Year 1 foundation A Flashcards
Metabolism Key stages
Glycogenesis- glucose to glycogen
Glycogenolysis- glycogen to glucose
Glycolysis (anaerobic)- glucose to pyruvate
Gluconeogenesis- Amino acids + fatty acids to glucose
Beta oxidation- fatty acids converted to acetyl coA entering the Krebs cycle
Link reaction- co enzyme a + Acetate (from pyruvate) creates Acetyl coA
Krebs cycle- oxidation of Acetyl coA
ETA- utilises O2, Nadh, Fadh2 to create ATP
Endochondral ossification Key points
Bone replaces existing hyaline cartilage model, in intramembranous bone develops from mesenchyme or fibrous tissue.
Form all bones in the body except skull, mandible and clavicles.
Cells involved:
Osteoblasts- build bone, secrete osteoid
Osteocytes- matured osteoblasts surrounded in cartilage
Osteoclasts- Bone resorption
Chondrocytes- produce and maintain cartilagenous matrix ( from mesenchyme stem cells)
Interstitial- bone length e.g in epiphyseal growth plate or articular cartilage
Appositional- bone width e.g. in endosteum/peristeum
Inheritance Key terms
Autosomal Dominant- only one copy of allele required for expression e.g. Huntington
Autosomal recessive- two copies of same allele required e.g. sickle cell
X linked recessive- allele on X only, predominantly male e.g. hemophilia
X linked dominant- only one copy of allele on X needed, higher incidence in males e.g. Rett syndrome
Co dominance-Alleles equally expressed, both phenotypes present e.g. blood type
Penetrance- the proportion of people with a particular genetic change who exhibit signs and symptoms of a genetic disorder
Incomplete penetrance- Mutation is present but the phenotype is not i.e. BRCA 1/2 may not necessarily cause cancer if you have it
Interpreting Pedigree diagrams
Autosomal dominant- Does not skip generation, affects both. Typically associated with overproduction of proteins
Autosomal recessive- tends to skip generation, affects both. Typically associated with lack of function
X linked recessive- from mother who is a carrier (linkage cannot be confirmed), predominantly males. Daughters less likely, need two affected alleles
X linked dominant- 100% incidence from affected daughters if the father is affected.
Types of transport
Simple diffusion- non polar, small compounds e.g O2
Facilitated diffusion- down electrochem gradient via protein channel
Primary active transport- against electrochem gradient using ATP
Secondary active transport- against electrochem gradient, ion moving down conc gradient. e.g. Na+/ K+ pump
Ion channel- gated by ligand or ion, down electrochem gradient
ionophore mediated- ion transport down electrochem gradient
Endocytosis- into cell, forming membrane around substance
Exocytosis- out cell, vesicles fuse with membrane to release substance
pinocytosis- liquid droplets ingested by living cells
Phagocytosis- uptake of solid particles by a cell
Types of cell junctions
Tight junctions- stops movement of substances between cells, interlocking junctional protein joins adjacent cell
Adhering junctions- maintains cell position, connect to other cells via integrins. Integrins attach cytoskeleton to ECM. Integrins are transmembrane receptors that facilitate cell ECM adhesion.
Gap junctions – Allows movement of substances between cells. Formed by 6 connexins. 2 connexons aligned together forms a channel between 2 cells. Passage for excitatory signals e.g. muscle and cardiac cells.
Types of transporters
Uniporters- single substances move in a single direction
Symporters- two substances move in the same direction
Antiporter- two substances move in the opposite direction e.g. Na+/ K+ pump or Na+/ Ca2+
Cell receptor- GPRC
Structure- 7 alpha helices joined by 3 intracellular and extracellular loops
Extracellular ligand binds-> conformational change -> G protein binds -> GDP bound to alpha sub unit is substituted by GTP -> alpha and beta unit separate -> alpha stimulate adenyl cyclase converting ATP to cAMP->cAMP stimulates pkA-> pkA phosphorylates activates transcription proteins which bind to promoter regions in the DNA
Example- adrenaline binds to a GPCR to increase HR, vasodilation, glycogenolysis.
Cell receptor- Tyrosine kinase
Extracellular ligand binds -> causes conformational change (dimerisation)-> autophosphorylation of dimers -> phosphorylated dimers activate relay proteins-> relay proteins cause a cellular response
Example- Insulin activates the insulin receptor tyrosine kinase (IR), which phosphorylates and recruits different substrate adaptors such as the IRS family of proteins causing effects such as glycogenesis.
Stages of the cell cycle
G0 🡪 Resting phase G1 🡪 Organelles replicated S Phase 🡪 DNA synthesis G2 🡪 Cell growth and preparation for mitosis M 🡪 Mitosis (not in interphase)
DNA synthesis process
Topoisomerase enzyme unwinds supercoiled helix
(DNA) Helicase enzyme breaks hydrogen bonds between the base pairs of DNA, creating a replication fork
LEADING STRAND
DNA primase adds an RNA primer to the template to begin the 5’ end of new strand (DNA is read 3’ to 5’ adding to the OH group)
DNA polymerase III binds to primer and continues to make the leading strand by adding bases
LAGGING STRAND
DNA primase adds RNA primer to template
DNA polymerase III binds to primer and adds DNA in chunks, forming okazaki fragments , fragments are joined by DNA ligase
RNA primers are cut and DNA is filled in using DNA polymerase
Telomeres are repetitive nucleotide sequences
Cell cycle checkpoints
Checkpoints-examines the internal and external conditions of a cell to determine whether to continue with a cell cycle
G1 🡪 Commit to cell division; Site of action of p53
Located before S phase
G2 🡪 Ensure DNA fidelity
Before Mitosis
Spindle 🡪 Ensures that chromatids are attached to tubules correctly
During metaphase in mitosis
Cyclins
Cyclins - assist the cell cycle. Different cyclins peak at different stages G1 🡪 Cyclin D S 🡪 Cyclin E G2 🡪 Cyclin A Mitosis 🡪 Cyclin B
CDK’s (cyclin dependent kinases)- CDK’s phosphorylate and activate cyclins
Protein synthesis- Transcription (within the nucleus)
DNA 🡪 mRNA
DNA Helicase ‘unzips’ DNA to expose the template DNA
RNA polymerase binds to a promotor region
RNA polymerase adds complimentary RNA nucleotides (T 🡪 U)
DNA read 3’ 🡪 5’. Therefore, pre-mRNA is made in 5’ 🡪 3’
Pre-mRNA has its introns cut out using a splicesosome
(introns = into the bin)
mRNA moves from the nucleus to the ribosome for translation
Protein synthesis- Translation (ribosomes)
mRNA 🡪 Polypeptide
Ribosomes are found on the endoplasmic reticulum (RER)
mRNA is read in triplet codons by the ribosome and tRNA molecules
AUG is the start codon
Small sub-unit 🡪 Matches tRNA anti-codons to mRNA codons
Large sub-unit 🡪 forms peptide bonds between the newly attached amino acids (condensation reaction)
UAG, UGA, UAA are the 3 stop codons
