Molecular cell biology
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Molecular cell biology - Leaderboard
Molecular cell biology - Details
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| What is cell theory? | Cell theory is that the cell is the structural unit of life that contains metabolic and genetic elements. cells can only arise by division of a preexisting cell. Modern cell theory is that energy flow occurs in cell, heredity information is passed from cell to cell and that all cell have the same basic chemical composition. |
| What are the two major cell types and what makes them different | Prokaryotes have circular DNA free in the cytoplasm, Eukaryotes have a 'true nucleus' linear DNA molecules held in a membrane bound nucleus, contain subcellular organelles to compartmentalise |
| Subdivisions of prokaryotes? | Bacteria and eubacteria |
| Where is dna located in prokaryotic cells, and how its structured | Nucleoid - not membrane bound, formed into a single loop and does not have introns, genes are grouped into operons |
| Describe the plasmid in a prokaryote | Small loops of non essential DNA and is smaller than genomic DNA. passes vertically during cell division or horizontally by bacterial conjugation. natural plasmids may carry antibiotic resistant genes. easil manipulated in vitro. |
| Describe the difference between vertical and horizontal transmission of plasmid | Vertical transmission is when a bacteria goes through binary fission (asexual reproduction), horizontal transmission involves conjugation. |
| What is conjugation? | Once replication of the plasmid is completed a donor will produce a pilus which makes contact with the recipient bacterium. pore in the membrane if formed to create a continuous conjugation tube. replic plasmid becomes linear and travels to the recipient where it becomes circular. |
| Ribosomes in prokaryotes | Free in cytoplasm (not attached to membrane), composed of protein and rRNA and function to translate mRNA to protein, sedimentation 70s. |
| Storage granules in prokaryotes | Store of carbon, either store glycogen or poly-ß-hydroxybutyrate but not both. Glycogen granules dispersed through cytoplasm visible when stained, poly-ß-hydroxybutyrate stains with the fat stain Sudan black |
| What are mesosomes? | Aggregates of tubular membrane structures, derived directly from plasma membrane |
| What are the internal membranes in prokaryotes | Lamellae, vescles or tubules, appearance in EM depends on bacteria type |
| What are bacterial microcompartments? | Protein shells filled with enzymes for key activities,carboxysomes help autotrophic prokaryotes fix carbon via calvin cycle, pdu are involved in propanediol utilisation |
| Plasma membrane in prokaryotes | Phospholipid bilayer embedded with proteins, do not have cholesterol which are replaced by hopanoids,stabalising membrane |
| Plasma membrane function | Contains cytoplasm and regulates movement of materials, site of cell wall synthesis, no mitochondria enzymes for energy gen need to be organised within plasma membrane |
| Outer membrane function | Gram neg, protects invading bacteria from host defence, essential nutrients pass via porins |
| Function of bacterial cell wall in prokaryotes | Resists internal osmotic pressure, prevents bursting in hypotonic media |
| What is in the cell wall | Peptidoglycan, strength is due to cross linking of peptide chains, prevents sugar units of polymer sliding over. |
| Capsule in prokaryote | Layer of polysaccharide and glycoprotein surrounding the bacteria |
| What is the periplasm | The space between peptidoglycan layer and the plasma membrane, filled with loose peptidoglycan network and enzymes for nutrient acquisition. |
| Flagellum in prokaryotes | Composed of flagellin low amounts of sulphur containing aromatic amino acids and high levels of aspartic and glutamic acid |
| What colour do gram negative and gram positive bacteria | Gram positive bacteria are purple, gram negative are pink what colour do gram negative and gram positive bacteria |
| What is the structure of peptidoglycan | Homogeneous |
| Teichoic acid | Glycerol ribitol or manitol polymers in gram positive cell walls |
| Describe the gram negative cell wall | Thin layer of peptidoglycan,overlaid by a lipid layer similar to plasma membrane |
| Microbial diversity | Considers the vast array of microorganisms |
| What are acidophiles | Bacteria that can grow at a pH of 3 or below, they need to maintain a net outflow of protons to maintain the internal pH |
