Topic 4A (Plant structure, function and drugs)

In plants, what is starch stored as and where

- it is stored as granules/grains

- stored in amyloplasts (& other plastids such as chloroplasts)

Explain the conditions needed for increased bacterial growth (4 marks)

- Oxygen for aerobic respiration (releasing energy)

- glucose for respiration and amino acids for protein synthesis

- optimum temperature for enzyme activity

- optimum pH for enzyme activity

[- water for metabolic reactions(like hydrolysis) and transport ]

Explain the structure of cellulose (4marks)

- Cellulose is a polymer of B-glucose which is joined together by 1,4 glycosidic bonds

- alternate/ consecutive B glucose are inverted (rotated to 180°), allowing celloluse to be straight chained

-B glucose chains are held by H-bonds, forming microfibrils.

- Due to the inversion and many H-bonds between, cellulose has high tensile strength

Name a tissue which gives plants support and is involved in transport of water and mineral ions

xylem

Explain how a double-blind clinical trial would be performed for a new cancer drug and suggest why it is important (4marks)

- A group of patients are given (new cancer) drug while

- another group is given placebo/old drug

- neither the doctor nor the patients know who has been given placebo or new drug

- To see if new drug works better than placebo/old drug and reduce bias

Suggest three reasons why a species of tree becomes endangered

(3marks)

Explain how the arrangement of cellulose molecules and secondary thickening in xylem vessels contributes to the physical properties of the cell wall

(5 marks)

- cellulose molecules join together by hydrogen bonds to form microfibrils

- microfibrils are arranged in a mesh (or bundle)

-which are held together by pectin/pectate

-Secondary thickening results in secondary cell wall where microfibrils are arranged at different angles, adding strength to cell wall

- secondary cell wall also (usually) has lignin, a ring like structure which makes cell wall impermeable to water/ waterproof

Oregano oil contains antimicrobial substances, which can be used for making packages.

Explain why this packaging may be chosen over traditional oil-based plastic packaging (2 marks)

- Plant based packaging is bio-degradeable and sustainable

- they also prevent bacteria/microbial growth

(- this extends the shelf life of food products, reducing food waste )

Describe phase-I and phase-II of drug testing (5marks)

Phase-I:

- select a small number of healthy volunteers (~100)

- tests for side effects and dosage

Phase-II:

- small(/larger number) of patients with disease, (~100-500)

- to identify effective/appropiate dosage of drug found in phase II

- uses double blind trial/placebo

Compare and contrast the structures of phloem sieve tubes and xylem vessels

(6marks)

[similarity & differences ]

- Both contain cellulose

- Both don't have nucleus

- Both have tubular structure

- Xylem vessels are hollow but phleom ST are not hollow

- xylem has lignin but phloem sieve tubes do not

- phloem ST have sieve plates(end walls), whereas xylem vessels do not

(phloem has plasmodesmata, xylem does not. Instead they have pits)

Describe phase III of drug testing

- Select large number of patients with disease (1000-3000)

- uses double blind trial/placebo

- effective dosage is found in phase II, not III

(in phase III the side effect and effectiveness are monitored over large no. of people )

Give two functions of a vacuole

- provides support

-stores substances like sugar and water (in cell sap)

Suggest one reason for the difference in bacterial survival on the pine board and plastic board,

( i.e the pineboard has less bacteria survival)

- pine board or wood has antimicrobial property

phloem is connected to other cells by __________ in plants

plasmodesmata

(also in phloem, sieve tube elements are connected to companion cells via plasmodesmata)

Name a structural molecule present in plant cell wall and in prokaryotic cell wall (2marks)

plant cell wall = Cellulose

prokaryotic cell wall = Peptidoglycan

what is centriole and give their function

- Cylindrical bundles of microtubules

- produce spindle fibers to seperate chromosomes /chromatids during anaphase

Function of pits in xylem ( 2marks)

- allows lateral movement of water and mineral ions between adjacent cells/tissues

Explain what is meant by sustainable

- A source that is renewable and biodegradeable/ can be broken down by decomposer

(- carbon neutral so there is less pollution )

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