Paper 1 EQs Flashcards
(22 cards)
(2022) Describe the structure and function of the nucleus
(4)
Structure
1. Double membrane and pores/nuclear envelope and pores
2. Chromosomes/chromatin
3. Nucleolus
Function
4. Stores genetic material for polypeptides
5. DNA replication occurs
6. Transcription occurs
7. Production of ribosomes
(2022) Name the main polymer that forms the following cell walls
Plant
Fungi
(1)
Plant - Cellulose
Fungi - Chitin
(2022) Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria
becoming a common cause of infection acquired when in hospital. (3)
- Some bacteria have resistant alleles
- Non resistant bacteria die
- More antibiotics used in hospital compared with elsewhere so high frequency of resistance allele
(2022) Describe how the scientists could use aseptic techniques to transfer 0.3 cm3 of C. difficile in liquid culture from a bottle onto an agar plate. (3)
- Wash hands with soap/disinfect surfaces
- Flame neck of bottle
- Lift agar plate lid slightly
- Work close to upward air movement
- Use sterile spreader
(2022) Give two features of all prokaryotic cells that are not features of eukaryotic cells (1)
- No membrane-bound organelles#
- Single circular/loop DNA
- DNA free in cytoplasm
- DNA not associated with proteins/histones
- Murein/peptidoglycan in cell wall
- Prokaryotes have smaller ribosomes (70s)
(2022) Describe viral replication (3)
- Attachment proteins attach to receptor
- Viral nucleic acid enters cell
- Nucleic acid replicated in cell/reverse transcriptase makes DNA from RNA
- Cell produces viral protein/capsid/enzymes
- Virus assembled and released from cell
(2022) Define the quaternary structure of a protein (1)
More than one polypeptide chain
(2022) Explain how two enzymes with different amino acid sequences can catalyse the same reaction. (2)
- Both active sites have similar/identical tertiary
structures - So form enzyme-substrate complexes with the
same substrate
(2022) Give three differences between DNA molecules and
tRNA molecules (3)
- Deoxyribose v ribose
- Double-stranded v single-stranded
- Many nucleotides v few
- Thymine v uracil
- Linear v clover leaf structure/double helix v clover leaf structure
- Does not bind to amino acid v does bind to
amino acid; - No exposed bases v anticodon
(2022) Describe how the scientists would remove large organelles from a suspension of cell contents (2)
- Use centrifuge/centrifugation at
slow/low/increasing sequence of speeds - Large/dense organelles removed in first/early pellet
(2022) To observe the fish gills with the optical microscope, the scientists used two different stains. The first stain binds to DNA; the second stain binds to the red blood cells.
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. (2)
- Red blood cells do not have a nucleus/DNA
- Haemoglobin
(2022) Describe the transport of carbohydrate in plants. (5)
- Sucrose actively transported into phloem cell/sucrose is co-transported/moved with H+ into
phloem cell - By companion/transfer cells
- Lowers water potential (in phloem) and water
enters (from xylem) by osmosis - Produces higher hydrostatic pressure/produces hydrostatic pressure gradient
- Mass flow to respiring cells/mass flow to storage tissue/organ
- Unloaded/removed from phloem by active
transport
(2022) Compare and contrast the structure of starch and the structure of cellulose. (6)
- Both polysaccharides/both are glucose polymers/both are made of glucose monomers
- Both contain glycosidic bonds between monomers
- Both contain carbon, hydrogen and oxygen/C, H and O
- Starch has α-glucose and cellulose has β glucose
- Starch molecule is helical/coiled and cellulose molecule is straight
- Starch molecule is branched and cellulose is not/unbranched
- Cellulose has micro/macro fibrils and starch does not
(2022) Describe the complete digestion of starch by a mammal. (4)
- Hydrolysis
- Of glycosidic bonds
- Starch to maltose by amylase
- Maltose to glucose by disaccharidase/maltase
- Membrane-bound disaccharidase/maltase
(2017) Give the two types of molecule from which a ribosome is made (1)
- rRNA
- Protein
(2017) Describe the role of a ribosome in the production of a polypeptide. Do not include transcription in your answer. (3)
- mRNA binds to ribosome;
- Idea of two codons/binding sites
- Allows tRNA with anticodons to bind/associate
- Catalyses formation of peptide bond between amino acids held by tRNA molecules
- Moves along mRNA to the next
codon)/translocation described
(2017) In a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of the pre-mRNA.
Explain why. (2)
- Introns in pre-mRNA
- Removal of sections of pre-mRNA)/splicing
(2017) Describe the structure of glycogen. (2)
- Polysaccharide of α-glucose/polymer of α-glucose
- Joined by glycosidic bonds/branched structure
(2017) Suggest how glycogen acts as a source of energy.
Do not include transport across membranes in your answer. (2)
- Hydrolysed to glucose
- Glucose used in respiration
(2017) Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients. (2)
- Membrane folded so increased/large surface area
/Membrane has increased/large surface area for fast diffusion/facilitated diffusion/active transport/co-transport - Large number of protein channels/carriers in membrane for facilitated diffusion
- Large number of protein carriers in membrane for active transport
- Large number of protein channels/carriers in membrane for co-transport;
(2017) Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut. Some of these cells have membranes with a carrier protein called NHE3.
NHE3 actively transports one sodium ion into the cell in exchange for one proton (hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3 does this. (3)
- Co-transport;
- Uses hydrolysis of ATP
- Sodium ion and proton bind to the protein;
- Protein changes shape to move sodium ion
and/or proton across the membrane
(2017) High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid.
Explain how. (3)