| What can acidophiles be used for commercially | Can be used to leach metals from low grade ores |
| What are alkalophiles | Bacteria that are inhibited by pH 8-9 or above, must maintain a net inflow of protons to preserve internal pH, example is Vibrio cholerae |
| What are the three groups of oxygen requirements for bacteria | Aerobes - depend on molecular oxygen facultative anaerobes - use oxygen if available anaerobes - cannot use oxygen |
| Aerobic bacteria | Found in terrestrial and aquatic habitats, don't grow in static liquid culture, require shaking |
| Facultative anaerobes | Commonly used andmedically significant E.coli, require fermentable sugars |
| Anaerobic bacteria | Some killed by oxygen (obligate),others are tolerant, depends on superoxide dismutase |
| What is the importance of superoxide dismutase | Destroys toxic superoxide radicals dormed during oxidation, converts superoxide radical to hydrogen peroxide and oxygen |
| Temperature - Psychrophiles | Grow well at 0 optimum near 15, found in arctic, membranes are high in unsaturated fatty acids |
| Psychotrophs | Grow at 0 but optimum is between 20-30, present in soil, cause of food spoilage |
| Mesophiles | Growth optimum around 20-40, majority are mesophiles, includes bacteria that live in association with or cause disease in animals |
| Thermophiles | Optimum about 55-65, grow in compost, enzymes and nucleic acids are heat stable, membrane lipids more saturated than mesophiles |
| Hyperthermophiles | Grow above 90, optimum between 80-113, includes species which grow in hot areas of ocean |
| Black smoker' bacteria | Grow in sulphide chimneys, grow at 113 ' |
| Halophiles | Can tolerate high salt levels can colonise saline lakes, cell wall may be damaged from low salt concentrations |
| Are eukaryotes unicellular or multicellular | Eukaryotes can be both unicellular and multicellular |
| DNA molecules in Eukaryotes | Have linear DNA molecules packaged as chromosomes enclosed in nucleus, have membrane bound organelles |
| Unicellular eukaryotes | Most complex eukaryotes, perform all functions, unicellular when food available, when food is scarce they aggregate and specialise to form primitive multicellular organism |
| What are Eukarytotic cell membranes composed of | Phospholipids and protein, spontaneously assemble to form closed bilayers |
| Eukarytoic cell membranes: two faces | The two faces of the cell membrane are asymmetric in terms of lipid and protein composition Cytosolic face is the inner part, exoplasmic face is the outer part. |
| Functions of plasma membranes | Regulation of transport balance of chemical conditions chemical reaction site detects signals interacts with other cells/extracellular (multicellular) |
| Name the organelles of the eukaryotic cell | Nucleus, ER, golgi complex, mitochondria, lysosomes (ac), peroxisomes, cytosol, cytoskeleton |
| Nucleus | Contents are in contact with cytoplasm via nuclear pores which pass through both membranes Large dense region= Nucleolus, rich in protein and RNA |
| What does the nucleus separate | Separates DNA from the cytosol; transcription from translation |
| ER- two types and what they do | Extensive membrane structure forming interconnected sacs and tubules Rough ER= ribosomes attached to surface, plays role in synthesis of membrane-bound and secreted proteins Smooth ER = no ribosomes, plays role in producing lipids |
| ER | Lipid synthesis, membrane protein synthesis, Ca 2+ ion storage, detoxification Key features: interconnected closed membrane tubules and vesicles |
| Ribosomes | Multi-subunit structures, 50% protein, 50% ribosomal RNA rRNA key to structure and function of ribosomes synthesis of proteins 40s and 60s subunit= 80s |
| Mitochondria | Contains DNA and ribosomes, can direct production of some of own proteins self replicating = binary fission site of ATP production, aerobic metabolism, important role in apoptosis Key features: outer membrane intermembrane space inner membrane matrix |
| What is apoptosis? | Programmed cell death |
| Mitochondrial DNA | Genes exhibit cytoplasmic inheritance and encode rRNAs, tRNAs, mitochondrial proteins size and coding capacity of mtDNA varies products of mitochondrial genes are not exported mutations cause genetic diseases, leigh syndrome, optic neuropathy |
| Golgi complex | Stack of flattened membranous sacs vary in number sacs form from parts of rough ER which break off and fuse Inner face is close to the nucleus ensures that vesicles budding off outer face can fuse with plasma membrane packages lysosomal proteins and proteins to be secreted from cell |
