Cell Biology Theme 1

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  • Created by: Splodge97
  • Created on: 13-05-17 15:10
What is a prokaryote?
Cell without a defined nucleus (DNA in a circular nucleosome) or membrane bound organelles
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What is the endomembrane system?
Diifferent membranes suspended in the cytoplasm of eukaryotic cells, dividing it into structural/functional compartments
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What are peroxisomes?
Organelles involved in the catabolism of long chain, branched fatty acids and amino acids; they also reduce hydrogen peroxide and synthesise phospholipids
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What is the nuclear lamina comprised of?
Dense network of collagen IV, may be associated with protiens (provides nucleus with mechanical support, regulates division/DNA replication)
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What is the nucleosome comprised of? What does it do?
Small sphere in nucleus, formed from RNA and proteins, site of ribosome synthesis and assembly
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What is the fuction of the RER?
Involved in lipid/protein synthesis
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What is the function of the SER?
Steroid hormone sysnthesis and Ca2+ secretion (in specialised cells)
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What is the role of the Golgi apparatus?
Modifies proteins and lipids from the ER (cisternae provide large SA for enzymes)
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What is gylosylation?
Attachment of molecules (polypeptides/lipids) to carbohydrates
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What is the pH of lysosomes?
pH 5 (ideal for hydrolytic enzymes)
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How do macrophages engulf debris in phagocytosis?
Via rearrangement of actin filaments
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What is pinocytosis?
When ECF (containing proteins and sugars) is invaginated and released to organelles - not endocytosis as molecules not invaginated to vesicles (so doesn't form early endosome etc.)
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What are the flattened sacs of the mitochondria?
Cristae
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What is the effect of acetylation?
Addition of negative acetyl group to positive histone tail (formed from lysine and arginine at N-terminus) weakens its attraction to negative DNA (so transcription enabled)
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Where does PCR occur?
In vitro (outside the body, in a controlled environment)
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Where does the replication origin normally occur?
Helicase binds to areas of A=T repeats as fewer H-bonds (so less energy to break)
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What occurs at the replication fork?
Replication origin meets double stranded DNA (where DNA helicase and topoisomerase open double strand)
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In what direction are new strands of DNA built by DNA polymerase in semi-conservative replication?
in 5'-3'!! But DNA polymerase moves along existing strand in 3'-5' direction in leading strand (as added anti-parallel)
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What part of DNA polymerase can cleave incorrect dNTP's?
Nuclease active site
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What bonds form to add dNTPs to the existing strand?
H-bonds and phosphodiester bonds
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What is necessary for DNA polymerase to bind?
RNA primer (creates small section of double stranded DNA)
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How are dNTPs added to the lagging strand?
Okazaki fragments (still added in 5'-3' direction via jumping, but DNA polymerase moves along the parent strand in the 5'-3' direction (opposite to leading strand))
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What is phylogeny?
DNA hybridisation and/or ribosomal fragment analysis to deduce how closely related organisms are
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What is endosymbiosis?
Ingestion of primitive prokaryote by primitive eukaryote (how we gained mitochondria)
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What are bacterial capsules formed from?
Polysaccharides (which retain water and nutrients)
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Describe gram positive bacteria
Have a plasma membrane surrounded by a thick layer of peptidoglycan which has glycopolymers within it (providing mechanical strength, aiding adhesion and increasing permeability)
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What do osteoblasts secrete?
Dense, crosslinked collagen and specialised proteins to form bone
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What are the collagen associated proteins? How are they arranged?
Fibronectin and integrin (dimers). Integrin attaches to adaptor proteins on actin filaments at one end and fibronectin at the other; fibronectin is attached to collagen. Moves cell along collagen (when fibronectin and adaptor protein attach/detach).
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Where is collagen I present?
Skin, tendons, bone, dentine
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Where is collagen II present?
Cartilage and vitreous humour (of eye)
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Where is collagen III present?
Alongside collagen I in skin, muscle and blood vessels
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Where is collagen IV present?
Forms sheets in the basal lamina and nuclear lamina
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Where is collagen V present?
Alongside collagen I in foetal membranes and the placenta
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What is elastin?
Loose, unstructured polypeptide interwoven with collagen. Fibrillin essential for its formation.
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How do glycosaminoglycans allow joints to resist compression?
Negative polysaccharide which attracts Na+, lowering water potential so incompressible water accumulates
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What are proteoglycans?
GAG's linked to proteins, aggregate to form ground substance
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What is added to single DNA strands to identify specific nucleotide sequences?
Labelled oligonucleotide probe
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What is a nucleosome (in DNA)?
