4.1.1.3 Cell Specialisation

Question 1

Function of sperm cell:

Answer 1

• Male sex cell
• To fertilise a female egg cell
• Contains half a set of chromosomes and passes these onto offspring

Question 2

Adaptations of sperm cells:

Answer 2

• Have many mitochondria which release E through aerobic respiration, this is needed to allow the sperm to have enough E to swim to the egg and fertilise it
• The sperm cell has a long tail (flagellum) which produces a swimming movement
• The sperm head (acrosome) has enzymes which breakdown a small part of the egg cell membrane to allow the head to enter with its chromosomes
• The nucleus of the sperm has half a set of chromosomes - on fertilising the egg a complete set is combined to make a new human

Question 3

Function of nerve cells/neurons:

Answer 3

To quickly send and receive electrical messages to and from the brain and nervous system

Question 4

Adaptations of nerve cells/neurons

Answer 4

• Has a long, thin shape which allows impulses to travel long distances in the body and makes it faster to send electrical messages
• Its axon is covered in rings of myelin sheath
  
  • The myelin sheath stops the electrical signals from travelling down the axon because it is an electrical insulator
  • This means the electrical signals have to jump between gaps of the myelin sheath, speeds up the conduction of electrical impulses and allows them to travel much faster

Question 5

Function of muscle cells:

Answer 5

• To control all the muscles in the body by contracting and relaxing
• When it contracts it gets shorter and when it relaxes it gets longer

Question 6

Adaptations of muscle cells:

Answer 6

• Have many mitochondria which release E through aerobic respiration as muscle cells make up all the muscles in the body and need a lot of E
• Elongated
• Can contract

Question 7

Function of root hair cells:

Answer 7

• Efficient uptake of water and mineral ions
• Root hair cells absorb water by osmosis
• Root hair cells absorb minerals (nitrate ions) by active transport

Question 8

Adaptations of root hair cells:

Answer 8

• Large surface area with a projection/root hair - large SA for diffusion
• Thin cellulose walls - short diffusion pathway
• Many mitochondria for aerobic respiration - releases a lot of E for active transport
• Adapted for efficient uptake of water by osmosis, and mineral ions by active transport
• Large vacuole - for temporarily storing water before it is transported up through the cell
• Ability to change shape

Question 9

Function of phloem cells:

Answer 9

Phloem tissue transports dissolved sugars and amino acids from the leaves to the rest of the plant for immediate use or storage - this movement of food molecules through phloem tissue is called translocation

Question 10

Adaptations of phloem cells:

Answer 10

• Composed of tubes and elongated cells, made of living cells lined end to end, found in the vascular bundle
• The cell walls between phloem cells break down to form perforated sieve plates
• These allow water carrying dissolved food (sugars and amino acids) to move freely along the tubes from one phloem cell to the next through pores in the end walls
• Supported by companion cells (which contain nucleus and mitochondria) that keep them alive - the mitochondria of the companion cells transfer the energy needed for translocation to occur
• Cells that have lost most of their internal structure – e.g. no vacuole or nucleus - this helps to reduce any resistance during translocation and allows efficient movement of substances
• Vessels contain cytoplasm
• Two-way flow allows substances to be transported all around the plant

Question 11

Function of xylem ells:

Answer 11

Xylem tissue transports water and mineral ions from the roots to the stems and leaves in the transpiration stream - process called transpiration

Question 12

Adaptations of xylem cells:

Answer 12

• Mature xylem consists of elongated dead, hollow cells arranged end to end to form continuous hollow vessels (tubes)
• Mature xylem vessels contain no cytoplasm
• Have tough walls containing a woody material called lignin that builds up in spirals in cell walls. Lignin makes spirals very strong, to withstand the pressure from the water + provide support. - adapted for transport of water in transpiration stream
• The contents and end walls break down to form a hollow centre (lumen) - reduces resistance during transpiration and allows more efficient transport of water and mineral ions

Question 13

Diagram of a sperm cell:

Answer 13

Question 14

Diagram of nerve cell/neuron:

Answer 14

Question 15

Diagram of muscle cells:

Answer 15

Question 16

Diagram of a root hair cell:

Answer 16

Question 17

Diagram of phloem cell:

Answer 17

Question 18

Diagram of a xylem cell:

Answer 18