Topic 2 Cells : 2.1.1 Structure of eukaryotic 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 ( in both animal and plant cell)

Answer 2

Phospholipids :
1) hydrophilic phosphate heads
- attracted to water
2) Hydrophobic fatty acids tails
- repelled from water
3) Phospholipid Bilayer
4) Proteins

Question 3

Describe the function of the cell-surface membrane

Answer 3

● Selectively permeable → enables control of passage of substances in / out of cell
● Molecules on surface → allow cell recognition

Question 4

Describe the structure of the nucleus

Answer 4

1) Nuclear envelope
- double membrane
- has nuclear pores
2) Nucleoplasm
3) Nucleolus
4) Protein/histone bound, linear dan
- chromatin = condensed
- chromosome = highly condensed

Question 5

Describe the function of the nucleus

Answer 5

● Holds / stores genetic information which codes for polypeptides (proteins)
● Site of DNA replication
● Site of transcription (part of protein synthesis), producing mRNA
● Nucleolus makes ribosomes / rRNA

Question 6

Describe the structure of a ribosome

Answer 6

● Made of ribosomal RNA and protein (two subunits)
● Not a membrane-bound organelle

Question 7

Describe the function of a ribosome

Answer 7

Site of protein synthesis (translation)

Question 8

Describe the structure of rough (rER) & smooth endoplasmic reticulum (sER)

Answer 8

rER : ribosomes + system of membranes

sER : system of membranes

Question 9

Describe the function of rER and sER

Answer 9

rER :
● Ribosomes on surface synthesise proteins
● Proteins processed / folded / transported inside rER
● Proteins packaged into vesicles for transport eg. to Golgi apparatus

sER :
● Synthesises and processes lipids
● Eg. cholesterol and steroid hormones

Question 10

Describe the structure of Golgi apparatus and Golgi vesicles

Answer 10

• Golgi apparatus : flattened membrane sacs
• Golgi vesicle : small membrane sac

Question 11

Describe the function of Golgi apparatus and Golgi vesicles

Answer 11

Golgi
apparatus :

● Modifies protein, eg. adds carbohydrates to produce glycoproteins
● Modifies lipids, eg. adds carbohydrates to make glycolipids
● Packages proteins / lipids into Golgi vesicles
● Produces lysosomes (a type of Golgi vesicle)

Golgi
vesicles :

● Transports proteins / lipids to their required destination
● Eg. moves to and fuses with cell-surface membrane

Question 12

Describe the structure of lysosomes

Answer 12

• membrane
• hydrolytic enzymes

Question 13

Describe the function of lysosomes

Answer 13

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

Question 14

Describe the structure of mitochondria

Answer 14

• outer membrane
• cristae
• matrix, containing : small (70s) ribosomes , circular DNA

Question 15

Describe the function of mitochondria

Answer 15

● Site of aerobic respiration
● To produce ATP for energy release
● Eg. for protein synthesis / vesicle movement / active transport

Question 16

Describe the structure of chloroplasts in plants and algae

Answer 16

• double membrane
• stroma containing : thylakoid membrane, small ribosomes, circular DNA, lipid droplets
• lamella : thylakoids linkning grana
• grana : stacks of thylakoids

Question 17

Describe the function of chloroplasts in plants and algae

Answer 17

● Absorbs light energy for photosynthesis
● To produce organic substances eg. carbohydrates / lipids

Question 18

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

Answer 18

● Composed mainly of cellulose (a polysaccharide) in plants / algae
● Composed of chitin (a nitrogen-containing polysaccharide) in fungi

Question 19

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

Answer 19

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

Question 20

Describe the structure of the cell vacuole in plants

Answer 20

• tonoplast membrane
• cell sap

Question 21

Describe the function of the cell vacuole in plants]

Answer 21

● Maintains turgor pressure in cell (stopping plant wilting)
● Contains cell sap → stores sugars, amino acids, pigments and any waste chemicals

Question 22

Describe how eukaryotic cells are organised in complex multicellular
organisms

Answer 22

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

Question 23

Suggest how you can apply your knowledge of cell features / organelles to
explain adaptations of eukaryotic cells

Answer 23

● [Named cell] has many [named organelle, eg. ribosomes]
● To [link organelle function to cell function eg. increase rate of protein synthesis, making many antibodies]