Plants Structure and Function

Question 1

How does suberin in the cell wall of cork tissues and lignin in the cell wall of wood affect its permeability

Answer 1

reduces the permeability so that water and dissolved substances cannot pass through

Question 2

What is the first layer of the cell wall?

Answer 2

the middle lamella

Question 3

when is the middle lamella made

Answer 3

when the plant cell divides into two new cells

Question 4

What is the middle lamella made of and what does the substance do

Answer 4

pectin
it is a polysaccharide that acts like glue and holds the cell wall of adjacent plant cells together

Question 5

How does pectin hold plant cells together

Answer 5

pectin has lots of negatively charged carboxyl groups and these combine with positive calcium ions to form calcium pectate. the calcium pectate binds to the cellulose on either side

Question 6

What is the primary cell wall

Answer 6

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

Question 7

What is the secondary cell wall

Answer 7

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. Hemicellulose help to harden it further

Question 8

What are the two isomers of glucose

Answer 8

a-glucose
b-glucose

Question 9

what is the difference between a-glucose and b-glucose

Answer 9

a-glucose has hydrogen on top for both sides while hydroxide is on the bottom for both sides

b-glucose has hydrogen on top for one one side and hydroxide on top for the other side. a hydrogen is also on the bottom on one side and a hydroxide is on the bottom on the other side.

Question 10

Difference between starch and cellulose

Answer 10

starch is made up of alpha glucose while cellulose is made up of beta glucose held together by 1,4-glycosidic bonds

Question 11

What happens as a result of cellulose being made from beta glucose

Answer 11

one of the monomer units has to be inverted so the bonding can take place. This means that the hydroxyl groups stick out on both sides of the molecule

because of this, hydrogen bonds can be made between the partiallt positively charged hydrogen atoms of the hydroxyl grouos and the partially negatively charged oxygen atoms in other areas of the glucose molecule. this is called cross linking and it holds the neighboring chains firmly together

Question 12

what is the function of hemicellulose and other short chain carbohydrates in the cell wall

Answer 12

the matrix of hemicellulose and other short chain chain carbohydrates hold together the cellulose microfibers that are deposited in layers. they act like glue, binding to each other and to the cellulose molecules. mannose, xylose, and arabinose are examples of the sugars involved.

Question 13

What is the plasmodesmata

Answer 13

cytoplasmatic bridges between plant cells that allow communication between the cells

Question 14

How does the plasmodesmata form

Answer 14

it is produced as cells divide- the two cells do not divide completely and threads of cytoplasm remain between them. The threads pass through gaps in the newly formed cell wall and signaling substances can pass from one cell to another through the cytoplasm

When secondary thickening takes place hemicellulose and lignin are deposited in the cell wall making it thicker. In the areas around the plasmodesmata, this process doesn’t happen, leaving thin areas of the cell wall called pits

Question 15

What is the symplast

Answer 15

the interconnected cytoplasm of the cells

Question 16

What is the membrane that surrounds the permanent vacuoles

Answer 16

the tonoplast

Question 17

what is the function of the tonoplast

Answer 17

controls the movement of cells into and out of the vacuole, and so it controls the water potential of the cell.

Question 18

what is the vacuole filled with

Answer 18

cell sap, which is a solution of various substances in water.

Question 19

what is the function of the cell sap

Answer 19

it causes water to move into and out of the cell by osmosis, and this keeps the cytoplasm pressed against the cell wall. This keeps the plant cell turgid and the whole plant stays upright

Question 20

What are chloroplasts

Answer 20

organelles adapted row carry out photosynthesis. containing the green pigment chlorophyll

Question 21

Which plants contain the genetic information to make chloroplasts

Answer 21

almost all plant cells

Question 22

List 5 similarities between mitochondria and chloroplasts

Answer 22

Large organelles with a biconcave shape

contain their own DNA

are surrounded by an outer membrane

have an enormously folded inner membrane that gives a greatly increased surface area where enzyme controlled reactions takes place

are thought to have been free living prokaryotic organisms that were engulfed by and became part of other cells

Question 23

Differences between chloroplasts and mitochondria

Answer 23

Chloroplasts are the site of photosynthesis

Chloroplasts contain chlorophyll

Question 24

What are amyloplasts

Answer 24

organelles that store starch