3.2.1.1 Eukaryotic cells

Question 1

How to eukaryotic cells become specialised for specific functions

Answer 1

. Changes shape e.g. forming long extensions such as axons

. Membrane folds, increasing SA

. Increased number of specific organelles, linked to cell function

Question 2

Describe the structure & function of the nucleus

Answer 2

• stands of DNA wrapped around histones
• surrounded by a (double) membrane envelope
• stores DNA, codes for proteins & functional RNA’s
• stable structure for long term storage of info.
• membrane controls entry & exit of molecules, protecting DNA from damage.
• contains nucleus:
  . Dense region of DNA & protein
  . Synthesises ribosomes

Question 3

Describe the function & structure of mitochondria

Answer 3

• rod shaped, with san outer membrane & an inner membrane folded into cristae
• fluid matrix contains enzymes, 70s ribosomes and circular DNA
• site of aerobic respiration

Question 4

Structure & function of chloroplasts

Answer 4

• disc shaped, with a double membrane surrounding a fluid stomata, containing enzymes 70s ribosomes and circular DNA
• contains stacks of membrane discs, thylakoids- hold the chlorophyll
• site of photosynthetic
• light energy absorbed by chlorophylls in thylakoid

Question 5

Structure & function of cell membrane

Answer 5

• phospholipid bilayer with embedded proteins & glycoproteins
• controls the diffusion of molecules and ions between the cytoplasm and the surrounding fluid
• signalling to other cells

Question 6

Structure & function of the cell wall

Answer 6

• plants: made of cross linked cellulose fibres, embedded in a matrix
• provide mechanical strength to prevent cells bursting due to osmotic pressure
• middle lamellae between cells - cement of pectin & lignin
• attach plant cells together = mechanical strength
• fungi: made chitin,
• algae: cellulose and glycoprotein

Question 7

Structure & function of Golgi apparatus & vesicles

Answer 7

• stack of unflattened sacs -of membranes
• many proteins embedded in the membrane surfaces
• modifies proteins & lipids
• packaging molecules into vesicles for transport
• vesicles:
  . Small membrane bound spheres
  . Transport large molecules for exocytosis/ add membrane to diff. Organelles

Question 8

Structure & function of lysosomes

Answer 8

• small hollow membrane spheres containing hydrolytic (digestive) enzymes
• digests pathogens and large molecules ingested into the cell
• destroys damaged organelles

Question 9

Structure & function of ribosomes

Answer 9

• small spherical organelle made of 2 sub-units
• proteins synthesis (translation)

Question 10

Structure & function of rough endoplasmic reticulum

Answer 10

• flattened discs of membranes, with ribosomes on outer surface forming a large SA
• synthesis of proteins for transport in vesicles
• synthesis of proteins which form part of membranes

Question 11

Structure & function of smooth endoplasmic reticulum

Answer 11

• large network of membrane tubules
• synthesis of lipids and carbohydrates

Question 12

Structure & function of cell vacuole

Answer 12

• fluid filled sac surrounded by a membrane
• temporary food store
• help to maintain turgor pressure