Topic 2 Flashcards
How are the lungs adapted for gas exchange.
-contain alveoli that have a large surface area
-surrounded by capillaries that are one cell thick so short diffusion distance
-steep concentration gradient between alveoli and blood
What is Fick’s law
Rate of diffusion is quicker when there is larger surface area and concentration difference but smaller distance
Structure of amino acids
-Two amino acids= dipeptide
-Three or more amino acids= polypeptide
Describe primary structure of a protein
Two amino acids join as a dipeptide via condensation reaction with peptide bond, process repeated to from polypeptide chains. Sequence of amino acids in polypeptide chains is primary structure.
Secondary structure of a protein
Amino acid chain folds into alpha helixes or beta pleated sheets with hydrogen bonds
Tertiary structure of a protein
3D folding of secondary structure into complex shapes. Forms ionic/H+ bonds and disulphide bridges. Shape is determined by bond present.
Quaternary structure of protein
3D arrangement of more than one polypeptide, not all proteins have this
Structure of fibrous proteins
-long/parallel polypeptides
-little tertiary/quanternary structure
-insoluble
-used for structural purposes (i.e collagen)
Structure of globular proteins
-complex tertiary/quaternary structure
-souluable
- compact and spherical
-many uses (Haemoglobin, hormones,antibodies and carrier proteins)
Structure of a cell membrane
Cell membrane forms a phospholipid bilayer. Phosphate head is hydrophilic and fatty acid tail is hydrophobic.
What does the fluid mosaic model tell you and what evidence is there
Shows cell membranes are fluid and have a mosaic like arrangement of proteins.
Evidence: -Phospholipids naturally form bilayers in water
-Microscope image shows proteins on membrane
-lipid soluble substances pass more easily than water soluble
Define diffusion
Movement of molecules from high to low concentration down concentration gradient. No energy required.
Define facilitated diffusion.
Transport Polar molecules and ions across membranes using channel proteins. Down concentration gradient from high to low concentration, no energy required.
Osmosis
Net movement of water molecules from high to low concentration through partially permeable membrane, no energy required.
Active transport
Transports all types of molecules through carrier proteins that change shape against concentration gradient from low to high concentration. Requires energy supplied by ATP.
Exocytosis
Used for bulk movement of substances out of cell, vesicles fuse with cell surface membrane releasing contents.
Endocytosis
Used for bulk movement into cell, vesicles created by cell surface membrane bringing contents into the cell.
For unaffected lungs how is water removed out of mucus (too much water)
1)Na+ pumped across basal membrane
2)Na+ diffuses through sodium channels in apical membrane
3)Cl- diffuses down electrical gradient
4)water drawn out by osmosis, as high Salt in tissue fluid and low in mucus
Too little water in mucus for unaffected lungs
1)Cl- pumped into cell across basal membrane
2)Cl- diffuses through open CFTR channel
3)Na+ diffuses down electrical gradient into mucus
4)water is drawn in mucus via osmosis
Why can’t people with CF regulate water in mucus
CFTR channel is absent or not functional. Na+ channel is permanently open. So water constantly being removed and mucus becomes more viscose (sticky)
Effect of CF on digestive system
Pancreatic duct blocked with mucus, impairing release of digestive enzymes, food not digested properly resulting in lost energy (malabsorption syndrome)
Effect of CF on reproductive system
Females less likely to become pregnant due to mucus in cervix.
Males may have mucus blocking sperm duct.
Factors affecting rate of enzymes
-enzyme concentration (higher concentration more substrates so higher rate of reaction, but if concentration too high then more substrates than enzymes)
-temperature (highest rate at optimum temperature as kinetic energy of ezymes increase so more substrate binding, but past optimum temp rate of reaction drops as enzymes denature)
-pH (values a over or below correct pH alter bonds in structure so active site changes shaper and substrate can’t bind)
Describe DNA (structure)
DNA made of nucleotides composed of sugar, phosphate groups and bases. DNA is double stranded and forms a double helix due to the complementary base pairing of nucleotides
—>Bases=adenine/guanine(purine) and cystonine/thymine (pyrimidine)
—>Pairing=A-T and C-G
—>Sugar=deoxyribose
—>Bonding= phosphodiester bonds between phosphate group and carbon 5 and H+ bonds between bases
RNA structure
Single-stranded, not usually folded, carries codons (triplets of bases) which attach to tRNA anticodons via H+ bonds
-Pairing = A-U and C-G (U is uracil)
-Sugar= ribose
-Bonding= Same as DNA
What is tRNA
Carries anticodons that are complementary to codons carried by mRNA, they transport amino acids to ribosomes.
