6.4 Specialised Cells and Tissues

Question 1

How are Erythrocytes specialised?

Answer 1

• Biconcave shape - increases SA:V ratio to aid diffusion
• No nuclei + few organelles - increases space available for haemoglobin
• Flexible - can squeeze through narrow capillaries

Question 2

How are neutrophils specialised?

Answer 2

• Multi-lobed nucleus - easier to squeeze through small gaps to get to site of infections
• Granular cytoplasm - contains many lysosomes containing enzymes that attack pathogens

Question 3

How are sperm cells specialised?

Answer 3

• Tail/flagellum - capable of movement
• Contain many mitochondria - supply of energy needed to swim
• Acrosome containing digestive enzymes - released to digest protective layers around ovum and allow sperm to penetrate -> leads to diffusion
• Helical mitochondria - maximise energy production in limited space

Question 4

How are palisade cells specialised?

Answer 4

• Contain chloroplasts - absorbs large amounts of light for photosynthesis. Can move within cytoplasm to absorb more light
• Rectangular cells - efficient packing to maximise light absorption
• Thin cell walls - increase rate of diffusion of CO2
• Large vacuole - maintain turgor pressure

Question 5

How are root hair cells specialised?

Answer 5

Root hairs (long extensions) - increases surface area of cell -> maximises uptake of water and minerals from soil

Question 6

How are guard cells specialised?

Answer 6

• Exist in pairs - form stomata for gas exchange
• Can lose water - become less swollen to close stomata and prevent water loss
Thicker inner cell wall - cell does not change shape symmetrically with volume (enables opening of stomata)

Question 7

Describe and explain the adaptations of the squamous epithelium.

Answer 7

• Made from specialised squamous epithelial cells
• Very thin - composed of squat/flat cells
• .˙. Present for rapid diffusion across a surface
• Forms lining of lungs -> allows rapid diffusion of oxygen into blood

Question 8

Describe and explain the adaptations of the ciliated epithelium.

Answer 8

• Made from ciliated epithelial cells
• Cilia on one surface that move in rhythmic manner - can create a current to move objects/fluids
• Goblet cells present - release mucus to trap unwanted particles present in air, prevents them from reaching alveoli

Question 9

Describe and explain the adaptations of cartilage.

Answer 9

• Connective tissue found in outer ear, nose, ends of + between bones
• Contains elastin + collagen fibres - firm and flexible
• Composed of chondrocyte cells embedded in extra cellular matrix
• Prevents ends of bones from rubbing together and causing damage

Question 10

Describe and explain the adaptations of muscle.

Answer 10

• Can contract to move bones
• Multiple types of muscle fibres:
• E.g. Skeletal muscle fibres (attached to bone) - contain myofibrils which contain contractile proteins

Question 11

Describe and explain the adaptations of the epidermis.

Answer 11

• Layer of closely packed cells covering surface of plants
• Covered by waxy, waterproof cuticle - reduces water loss
• Stomata present in epidermis - gas exchange

Question 12

Describe and explain the adaptations of xylem tissue.

Answer 12

• Responsible for water + mineral transport
• Composed of vessel elements (elongated dead cells)
• Walls of xylem strengthened with lignin (waterproof material) - provides structural support

Question 13

Describe and explain the adaptations of phloem tissue.

Answer 13

• Responsible for organic nutrient transport from leaves and stems to all parts of plants
• Composed of columns of sieve tube cells separated by sieve plates (perforated walls)