| Lysosomes | Single membrane-bound organelles containing hydrolytic = degrade materials taken up by endocytosis and cell debris degrade damaged newly synthesised proteins |
| Peroxisomes | Single membrane-bound organelles contain catalase and urate ocidase = breaks down very long chain fatty acids via beta oxidation oxidation of toxins |
| Cytosol | Enclosed by the plasma membrane not static contents continuously moving key features: cytoskeleton polyribosomes metabolic enzymes |
| Cytoskeleton | Lattice like array of filaments and fine tubules involved in cell movement, division, maintenance, trafficking organelles 3 major components: microfilaments = actin microtubules intermediate filaments |
| Microfilaments | F-actin filaments are double helices of polymerised G-actin subunits fibres expand and contract by further polymerisation and depolymerisation, ATP dependent Interact with other filaments and 'motor' to create movement,contraction can cause shape change |
| Actin and myosin in Eukaryotic cells | Actin microfilaments work with myosin in muscle fibres myosin filaments walk along the tethered actin, pulling the filaments towards the centre to cause muscle contraction |
| Microtubules | Microtubules are polymers of tubulin that form part of the cytoskeleton tubes of tubulin: grow by polymerisation from specific microtubule organising centres microtubules can form trackways in cellsalong which motor proteins (kinesins) drag vescles, organelles. Play a fundamental role in partitioning of chromatids in cell divisions |
| Microtubules role in cell division | Partitioning of chromatids chromatids are one of two strands of a newly copied chromatid, two joined together at centrimere they are called sister chromatids and are genetically identical |
| Intermediate filaments | Different types that differ in composition and function, may have role in maintaining cell shape, tissue integrity |
| What are the specialised features of plant cells? | Chloraplasts, vacuoles and specialised peroxisomes plant cells have a rigid cell wall can communicate with eachother |
| Vacuoles | Make up 80% of plant cell store water, ions, nutrients, degrade macromolecules inflow of water by osmosis causes vacuole expansion and maintenance of turgor pressure expansion of vacuole involved in cell elongation |
| Chloraplasts | Double membrane bound, contain their own DNA Thylakoid membranes, fused into stacks in places, contains chlorophyll photosynthetic plant cells, contain chloraphyll to absorb light and generate NADPH and ATP |
| Specialised peroxisomes | Found in leaves involved in photorespiration (oxygen to carbon dioxide) Glyoxysomes found in germinating seeds, carry out glyoxylate cycle to convert fatty acids into sugars |
| Plant cell wall | Rigid cell wall comprised mainly of cellulose cross linked by hemicellulose, pectin, and lignin |
| Plasmodesmata | Directly connect the cytosol of adjacent cells in higher plants |
| Name the different tissues that cells that are organised into | Epithelia, nervous tissue, connective tissue, muscle, blood |
| What is the process of cells going to tissues | Differentation |
| Why are the layers of the early embryo important? | They give rise to the cell types, goes from xygote to blastocyst and then gastrula Germ cells = sperm or egg endoderm (internal) layer = lung alveoli, thyroid, pancreatic cell Mesoderm (middle) layer = cardiac muscle, skeletal muscle, tubule cell of kidney, RBC, smooth muscle. Ectoderm (External layer) = epidermis skin cells, neuron, pigmant cell. |
| Cells produced at 50-cell stage? | Cells that are produced at the 50- cell stage are called Embryonic stem cells, these cells are totipotent except foetal membranes) |
| What is totipotent? | Ability of a single cell to divide and produce all of the differentiated cells in an organism. |
| What is a pluripotent stem cell? | A pluripotent stem cells give rise to cells to a particular tissue |
| What is a monopotent stem cells | Monopotent stem cells can produce only one cell type |
| Can adult cells be reprogrammed? | Adult cells can be reprogrammed by manipulating the expression of key regulatory genes to produced induced PS cells, derived from blood or skin cells. |
| Differentiated cells | Differentiated cells express different subsets of genes: transcribed genes (transcriptome), and translated proteins (proteome). |