What are the two stages involved in protein synthesis
1)Transcription (in nucleus involving DNA/mRNA)
2)Translation (in ribosomes involving mRNA/tRNA)
Describe transcription
1)H+ bonds between complementary bases break and DNA unwinds into two strands
2)one strand used as template (antisense strand) to make mRNA molecule, As free nucleotides line up complementary mRNA forms (adjacent joined by phophodiester bonds), this is catalysed by RNA polymerase
4)mRNA moves out of nucleus through a pore and attached to ribosome (site or translation)
Describe translation
1)tRNA binds to specific amino acid from cytoplasm depending on anticodon (activation)
2)complementary anticodons bind to mRNA codons held by H+ bonds
3) ribosome joins the amino acids attached to two tRNA molecules by a peptide bond then tRNA detaches, process repeated until formation of polypeptide chain/stop codon on mRNA reached.
What is a gene
Sequence of bases on DNA which codes for a series of amino acids in a polypeptide chain.
What is the genetic code
The order of bases on DNA is called the genetic code, consists of triplets of bases (each triplet coding for an amino acid). Amino acids joined by polypeptide bonds and form polypeptide chain.
What are the features of the genetic code
—>Non-overlapping- each triplet read once and triplets don’t share bases
—>Degenerate- more than one triplet codes for same amino acid
—> triplet code- each three bases code for one amino acid, contains start/stop codons which start/stop protein synthesis.
What does semi conservatives DNA replication ensure
Ensures genetic information of cells is passed from one generation to another.
What does conservative replication conserve
Both strands of parent DNA
What happens in dispersive replication
Individual DNA strands are a mixture of new/old DNA
How did Meselsons and Stahl prove semiconservative DNA replication
—->DNA N15, incorporated heavy nitrogen more dense. Placed into N14 then replicated = medium band of DNA. (remove conservative = both parent).
—->Replicated again contain light and medium which got rid of N15 = semi-conservative proven
Process of DNA replication (steps)
1)H+ bonds break and double helix unwinds, catalysed by DNA helicase
2)Complementary base pairing occurs between template strand and free nucleotides
3)adjacent nucleotides joined by phophodiester bonds, catalysed by DNA polymerase, 2 identical daughter strands created
What is molecular phylogeny
Uses molecular data like DNA sequences to identify molecular relationships by comparing organisms .
Structural differences between Haemoglobin and collagen
-Haemoglobin is a globular protein and collagen is a fibrous protein
-Heamoglobin has 4 polypeptide chain and but collagen has 3 polypeptide chain
-Haemoglobin is soluable and collagen is insoluable
What’s genetic screening
Used to determine if DNA of an individual contains alleles for genetic disorders
What is Chronic villus sampling
Carried out 8-12 of pregnancy. Sample of embryonic tissue taken from placenta and DNA analysed.
Amniocentesis
14-16 weeks of pregnancy. Amniotic fluid containing foetal cells taken by needle. Grow foetal for 2-3 weeks in culture and analyse DNA.
Pre-implantation genetic disorders
Embryos created through IVF are tested for genetic disorders before implanted into women uterus.
Social/ethical issues around genetic testing
-harm of foetus and chance of miscarriage
-outcome of test could lead to abortion (right to live)
-cost of bringing up baby with disorder
-emotional/mental issues
Key terms
Allele-different forms of a gene
Genotype-all alleles in organism
Phenotype-observable characteristics resulting with genotype interacting with environment
Recessive-allele producing features only if 2 copies are present
Dominant-allele only needing one copy to produce features
Homozygote-individual with two identical alleles of a gene
Heterozygote-individual with two different alleles of gene