6 Markers (1) Flashcards
Describe the gross structure of the human gas exchange system and how we breathe in and out. [6]
Structure: trachea, bronchi, bronchioles, alveoli
Breathing in - diaphragm and external intercostal muscles both contract
Causing volume increase and pressure decrease in thoracic cavity so air moves down pressure gradient from atmosphere into lungs
Breathing out - Diaphragm relaxes and internal intercostals muscles contract
Causing volume decrease and pressure increase in thoracic cavity meaning air moves down pressure gradient from lungs to atmosphere
Describe the cohesion-tension theory of water transport in the xylem. [6]
Water lost from leaf because of transpiration
Lowers water potential of leaf cells
Water pulled up xylem creating tension
Water molecules cohere by hydrogen bonds
Forms continuous water column
Adhesion of water molecules to walls of xylem
Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.
Do not include details of transcription and translation in your answer. [6]
DNA in nucleus is code for protein
Ribosomes produce protein
Mitochondria product ATP for protein synthesis
Golgi apparatus package/modify
Vesicles transport
Vesicles fuse with cell surface membrane
Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying cells. [6]
TEM use electrons and optical use light
TEM allows greater resolution
So TEM can allow smaller organelles to be observed
TEM view only dead specimens and optical can view live
TEM does not show colour and optical can
TEM requires thinnger specimens and more complex preparation
Describe three aseptic techniques she would have used when transferring a sample of broth culture on to an agar plate.
Explain why each was important. [6]
Keep lip on Petri dish
To prevent unwanted bacteria contaminating the dish
Wash hands
To prevent contamination from bacteria on hands
Flame the neck of the culture container
To maintain a pure culture of bacteria
The movement of substances across cell membranes is affected by membrane structure.
Describe how. [6]
Phospholipid bilayer allows movement of non-polar lipid-souble substances
Phospholipid bilayer prevents movements of polar lipid-insoluble substances
Carrier proteins allow active transport
Carry proteins allow facilitated diffusion
Number of carrier proteins determines how much movement
Cholesterol affects permeability
Describe the difference between active and passive immunity. [6]
Active involves memory cells, passive does not
Active involves production of antibody by plasma cells
Passive involves antibody introduced into body from outside source
Active long term, because antibody produced in response to antigen
PAss short term because antibody given is broken down
Active can take time to develop, passive fast acting
When a vaccine is given to a person, it leads to the production of
antibodies against a disease-causing organism.
Describe how. [6]
Vaccine contains antigen from pathogen
Macrophage presents antigen on its surface
T cell with complementary receptor protein binds to antigen
T cell stimulates B cell
With complementary antibody on its surface
B cell divides to form clone all secreting same antibody
Describe how the structure of a protein depends on the amino acids it contains. [6]
Structure determined by position of amino acid
Primary structure is sequence of amino acids
Secondary structure formed by hydrogen bonding between amino acids
Tertiary structure formed by interactions between R groups
Creates active site in enzymes
Quarternary structure is more than 1 polypeptide chain bonded
Explain the properties that make water important for organisms. [6]
A metabolite so takes part in metabolic reactions
A solvent for metabolic reactions and transporting substances
High specific heat capacity so buffers changes in temperature
Large latent heat of vapourisation so provides a cooling effect through evaporation
Cohesion between water molecules so supports columns of water
Cohesion between water water molecules so produces surface tension supporting small organisms
Describe the roles of iron ions, sodium ions, and phosphate ions in cells. [6]
Iron
Haemoglobin binds with oxygen
Sodium
Sodium moved out by active transport by Na K pump
Cotransport of glucose/amino acids into cells
Phosphate
Joins nucleotides in backbone of DNA
Used to produce ATP
Part of phospholipid bilayer
Compare and contrast the DNA in eukaryotic cells with the DNA in
prokaryotic cells. [6]
Nucleotide structure is identical
Nucleotides joined by phosphodiester bond
Eukaryotic DNA is longer
Eukaryotic DNA contains introns, prokaryotic does not
Eukaryotic DNA is linear, prokaryotic DNA is circular
Eukaryotic DNA is associated with histones, prokaryotic DNA is not
Describe how mRNA is formed by transcription in eukaryotes. [6]
Hydrogen bonds between DNA bases break
One DNA strand acts as a template
Free RNA nucleotides align by complementary base pairing
RNA polymerase joins adjacent RNA nucleotides
By phosphodiester bonds between adjacent nucleotides
Pre-mRNA is spliced to remove introns and form mRNA
Describe how a polypeptide is formed by translation of mRNA. [6]
mRNA attaches to ribosomes
tRNA anticodons bind to complementary mRNA codons
tRNA brings a specific amino acid
Amino acids join by peptide bonds
With the use of ATP
tRNA released after amino acids form polypeptide
Describe how mRNA is produced in a plant cell. [6]
The DNA strands separate by breaking the H bonds
One strand acts as a template
Complementary base pairing
RNA nucleotides joined by RNA polymerase
pre-mRNA formed
Splicing, introns removed to form mRNA
