3.2.1.1 Structure of Eukaryotic cells ( 3.2 Cells)

Question 1

what are the distinguishing features of eukaryotic cells

Answer 1

• Cytoplasm containing membrane - bound organelles
• So DNA enclosed in a nucleus

Question 2

Describe the structure of the cell-surface membrane

Answer 2

Hydrophobic phosphate heads
• point to / are attracted to water
Hydrophilic fatty acid tails
• Point away / repelled from water

Question 3

Describe the function of the cell-surface membrane

Answer 3

• Selectively permeable - enabled control of passage of substances in or out of cell
• Molecules / receptors / antigens on surface - allow cell recognition

Question 4

Describe the structure of the nucleus

Answer 4

Nuclear envelope :
• Double membrane
• Has nuclear pores
Nucleoplasm
Nucleolus
Protein / justine - bound , linear DNA :
• chromatin = condensed
• Chromosome = highly condensed

Question 5

describe the function of the nucleus

Answer 5

• Stores genetic information which codes for polypeptides
• Site of DNA replication
• Site of transcription , producing mRNA
• Nucleolus makes ribosomes

Question 6

Describe the structure of a ribosome

Answer 6

• Made of ribosomal RNA and protein
• Not a membrane bound organelle

Question 7

Describe the function of a ribosome

Answer 7

Site of protein synthesis ( translation )

Question 8

Describe the function of rough endo plastic reticulum and smooth

Answer 8

rER :
• Ribosomes on surface synthesise proteins
• Proteins processed / folded / transported inside rER
sER:
• Synthesises and processes lipids
• e.g. cholesterol and steroid hormones

Question 9

Describe the function of Golgi apparatus and Golgi vesicles

Answer 9

Golgi apparatus :
• Modifies proteins , e.g adds carbohydrates to produce glycoprotein
• Modifies lipids , e.g. adds carbohydrates to make glycolipids
• Packages proteins / lipids into Golgi vesicles
• Produces lysosomes

Golgi vesicles :
• Transports proteins / lipids to their required destination
• E.g. moves to and fuses with cell surface membrane

Question 10

Describe the function of lysosomes

Answer 10

• Release hydrolytic enzymes (lysozymes)
• To break down / hydrolyse pathogens or worn-out cell components

Question 11

Describe the structure of mitochondria

Answer 11

Cristae - Inner membrane fold
Matrix :
containing small (70s) ribosomes
Circular DNA

Question 12

Describe the function of mitochondria

Answer 12

• Site of aerobic respiration
• To produce ATP for energy release
• E.g. for protein synthesis

Question 13

Describe the structure of chloroplasts in plants and algae

Answer 13

• Double membrane
• Stroma containing :
  • Thylakoid membrane
  • small (70s) ribosome
  • Circular DNA
  • Starch granules / lipid droplets
• Lamella - thylakoid linking grana
• Grana - stacks of thylakoid

Question 14

Describe the function of chloroplast in plants and algae

Answer 14

• Absorbs light energy for photosynthesis
• To produce organic substances e.g. carbohydrates

Question 15

Describe the structure of the cell wall in plants , algae and fungi

Answer 15

• Composed mainly of cellulose in plants / algae
• Composed of chitin in fungi

Question 16

Describe the function of the cell wall in plants , algae and fungi

Answer 16

• Provides mechanical strength to a cell
• So prevents cell changing shape or bursting under pressure due to osmosis

Question 17

Describe the structure of the cell vacuole in plants

Answer 17

• Tonoplast membrane
• cell sap

Question 18

Describe the function of the cell vacuole in plants

Answer 18

• Maintains turgor pressure in cell
_ Contains cell sap - stores sugars , amino acids

Question 19

Describe how eukaryotic cells are organised in complex multicellular organisms

Answer 19

•Tissue - group of specialised cells with a similar structure working together to perform a specific function , often with the same origin
• Organ - Aggregations of tissues performing specific functions
• Organ system - Group of organs working together to perform specific functions