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BIOSCI 107 (modules 1-3) > CSF (week 3) > Flashcards

CSF (week 3) Flashcards

cell SF, harvesting chemical energy, cell signalling (91 cards)

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1
Q

what is the endomembrane system

A

a network of membrane-bound organelles in a eukaryotic cell that works together to make, package, and ship molecules

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2
Q

what organelles are in the endomembrane system

A

plasma membrane, nuclear envelope, endoplasmic reticulum, lysosomes and vesicles, golgi apparatus

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3
Q

amphipathic meaning

A

contains both hydrophobic and hydrophilic regions

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4
Q

what is the plasma membrane - structure and characteristics

A

a selectively permeable barrier around the cell consisting of a mosaic of molecules in a phospholipid bilayer. it is dynamic and cell-specific.

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5
Q

6 functions of PM proteins

A
  • transport
  • enzymatic activity
  • cell signalling
  • intercellular recognition (e.g glycoprotein molecular signals)
  • intercellular joining/linkers (e.g cadherins)
  • connection to cytoskeleton or extracellular components
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6
Q

describe structure of the nucleus

A
  • has a double membrane (nuclear envelope) to protect DNA
  • nucleolus within the nucleus produces rRNA and ribosome sub-units
  • has nuclear pores for entry/exit (provide molecular segregation)
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7
Q

explain the levels of organisation of DNA

A
  • double helix structure
  • is wrapped around histones
  • to form nucleosomes (8 histones in a nucleosome).
  • chains of histones/nucleosomes form chromatin,
  • which can further condense into chromatin fibres,
  • which condense into chromosomes.
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8
Q

what types of membrane proteins aren’t embedded in the membrane

A

peripheral membrane proteins - associated, but not embedded

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9
Q

what are ribosomes made up of and where

A

ribosomes consist of small and large subunits made of rRNA and proteins. the subunits and rRNA are made in the nucleolus, and assembled in the cytoplasm.

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10
Q

what are the two sites of translation/ribosomes, where do they end up, and why is this segregation important?

A

proteins can be synthesised by ribosomes on the RER into the RER lumen, or in the cytosol by ribosomes floating free in the cytosol.

RER proteins are either used in the membrane, organelles, or are secreted, while ribosomes in the cytoplasm produce proteins which function in the cytosol.

separation allows for more efficient protein production, as proteins can be made right where they are intended to function.

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11
Q

how do proteins leave the RER after translation

A

the RER membrane surrounds it and forms a transport vesicle which travels to the golgi

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12
Q

when might DNA occupy various forms/structures

A

during interphase DNA usually exists as chromatin, except it must be unwound during replication and transcription.
DNA condenses to chromosomes during cell division.

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13
Q

functions of the smooth ER

A

SER functions are very **cell-specific.
**-storage for cell-specific molecules, proteins, enzymes (e.g detoxifying enzymes in the liver or calcium in muscle cells)
-synthesis of lipids (e.g phospholipids, steroids)

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14
Q

describe the structure and function of the golgi

A

consists of sacs called cisternae, usually 3-20 per golgi. looks like a stack of pita breads.

makes things to be used in the membrane, in lysosomes, or secreted.

proteins are recieved from the RER at the cis side and travel through the cisternae to the trans side, receiving modification at each step. they mature at the exit cisternae to travel via vesicles to their destination.

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15
Q

describe structure and function of lysosomes

A

lysosomes are endomembrane system vesicles formed from the golgi apparatus/RER, containing powerful digestive enzymes and a very low pH.

they digest old organelles and substances from outside the cell like pathogens. once a lysosome digests material, nutrient waste is released to be reused (e.g amino acids and lipids), and then the lysosome (containing the waste) leaves the cell via exocytosis.

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16
Q

how do lysosomes maintain a low internal pH

A

proton pumps pump in H+ ions

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17
Q

what is it called when a lysosome digests its own cell’s organelles

A

autophagy

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18
Q

describe microfilaments structure, function, and features

A

7nm thick, made of actin molecules in two long, twisting chains. found around the periphery of the cell. dynamic.
- bear tension and weight
- aid ameboid motility
- core component of microvili

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19
Q

what is meant by dynamic in terms of cytoskeleton components

A

able to assemble and disassemble as needed

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20
Q

what is ameboid motility

A

cell movement by rearrangement of the cytoskeleton

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21
Q

describe intermediate filaments structure, function, and features

A

8-12nm. can consist of various substances, e,g keratin or vimentin. found in the cytoplasm, rather than cell periphery. more permanent, less dynamic.
- contribute to cell structure and organelle placement, like scaffolding.

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22
Q

function of cytoskeleton (common to all types of filaments)

A

assist cell size, shape, and integrity.

