Structure Of Eukaryotic Cells

Question 1

Cell/ Plasma membrane

Answer 1

• made up of Phospholipids
• it separates contents of the cell from the outside environment
• controls the entry and exit of materials

Question 2

Nucleus

Answer 2

• surrounded by a double membrane - nuclear envelope
• has large holes called nuclear pores - allow RNA through
• contains chromatin - form chromosomes take when a cell is not dividing
• chromatin consists of the chemical DNA wrapped around small proteins called histones
• darker stained area - nucleolus - make ribosomes

Question 3

Mitochondria

Answer 3

• has two membranes
• inner membrane is folded and these folds are called cristae
• liquid inside is known as matrix - contains enzymes for early respiration
• respiration occurs here - inner membrane contains the enzymes for later stages of respiration

Question 4

Endoplasmic reticulum

Answer 4

• extensions of the nuclear membrane that are highly folded
• the fluid filled spaces (cytosol) between the folds are involved in transporting materials
• two types - smooth (SER) and rough ((RER)
• the rough is studded with ribosomes
• RER: involved in protein synthesis using ribosomes on the surface
• SER: involved in production of Phospholipids, cholesterol and some hormones

Question 5

Ribosomes

Answer 5

• are made in nucleolus
• smallest organelle (20 nm in diameter)
• function is protein synthesis
• if attracted to ER (RER) then they produce proteins that are to be exported out of the cell
• if free floating ribosomes, then they make proteins inside cells

Question 6

Lysosome

Answer 6

• smaller vesicles formed by RER - contains many digestive enzymes
• they break down unwanted substances like worn-out mitochondria
• they vary in size, shape and number in different cells

Question 7

Centrioles

Answer 7

Form spindle fibres

Question 8

Microvilli

Answer 8

• small extensions of the cell membrane
• found only in certain cells e.g. the intestine
• they increase the surface area for the absorption of materials

Question 9

Cilia and Flagella

Answer 9

• in eukaryotes, flagella and cilia are structurally the same
• hair like extensions that stick out from the cell surfaces
• long - flagella forms tail of sperm cells
• short - ciliated epithelium
• flagella - 112 (1 or 2 of)
• cilia - large numbers

Question 10

Golgi apparatus

Answer 10

• a group of flattened cavities
• it makes enzymes and other ER, completes any modifications needed
• then packages them into small vesicles ready for export
• constantly changes shape with new substances entering and leaving

Question 11

Vesicles

Answer 11

• small membrane bound structures which bud off from the Golgi apparatus to transport substances out of the cell

Question 12

Cell wall

Answer 12

• made of cellulose
• arranged into microfibrils from parallel strands
• hydrogen bonds (weak but strong with loads of them)
• strong + flexible

Question 13

Chloroplasts

Answer 13

• highly structured, membrane - rich organelles
• contains outer membrane, inner membrane folded into stacks Known as thylakoids
• liquid inside chloroplasts is known as stoma - where enzymes for photosynthesis are
• chlorophyll stored in thylakoids - granum

Question 14

Vacuole

Answer 14

Stores cell sap