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FUNMED > Cellular Biology > Flashcards

Cellular Biology Flashcards

1
Q

What is the role of SER?

A

Synthesis of carbs and lipids, storage of molecules and drug detoxification in the liver and kidneys

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2
Q

What is the role of RER?

A

Ribosomes: mRNA –> protein
ER: folds and modifies proteins produced by ribosomes

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3
Q

What is the role of the Golgi apparatus?

A

Synthesis and packaging of secretions (packing enzymes into vesicles for exocytosis)

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4
Q

What is the role of lysosomes?

A

Originate at Golgi and contain digestive enzymes, work to defend against disease, remove debris (autophagy and autolysis)

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5
Q

What is the role of peroxisomes?

A

Originate at RER and are involved in fatty acid metabolism and detoxification of free radicals

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6
Q

What does the cell cytoskeleton consist of?

A

Actin microfilaments, intermediate filaments, tubulin micotubules

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7
Q

What is the role of actin microfilaments in the cell cytoskeleton?

A

Maintain cell shape, facilitate movement (with aid of myosin) for organelle and vesicle movement

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8
Q

What is the role of intermediate filaments in the cell cytoskeleton?

A

Provide tensile strength

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9
Q

What is the role of microtubules in the cell cytoskeleton?

A

Provide cell scaffold and forms tracks for movement and mitotic spindle

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10
Q

What is hyaluronic acid a type of?

A

Glycosaminoglycan

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11
Q

What type of collagen is in the basement membrane?

A

Type 4 (floor, four)

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12
Q

What is elastin?

A

Polymer of tropoelastin associated with fibrillin to form elastic fibres

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13
Q

What is fibronectin?

A

Present in ECM and plasma (soluble form) and works to bind cells and ECM, cellular attachment and matrix organisation (guides cell migration, development and repair)

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14
Q

What are the principle components of the extracellular matrix?

A

GAGs, proteoglycans, fibrous proteins and basement membrane

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15
Q

What are tight junctions?

A

Cellular junction which prevents molecules from passing across the epithelium

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16
Q

What are adherens junctions?

A

Tethers adjacent cells together

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17
Q

What are desmosomes?

A

Resists mechanical stress

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18
Q

What are gap junctions?

A

Allow passage of small molecules between adjacent cells

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19
Q

What are hemidesmosomes?

A

Anchors epithelia to the basement lamina

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20
Q

Why are non-cilia present on nearly all cells?

A

Act as sensory antennae

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21
Q

What are pseudopodia?

A

Cell protrusions which are involved in cell crawling

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22
Q

Outline the 4 main phases of the cell cycle

A

G1 and G2 - allows monitoring of internal and external environment to ensure suitable to progress, as well as checkpoints
S - chromosome duplication
M - mitosis

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23
Q

Describe prophase

A

Chromatin condenses, nucleolus disappears, nuclear envelope breaks down, sister chromatids join at centromere, centrioles move to opposite poles, microtubules form radiating array and chromosomes attach by a kinetochore

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24
Q

Describe metaphase

A

Chromosomes align in mid-line, cohesion holds chromatids together and at this point is broken down except for at centromere

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25
Q

Describe anaphase

A

Securin hydrolysed (inhibitor of separase) –> separase hydrolyses remaining cohesion separating the sister chromatids –> elongation of polar microtubules pulls chromatids to opposite poles

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26
Q

Describe telophase

A

Chromosomes reach opposite poles, chromatin uncoils, nuclear envelope reforms, contractile ring of actin and myosin pinches the cell until it cleaves into two daughter cells

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27
Q

When does random recombination occur?

A

In prophase I between homologous pair of non-sister chromatids due to crossing over of chromatid tails at the chiasmata

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28
Q

What is the role of cyclin-dependent kinases (CDKs) in the cell cycle?