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23
Q

describe the structure of an ATP molecule

A

adenosine associated with three phosphates

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24
Q

describe microtubules structure and functions

A

25nm outer diameter. consist of tubulin, of alpha and beta subtypes. 15nm inner diameter of tubular structure, with lumen inside. dynamic.
- support movement of cell structures like cilia/flagellum
- are a ‘road’ for movement of organelles, vesicles, and proteins.
- form the mitotic spindle for chromosome separation during cell division

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25
3 main types of fuel for the body, and what they break down into
carbs; simple sugars proteins; amino acids fats; simple fats
26
describe glycolysis - what happens, location, conditions.
first step of respiration; lysis of glucose. occurs in the cytoplasm in absence of oxygen.
27
glycolysis products and reactants
P: glucose R: 2 pyruvate, 2 H2O, 2 ATP, 2 NADH
28
describe the significance of the 3rd step of glycolysis
it commits glucose to glycolysis. phosphofructokinase enzyme catalyses the irreversible phosphorylation of fructose-6-phosphate -> fructose-1,6-biphosphate.
29
what is phosphofructokinase, what is it stimulated and inhibited by.
enzyme which is the gatekeeper of glycolysis. catalyses the third step, which is the irreversible phosphorylation of fructose-6-phosphate to fructose-1,6-biphosphate. stimulated by AMP, inhibited by ATP and citrate.
30
why does AMP stimulate phosphofructokinase
because it is a product of ATP breakdown, therefore signlas that ATP is being used/depleted
31
why do citrate and ATP inhibit glycolysis?
because citrate is a product of the CAC, implying that it is running smoothly. ATP presence means that energy levels are already high/available.
32
describe pyruvate oxidation - what is it, location, conditions.
pyruvate enters the cell through a transport protein to be converted to acetyl CoA by losing a carbon and binding to coenzyme A, allowing it to enter the CAC. this occurs in the matrix, and requires oxygen.
33
reactants and products of pyruvate oxidation
R: 2 pyruvate P: 2 CO2, 2 NADH, 2 acetyl CoA
34
describe the CAC
a series of steps and intermediates, producing mainly electron carriers for oxidative phosphorylation. occurs in the mitochondrial matrix and requires oxygen.
35
reactants and products of CAC
R: acetyl CoA (2) P: 2 ATP, 2 FADH2, 4 CO2, 6 NADH
36
why does the CAC require oxygen
because it requires acetyl CoA, which must be OXIDISED from pyruvate
37
what state are electron carriers in when they reach the ETC
reduced
38
what is an 'acetyl' molecule
a 2 carbon molecule resulting from the loss of a carbon from pyruvate
39
what happens to NADH produced during glycolysis during aerobic and anaerobic conditions
oxygen present: sends its electrons via electron shuttles to the matrix, to be used in the ETC oxygen absent: it is oxidised back to NAD+ to be reused in further glycolysis so ATP can be produced quickly without oxygen
40
define substrate phosphorylation
ATP production via transfer of a phosphate group from a substrate directly to ADP, facilitated by an enzyme
41
where/when does substrate phosphorylation occur?
whenever ATP is produced in respiration prior to oxidative phosphorylation; - during glycolysis in the cytoplasm - CAC in the matrix
42
reactants (what is needed) and products of oxidative phosphorylation
needed: reduced electron carriers, oxygen, H+, ADP + P products: 26-28 ATP
43
describe the ETC in detail
NADH and FADH2 oxidise as they donate electrons, which are transferred through a series of protein complexes in the inner membrane (pulled by oxygen), producing a bit of energy at each complex to simultaneously pump H+ outside of the matrix to form an electrochemical gradient. (except complex II - isn't a protein pump) NADH transfers electrons at complex I, and FADH2 at complex II. Coenzyme Q transfers these directly to complex III, to cytochrome C, which transfers them to complex IV, which transfers them to oxygen, the final electron acceptor, which forms H2O.
44
what is cytochrome C
a small, mobile carrier protein transferring electrons between CIII and CIV
45
what complex in the ETC doesn't pump H+ ions
complex II
46
explain chemiosmosis
H+ ions rush down the concentration gradient through the enzyme ATP synthase, which acts a turbine which the movement of H+ powers.
47
where are insulin and glucagon secreted
the pancreatic islets/islets of langerhaans. - insulin; beta cells - glucagon; alpha cells
48
which complex in the inner mitochondrial membrane is NOT transmembrane
complex II - it is peripheral
49
what is the significance of 7mmol/L
it is the fasting blood sugar level that signals diabetes
50
what happens if we have no functional insulin?
we can't take glucose into our cells, therefore blood accumulates too much glucose, which cannot be used for energy or storage
51
what type of diabetic is insulin dependent
a type 1 diabetic, as they produce no insulin, therefore must get replacement insulin.
52
which type of diabetic is more likely to have developed diabetes in youth
type 1
53
what is the cause of type 1 diabetes, and typical triggers of this
the autoimmune attack on the pancreatic beta-cells causes type 1 diabetes as no insulin can be produced. often triggered by genetics, other autoimmune conditions, or environmental factors.
54
how is ATP actually used as energy
it is hydrolysed to ADP, releasing energy
55
in respiration, glucose is reduced/oxidised?
oxidised
56
what are cristae
