TEST 1 SAQ : Intro-Tissue

Question 1

Describe the negative feedback system in blood glucose and temperature homeostasis

Answer 1

Stimulus: Blood glucose levels rise after eating
 Detected by pancreas –> releases insulin
 Insulin facilitates glucose uptake by cells
 Insulin stimulates liver to convert glucose to glycogen for storage

Stimulus: Blood glucose levels drop
 Detected by pancreas –> releases glucagon
 Glucagon signals liver to break down glycogen into glucose
 Glucose released into bloodstream

Stimulus: Body temperature rises
 Detected by thermoreceptors in skin and brain
 Signal sent to hypothalamus
 Hypothalamus activates sweating
 Blood vessels dilate (vasodilation) to release heat

Stimulus: Body temperature drops
 Detected by thermoreceptors in skin and brain
 Signal sent to hypothalamus
 Hypothalamus activates shivering
 Blood vessels constrict (vasoconstriction) to conserve heat

Question 2

Explain how blood clotting and child birthing work via positive feedback mechanisms.

Answer 2

Stimulus: Labor begins, fetus head presses against cervix
 Detected by stretch receptors in cervix
 Signal sent to hypothalamus
 Hypothalamus releases oxytocin
 Oxytocin stimulates uterine contractions
 Stronger contractions push fetus against cervix
 Stretch receptors in cervix further stimulated
 Signal sent to hypothalamus for more oxytocin release
 Positive feedback loop continues until birth

Stimulus: Blood vessel injury
 Platelets adhere to site of injury
 Release of chemicals (e.g., thromboxane)
 Chemicals attract more platelets to injury site
 Platelets release additional chemicals
 Chemical cascade accelerates platelet aggregation
 Formation of stable blood clot to seal wound
 Positive feedback loop continues until clotting is complete

Question 3

List down the types of bonds and explain each in detail.

Answer 3

Ionic Bonds
* Electrons are transferred /donated
* Atom losing electron – cation and atom gaining electron – anion
* Resulting ions attract each other due to opposite charges.

2. Covalent Bonds
   * Electrons are shared between atoms
   * Types
   * based on number of electrons shared (single, double, triple)
   * strength of the bond (polar and non-polar)

Question 4

List down the functions of lipids and proteins

Answer 4

Functions of Lipids
* Essential structural components of cell – cholesterol and phospholipid*
* Next source of energy next to carbohydrate; energy reserves -twice the amount of energy
carbohydrate
* Insulation - help maintain body temperature
* Cushion effect - protect body against knocks and injuries

Functions of proteins
* Support - structural proteins
* Movement - contractile proteins cause muscular contraction
* Transport -transport proteins carry gases –e.g hemoglobin
* Metabolic regulation- that catalyse chemical reactions -enzymes
* Defense – antibody, tough protein coats of skin, nails

Question 5

List down the types and functions of nucleic acids

Answer 5

2 types
Deoxyribonucleic acid ( DNA )
Ribonucleic acid ( RNA )

Differences:
Sugar: Deoxy ribose/Ribose
Strands: Two/One
Base difference: thymine/uracil
Function: inheritance/protein synthesis

Question 6

Explain the components and functions of cell membrane

Answer 6

Composed of:
1. Lipids
1. Phospholipids
* Major component in the cell membrane - Arranged in bilayer
* Hydrophilic (likes water) head
* Hydrophobic (hates water)Tail
2. In between phospholipid layer, have cholesterol

2. Carbohydrates
3. Glycolipids - made of carbohydrates and lipids
4. Glycoproteins - made of carbohydrates and proteins
5. Proteins
6. Transmembrane proteins extends throughout the membrane from inside to outside(e.g., channels)
7. Surface proteins found only on the surface (e.g., receptors)

Question 7

Define osmosis? what happens to RBC in different tonic solution

Answer 7

ovement of water molecules from higher water concentration zone to lower water concentration zone across a semi-permeable
membrane (where solutes cannot move)

1. RBC in hypotonic solution
2. Water concentration of solution is more than water concentration in RBC
3. Water moves into the cell
   –> increased water content in cell –> cell bursts or lyses
4. RBC in hypertonic solution
5. Water concentration of solution less than water concentration in cytoplasm
6. Water moves out of the cell–>outside–>cell shrinks (crenation)
7. RBC in isotonic solution
8. Water concentration of solution is equal to water concentration in cytoplasm
9. No water movement across the cell

Question 8

List down the phases of mitosis and explain each phase.

Answer 8

Mitosis is divided into 4 stages, followed by Cytokinesis

o Mitosis divided into 4 stages

• Prophase
• Chromatin becomes chromosomes
• Centrioles appear at the poles – forms spindle
• Metaphase
• Chromosome line up at midplane of the cell
• Anaphase
• Chromosome pair separate –>chromatid–> pulled by spindle to poles
• Telophase
• Nucleolus & nuclear membrane for the daughter cells reappear
• Mitotic spindle disappears, chromosomes becomes chromatin

o Cytokinesis
* Cytoplasm separates

Question 9

Define exocrine glands. List and briefly explain the types of exocrine glands.

Answer 9

Exocrine glands - glands secretes mucous/ serous / both, secrete onto epithelial surfaces
through ducts

o Merocrine secretion- Secretions produced is released as vesicles. E.g. Sweat -sweat gland

o Apocrine secretion - Part of the cell breaks and released as secretion e.g., milk - mammary glands

o Holocrine secretion - cells bursts to release the secretion. E.g Sebum - Sebaceous glands

Question 10

Explain the structure, location and function of simple columnar epithelium.

Answer 10

 Structure - single layer of tall, thin cells; nucleus towards bottom
 Location - Stomach, intestinal lining, gall bladder
 Functions - Secretion, absorption