:V ratio - enzyme can act on it faster
• Pancreatic & intestinal lipase : Fat → fatty acid + glycerol

Question 10

Define absorption

Answer 10

the process whereby digested food substances are absorbed into the body cells

Question 11

How are glucose & amino acids absorbed?

Answer 11

• diffuse into blood capillaries
• absorbed by AT into blood capillaries

Question 12

How are fats absorbed?

Answer 12

Fatty acids & glycerol diffuse into epithelium & form minute globules which enter the lacteal

Question 13

Define assimilation

Answer 13

the process whereby some of the absorbed food substances are converted into new protoplasm or used to provide energy

Question 14

How is glucose utilised?

Answer 14

• Used for respiration to produce energy for the body’s activities
• Excess glucose - stored as glycogen, converted back when body needs energy
• Insulin regulates glucose-glycogen balance

Question 15

How are AAs utilised?

Answer 15

• Converted into new protoplasm that is used for growth and repair of worn-out body cells
• Used to form enzymes and hormones
• Excess - deaminated in liver

Question 16

How are fats utilised?

Answer 16

• When there is sufficient supply of glucose, fats - used to build protoplasm
• When glucose is in short supply, fats - broken down to provide energy
• Excess fats are stored as adipose tissue

Question 17

What are the functions of liver?

Answer 17

1. Regulation of blood glucose concentration:
   - Keeps BGC in blood relatively constant
   - When glucose level in blood is too high, liver secretes insulin to stimulate liver cells to convert excess glucose → glycogen, Reduce BGC
   - When glucose level in blood is too low, liver secretes glucagon to stimulate liver cells to convert stored glycogen → glucose, raise BGC
2. Iron storage:
   - Worn out red blood cells are destroyed in the spleen. Their haemoglobin is transported to liver.
   - When broken up, iron - produced, which are stored in liver & used in synthesis of new RBCs. Breakdown also produces bile
3. Production of bile: Liver produces bile, which emulsifies fats into small fat droplets which increases the SA:V for lipase to act on
4. Deamination of AA:
   - Amino group is removed & converted to urea. Urea is removed from the body in the urine.
   - Remains of amino acids - converted to glucose
5. Protein synthesis: Liver uses AA from the diet to synthesise proteins such as prothrombin and fibrinogen, which are essential for blood clotting
6. Detoxification: The process of converting harmful substances into harmless products.
   - Alcohol dehydrogenase converts alcohol into acetaldehyde
   - Acetaldehyde broken down by alcohol anhydrous into acetate

Question 18

Harmful effects from excessive alcohol consumption

Answer 18

• Liver cirrhosis, lead to liver failure & death
• Slows down brain function, increase reaction time
• Reduced self-control
• Causes symptoms of ‘drunkenness’
• Addiction
• Increases risks of gastric ulcers

Question 19

Patient with stomach cancer will need to have their stomach removed surgically. What are the effects of the removal of stomach and the changes to the lifestyle of such patient?

Answer 19

• Without the stomach, protein cannot be digested into polypeptide as efficiently as a normal person
• The patient will have to change his/her diet by consuming less protein
• The patient is also more prone to infection of the gut as bacteria are not killed by the hydrochloric acid (in the gastric juice) in the stomach

Question 20

Explain how will a blockage in the bile duct affect digestion

Answer 20

• Bile is prevented from being transported to the duodenum
• Since bile emulsify fats into smaller droplets of fats to increase the SA:V for lipase to act on, when bile is prevented from being transported to the duodenum, the digestion of fats in the small intestine become inefficient/slower

Question 21

Gallstones may become large enough to block the bile duct. Suggest how this affects digestion of fats?

Answer 21

• Blockage of bile duct prevents bile from entering duodenum
• Lack of bile prevents emulsification of fats which reduces the SA available for breakdown of fat by lipase
• Results in less fats being digested

Question 22

Types of white blood cells

Answer 22

1. Phagocytes: Carry out phagocytosis (engulf & digest foreign particles such as bacteria)
   - Lobed nucleus & granular cytoplasm
2. Lymphocytes: Produce antibodies, stimulated by the entry of disease-causing organisms into bloodstream
   - Large, rounded nucleus & small amnt of non-granular cytoplasm- Round in shape & show only limited movements
   - Form in lymph nodes

Question 23

Components of plasma

Answer 23

90% water, 10% mixture of various dissolved subs:
- Soluble proteins: fibrinogen, prothrombin, anitbodies, enzymes
- Dissolved MS: hydrogencarbonates, sodium, potassium
- Food subs: glucose, AA, fats & vitamins
- Excretory products: urea, uric acid, creatinine
- Hormones: insulin, glucagon

Question 24

Functions of plasma

Answer 24

• Transports blood cells, platelets & various dissolved substances arnd body
• Important role in controlling blood pressure, water levels & body temp

Question 25

Main functions of the blood

Answer 25

• Acts as a transport medium carrying various substances from one part of the body to another
• Protects the body against disease-carrying organisms (pathogens)
• Blood clotting @ wounds prevents excessive loss of blood

Question 26

How is oxygen transported by blood

Answer 26

• As blood passes through lungs, oxygen diffuses from the alveoli into the blood
• Haemoglobin in RBC combine reversibly with oxygen to form oxyhaemoglobin (bright red)
• RBC transport oxyhaemoglobin to all tissues of body
• Oxygen diffuses in solution into the tissue cells

Question 27

Protective functions of blood

Answer 27

• Clotting/coagulation of blood
• Phagocytosis
• Production of antibodies

Question 28

How is someone affected by haemophillia (a hereditary disease) ?