Octomer of eight DNA strands coiled around eight histones (creating a disc)
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What are chromosomes comprised of?
Highly looped and folded chromatin fibres
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What is an autotroph?
Microorganism which uses CO2 directly unlike heterotrophs (use organic molecules to gain carbon)
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What are auxotrophs?
Mutant bacteria created in the lab which require specific growth factors
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What is the difference between lopotrichous and peritrichous bacteria?
Lopotrichous = many flagella in same direction. Peritrichous = many flagella in different directions
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What is an operon?
Cluster of genes in a DNA sequence with similar function so are transribed as one mRNA strand by a single promoter
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What is transformation?
Horizontal gene transmission in bacteria where DNA is uptaken by the bacteria themselves
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What is transduction?
Horizontal gene transmission in bacteria where a virus injects its DNA into the bacterium, infecting it
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Describe the structure of an antibody
Two arms, each with a light (three beta pleated sheets) and heavy (five beta pleated sheets) chain; binds to antigen at variable region
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What is immunohistochemistry?
Identifies if specific protein present on a tissue biopsy by adding primary antibody (generated in animals) then a secondary labelled antibody (to amplify the effect)
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What is immunoblotting?
Protein extracted from cell/liquid sample then separated by gel electrophoresis (made equally negative by SDS) which sorts by size. Electric current used to transfer to nitrocellulose sheet, labelled antibody added
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What is ELISA (enzyme-linked immunosorbant assay)?
Cell/protein extracts from a liquid sample are attached to plastic wells - primary then labelled secondary antibodies added
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Describe the structure of gram-negative bacteria
Have three outer layers (with periplasm between each) - 1st the plasma membrane, 2nd a thin peptidoglycan layer and 3rd a lipopolysaccharide/protein layer
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What forms peptidoglycan? What is its function?
Glycan sugar strands with AA side chains - increases cell wall rigidity
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What is the meurin sacculus?
Large peptidoglycan layer encasing bacteria
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What does periplasm contain?
Degradative enzymes for cell wall remodelling, transport proteins and molecular chaperones (for assembly/disassembly of other molecules)
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What is the role of porins?
In outer membrane of gram-negative bacteria, regulate influx/efflux into/out of peptidoglycan layer
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What is the role of lipopolysaccharides in the outer membrane of gram negative bacteria?
Act as toxins, pack together to become impermeable (preventing destruction by phagocytes), aid cell adhesion
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Describe the structure of rough lipopolysaccharides
Lipid covalently bonded to an inner and outer core
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Describe the structure of smooth lipopolysaccharides
Lipid covalently bonded to an inner and outer core - outer core has o-polysaccharide attached which acts as an antigen
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What are archae?
Class between bacteria and eukaryotes - occur in harsh environments and plaque. Same size as bacteria but DNA associated with histones and no cell walls (or cell walls of pseudomurein)
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Describe the process of binary fission
How bacteria divide - bacteria elongate, then MinE proteins wrap around nucleolus to form Z ring. This attached to the cell wall and contracts to form the septum so bacteria splits into two identical daughter cells.
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What is the viable count method of measuring bacterial growth?
Uses agar plate, assumes each colony originated from a single cell (doesn't take into account some from multiple/some failed to multiply)
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What is the turbidity method of measuring bacterial growth?
Light shone through shake flask containing bacteria; more bacterria means less light passes through (but death rate slow as dead bacteria still block light)
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What is the generation time and how is it calculated?
Time taken for bacteria to double - calculated by time/number of generations (given by 3.3(logN-logNo))
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What is an amphipathic molecule?
Has both a hydrophilic and hydrophobic region
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What is the role of monomer sequestering proteins?
Hold actin monomers when there is a surplus (later added at the + end)
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What structures do actin filaments form?
Filopodia, microvilli, contractile bundles (actomyosin complexes in muscle cells), the contractile ring and the cell cortex (ust below plasma membrane to support cell and allow movement)
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What are microtubules formed from?
Hollow cylinders of the hetrodimer tubulin
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What is the role of motor proteins?
Microtubule associated proteins kinesin and dynein (move in opposite directons) which bind and unbind to microtubules in sequence to move molecules/organelles (attached to their tails) along them using ATP
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What structures do microtubules form?
Cilia, flagella
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What is nuclear lamins?
Intermediate filament which forms the nuclear lamina
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What are neurofilaments?
Intermediate filaments in nerve cells
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What is vimentin?
Cytosolic intermediate filament in connective tissue
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What is keratin?
A diverse cytosolic intermediate filament in epithelial cells
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What forms the exracellular matrix?
Collagen, elastin (and other proteins), polysacharrides and cells (mainly fibroblasts)
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Card 4

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