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

• nuclear envelope = double membrane
• nuclear pores
• nucleoplasm = granular, jelly material
• chromosomes = linear DNA, histones wrapped around DNA
• nucleolus = smaller spheres - rRNA production and makes ribosomes
  F: site of DNA replication & transcription
  F: contains the genetic code for each cell

Question 3

Describe the function & structure of mitochondria

Answer 3

• rod shaped, double membrane - inner membrane folded into cisternae
• fluid mitochondrial matrix contains enzymes, 70s ribosomes and circular DNA
• F: site of aerobic respiration, ATP production

Question 4

Structure & function of chloroplasts

Answer 4

• disc shaped, with a double membrane surrounding a fluid stomata = containing enzymes and circular DNA
• contains stacks of membrane discs, thylakoids- hold the chlorophyll
• F: site of photosynthesis
• 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 micro fibrils of cellulose, embedded in a matrix
• provide mechanical strength to prevent cells bursting due to osmotic pressure
• (middle lamellae between cells - cement of pectin & lignin)
• provides mechanical strength to the cell
• fungi: made chitin,
• (algae: cellulose and glycoprotein)

Question 7

Structure & function of Golgi apparatus & vesicles

Answer 7

• folded membranes making cisternae
• many proteins embedded in the membrane surfaces
• F: modifies proteins & lipids, produce secretory enzymes
• F: 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 digestive (hydrolytic) enzymes
• F: digests pathogens
• F: ingest larger molecules into the cell
• F: destroys damaged organelles

Question 9

Structure & function of ribosomes

Answer 9

• small spherical organelle made of 2 sub-units (80s = larger, 70s = smaller
• proteins synthesis (translation&DNA replication)

Question 10

Structure & function of rough endoplasmic reticulum

Answer 10

• flattened discs of membranes, with ribosomes on outer surface forming a large SA
• protein synthesis -> 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 & storage 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 keep the cell turgid -> provide support