Unit 1: B1 Cell structure and function

Question 1

What is the cell theory?

Answer 1

Cell theory states that cells are the fundamental unit of structure, function, and organization in all living organisms.

Question 2

Name key organelles found in prokaryotic cells and their functions.

Answer 2

• Nucleoid: Contains genetic material (DNA).
• Plasmids: Small DNA molecules for genetic advantages like antibiotic resistance.
• 70S Ribosomes: Protein synthesis.
• Capsule: Protects against desiccation and immune response.
• Cell Wall: Provides structure and protection.

Question 3

What organelles are specific to plant cells, and what are their functions?

Answer 3

• Cell Wall: Provides rigidity and support.
• Chloroplasts: Photosynthesis.
• Vacuole: Stores nutrients and waste products; maintains turgor pressure.
• Tonoplast: Membrane surrounding the vacuole.
• Amyloplasts: Store starch.
• Plasmodesmata: Channels for communication between cells.
• Pits: Thin regions in the cell wall for transport.

Question 4

List the organelles found in both plant and animal eukaryotic cells.

Answer 4

• Plasma membrane, cytoplasm, nucleus, nucleolus, endoplasmic reticulum (smooth and rough), Golgi apparatus, vesicles, lysosomes, 80S ribosomes, mitochondria, centrioles.

Question 5

How do plant and animal cells differ in structure?

Answer 5

Plant cells have a cell wall, chloroplasts, and a large central vacuole, which are absent in animal cells. Animal cells have centrioles, which are rare in plant cells.

Question 6

What is the difference between gram-positive and gram-negative bacterial cell walls?

Answer 6

• Gram-positive: Thick peptidoglycan layer, retains crystal violet dye, appears purple.
• Gram-negative: Thin peptidoglycan layer, outer membrane, does not retain crystal violet, appears pink after counterstaining.

Question 7

Why do gram-positive and gram-negative bacteria react differently to antibiotics?

Answer 7

Gram-positive bacteria are more susceptible to antibiotics targeting peptidoglycan synthesis, while gram-negative bacteria have an outer membrane that provides additional protection.

Question 8

How can cell organelles be identified using microscopy?

Answer 8

• Light microscopes: Show basic cell structures like the nucleus and cell wall.
• Electron micrographs: Provide detailed ultrastructure, such as ribosomes, endoplasmic reticulum, and mitochondria.

Question 9

How do you calculate the magnification of a cell or organelle from an image?

Answer 9

Magnification = Image size ÷ Actual size.

Question 10

What are the main types of endoplasmic reticulum and their functions?

Answer 10

• Rough ER: Synthesizes and transports proteins; has ribosomes attached.
• Smooth ER: Synthesizes lipids and detoxifies chemicals.