Cells

Question 1

Characteristics of cells

Answer 1

Cells are the basic structural, functional and biological unit of living organisms.

The smallest unit of life that can replicate independently.

Differentiation - the process by which cells assume their specialised structure.

200~ different cell types in the body

Question 2

Functions of plasma membrane:

Answer 2

The plasma membrane is the gatekeeper of the cell

Defines the cells boundary

Separates the intracellular and extracellular spaces (inside and outside the cell)

Question 3

Plasma membrane (phospholipid)

Answer 3

Phospholipid - polar hydrophilic head + 2 hydrophobic fatty acid tails

Question 4

Function of cholesterol

Answer 4

Cholesterol molecules fill in the gaps between unsaturated fatty acid tails

• they stabilise and regulate the fluidity of the bilayer.

Question 5

Integral proteins

Answer 5

Integral proteins - incorporated within the membrane: transport (channels or carriers), enzymes, receptors

Question 6

Peripheral proteins

Answer 6

Peripheral proteins - associated with the inner or outer surface: cell recognition, cytoskeleton

Question 7

Specialised cells: Muscle cells

Answer 7

Function = Movement
Specialisations - elongated and elastic allow muscles to contract and relax for movement

Large number of mitochondria allows mass energy to be produced

Stores Glycogen Energy required for the contraction of the cell

Question 8

Specialised cells: Nerve cells

Answer 8

Function = Communication

Specialisations - long axon - signal long distances

Numerous dendrites - receive numerous signals

Axon terminal - control activity

Question 9

Specialised cells: Red blood cells

Answer 9

Function = carry oxygen from the lungs to respiring tissues

Specialisations - haemoglobin - binds oxygen

No nucleus - more haemoglobin can fit and squeeze through small vessels

Biconcave shape - increase surface area

Question 10

Specialised cells: Spermatozoon

Answer 10

Function = involved in sexual reproduction

Specialisations - nucleus contains genetic information

Flagella (tail) - movement

Mitochondria - energy

Acrosome (lysosome) - break down outside of the egg

Question 11

3 factors that bind cells together

Answer 11

glycoproteins, wavy contours of the membrane, special cell junctions (desmosomes, tight junctions, gap junctions)

Question 12

tight junctions

Answer 12

Integral proteins fuse together to prevent molecules from passing between cells

These junctions are found in epithelial cells in the intestinal tract.

Question 13

desmosomes

Answer 13

Anchoring junctions that act as ‘rivets’ to keep cells from tearing apart

Found in areas that can be stretched e.g. skin

Question 14

gap junctions

Answer 14

communicating junctions that allow ions and small molecules to pass from cell to cell

They are found in a variety of cell types e.g. cardiac muscle cells.