2.1.5 - Eukaryotic cells 3

Question 1

define a cell wall

Answer 1

freely permeable wall around plant cells, made mainly of insoluble cellulose

Question 2

what is the function of the cell wall?

Answer 2

• give support and strength

Question 3

what is suberin?

Answer 3

a chemical that impregnates cellulose cell walls in cork tissues and makes them impermeable

Question 4

What is lignin?

Answer 4

polymer in the cell walls of many plants, making them rigid and woody

Question 5

What is the middle lamella of the plant cell wall?

Answer 5

the first layer of the plant cell to form when a plant cell divides, made mainly of pectin that binds the layers of cellulose together

Question 6

what is pectin?

Answer 6

a polysaccharide that holds cell walls of neighbouring plant cells together and is part of the structure of the primary cell wall

Question 7

what is special about pectin that allows it to form calcium pectate?

Answer 7

• the negatively charged carboxyl (-COOH) group
• they combine with positive calcium ions to form calcium pectate
• this binds with cellulose

Question 8

what are primary cell walls?

Answer 8

the first very flexible plant cell wall to form, with all cellulose microfibrils orientated in a similar direction

Question 9

what are the secondary cell walls?

Answer 9

the older plant cell wall in which the cellulose microfibrils have built up at different angles to each other, making the cell wall more rigid

Question 10

After the secondary cell walls, what hardens the cell wall further?

Answer 10

• hemicelluloses

Question 11

what are plant fibres?

Answer 11

• long cells with cellulose cell walls that have been heavily lignified so they are rigid and very strong

Question 12

what are plasmodesmata?

Answer 12

cytoplasmic bridges between plant cells that allow communication between the cells

Question 13

what is the symplast?

Answer 13

the interconnected cytoplasm of plant cells, connected by plasmodesmata

Question 14

How does the plasmodesmata allow plant cells to communicate?

Answer 14

• when cell divides plasmodesmata are formed
• the two cells don’t separate completely
• threads of cytoplasm remain between them
• these threads pass through gaps in the cell wall
• signalling substances can pass from one cell to another through the cytoplasm

Question 15

What are differences between prokaryotic and eukaryotic cells?

Answer 15

• eukaryotic is bigger
• prokaryotic may have a slime capsule/ layer
• prokaryotic = mesosomes, 70s ribosomes, plasmids
• Eukaryotic = 80s ribosomes, golgi body, lysosomes, RER, SER, cytoskeleton

Question 16

what features does a plant cell have that an animal cell doesn’t?

Answer 16

• permanent vacuole
• cell wall
• chloroplast