A

Act at different parts of the cell cycle and must be active in order for the cell cycle to progress. Cyclins activate CDKs and cyclin-dependent kinase inhibitors (CKIs) inhibit CDKs and prevent cell cycle progression

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29
Q

Name the three checkpoints in the cell cycle

A

End of G1, End of G2, Spindle checkpoint (metaphase of M)

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30
Q

Describe the checkpoint just prior to the S phase in mitosis

A

If there is an issue in the environment (growth factors, cell size, DNA damage, nutrients), progression is halted by CKI p16 which inhibits CDK4 OR 6 so that it can’t be activated.

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31
Q

Describe the checkpoint at the end of G2 phase in mitosis

A

If there is an issue in the environment (cell size, DNA damage, DNA replication), then phosphatase is inactivated in order to inhibit the cyclin-CDK

If there is no issue then a phosphatase is activated to remove the inhibitory phosphates ont he CDK1-cyclin B complex to allow cell cycle progression

32
Q

Describe the spindle checkpoint in mitosis

A

Occurs during metaphase whereby the tension in the microtubules is ‘sensed’ and if it is normal then this initiates entry into anaphase

33
Q

What may cause retinoblastoma?

A

Mutation in RB1 gene leading to non-functional Rb protein in retinal cells and E2F proteins are therefore free to drive cell cycle (proliferation) with the need for CDK activation –> tumour of the retina

34
Q

Outline 2 anti-mitotic chemotherapy drugs

A

Vinca alkaloids - prevent microtubule formation

Taxanes - prevent microtubule disassembly

35
Q

Outline 2 biologic chemotherapy drugs

A

Antibody-drug conjugate - antibody works to target the drug to tumour cells
Antibody-GFR inhibitors - antibodies bind to growth factor receptors to prevent signalling

36
Q

Describe what happens during apoptosis

A

Membrane blebbing –> membrane shrinkage –> apoptotic body formation –> nuclear collapse (fragmentation and chromatin condensation) –> engulfment by macrophages

37
Q

Which molecules are involved in the initiation and execution of apoptosis?

A

Caspases
Initiation - caspase 2, 8 and 9
Execution - caspase 3, 6 and 7

38
Q

What is involved in necrosis?

A

Membrane disruption, respiratory poison and hypoxia lead to ATP depletion, metabolic collapse, cell swelling and rupture –> inflammation

39
Q

Name the two stages of differentiation

A

Specification and differentiation

40
Q

Describe the two stages of differentiation

A

Specification - when a cell is capable of differentiating autonomously when placed in a neural environment but not when in a non-neutral environment (reversible process)
Diferentiation - cell differentiates autonomously when placed even into another embryonic region

41
Q

Describe autocrine signalling

A

When a ligand binds to receptors on the same cell or group of cells

42
Q

Describe contact-dependent signalling

A

When a membrane-bound signalling molecule binds to a complementary target cell

43
Q

Describe paracrine signalling

A

Where the cell releases signals to the local cells

44
Q

Describe synaptic signalling

A

When there is neurotransmitter release over the synapse to the dendrites

45
Q

Describe endocrine signalling

A

Secretes chemical signal into the blood/lymphatics where it circulates and reaches distant target cells

46
Q

Outline the intracellular pathway triggered by receptor binding

A

Signal + receptor bind –> relay proteins in cell –> adaptor proteins (don’t convey signal, just connect) –> relay proteins –> messenger proteins (convey from one part of cell to another) –> amplifier proteins –> transducer proteins (signal conversion) –> bifurcation proteins spread signals between many pathways –> integrator protein (integrate different signals) –> latent gene regulatory proteins activated near cell surface –> migrate to the nucleus to stimulate gene transcription

47
Q

How does ACh action differ on cardiac and skeletal muscle?

A

Inhibitory effect on cardiac muscle (slows HR), excitatory effect on skeletal muscle (contraction)

48
Q

How can signals elicit different responses in cells?

A

Varies according to receptor proteins, particular signal subset and intracellular machinery

49
Q

How does an enzyme active site bind to the substrate?

