IMMS 1 Flashcards
Describe the structure and function of mitochondria
- Aerobic respiration, synthesis of ATP.
- Double membrane.
- Contains ring of maternal DNA.
Describe the structure and function of rough endoplasmic reticulum
- Interconnected cisternae with ribosomes on external surface.
- Protein synthesis.
Describe the structure and function of smooth endoplasmic reticulum
- Same as rER without ribosomes.
- Makes and transports lipids.
Describe the structure and function of golgi apparatus
- Made of ER.
- Modifies and packages proteins by adding sugars, then secretes them in vesicles via exocytosis.
- Proteins enter in cis side and leave through trans side.
Describe the structure and function of vesicles
- Storage.
- Transport.
- Exchange.
- Some e.g. lysosomes break down waste. pH around 5.
Describe the structure and function of cytoskeleton
- Supports cell.
- Microfilaments made of actin.
- Microtubules made of tubulin.
- Intermediate filaments vary from cell to cell.
Describe the structure and function of the nucles
- Contains DNA.
- Double membrane.
- Contains nucleolus.
- Produces rRNA.
Describe the structure and function of the cell membrane
- Compartmentalisation.
- Barrier from outside.
- Controls what enters/ leaves cells.
- Is a phospholipid bilayer.
- Semipermeable.
List and describe the components of a cell membrane
- Phospholipids (hydrophilic head, hydrophobic tail)
- Cholesterol for stability/fluidity.
- Glycoproteins (protein with carbohydrate chain).
- Glycolipids (lipids with carbohydrate chain).
List and describe the proteins in the cell membrane
- Channel proteins: Pores for water-soluble molecules.
- Carrier proteins: Change shape to allow passage of molecules.
List and describe different types of anchors in cells
- Tight junction: Seals neighbouring cells to prevent leakage.
- Adherent junction: Joins actin bundles in neighbouring cells.
- Desmosome: Joins intermediate filaments in neighbouring cells.
- Gap junction: Allows electrical activity.
- Hemidesmosomes: Anchors intermediate filaments to basal lamina.
Describe endocytosis and list the three types
Active process to engulf molecules into a cell.
- Phagocytosis (solids)
- Pinocytosis (liquids)
- Receptor mediated
Describe exocytosis
Active process to remove molecules from a cell
Describe diffusion
Passive movement of molecules from high to low concentration, down a gradient.
Describe facilitated diffusion
Passive movement of molecules using carrier or channel proteins, down a gradient.
Describe active transport
Active process working against a gradient
Describe three energy stores within cells
Lipids, licofuscin and glycogen.
Define homeostasis
Maintaining a constant internal environment
List and describe the three types of cell communication
- Autocrine: Cell communicating with self e.g. immunity
- Paracrine: Cell communicating with nearby cells e.g. synpases, NMJ, clotting cascades.
- Endocrine: Cells communicating with distant cells. Slow acting and long lasting e.g. hormones - pituitary, thymus etc.
Describe the structure and action of peptide hormones
- Proteins/ short chain amino acids
- Fast acting
- Large and hydrophilic so cannot pass through membranes
- This means they have extracellular receptors
Describe the structure and action of steroid hormones
- Synthesised from cholesterol
- Lipid soluble, so cross membrane using transport proteins.
- This means it has an intracellular receptor: Travels in blood bound to carrier proteins and acts directly on nucleus.
Describe the structure and action of amino acid derivatives
- Synthesised from tyrosine
What % and L of water is distributed through the body?
42L (60%)
Intracellular - 28L (40%)
Extracellular - 14L (20%) - 11L interstitial
3L plasma
Define osmosis
Process by which water molecules pass through a semipermeable membrane from an area of high to low water potential.
Define osmolality
Measure of number of dissolved particles per Kg of solvent
Define osmolarity
Measure of number of dissolved particles per L of solvent
Define osmotic pressure
Pressure applied to a solution, by a pure solvent, to prevent inward osmosis
Define oncotic pressure
A form of osmotic pressure exerted by proteins. Tends to pull water into a solution
Describe the role of ADH in water homeostasis
- Low water volume = inc. osmolarity.
- Causes water to move out of osmoreceptors (in AV3V area of hypothalamus), towards the higher solute concentration, via aquaporin 1.
- This causes osmoreceptors to shrink, triggering an action potential.
- This AP triggers the supraoptic nucleus of the hypothalamus to release ADH.
- Secreted from posterior pituitary and acts on collecting ducts of kidney. (Binds to V2 receptors on basolateral surface.)
