The structure and function of plants

Question 1

Name four structures which are found in plant cells but not in animal cells

Answer 1

Chloroplasts, permanent vacuole, cellulose cell wall and plastids like amyloplasts

Question 2

Describe the structure of the permanent vacuole found in plant cells

Answer 2

It contains cell sap surrounded by a membrane known as the tonoplast membrane

Question 3

What is the function of chloroplasts?

Answer 3

To carry out photosynthesis

Question 4

What are plasmodesmata

Answer 4

Cytoplasmic bridges that connect the cytoplasm of neighboring cells

Question 5

Give two organelles found in animal cells which are not typically found in plant cells

Answer 5

Centrioles and lysosomes

Question 6

What is the middle lamella?

Answer 6

A layer which is made up of calcium pectate and joins the cell walls of adjacent plant cells together

Question 7

What are bordered pits?

Answer 7

Unlignified sections of xylem vessels which allow water to move laterally between cells

Question 8

Describe the structure of starch

Answer 8

Made of amylose and amylopectin, coiled and branched

Question 9

What is the function of starch?Where is it found?

Answer 9

A store of energy in plant cells. The majority of starch content of plant cells is found inside membrane bound plastids called amyloplasts

Question 10

Describe the structure of cellulose

Answer 10

Straight chains of beta glucose joined by beta 1,4 glycosidic bonds. Hydrogen bonding between chains strengthens cellulose.

Question 11

What does the xylem transport and in which direction?

Answer 11

The xylem transports water and minerals up the plant from roots to shoots

Question 12

What does the phloem transport and in which direction?

Answer 12

Cell sap and sugars from source to sink

Question 13

What is secondary thickening?

Answer 13

The lateral growth of cambium tissue in plants to increase the thickness of the plant stem and vascular tissue

Question 14

What are the sclerenchyma fibers?

Answer 14

A type of supportive tissue found in plants made up of cells with lignified cell walls

Question 15

How can humans use the properties of plant fibers to create materials?

Answer 15

Plant fibers are made of long structural polysaccharide chains. They’re joined and strengthened by many hydrogen bonds which make the fibers tough. An example is cotton

Question 16

Describe the structure and function of the vascular system in the stem of dicotyledons

Answer 16

Vascular bundles organised around a central pith. Xylem on the inside of the bundle to provide support and flexibility, phloem on the outside. Cambium is found between the two.

Question 17

Relate the structure of the xylem to its function

Answer 17

-Long columns made of dead tissue to transport water
-Contain bordered pits, allowing the sideways movement of water between the vessels.
-Walls impregnated with lignin, providing structural support

Question 18

Define translocation

Answer 18

The movement of organic compounds in the phloem, from sources to sinks

Question 19

Summarize the mass-flow hypothesis of translocation

Answer 19

-Sugar loaded into sieve tubes via active transport
-Lowers water potential causing water to move in from the xylem
-Hydrostatic pressure causes sugars to move towards the sink

Question 20

Give evidence for the mass-flow hypothesis

Answer 20

● Sap is released when the stem is cut: must be pressure in phloem

● Sap exuding from the stylet (mouthpart) of an aphid inserted into sieve
tubes provides evidence that sugars are carried in the phloem

● There is a higher sucrose concentration in the leaves than the roots

● Autoradiographs produced using carbon dioxide labelled with
radioactive carbon provide evidence for translocation in the phloem

Question 21

What is the role of Mg2+ (magnesium ions) in plants?

Answer 21

It’s used to produce chlorophyll

Question 22

What is the role of Ca2+ in plants?

Calcium ions

Answer 22

It’s used to strengthen cell walls in plants

Question 23

What is the role of nitrate ions in plants?

Answer 23

They are used in the synthesis of amino acids, which are then used to produce proteins

Question 24

What are the conditions required for bacterial growth?

Answer 24

Sufficient nutrients, an appropriate t°, high moisture levels, high oxygen levels for aerobic bacteria, a well regulated pH

Question 25

Describe the phases of population growth

Answer 25

Lag phase: period of slow population growth
Log phase: rapid population growth in which birth rate exceeds death rate
Stationary phase: stability in which population numbers generally remain constant

Question 26

How can plant based chemicals be used in healthcare?

Answer 26

• Many plants can provide antimicrobial properties. For example tea tree oil has certain antifungal and antibacterial properties
• Lots of plants can have other therapeutic properties. For
  example poppy stems can be used to extract morphine which is used as an analgesic to relieve pain

Question 27

What was William Withering’s digitalis soup?

Answer 27

One of the first examples of drug testing where the correct dose of digitalis from the poisonous foxglove plant to treat heart disease was determined by William Withering.

Question 28

What are double blind trials?

Answer 28

Where neither researchers or participants know whether a drug is a placebo or the real thing. It eliminates researcher bias.

Question 29

What is a placebo?

Answer 29

A replica of the drug being tested that can’t be told apart from the real thing but has no effects on the patients

Question 30

Explain how placebos are used in drug testing.

Answer 30

They are used to find out whether the drug being tested is actually effective or if any positive effects are actually related to psychological processes

Question 31

Summarize the process of three-phased testing

Answer 31

1. Drug tested on healthy individuals to check for side effects
2. Drug tested on a group of patients
3. drug tested on a large number of patients, one group receiving existing treatment and the other receiving new treatment.