A

Has amino acid side chains which align to bind the substrate through hydrogen bonding, salt bridges and hydrophobic interaction

50
Q

Define absolute specificity

A

Enzyme which only catalyses one type of reaction for a single substrate

51
Q

Define group specificity

A

Enzyme which catalyses one type of reaction for similar substrates

52
Q

Define linkage specificity

A

Enzyme which catalyses one type of reaction for a specific type of bond

53
Q

What is a cofactor?

A

Non-protein component of an enzyme required for it’s activity

54
Q

What is a prosthetic group?

A

A non-dissociable co-factor

55
Q

What is an apoenzyme?

A

An enzyme lacking a cofactor, and is therefore inactive

56
Q

What is a holoenzyme?

A

An enzyme with a cofactor, an activated enzyme

57
Q

What is a coenzyme?

A

A dissociable non-protein component which participates in the enzyme reaction and frequently interacts with multiple enzymes

58
Q

What is an isoenzyme?

A

Different forms of an enzyme, which catalyse the same reaction, in different tissues of the body

59
Q

What is a proenzyme/zymogen?

A

When an enzyme is initially synthesised in an inactive form and requires proteolytic conversion to activate

60
Q

How do competitive inhibitors work?

A

Have a structure similar to the substrate and compete for the active site of the enzyme

61
Q

How do non-competitive inhibitors work?

A

Bind to an allosteric site of the enzyme and distorts the shape of the active site to prevent substrate binding

62
Q

Which molecule is involved in adhering a cell to it’s basement membrane?

A

Laminin

63
Q

Describe the structure of collagen

A

Every 3rd amino acid is glycine which allows it to have a tight, coiled structure

64
Q

Why are fatty acids important in the body?

A

Energy store, precursors of phospholipids (cell membrane), needed as we can’t make omega 3 or 6 fatty acids,

65
Q

Why is cholesterol important in the body?

A

It’s a precursor of vitamin D and bile acids

66
Q

Describe how statins and phytosterols work

A

Statins - target cholesterol synthesis to prevent amount

Phytosterols - reduce cholesterol uptake from the diet

67
Q

What is a secondary active transporter?

A

Where uphill solute transport is possible if coupled to the downhill movement of another solute/ion

68
Q

What is a primary active transporter?

A

Uphill solute transport possible if coupled to ATP hydrolysis

69
Q

Define symport and antiport

A

Symport - when the transport molecule and ion move in the same direction
Antiport - when the transport molecule and ion move in different directions

70
Q

What is CFTR and what’s it’s function?

A

Chloride ion channel on the plasma membranes of the lung, intestine and pancreatic epithelia which is required to release chloride in order to allow outflow of sodium and water to reduce the viscosity of surface mucus

71
Q

What is the consequence of a CFTR mutation?

A

Viscous mucus reduces function of epithelial cells, causes chronic infection, inflammation and fibrosis

72
Q

What is a chiral carbon?

A

A carbon atom that covalently bonds to 4 different groups

73
Q

What are the different types of enantiomer?

A

D-form (most common) - when the -OH group is attached to the right of the chiral carbon
L-form - when the -OH group is attached to the left of the chiral carbon

74
Q

What is an amino sugar?

A

A sugar which has an amine (NH2) group in place of -OH in a sugar molecule

75
Q

Describe the structure of glycogen

A

Glucose monomers with alpha-1,4 glycosidic bonds and alpha-1,6 glycosidic bonds for branches

76
Q

What is heparin?

A

Molecule that activates antithrombin III (the main inhibitor of thrombin and factor Xa) allosterically to thin the blood (an anticoagulant)

77
Q

What are bacterial lipopolysaccharides (LPS)?

A

Present on bacteria, and stimulates innate immune cells via TLR4 recognition of the bacterial LPS and causes an inflammatory reaction and a signalling cascade designed to clear infection

FUNMED (8 decks)

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