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How well do you know your basics in H2 Biology?

Core Idea 1: The Cell and Biomolecules of Life is the most basic and fundamental topic in all of A Level Biology. Regardless of whether you take H1 or H2, or other specifications with AS and A Level, this topic is bound to be taught and tested. This topic is a foundational topic that interlinks with the more complex themes and ideas in other chapters. 

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Attempt this short quiz to find out how good you are at your basics!

A. Cells  

Candida albicans is a yeast-like fungus that lives in human lungs. It is the causative agent of one of the opportunistic 

infections that may develop during AIDS. C. albicans is eukaryotic. The diagram shows its structure.

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C. albicans uses a transport protein, TMP1, to absorb sugar molecules from the inside of the mouth. TMP1 is encoded by a gene within the nucleus and is produced when sugars are present in the surroundings. Explain how the structures within the cell shown in the diagram, are involved with the production of functioning TMP1. [4]

B. Membranes

The diagram shows a plasma (cell surface) membrane.

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Outline the functions of the following components of the plasma membrane. [4]

C. Biomolecules 

The diagram shows the structure of part of a cellulose molecule.

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Explain why cellulose is suitable as a component of plant cell walls. [4]

D. Enzymes

Students investigated the effect of pH on the activity of collagenase extracted from the bacterium Bacillus licheniformis at 50°C. The results are shown in the diagram.

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With reference to the diagram, describe and explain the effect of pH on the activity of collagenase. [4]

Answers

Q1

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  • nucleus transcribes DNA to mRNA that enters nuclear pore to ribosome for protein synthesis ;

  • RER transports protein to Golgi body for addition of carbohydrates / modification of proteins ; 

  • Golgi body packages protein into vesicles that fuse with the cell surface membrane ;

  • mitochondrion, provides / produces / synthesises, ATP in correct context ;

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Q2

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  • K permits movement of, ions/(small) water soluble molecules/charged/polar/hydrophilic, via facilitated diffusion/active transport ; 

  • L cell recognition/(surface) antigen/receptor/cell adhesion/cell marker/binding site/forms hydrogen bonds with water to stabilise membrane structure ; 

  • M barrier to, water soluble compounds/ions and allows passage of lipid soluble substances ;

  • N regulates, fluidity/stability by restricting movement of phospholipids or influences permeability of membrane ;

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Q3

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  • hydrogen bonding between (cellulose) molecules form fibrils and fibres ;

  • (cellulose molecule) is straight / linear, allowing molecules lie parallel to each other which gives strength (to cell wall) to, prevent cell bursting / withstand (turgor) pressure / AW ; 

  • ref. to fibres at angles / criss-cross / AW ; 

  • idea of many gaps, in wall / between fibres, allowing passage of water / named) substances / making cell wall permeable ;

  • AVP ; e.g. cellulose is insoluble or many –OH groups (for hydrogen bonding) 

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Q4

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  • as pH increases the activity increases until optimum peak at pH 7 and then decreases ;

  • partial denaturation in, acid and alkaline conditions / AW ;

  • (ionisable) R-groups in, active / catalytic, site affected and hydrogen bonds / ionic bonds, break / disrupted ; 

  • active site (shape) / (enzyme) tertiary structure, changes, so substrate / collagen, no longer fits into active site / fewer ESC complexes formed ;  

  • AVP ; e.g. detail of R groups 

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