Describe the RAAS system
Renin-angiotensin-aldosterone system:
- Macula densa of kidney detects low blood pressure or sodium concentration.
- Renin produced by granular cells in JGA converts angiotensinogen into angiotensin I.
- This circulates in blood until it reaches the lungs where ACE converts it into angiotensin II.
- Angiotensin II then acts directly on blood vessels, the adrenal gland (to increase release of aldosterone, which increases sodium re-absorption), and causes an increase in the release of ADH.
What is the most common intracellular electrolyte?
Potassium (K)
What are the most common extracellular electrolytes?
Sodium (Na), Chloride (Cl) and Bicarbonate (HCO3)
What are two other, less common, extracellular electrolytes?
Urea and glucose
Outline DNA replication, naming enzymes involved
1) Double helix unwinds - Topoisomerase.
2) Then unzips - Helicase.
3) Free nucleotides bind to complementary bases via Hydrogen bonds (A two bonds to T, C three bonds to G).
4) DNA Polymerase then creates covalent bonds.
5) Two new DNA molecules are created, each with one parent strand and one new strand
What direction does DNA Polymerase read and synthesise DNA?
Read 3’ - 5’
Synthesised 5’ - 3’
What is a primer?
Short strand of DNA which is the starting point for DNA synthesis, as DNA Polymerase can only add nucleotides to existing strands of DNA.
What is an Okazaki fragment?
There is a leading and lagging strand during DNA replication. The lagging strand is synthesised discontinuously, making short fragments of double stranded DNA. These short fragments are Okazaki fragments.
Outline transcription
1) DNA unwinds and unzips.
2) RNA polymerase creates a single strand of anti-parallel RNA (starts at promoter, ends at stop codon)
3) This forms a strand of pre-mRNA. Splicing occurs to remove introns (non-coding sections) and leave on extons (coding sections). This produces mature mRNA.
4) Many different combinations of exons means many different proteins can be formed.
Outline translation
1) mRNA attaches to and is read by a ribosome in the cytoplasm.
2) Codons bind to complementary anticodons on tRNA molecules which carry amino acids.
3) The AAs join by peptide bonds to form a protein.
What is a mis-sense mutation?
Point mutation where one nucleotide difference means a different codon and so amino acid is coded for.
What is a non-sense mutation?
Point mutation which leads to the production of a stop codon, forming an incomplete protein.
Outline the cell cycle
Mitosis (occupies small %)
G1 - Growth of cell, new organelles, proteins synthesised.
S - Synthesis, DNA is replicated and checked for mutations.
G2 - More cell growth, proteins for division are synthesised
What is Mendel’s 2nd Law?
The Law of Independent Assortment - Alleles of one gene will sort into gametes independently of the alleles of another gene
What is gonadal mosaicism?
When a person has 2+ populations of cells in their gonads and one is healthy while the other is genetically abnormal (i.e. any mutations)
How does gonadal mosaicism arise?
When a mutation occurs in one cell of the developing embryo and goes on to become gametes, all containing the same mutation
Describe autosomal dominant inheritance
- Disease manifests in heterozygous state.
- Males and females both affected.
- Can be seen in multiple generations.
- Can be transmitted between both sexes.
- 50% chance of offspring being affected.
Describe autosomal recessive inheritance
- Disease manifests in homozygous state.
- Usually only seen in 1 generation.
- 25% chance off offspring being affected.
- 50% chance of offspring being a carrier.
Describe X-Linked inheritance
- Disease caused by mutations in gene on X chromosome.
- Usually only men affected and woman are carriers.
- Cannot be passed from father to son (as father gives X chromosome to daughter.)
Define lyonisation
When one copy of the X chromosome in females is inactivated during embryological development.
What is Knudson’s 2-hit hypothesis?
The idea that non-inherited cancer requires 2 acquired mutations, whereas inherited cancer only requires one acquired mutation, as 1 is already inherited. Therefore more likely to develop an inherited cancer.
Define penetrance
Proportion of carriers of a gene/set of genes showing the characteristic phenotype.
Define variable expression
Variation in clinical features (type and severity) of a genetic disorder between individuals with the same gene alteration.
Define sex limitation
Expression of a particular characteristic limited to one gender, even though both carry the gene for the characteristic e.g. BRCA gene in women.
Define multifactorial disease
Disease due to a combination of environmental and genetic factors.
When calculating risk of inheriting a disease from pedigrees, what calculation would you use?
Chance of parent 1 being a carrier (usually work out from pedigree) * Chance of parent 2 being a carrier (usually given prevelance in general population) * Risk to child if both parents are carriers
