Topic 2 Flashcards
1
Q
What are the properties of gas exchange surfaces?
A
- Large surface area to volume ratio of alveoli
- Lots of capillaries and thin walls in diffusion pathway
- Concentration gradient
2
Q
How does surface area to volume ratio affect different organisms gas exchange?
A
- As an organism gets larger the sa:v ration decreases.
- Smaller sa:v means more need for exchange surface/system
3
Q
What is Fick’s law?
A
rate of diffusion ∝ (surface area x difference in concentration) / thickness of exchange surface
4
Q
How does Fick’s law explain adaptation of mammalian gas exchange surfaces?
A
- Rate of diffusion is proportional to surface area
- Diffusion distance shortened due to flattened cells forming alveoli and capillary walls
5
Q
What are the adaptations of the lungs?
A
- Large surface area
- Large capillary network for blood supply
- Short diffusion distance
- Alveoli + cilia hair
6
Q
How are alveoli adapted for gas exchange?
A
- Large blood supply to create steep concentration gradient
- Wall is one cell thick
7
Q
What is the structure of a cell membrane?
A
- Phospholipid bilayer with hydrophilic phosphate head + hydrophobic fatty acid tail
- Contains proteins, cholesterol, glycoproteins and glycolipids
- Lipid bilayer closes so no exposed hydrocarbon chain to form stable layer.
8
Q
What is the ‘Fluid Mosaic model’?
A
- Molecules are dynamic and move in the plane of the membrane instead of static for cell movement and interactions and signalling
9
Q
What is the function of integral proteins?
A
- Embedded into the membrane and transport substances across membrane
- Channel proteins allow water-soluble molecules to cross
- Carrier proteins bind and change shape of proteins
10
Q
What is the function of peripheral proteins?
A
- Attaches to the outer surface
- Act as receptors to bind to + recognise
11
Q
What are glycoproteins?
A
- Proteins with a carbohydrate attached
- Act as a recognition site, help form tissue, provide stability and act as receptors
12
Q
What are glycolipids?
A
- Proteins with a lipid attached
- Act as a recognition site, help form tissue, provide stability and act as receptors
13
Q
What is the role of cholesterol?
A
- Lipid molecule
- Found between phospholipids where is maintains membrane fluidity
14
Q
What is diffusion?
A
- Overall net movement of molecules or ions from high to low conc, down conc gradient
- Passive transport as without ATP
- Continues until equilibrium
15
Q
What is facilitated diffusion?
A
- Across a partially permeable membrane via transmembrane integral proteins
- For large, polar molecules
16
Q
What do Channel proteins do vs Carrier proteins?
A
- Channel are selective to particles and open and close from one side of the membrane to the other
- Carrier have specific molecules bind and change in shape to transport across membrane.
17
Q
What is osmosis?
A
- Net movement of water molecules across a partially permeable membrane, down water potential gradient.
- Low conc of solution to high conc of solute
18
Q
What is active transport?
A
- Movement from low conc to high conc against a concentration gradient
- Requires ATP and carrier proteins.
- ATP hydrolysed to ADP and Pi which causes carrier protein to change shape.
19
Q
What is endocytosis?
A
- Takes substances in
- Membrane fuses enclosing substance in a vesicle
20
Q
What is exocytosis?
A
- Release of substances
- Secretory vesicle moves to cell surface membrane to release material
21
Q
What are enzymes?
A
- Biological catalysts which speed up the rate of reaction
- Catalyses reaction by lowering activation energy
- Activation energy is energy requires to start a reaction
22
Q
What are substrates?
A
- Any molecules catalysed by an enzyme
- Only binds with specific active sites - complementary binding
- Form enzyme-substrate complexes with enzymes
23
Q
What is the induced fit model?
A
- Specific shape substrate will induce an active site
- Binding causes active site to change its shape allowing reaction to be catalysed.
24
Q
How do enzyme and substrate conc affect rate of reaction?
A
- More enzymes produce more enzyme substrate collisions so increase rate.
- More substrate means more collisions but when all active sites are full it does not effect rate.
25
Q
What is DNA?
A
- Deoxyribonucleic acid
- Contains all genetic material + hereditary material
- It is a polynucleotide (polymer chain of nucleotides)
26
Q
What is a nucleotide made up of?
