2022 a level paper 1

• Describe the structure and function of the nucleus. (4 marks)

  The structure consists of:

  nuclear envelope and pores

  nucleoli

  The function is:

  to store genetic information

  production of tRNA
• Name the main polymer in plant cell walls.

  cellulose
• Name the main polymer in fungal cell walls.

  chitin
• Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria becoming a common cause of infection acquired when in hospital.

  some bacteria carry alleles for resistance. the bacteria which do not carry resistant alleles and are non resistant bacteria end up dying. therefore there is a higher percentage of bacteria with resistant alleles
• Name another disaccharide formed from two glucose molecules.

  maltose
• Give two features of all prokaryotic cells thar are not features of eukaryotic cells.

  cell wall made from meurin

  no membrane bound organelles
• What is the type of bond that maintains the helical structure of the polypeptide?

  hydrogen bond
• Compare and contrast the structure of starch to the structure of cellulose.

  they are both polysaccharides

  both contain glycosidic bonds

  both contain carbon, hydrogen and oxygen

  starch made from alpha glucose where as cellulose made from beta glucose

  starch is branched whereas cellulose is not branched
• Describe the complete digestion of starch by a mammal.

  glycosidic bonds are hydrolysed. starch is hydrolysed into maltose by amylase, maltose is hydrolysed into glucose by maltase
• why did scientists use biomass instead of number os individuals of each plant species?

  too time consuming
• how the plant species index of diversity would be different in areas previously used to grow crops on?

  the land previously used to grow crops will have a lower plant bio diversity. therefore, farming reduces biodiversity of fungi
• evaluate weather more trehalose in the diet could be a factor in the increased number of antibiotic-resistant c. difficile infections

  i believe trehalose isn't a factor in the increased number of infections as the experiment was carried out in a lab and not a individual meaning its artificial. there may be other disaccharide's within the diet which could affect the bacteria as well as other bacterial species within the body may affect the bacteria.
• 2 features of prokaryotic cells that aren't features of eukaryotic cells

  no membrane bound organelles and cell walls are made from meurin.
• suggest how the properties of the AP's allow them to be positioned across the membrane and create a Chanel.

  the hydrophobic side will face the hydrophobic part of phospholipid bilayer whilst the hydrophilic side will not. the allows for the hydrophilic side to create a channel and allow ions to pass through.
• Assess why the APs do not damage the eukaryotic cells of the organisms that produce them

  cholesterol helps to give structural support to eukaryotic membrane. this prevents the APs from making a channel in eukaryotic membranes.
• 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

  the monoclonal antibody will bind to the antigen forming an antibody-antigen complex. the gold attached to monoclonal antibodies will interact with the electrons in the TEM. the TEM is used as it has a high resolution.
• describe viral replication

  attachment proteins attach to receptors on a host cell and viral nucleic acid will enter the cell. the nucleic acid will be replicated and the cell will produce protein. the virus will be assembled and released from the cell.
• suggest how 2 enzymes with different amino acid sequences can catalyse the same reaction

  the enzymes may have the same tertiary structure and therefore form enzyme substrate complexes with the substrate.
• Describe what the scientists should place in the control tubes in this investigation

  they should place the same volume of buffer solution, the same mass of enzymes and substrates.
• Give three conclusions you can make from Figure 8.

  enzyme p and q are active in ph 8.4

  q is not active at ph 7.4

  substrates are hydrolysed
• Explain the rate of transpiration between 5 am and midday shown in Figure 9.

  as temperature increases the rate of transpiration increases.

  stomatas open at 5am allowing for gas exchange

  some stomatas close at midday reducing the rate of transpiration
• Describe an experiment that you could do to investigate whether the mangrove root cells have a lower water potential than sea water.

  measure the mass of the fresh mangrove root before and after the experiment. place mangrove root in the sea water for 20 minutes. remove form the sea water and dry with a tissue paper to remove excess water. if the mass has increased that means water has been absorbed by osmosis
• Complete Table 3 to give three differences between DNA molecules and tRNA molecules

  deoxyribonucleic acid vs ribonucleic acid, single stranded vs double stranded, thymine vs uracil
• Describe how the scientists would remove large organelles from this suspension of cell contents.

  they remove large organelles by centrifuging the suspension at a lower speed which forms a pellet at the bottom

  of the tube as denser organelles will sink and the organelles will be removed in the first pellet.
• Explain the position of the bands of ribosomes in tubes A and B in Figure 10

  a= ribosomes are bound to rough endoplasmic reticulum so there are denser and move to the bottom.

  b=there are only free ribosomes present as the detergent has dissolved the membrane
• Explain why a second stain would be needed to stain the red blood cells. Suggest which molecule the stain could bind to in the red blood cells.


  red blood cells do not have a nucleus the molecule which would bind is haemoglobin
• Explain how this difference would affect gas exchange


  difference= more cells are present between the water and capillary

  explanation = therefore there is a longer pathway for diffusion and slower gas exchange
• describe the transport of carbohydrate in plants

  sucrose is loaded and actively transported into phloem by companion cell, this decreases the water potential so water enters phloem from xylem by osmosis. sucrose is unloaded from phloem by active transport