EXAM QUESTIONS - SPRING MOCK Flashcards
A student investigated the difference in the reducing sugar content of two fruit juices.
He performed a biochemical test on each fruit juice using Benedict’s solution. He then used a colorimeter with each test result.
a) Describe how the results from the colorimeter can identify the fruit juice containing the high sugar content. [ 1 mark]
b) The student controlled variables in the test using Benedict’s solution.
Give two variables the student controlled. [2 marks]
a) HIGHER abundance OR LOWER transmission (has more sugar)
b)
> Temperature (of water bath)
> Benedict’s solution VOLUME
> Benedict’s solution CONCENTRATION
> Fruit juice VOLUME
> Duration of heating
Iodine solution stains fresh apple tissue black. When iodine solution is added to apples stored for a week, the stain is less black.
The water potential of apple juice decreases when apples are stored.
Suggest why the water potential of apple juice decreases when apples are stored. [2 marks]
Starch is hydrolysed [1]
Maltose is soluble so reduces WP [1]
OR
Starch is insoluble.
Give two features of all prokaryotic cells that are not features of eukaryotic cells [1 mark]
> No membrane-bound organelles [1]
Single circular/loop of DNA [1]
DNA is free in cytoplasm [1]
DNA not associated with proteins/histones [1]
Murein in cell wall [1]
Many multicellular organisms produce antimicrobial polypeptides (APs) that protect them against prokaryotes.
The amino acids on one side of each AP helix have hydrophobic properties.
The amino acids on the opposite side of each helix have hydrophilic properties.
Suggest how these properties of the APs allow them to become positioned across the membrane and make a channel through which ions can pass [2 marks]
- Hydrophobic side faces the fatty acid tail of phospholipid bilayer. [1]
- Hydrophilic sides allow ion movement through membrane / forms a channel [1]
Many multicellular organisms produce antimicrobial polypeptides (APs) that protect them against prokaryotes.
The APs damage prokaryotic cells but do not damage the eukaryotic cells in the organisms that produce them.
Prokaryotic cell membranes do not contain cholesterol.
Assess why the APs do not damage the eukaryotic cells of the organism that produce them. [2 marks]
- Cholesterol stabilises the membrane [1]
- So APs do not make the channels in the eukaryotic membranes [1]
Plants produce ATP in the light-dependent reaction of photosynthesis. Explain why plants cannot use this as their only source of ATP. [2 marks]
- Need more ATP (than can be produced in photosynthesis)/not enough; [1]
- Photosynthesis cannot produce ATP in dark; Cannot be produced in cells lacking chlorophyll /chloroplasts/ ATP cannot be transported; [1]
Give two ways in which the properties of ATP make it a suitable source of energy in biological processes. [2 marks]
- Energy released in small / suitable amounts;
- Soluble;
- Involves a single / simple reaction;
Humans synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesise such a large amount of ATP. [2 marks]
- ATP cannot be stored / is an immediate source of energy;
- ATP only releases a small amount of energy at a time
Many multicellular organisms produce antimicrobial polypeptides (APs) that protect them against prokaryotes.
Scientists observed these APs on prokaryotes using a transmission electron microscope. They stained the APs using a monoclonal antibody with gold attached to it.
Suggest how these techniques allowed observation of APs on prokaryotes. [3 marks]
- Antibody binds to AP
OR gold is present where AP located [1] - As antibody/tertiary structure is complementary to AP [1]
- Gold interacts with electrons in (TEM) [1]
- TEM used as it has a high resolution [1]
Describe viral replication [5 marks] MS
- Attachment proteins attach to RECEPTORS. [1]
- Viral NUCLEIC ACID enters cell [1]
- Nucleic acid replicated in cell OR reverse transcriptase makes DNA from RNA; [1]
- Cell produces (viral) protein/capsid/enzymes; [1]
- Virus assembled and released from host cell. [1]
Explain how two enzymes with different amino acid sequences can catalyse the same reaction [2 marks]
- Both active sites have similar/identical tertiary structures [1]
- So form enzyme-substrate complexes with the same substrate. [1]
Two enzymes, P and Q are proteins with quaternary structure which catalyse the same reaction, but they have different amino acid sequences.
Scientists investigated the effect of pH 8.4 and pH 7.5 on the activity of enzymes P and Q.
Describe what the scientists should place in the CONTROL tubes in this investigation. [3 marks]
- Same volume of each buffer solution. [1]
- Same concentration/mass of substrate at the start. [1]
- Same concentration/mass of DENATURED enzyme [1]
Give three differences between DNA molecules and tRNA molecules. [3 marks]
- Deoxyribose vs ribose;
- Double-stranded vs single-stranded;
- Many nucleotides vs few;
- Thymine vs uracil;
The action of the carrier protein (sodium-potassium pump) is linked to a membrane-bound ATP hydrolase enzyme.
Explain the function of this ATP hydrolase [2 marks]
- ATP to ADP + Pi releases energy [1]
- Energy allows ions to be moved against a concentration gradient [1]
OR
energy allows active transport of ions.
A zookeeper was bitten by a snake. The bite contained a venom which is a poison. He was given an injection of antivenom. This antivenom contained antibodies against this snake venom.
The antivenom did not give the zookeeper lasting protection against this snake venom.
Explain why [2 marks]
- Zookeeper is not producing antibodies / has passive immunity [1]
- No memory cells made. [1]