A
- Pentose sugar
- Phosphate group
- Organic base
27
Q
What are the organic bases in DNA?
A
- Guanine, adenine, cytosine, thymine
- A + T, C + G
- Either purine (two carbon rings) or pyrimidine (one carbon ring)
- Purine pairs with pyrimidine
28
Q
How are mononucleotides formed?
A
- Joined in condensation reaction
- By hydroxyl group of phosphate group + pentose sugar
- Forms phosphodiester bond
29
Q
What is the structure of DNA?
A
- Two polynucleotides twist to form a double helix
- Sugar and group form sugar-phosphate backbone
- Strands are held by hydrogen bonds
- Run antiparallel
- One runs 5’ to 3’, one runs 3’ to 5’
30
Q
What is RNA?
A
- Acts as a messenger molecule to transfer and regulate cell
- It is single stranded
- Pentose sugar is ribose
- Uracil instead of thymine
31
Q
What are genes?
A
- Sections of DNA used to code for a specific amino acids in a polypeptide
32
Q
What is a protein?
A
- Made of multiple polypeptides
- The primary structure determines the 3d shape the protein folds
- Structural, metabolic + transport roles
- Made up of carbon, hydrogen + oxygen
33
Q
What is the genetic code?
A
- Specific sequence of bases that code for a specific sequence of amino acids in protein synthesis
34
Q
What is the features of the genetic code?
A
- Triplet code
- Degenerate code
- Universal
- Non overlapping
35
Q
How is the code degenerate?
A
- An amino acid can be coded for more than one code.
- 20 amino acids, but 64 combinations of codons
- Valine can be coded for by GUU, GUC, GUA, GUG
36
Q
What is a codon?
A
- 3 bases that code for an amino acid
- There is start and stop codon
37
Q
What are start and stop codons?
A
- Start codon always AUG, codes for amino acid Methionine.
- Stop codon are UGA, UAA, UAG. tRNA molecules which do not have corresponding amino acid so no peptide bond can be formed.
38
Q
What is mRNA?
A
- From DNA and transfers genetic information from nucleus to cytoplasm
39
Q
What is transcription?
A
- DNA double helix is unzipped and hydrogen bonds break by the enzyme DNA helicase which moves along sugar-phosphate backbone
- Template antisense strand acts as a template for free RNA nucleotides to pair with complementary bases
- RNA nucleotides are joined to adjacent nucleotides by phosphodiester bonds by the enzyme RNA polymerase.
- Makes mRNA which leaves nucleus via nuclear pore
40
Q
What is tRNA?
A
- Transports amino acid to ribosome
- Binds to one amino acid and the specific mRNA codon creating a link
41
Q
What is translation?
A
- mRNA enters cytoplasm, moves to ribosomes
- tRNA molecules with their specific amino acid, move into ribosome and bind to mRNA (anticodon binds to start codon) by hydrogen bonding
- Second tRNA with complementary anticodon binds to next codon, bringing its specific amino acid
- allowing peptide bond to form between the amino acids
- tRNA detaches from mRNA and leaves into cytoplasm.
- Amino acids form the polypeptide primary structure.
42
Q
What is the structure of amino acids?
A
- Amine group
- Carboxyl group
- R groups (differ in size, polarity, charge)
43
Q
How are two amino acids joined?
A
- In condensation reaction between carboxyl and amine group
- A peptide bond is the covalent bons formed when two amino acids are joined
- Hydrolysis reaction breaks down amino acids
44
Q
How is a protein formed?
A
- A protein is formed when one or more polypeptide chain folds into a specific shape
45
Q
What is a polypeptide?
A
- A polymer of many amino acids joined by peptide bonds
46
Q
What is the primary structure of a protein?
A
- Sequence of amnio acids joined with peptide bonds
- Determines folding of polypeptide
47
Q
What is the secondary structure of a protein?
A
- Chains folding and shapes arise due to structure of amino acids
- Alpha-helix is when polypeptide coils and twists with hydrogen bonds
48
Q
What is the tertiary structure of a protein?
A
- 3d structure of amino acids
- Hydrogen bonds form between polar R groups
- Ionic bonds form between positive and negative R groups
- Disulphide link form between sulphur atoms in R groups
- Hydrophobic R group found in centre of protein and hydrophilic found on outside
49
Q
What is the quaternary structure of a protein?
