Edexcel A Level Biology Questions and Answers -Advanced Physiology, Evolution and Ecology

1. The diagram shows the structure of a cell membrane.  

i) Name the parts labelled A and B

ii) Explain how the structure of the membrane controls the transport of polar molecules.

2. Enzymes are involved in the breakdown of carbohydrates. 

(i) The diagram shows the structure of sucrose.

The enzyme sucrase breaks down sucrose into two monosaccharides.  Which type of reaction does sucrase catalyze? 

 A) condensation

 B) hydrolysis 

 C) phosphorylation 

 D) translocation

 (ii) Name the monosaccharides produced from the breakdown of sucrose.

(iii) The enzyme amylase breaks down the polysaccharide amylose into maltose. How many of these statements are true for amylose? 

1.   It contains 1,6 glycosidic bonds 
2.  It contains 1,4 glycosidic bonds 
3.   It has a helical structure
4.   It has a branched structure 

 A) 1  B) 2  C) 3 D) 4

3. The photograph shows part of a bacterial cell surrounded by viruses, as seen using an electron microscope

(i) Which of these structures would be present in a bacterial cell but absent in a palisade mesophyll cell? 

 A) cellulose cell wall and nucleoid

 B) cellulose cell wall and nucleolus

 C) peptidoglycan cell wall and nucleoid   

 D)  peptidoglycan cell wall and nucleolus 

 (ii) Which virus contains DNA? 

  A) Ebola  B) HIV  C) λ (lambda) phage  D) tobacco mosaic 

(iii) Explain why an electron microscope, rather than a light microscope, was used to produce this photograph.

Answers:

1.  i) A- phospholipid (bilayer)   B- (glyco) protein / (channel) protein / (integral) protein / (carrier) protein / (intrinsic) protein

Learn more: Practice test on Plasma Membrane

ii) The structure of the membrane controls the transport of polar molecules.

An explanation that makes reference to four of the following: 

•  polar molecules are (charged / water soluble / hydrophilic) 
• (phosphate / head} is hydrophilic / (fatty acids / tails)are hydrophobic 
•  (phosphate / head} on outer side / (fatty acids / tails) on inside
•  therefore (polar / charged / ionic) substances do not pass through the (hydrophobic centre / fatty acids / tails) 
• and so pass through (carrier / channel) proteins

2. (i)  B) hydrolysis  (ii) glucose and fructose 

Learn more: 

• Practice Test on Carbohydrates 
• Notes on Carbohydrates

(iii)  B) 2

3. (i)  C) peptidoglycan cell wall and nucleoid  ii) C) λ (lambda) phage

iii) An explanation that makes reference to the following:  

• the resolution is higher / better  
•  because the wavelength of electrons is short(er)

Learn more: Electron microscope vs Light Microscope