folds in the inner membrane of the mitochondria
57
what are the effectors and results of glucagon
liver, skeletal muscle, adipose tissue increased rate of glycogen breakdown to glucose
58
at what point does glucose exhaust its potential for energy to be made directly from it
the citric acid cycle, as all carbons have been broken down
59
what critically inhibits the electron transport chain in its final stages?
cyanide; inhibits complex IV, stopping transfer of electrons to oxygen, thus ceasing ATP production
60
what are the effectors and results of insulin
all body cells increases rates of: glucose uptake into target cells, rate of ATP generation, glucose conversion to glycogen
61
explain the structure of a G-protein couples receptor (GPCR)
transmembrane protein that passes through the membrane 7 times, each of the 7 domains is an alpha helix. extracellular regions are hydrophilic, and embedded part is lipophilic.
62
what are G-proteins
proteins embedded in the cytoplasmic side of the membrane that act as molecular switches, becoming either active or inactive depending on whether GTP or GDP is bound to them (GDP=inactive)
63
explain how GPCRs work
a ligand binds to GPCR, causing a conformational change and activating it. it then binds to a G-protein, whose GDP will be replaced with the higher-energy GTP which activates it and allows it to activate enzymes to carry out the cellular response, like adenylyl cyclase and phospholipase C.
64
what is GTPase activity
the ability to hydrolyses GTP back to GDP + P, reverting the G protein back to resting inactive state.
65
what bodily system relies heavily on ligand-gated ion channels
nervous system
66
explain ligand-gated ion channel's structure and function
transmembrane proteins with ligand-binding sites on the extracellular side. specific ligands bind, causing a conformational change resulting in the channel opening, allowing CERTAIN ions to enter down the concentration gradient. ligand dissociates and gate closes.
67
example of a neurotransmitter in synaptic signalling
acetylcholine which acts on muscle cells
68
example of paracrine signalling
FPF1, a protein growth factor which acts on neighboujring cells and helps with wound repair
69
4 main types of signalling
autocrine, paracrine, endocrine, synaptic
70
what is a protein 'kinase'
a kinase phosphorylates (adds a phosphate from ATP) a molecule; a protein kinase phosphorylates a protein.
71
what dephosphorylates a protein
phosphatase enzymes
72
where would the receptor for a lipid-soluble messenger be found
not in the membrane. in cytoplasm, or nucleus, as lipid-soluble things can just diffuse through the membrane
73
the GPCR/cAMP pathway is disrupted by:
cholera toxin
74
examples of lipid-soluble messengers
lipid-soluble hormones like oestrogen and testosterone, thyroid hormones, some gasses.
75
what are parts of a protein that are typically phosphorylated in a phosphorylation cascade
serine and threonine residues
76
finish sentence: activation usually _____ the start of _________
prompts, deactivation.
77
common second messengers in this course
Ca2+, cAMP, IP3
78
what type of messengers are received by membrane-bound receptors
water-soluble ligands (can't diffuse through membrane)
79
how is cAMP activated
adenylyl cyclase is activated by G-protein, converting ATP to cyclic AMP- cAMP.
80
what does adrenaline do in the skeletal muscle of a fleeing impala
acts as the ligand for a GPCR which triggers an amplifying response, ultimately leading to the activation of many glycogen phosphorylase enzymes. glycogen phosphorylase triggers the breakdown of glycogen into glucose-1-phosphate, which is converted to glucose-6-phosphate to enter glycolysis for energy to fuel muscle contraction.
81
what enzyme is associated with IP3
phospholipase C
82
what does cAMP/other second messengers do
activate downstream proteins
83
what is a PP/phosphatase
enzymes that dephosphorylate proteins, removing a phosphate and rendering the protein inactive but reusable.
84
what does phospholipase C, and its products, do
cleaves PIP2 phospholipid (in the membrane) into DAG - a lipid and IP3 - a triphosphate. these are both second messengers. DAG stays in membrane as it is a hydrophobic lipid, and IP3 diffuses across the cytosol for further signalling.
85
what does IP3 signal
diffuses through the cytoplasm to act as a ligand for an IP3-gated-calcium channel in the smooth endoplasmic reticulum, opening it and allowing Ca+ to flow OUT OF the SER down the conc. gradient.
86
where is Ca2+ found in high concentration, how is this maintained.
outside the cell, in mitochondrial matrix, and lumen of endoplasmic reticulum. maintained by calcium pumps.
87
why is it important that there are many steps in the cell signalling process
1. intermediates allow for coordination with other pathways 2. providing multiple control points 3. which can amplify the response significantly 3. and can allows for temporal and spatial specificity of responses despite shared messengers
88
what breaks down cAMP, and what breaks down this molecules?
phosphodiesterase enzyme breaks down cAMP and cGMP. caffeine blocks cAMP, and viagra blocks cGMP.
89
why are endocrine glands highly vascular
as they rely on the ability to release hormones effectively into the bloodstream
90
what organs are important in the deactivation of hormones
liver - deactivates hormones kidneys - excretes hormones
91
what is an IP3-gated-calcium channel important for?
muscle contraction as calcium is crucial

BIOSCI 107 (modules 1-3) (10 decks)

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