| Mechanism and Differentiation | Tissue specific gene expression is primarily regulated at the level of transcription, fine tuning at post-transcriptional and post-translation levels also occur. Signals received by the cell activate transcription factors to turn on certain genes. Inactive genes are characterised by methylation at CG doublets in their promoters |
| What are the four major classes of cell surface receptors | G-protein couples receptors Tyrosine kinase-linked receptors Ion channels receptors receptors with intrinsic enzymatic activity Singles generated at the plasma membrane are transduced to the nucleus via a complex series of secondary events |
| Name the secondary events in transducing signals from the plasma membrane | Binding of the second messengers to receptors and phosphylation |
| Apoptosis role | Has roles in embryogenesis, tissue homeostasis, damage limitation, control and functioning of immune system. Evolutionarily conserved and genetically controlled |
| What are the Two main gene families involved in apoptosis | Bcl-2 family (regulation) Caspase family (execution) Many accessory proteins - death domain proteins |
| Characteristics of apoptosis | Mild convolution, chromatin compaction, margination condensation of cytoplasm Breakup of nuclear envelope, nuclear fragmentation, Blebbing cell fragmentation Phagocytosis |
| Importance of Apoptosis | Too little apoptosis can lead to cancer, autoimmune diseases and prolonged viral infection Too much apoptosis leads to neurodegenerative diseases, autoimmune, tissue damage through trauma, progression of AIDS. |
| How does apoptosis become unregulated? | Genes controlling it become damaged or aberrantly expressed, inappropriate triggering of apoptosis, the interference by exogenous genes |
| Name cell types: Epithelia | Epithelial cells - from sheets that cover the inner and outer of the bodies surfaces Absorptive cells - have microvilli to increase their surface area ciliated cells - have cilia that beat to move substances over the sheet Secretory cells - secrete substances out onto the sheet |
| What are the main types of intestinal cells | Absorptive cells outnumbers others 10:1 Goblet cells: secrete mucous Paneth cells: secrete growth factors and antibacterial substances Enteroendocrine cells: secrete peptide hormones and serotonin into gut wall |
| Name 3 Neuron cell types | Neurons are specialised for communication, the axon conducts electric signals away from the cell body multipolar interneurons motor neurons sensory neurons |
| Cell types: rod cells, what are they? | Rod cells are specialised sensory cells in the retina, layers of disks contain light sensitive pigmant = rhodopsin Light evokes an electrical signal that is transmitted to the brain |
| Cell type: Erythrocytes, what are they? | Highly specialised, carry oxygen, protein component is haemoglobin loss of nuclei and internal membrane, cant replicate |
| Connective tissue, name some different connect tissues that arise from fibroblasts | Fills spaces between epithelial sheets and tubes Bone cell - osteoblasts/osteocytes Fat cells - adipocyte smooth muscle cell Cartilage cell - chondrocyte |
| What does fibroblast differentiation depend on | Depends on the etracellular matrix YAP and TAZ are transcription regulators that move to the nucleus in response to tension developed in the actin-myosin bundles in the cytoplasm |
| What does the transcription regulators YAP and TAZ stand for | YAP = yes associated protein TAZ = transcriptional coactivator with PDZ-binding motif |
| What are the different types of muscle cells | Cardiac muscle - in the wall of heart, adjacent cells connected by electrical conducting junctions to ensure synchronous contraction Skeletal muscle - striated muscle fibres, made from large multinucleated cells. control voluntary movement Smooth muscle - thin elongated cells non striated, control involuntary movement |
| What are the requirements for a multicellular organism | Interactions: Cell adhesion molecules tight junctions, gap junctions, adherens junctions Desomosomes Interactions between cells and their surroundings: Hemidesmosomes and focal adhesions basal lamina Extracellular matrix - integrity of tissues |
| Major classes of cell adhesion molecules | Homophilic interactions: Cadherins (E-cadherin) Ig-superfamily Heterophilic interactions: Integrins (alpha v beta 3) Selectins (P-selectin) |
| Tight junctions? | Sometimes cells need to form an impermeable barrier, tight junctions seal gaps between cells, the membranes are firmly pressed together and prevent leakage. |