Answer 28

• Normal blood-clotting mechanism is greatly impaired
• Slight injuries → bleed to death or die of internal bleeding

Question 29

Process of blood clotting

Answer 29

• When blood vessels are damaged, damaged tissues & platelets release thrombokinase (enzyme)
• Prothrombin (inactive) → Thrombin (active) by thrombokinase in the presence of calcium ions
• Fibrinogen → insoluble threads of fibrin (catalysed by thrombin) to form a mesh to trap blood cells

Question 30

Why blood does not clot in undamaged blood vessels?

Answer 30

-Due to presence of anti-clotting substance, heparin (produced in liver)

Question 31

How is heparin affected when there is an injury?

Answer 31

• When thrombokinase is released, it neutralises the action of heparin and so clotting will be able to take place
• When blood clots, a yellowish liquid, serum, is left behind which has the same composition as plasma, but lacks clotting factors

Question 32

Formation of pus

Answer 32

• In the process of phagocytosis, some of the phagocytes are killed
• dead phagocytes tgt w/ dead bacteria form pus

Question 33

Action of antibodies

Answer 33

• Destroy bacteria by attaching to them→ bacterial surface membrane to rupture
• Causing bacteria to clump tgt or agglutinate to be easily ingested by phagocytes
• Neutralising harmful substances (toxins) produced by bacteria

Question 34

What is tissue rejection and how?

Answer 34

• Organ from others - treated as foreign body by recipient’s immune system
• recipient’s lymphocytes - respond by producing antibodies to destroy transplanted organ

Question 35

Ways to prevent tissue rejection

Answer 35

• Tissue match: Tissues of both donor & recipient - genetically close as possible
• Use of immunosuppressive drugs: inhibit responses of recipient’s immune system

Question 36

Disadvantages of immunosupressive drugs on recipients

Answer 36

• has lower resistance to many kinds of infections
• continue taking the drugs for the rest of life

Question 37

How are substances transferred b/w cap & tissue cells?

Answer 37

• Dissolved food substances & oxygen diffuse from blood in cap. into tissue fluid & into cells
• Metabolic waste products diffuse from cells into tissue fluid & then through cap. walls into blood - blood transports these to excretory organs for removal

Question 38

Explain the process in a cardiac cycle

Answer 38

1. Atria contract, forcing blood into the relaxed ventricles
2. After a short pause, ventricles contract. Rise in pressure causes atrio-ventricular (AV) valves to close to prevent backflow, producing a ‘lub’ sound. Semi-lunar valves open - Blood flows from right ventricle & left ventricle into pulmonary arch & aortic arch respectively.
3. As ventricles contract, atria relax. Right atrium receives blood from venae cavae. Left atrium receives blood from pulmonary veins.
4. Ventricles then relax. Fall in pressure → semi-lunar valves to close to prevent backflow, procuing a softer ‘dub’ sounds. AV valves also open & blood flows from the atria into ventricles.
5. Atria contract again & the whole cycle repeats.

Question 39

What is ventricular systole?

Answer 39

contraction of ventricles

Question 40

What is ventricular diastole?

Answer 40

relaxation of the ventricles

Question 41

Causes of coronary heart disease

Answer 41

• Build up of fatty deposits/cholesterol in inner walls of coronary artery. This is called atherosclerosis.
• Rough inner surface of artery increases risk of blood clot being trapped in artery. Blood clot that forms in an artery is called thrombosis.

Causes lumen of coronary artery: blocked or narrowed
- greatly decreases amnt of O2 & glucose supplied to the heart muscle cells
- damaging/death of heart muscle cells as aerobic respiration cannot occur

Question 42

Factors increasing risk of CHD?

Answer 42

• Diet rich in cholesterol & unsaturated animal fats
• Emotional stress
• Smoking

Question 43

What are the preventive measures against CHD?

Answer 43

• Proper diet: Lower cholesterol level in blood & Polyunsaturated plant fats - substitute animal fats since they do not stick to inner surface of arteries
• Proper stress management
• Avoid smoking - Cigarette smoke contains nicotine & carbon monoxide - harmful & increases risk of CHD
• Regular physical exercise - Long-term beneficial effects on circulatory system, strengthens the heart, maintains elasticity of arterial walls, risk of HBP or hypertension can be greatly reduced

Question 44

Explain why chambers of the heart have walls of different thickness

Answer 44

• atria: lesser amount of muscular & elastic tissue > thinner walls as they don’t need to generate much force to pump blood into adjacent ventricles
• right ventricle: needs more muscles & elastic tissues to generate the force needed to pump blood to lungs
• left ventricle: most muscle & elastic tissues to generate the force needed to pump blood to the rest of the body under pressure

Question 45

Effects on the body of having a hole between 2 atria

Answer 45

• allows oxygenated & deoxygenated blood from left atrium & right atrium to mix
• reduces the amnt of O2 that can be pumped around the body
• body cells not able to carry out aerobic respiration effectively to release energy
• feel tired easily