Cell Biology

Question 1

Cell theory

Answer 1

1. All living things are composed of cells
2. The cell is the smallest unit of life
3. Cells only arise from pre-existing cells

Question 2

Caveats to cell theory

Answer 2

• Striated muscle fibres
• Aseptate fungal hyphae
• Giant Algae

Question 3

Striated muscle fibres

Answer 3

• Muscle cells fuse to form fibres that may be very long
• Consequently, they have multiple nuclei despite being surrounded by a single, continuous plasma membrane
• Challanges the idea that cells always function as autonomous units

Question 4

Giant Algae

Answer 4

• Certain species of unicellular algea may grow to very large sizes
• Challanges the idea that larger organisms are always made up of many microscopic cells

Question 5

7 basic functions integral to survival to all living things

Answer 5

MR SHENG

Answer 6

• Metabolism - Living things undertake essential chemical reactions
• Reproduction - Living things produce offspring, either sexually or asexually
• Sensitivity - Living things are responsive to internal and external stimuli
• Homeostasis - Living things maintain a stable internal environment
• Excretion - Living things exhibit the removal of waste products
• Nutrition - Living things exchange materials and gases with the environment
• Growth - Living things can move and change shape or size

Question 7

Functions of life in Paramecium

Answer 7

• Sensitivity: Paramecia are surrounded by small hairs called cilia which allow it to move
• Nutrition: Paramecia engulf food via a specialised membranous feeding groove called a cytostome
• Metabolism: Food particles are enclosed within small vacuoles that contain enzymes for digestion
• Excretion: Solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacoules
• Homeostasis: Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion
• Reproduction: Paramecia divide asexually (fission) although horizontal gene transfer can occur via conjugation