Specialised cells

Question 1

What are specialised cells ?

Answer 1

• In complex multicellular organisms, eukaryotic cells become specialised for specific functions
• These specialised eukaryotic cells have specific adaptations to help them carry out their functions
• For example, the structure of a cell is adapted to help it carry out its function (this is why specialised eukaryotic cells can look extremely different from each other)
• Structural adaptations include:
• The shape of the cell
• The organelles the cell contains (or doesn’t contain)

Question 2

Erythrocytes - functions/adaptations

Answer 2

• RED BLOOD CELLS
• Function: transport oxygen around the body and carbon dioxide to the lungs
• Adaptations:
• They are **biconcave in shape which increases the surface area **over which oxygen can be absorbed
• The** cytoplasm contains high amounts of the pigment haemoglobin** which can readily bind to oxygen
• No nucleus is present which makes more space inside the cell for haemoglobin molecules for maximum oxygen-carrying capacity
• ** Elastic membrane allows the cell to be flexible and change shape** as it squeezes through narrow capillaries

Question 3

Neutrophils - functions/adaptations

Answer 3

• WHITE BLOOD CELLS
• Function: destroy pathogens by phagocytosis and the secretion of enzymes
• Adaptations:
• Neutrophils have a very flexible shape that allows them to squeeze through cell junctions in the capillary wall
• **Their flexibility also enables them to form pseudopodia **(cytoplasmic projections) that engulf microorganisms
• There is a** large number of lysosomes present in the cell.** These digestive enzymes help to digest and destroy invading cells
• A flexible nuclear membrane further helps the cell to penetrate cell junctions. It is thought that this flexibility is what causes the characteristic lobed nucleus

Question 4

Sperm cells - functions/adaptations

Answer 4

• Function: reproduction - to fuse with an egg, initiate the development of an embryo and pass on fathers genes
• Adaptations:
• The head contains a nucleus that contains half the normal number of chromosomes (haploid, no chromosome pairs)
• The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
• The mid-piece is packed with mitochondria to release energy (via respiration) for the tail movement
• The tail rotates, propelling the sperm cell forwards and allowing it to move towards the egg

Question 5

Root hair cells - functions/adaptations

Answer 5

• Function: absorption of water and mineral ions from soil
  Adaptations:
• Root hair to increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower)
• Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance)
• Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
• Mitochondria for active transport of mineral ions

Question 6

Ciliated epithelium - functions/adaptations

Answer 6

• Function: moving substances across the surface of a tissue
  Adaptations:
• Have cilia (hair-like structures), which beat in a coordinated way to shift material along the surface of the epithelium tissue
• Goblet cells secrete mucus which helps to trap dust, dirt and microorganisms - preventing them from entering vital organs where they may cause infection

Question 7

Squamous epithelium - function/adaptations

Answer 7

• Function: provide a surface covering or outer layer. Found on a variety of organs and structures e.g. blood vessels and alveoli
  Adaptations:
• Squamous epithelium consists of a single layer of flattened cells on a basement membrane
• The layer of cells forms a thin cross-section which reduces the distance that substances have to move to pass through - it shortens the diffusion pathway
• It is permeable, allowing for the easy diffusion of gases

Question 8

Palisade cells - functions/adaptations

Answer 8

• Function: carry out photosynthesis to produce glucose and oxygen
  Adaptations:
• A large number of chloroplasts (the site of photosynthesis) are present in the cytoplasm to maximise the absorption of light for photosynthesis
• The tall and thin shape of the cells allows light to penetrate deeper before encountering another cell wall (cell walls absorb/reflect light) and for many cells to be densely packed together

Question 9

Guard cells-functions/adaptations

Answer 9

• Function: control the opening of the stomata to regulate water loss and gas exchange
  Adaptations:
• Inner cell walls are thicker (those facing the air outside the leaf) while the outer cell walls are thinner (those facing adjacent epidermal cells). The difference in the thickness of the cell walls allows the cell to bend when turgid
• The cytoplasm has a high density of chloroplasts and mitochondria. Scientists think that these organelles may play a role in the opening of the stomata

Question 10

Xylem cells - functions/adaptations

Answer 10

Function: transport tissue for water and dissolved ions
Adaptations:
- No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
- Cells are essentially dead, without organelles or cytoplasm, to allow free movement of water
- Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant

Question 11

Phloem vessel cells - functions/adaptations

Answer 11

• Function: transport of dissolved sugars and amino acids
  Adaptations:
• Made of living cells (as opposed to xylem vessels which are made of dead cells) which are supported by companion cells
• Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes that allow sugars and amino acids to flow easily through (by translocation)
• Cells also have very few subcellular structures to aid the flow of materials

Question 12

Muscle cells - functions/adaptations

Answer 12

Function: contraction for movement
Adaptations:
- There are three different types of muscle in animals: skeletal, smooth and cardiac (heart)
- All muscle cells have layers of protein filaments in them, these layers can slide over each other causing muscle contraction
- Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
- Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison

Question 13

Cartilage - functions/adaptations

Answer 13

Function: to provide support
- Cartilage is a strong and flexible tissue found in various places around the body
- One place is in rings along the trachea, called Tracheal rings
- These rings help to support the trachea and ensure it stays open while allowing it to move and flex while we breathe