A
- Proteins determined by more than one polypeptide chain
50
Q
What is a Globular protein?
A
- A spherical polypeptide with hydrophobic R group inside and hydrophilic R group outside
- Insoluble in water
- Eg. enzymes, hormones
51
Q
What are Fibrous proteins?
A
- Long chains of polypeptides with non polar R groups
- Soluble in water
- Eg. cartilage, collagen
52
Q
What is DNA replication?
A
- DNA double helix unzipped to break hydrogen bonds by DNA helicase
- Forms a replication fork with two exposed strands which acts as a template.
- Free DNA nucleotides pair with complementary based and DNA polymerase link adjacent nucleotides
- Phosphodiester bonds form in condensation reaction
53
Q
What is semi conservative replication?
A
- There is one original strand and one new strand
54
Q
What was the Meselson and Stahl experiment?
A
- E-coli is grown in heavy N15 isotopes
- Bacteria then moved to N14 meaning new nucleotides were light but original were heavy
- Spun in a centrifuge and produced medium DNA.
- New strand contained both light and heavy nitrogen
55
Q
What are mutations (gene + chromosome)?
A
- Changes to the genetic material of a cell
- Gene mutations are changes to vase sequence within a section of DNA or gene
- Chromosome mutations are changes to structure of whole chromosomes
- Important to evolution as increases genetic variation
56
Q
What are substitution mutations?
A
- Nucleotide is replaced with another nucleotide that has a different base
- Changes base sequence so changes the codon
57
Q
What are deletion mutations?
A
- Nucleotide removed from DNA sequence
- Shifts the reading chain so changes all amino acids
58
Q
What are insertion mutations?
A
- Additional nucleotide in DNA sequence
- Changed reading frame
59
Q
What are the type of affects of mutations?
A
- Silent - no change to protein function (explained by degenerate codon)
- Missense - change of amino acid form, so changes tertiary structure to non functioning protein
- Nonsense - previously coded amino acids becomes a stop codon (stops translation so polypeptide would end)
60
Q
What is sickle cell anaemia?
A
- Affects haemoglobin
- Substitution mutation changing encoded amino acid
- Forms insoluble fibres forming red blood cells to be distorted so less oxygen and inefficient transport
61
Q
What is cystic fibrosis?
A
- A mutation in the CFTR gene which leads to production of non functional chloride ion channel proteins
- Reduces the movement of water via osmosis into the mucus
62
Q
What impacts does cystic fibrosis have on the respiratory system?
A
- Cilia unable to move thick and sticky mucus so microorganisms are not removed from the lungs and lung infections occur more frequently
- Mucus builds up in the lungs and can block airways
- SA for gas exchange reduced
63
Q
What is genetic testing?
A
- Identifies abnormal alleles of genes in DNA.
- Confirms diagnosis, identifies carriers, test embryos
64
Q
How are embryos tested?
A
- Amniocentesis - prenatal testing where a needle collects amniotic fluid and are screened
- Chorionic villus - prenatal testing where small sample of placental tissue removed and screened
- Non - invasive prenatal diagnosis - DNA fragments of blood plasma.
- Pre implantation diagnosis - IVF for creation of embryos where they are removed and screened at 8-stage cell
65
Q
What is the difference between a genotype and a phenotype?
A
- Genotype is all the genetics of an organism
- Phenotype is the observable characteristics of an organism which are influence by both genotype and environment
66
Q
What is an allele?
A
- Genes of two or more different forms
- Gene is hereditary information where as allele is a form of a gene
67
Q
How are chromosomes formed?
A
- DNA is packaged with histone proteins that are called chromatin
- That coils and condenses to form chromosomes
68
Q
What are homologous chromosomes?
A
- A pair of chromosomes
- The position of a gene on a chromosome is called a locus
69
Q
What is homozygous vs heterozygous?
A
- If a pair of chromosomes have the same alleles at a locus
- If a pair of chromosomes have different alleles at a locus then it is heterozygous
70
Q
What are two dominant alleles called?
A
- Homozygous dominant
71
Q
What are two recessive alleles called?
A
- Heterozygous recessive
