Exam Qs Flashcards
Explain why rapid breathing is a symptom of carbon dioxide poisoning [4]
-raised CO2 level in blood reduces blood pH
-drop in pH detected by chemoreceptors
-impulses sent to the medulla oblongata
-more impulses sent along the motor neurones
-increased rate of contraction by the diaphragm and intercostal muscles
Explain why a change in the DNA sequence can change the phenotype of an organism [3]
-may cause a change to the amino acid sequence
-protein has different tertiary structure
-so function is altered
-example: enzyme produced has a different shaped active site
Explain why fast twitch muscle fibres contain more glycogen than slow twitch fibres [3]
-glycogen provides store of energy
-glycogen provoides glucose
- glucose used for respiration
- fewer capillaries in fast twitch means less glucose supplied
Describe the role of centromeres in mitosis [3]
-keep chromatids together
- bind/attach to spindle fibres
- during metaphase
- point at which chromatids separate during anaphase
Describe the process of rhodopsin formation in rod cells after exposure to bright light [2]
-reformation occurs in the dark
-retinal joins to opsin
-trans retinal is converted to cis retinal
Explain how the response of phytochrome to a light stimulus can cause an increase in plant growth [3]
-phytochrome far red formed (in light)
-phytochrome far red is the active form
-so phytochrome far red stimulates {mitosis/ cell division/ cell elongation}
-phytochrome far red {is a transcription factor /activates transcription factors /stimulates protein synthesis}
Explain why an increase in temperature increases germination [2]
-greater supply of glucose increases rate of respiration
-more energy so more frequent collisions between the enzyme and substrate
-starch is hydrolysed more quickly
Describe the role of ribosomes in the synthesis of lactase [3]
-mRNA binds to ribosome
-an anticodon on the tRNA pairs with the complementary codon on the mRNA
-ribosome moves along mRNA
-peptide bonds form between amino acids
Explain why the frequency of this allele may change from one generation to the next [3]
-allele may undergo mutation
-gene flow may cause alleles to be lost or gained from the population
-due to natural selection
-people with condition may not have children
Explain how breeding programmes in zoos maintain the genetic diversity of captive populations [3]
-use a stud book to prevent inbreeding
-animals exchanged between zoos
-animals selected to prevent inbreeding
compare and contrast the process of transcription with the process of DNA replication [4]
-DNA helicase is used in both
-both involve forming phosphodiester bonds
-RNA polymerase in transcription but DNA polymerase in DNA replication
-transcription forms one strand but DNA replication forms a double stranded DNA molecule
-transcription uses RNA nucleotides but DNA replication uses DNA nucleotides
Sweating is a thermoregulatory mechanism.
A student stated that loss of heat when sweating is related to the dipole nature of water molecules.
Justify this statement. [3]
-the water molecule has an uneven distribution of charge
-so hydrogen bonds form between water molecules
- it requires a lot of {heat} energy to break these bonds
- and allow water to evaporate/ high latent heat of evaporation
Explain how seeds are selected for storage in seed banks [3]
-taken from different plants
-to provide genetic variation
-x-rayed
-to check for viability
Describe how the tertiary structure of myosin is related to its function [3]
-folded into specific shape with globular head
- that can bind to actin
- has a site that can bind with ATP
-straight to form a bundle with other myosin molecules
