What are the definitions of digestion and egestion, and why is food important to be cooked and preserved?

Here are the answers to the questions on the paper:

SECTION A

1.

a)

i) Define Digestion

• Digestion: The process by which large, insoluble food molecules are broken down into smaller, water-soluble molecules that can be absorbed into the bloodstream.

ii) Define Egestion

• Egestion: The act of expelling undigested or unabsorbed food material (feces) from the body through the anus.

b) Draw a large well labeled diagram of the human alimentary canal.
I am unable to draw diagrams.

c) State three (3) reasons in each case why it is important for food to be

i) Cooked

• • Cooking kills harmful microorganisms (bacteria, parasites) that can cause foodborne illnesses.
• • It improves the taste, texture, and aroma of food, making it more palatable.
• • Cooking often softens food, making it easier to chew and digest.

ii) Preserved

• • Preservation prevents spoilage by inhibiting the growth of microorganisms (bacteria, fungi) that cause decay.
• • It extends the shelf life of food, allowing it to be stored for longer periods.
• • Preservation helps maintain the nutritional value and quality of food over time.

2.

a)

i) What is respiration?

• Respiration: The biochemical process in living organisms where organic substances (like glucose) are broken down, usually with oxygen, to release energy (ATP) for metabolic activities.

ii) Write down an equation that summarizes aerobic respiration.

$$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \to 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)}$$

b) Explain how oxygen from the atmosphere enters the blood stream.
Oxygen from the atmosphere enters the lungs and reaches the alveoli. Due to a higher partial pressure of oxygen in the alveoli compared to the blood in the surrounding capillaries, oxygen diffuses across the thin alveolar and capillary walls into the bloodstream. Here, it binds to hemoglobin in red blood cells to be transported.

c) State three (3) transport functions of blood

• • Transport of oxygen from the lungs to body tissues.
• • Transport of nutrients (e.g., glucose, amino acids) from the digestive system to cells.
• • Transport of waste products (e.g., carbon dioxide, urea) from cells to excretory organs.

3.

a) What is osmoregulation?

• Osmoregulation: The active regulation of the osmotic pressure of an organism's body fluids to maintain the homeostasis of the organism's water content; that is, it keeps the body's fluids from becoming too diluted or too concentrated.

b) Make a large well labeled diagram of the transverse section through the human kidney.
I am unable to draw diagrams.

c) Describe the function of the kidneys in regulating the water content of body fluids
The kidneys regulate water content by filtering blood and selectively reabsorbing water. When the body is dehydrated, the pituitary gland releases Antidiuretic Hormone (ADH), which increases the permeability of the kidney tubules and collecting ducts to water, leading to more water reabsorption and production of concentrated urine. Conversely, with excess water, less ADH is released, reducing water reabsorption and resulting in dilute urine.

d) Name the organs responsible for maintaining a fairly constant level of

i) Temperature

• • Skin (through sweating, vasodilation/vasoconstriction)
• • Hypothalamus (thermoregulatory center in the brain)

ii) Glucose

• • Pancreas (produces insulin and glucagon)
• • Liver (stores and releases glucose as glycogen)

4.

a) Distinguish between

i) Antigen and antibody

• • Antigen: A foreign substance, usually a protein or polysaccharide, that triggers an immune response in the body, leading to the production of antibodies.
• • Antibody: A protein produced by plasma cells (a type of white blood cell) in response to an antigen. Antibodies specifically bind to antigens to neutralize them or mark them for destruction by other immune cells.

ii) Active immunity and passive immunity

• • Active immunity: Immunity developed by an individual's own immune system after exposure to an antigen, either through natural infection or vaccination. It is long-lasting because memory cells are formed.
• • Passive immunity: Immunity acquired by receiving antibodies from an external source, such as from a mother to her baby through breast milk or placenta, or via injection of antiserum. It provides immediate but short-term protection as no memory cells are produced.

b) Explain why the body does not develop full immunity against some diseases e.g malaria
The body does not develop full immunity against some diseases like malaria because the causative agents, such as the Plasmodium parasite, have complex life cycles and exhibit significant antigenic variation. This means the parasite can change its surface proteins, making it difficult for the immune system to recognize and mount a sustained, effective response against all forms of the pathogen.

c) Why is prevention better than cure?
Prevention is better than cure because it avoids the onset of disease, thereby preventing suffering, health complications, and potential long-term damage to the body. It is also often more cost-effective and requires fewer resources than treating an established illness, which can involve expensive medications, hospital stays, and prolonged recovery periods.

d) Describe the mechanism of blood clotting.
The mechanism of blood clotting involves several steps:

1. When a blood vessel is injured, platelets adhere to the damaged site and release chemicals that attract more platelets, forming a temporary platelet plug.
2. Damaged tissue cells and activated platelets release clotting factors.
3. These clotting factors initiate a cascade of reactions that ultimately convert inactive prothrombin into active thrombin.
4. Thrombin then acts as an enzyme to convert soluble plasma protein fibrinogen into insoluble fibrin threads.
5. Fibrin threads form a mesh-like network that traps red blood cells and more platelets, forming a stable blood clot that seals the wound and stops bleeding.

5.

a) In a tabular form, differentiate between mitosis and meiosis.

Feature	Mitosis	Meiosis
Type of cells	Somatic cells	Germ cells (for gamete formation)
Number of divisions	One	Two
Number of daughter cells	Two	Four
Ploidy of daughter cells	Diploid (2n)	Haploid (n)
Genetic identity	Genetically identical to parent cell	Genetically different from parent cell
Purpose	Growth, repair, asexual reproduction	Sexual reproduction, genetic variation

b) State the secondary sexual characteristics in human females

• • Development of breasts.
• • Widening of the hips and pelvis.
• • Growth of pubic and axillary hair.
• • Onset of menstruation (menarche).

c) Using genetic symbols and diagrams, determine the genotypes and phenotypes of the offspring of a man and a woman who both have the sickle cell trait (heterozygous).
Let HbA represent the allele for normal hemoglobin and HbS represent the allele for sickle cell hemoglobin.
Parents are both heterozygous for sickle cell trait: Man (HbA HbS) x Woman (HbA HbS).

Punnett Square:

Gametes	HbA	HbS
HbA	HbA HbA	HbA HbS
HbS	HbA HbS	HbS HbS

Genotypes of offspring:

• 1 HbA HbA : 2 HbA HbS : 1 HbS HbS
• Ratio: 1:2:1

Phenotypes of offspring:

• 1 Normal (no sickle cell trait or disease)
• 2 Sickle cell trait (carriers, usually asymptomatic)
• 1 Sickle cell anemia (suffers from the disease)
• Ratio: 1:2:1

SECTION B

6.

a)

i) State the importance of clothes to humans.

• • Protection: Clothes protect the body from harsh weather conditions (cold, heat, rain), UV radiation, and physical injury.
• • Modesty and Social Acceptance: They fulfill social and cultural norms regarding modesty and are essential for social identification.
• • Hygiene: Clothes can provide a barrier against dirt and germs, contributing to personal hygiene.

ii) Give three (3) important properties that are necessary in a fabric used to make under wears like pants

• • Softness: To prevent irritation and ensure comfort against sensitive skin.
• • Absorbency: To wick away moisture (sweat) and keep the skin dry, preventing bacterial growth.
• • Breathability: To allow air circulation, which helps regulate temperature and reduces moisture buildup.

b) Describe how the following body parts should be taken care of

i) Teeth and mouth

• • Brush teeth at least twice a day with fluoride toothpaste.
• • Floss daily to remove food particles and plaque between teeth.
• • Visit the dentist regularly for check-ups and professional cleaning.
• • Limit