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Description
Flashcards by reynoldslaura, updated more than 1 year ago
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Created by reynoldslaura
almost 11 years ago
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| Question | Answer |
| What are the functions of the golgi apparatus? | To receive vesicle traffic from the endoplasmic reticulum, carry out quality control testing of proteins, glycosilation reactions, sorting and packaging of contents and targeting of products to final destinations |
| What is the main purpose of pinocytosis? | Balances fluid and solute loss via exocytosis- so cell volume and surface area remains constant |
| What is the evidence that genes are not lost from cells during development? | A nucleus from a differentiated cell in a tadpole body can be transplanted into an unfertilised egg and produce a frog |
| The nuclei of differentiated cells are totipotent. What does this mean? | That they have full genetic content and genes have not been lost |
| What happens in the nucleolus? | ribosomal RNA is synthesised, processed and packaged with ribosomal proteins to form ribosomal subunits that are destined for export to the cytoplasm |
| What molecule has the lowest mutation rate known and what is it? | Histone 4 (0.06 per 100 amino acid residues per 100 million years ) |
| What experiments showed that there is no specific base pair recognition by histones and that their role in all species is a structural one? | Heterologous nucleohistone reconstitution experiments |
| What is the function of importins? | They are proteins in the nuclear pore complex that recognise nuclear localisation signals (NLS) and allow proteins to be imported into the nucleus |
| Define secretion. | The release of useful products from a cell |
| How was the secretory pathway discovered? | By autoradiography |
| How do proteins get into the rER? | They contain a signal sequence- small sequence of hydrophobic amino acids that are guided to the rER membrane via a signal recognition particle |
| What is the function of the sER? | To synthesise and metabolise lipids and to carry out detoxification reactions |
| What are the functions of the rough endoplasmic reticulum? | It allows entry of proteins into the ER, inserts membrane proteins into the lipid bilayer, carries out simple glycosilation reactions and quality control protein folding |
| Define autophagy. | The digestion of material of intracellular origin |
| Define autolysis | The release of lysosomal enzymes into the cytosol |
| What is the function of adaptin? | It binds the cytosolic domain of the receptor and binds clathrin ensuring receptors are packaged and other integral proteins are not in receptor mediated endocytosis |
| What is the function of Hsc70? | It is a chaperone which acts to uncoat the clathrin coated vesicle in receptor mediated endocytosis |
| what is the function of clathrin? | It assembles into a lattice of pentagonal and hexagonal units which cover the cytosolic face of the coated pit in endocytosis. Its assembly provides the driving force for membrane curvature |
| What is the purpose of dynamin? | It uses the energy of GTP hydrolysis to sever the clathrin coated vesicle from the membrane in endocytosis |
| Define heterophagy? | Digestion of material of extracellular origin |
| I cell disease is caused by the deficiency of what enzyme? | N acetylglucosamine phosphotransferase |
| What checkpoint occurs at G1 ? | Cell is checked to ensure it is competent to start DNA duplication |
| What checkpoint occurs at G2? | Duplicated DNA is checked to ensure it has been copied without any major errors |
| What checkpoint occurs just before the M phase? | Checks to ensure chromosomes have separated properly and are properly attached to mitotic spindle before anaphase begins |
| What does checkpoint failure lead to? | Tumourgenesis |
| What is the reason for these specific checkpoints? | Allows for cell cycle arrest and repair of damaged DNA or activation of cell death- apoptosis |
| Define hyperplasia | An increase in the number of normal cells in a tissue or organ (can be a normal response to tissue damage) |
| Define dysplasia. | Abnormal development or growth of tissues, organs or cells (not necessarily cancerous) |
| Define dysplasia. | Abnormal development or growth of tissues, organs or cells (not necessarily cancerous) |
| What is the difference between necrosis and apoptosis? | Necrosis is passive cell death and affects a group of cells whereas apoptosis is active cell destruction and affects an isolated cell |
| Define cancer 'in-situ' | Cancer that involves only the place from which it began and has not spread e.g. a carcinoma 'in situ' is an early stage tumour |
| Define invasive cancer | Cancer that begins in one area but then spreads deeper into the tissues of that area |
| Define metastatic cancer. | Cancer that has spread from the place in which it started to other parts of the body |
| What is an oncogene and give an example? | An oncogene is a gene, that if mutated can drive tumourgenesis e.g. H-Ras |
| What is a tumour suppressor and give and example? | A gene which normally works to suppress tumourgenesis e.g. Rb and p53 |
| What is a tumour promoter? | A compound that sensitises the tissues to the action of a tumour inititator - predisposes the tissue to become a tumour |
| Which specific factor allows the transition from G2 to M phase? | MPF (maturation promotion factor) |
| To ensure proliferation of only cell suitable for division- how many checkpoints are there in the cell cycle? | 3 |
| Which factor controls the initiation of the transition from G1-S in yeast? | Cdc28 |
| What is a temperature sensitive mutation? | One that only manifests at high temperatures |
| What molecule triggers movement through the cell cycle? | Cyclin dependent kinases- bound by a cyclin molecule (thus they are activated) |
| What is the signal initiating exocytosis? | A sharp rise in cystolic Ca²⁺ concentration |
| Do we have pumps that transport chloride on its own? | NO! It is always co transported with something else. (e.g. Na⁺/K⁺/Cl¯ pump- transports sodium and potassium in equal proportions but pumps out 2x Cl¯ in order to transport equal amounts of +ve and- ve ions |
| Where are tight junctions found? | between two extracellular fluid compartments |
| What is the role of tight junctions? | To restrict the passage of substance from interstitial fluid to luminal compartments |
| Name two examples of places where you find tight tight junctions. | Colon, distal convoluted tubule |
| Name two places where you might find leaky tight junctions. | Where there is block fluid movement in epithelia, proximal convoluted tubule and the small intestine |
| How are tight junctions regulated? | TRICK QUESTION THERE IS NO REGULATION OF TIGHT JUNCTIONS- tight tight junctions are always tight and leaky junctions are always leaky |
| What is the purpose of gap junctions? | They link cell interiors together and thus allow them to be both chemically and electrically coupled |
| How are the channels at gap junctions formed? | From connexons- these are transmembrane protein assemblies. Two connexons come together to form an aqueous pore/channel. |
| Which type of muscle has NO gap junctions and thus cells are completely electrically isolated from one another? | Skeletal muscle cells |
| How can we assess electrical coupling between cells? | By measuring electric potential with microelectrodes and applying ohms law ( I= V/R) |
| How are gap junctions controlled? | Via intracellular pH (H⁺) and Ca²⁺ . If there are abnormal increases in either of these two substances then gap junctions close |
| What is the crucial protein channel linking Ca²⁺ signals to ATP production? | MCU 'mitochondrial calcium uniporter' - an intracellular ion channel in the mitochondria |
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