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BIOSCI 107 > L6&7 - Harvesting Chemical Energy/Cell Communication > Flashcards

L6&7 - Harvesting Chemical Energy/Cell Communication Flashcards

1
Q

Categories of fuel

A
  • carbohydrate => broken down to simple sugar
  • proteins => amino acids
  • fats => simple fats
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2
Q

Glycolysis products

A
  • 2 net ATP
  • 2 NADH
  • 2 pyruvate
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3
Q

Phosphofructokinase

A

Inhibited by: citrate, ATP

Stimulated by: AMP

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4
Q

Pyruvate oxidation products

A
  • NO ATP
  • 2 NADH (1 per pyruvate)
  • 2 CO2 (by-product)
  • Acetyl CoA (for citric acid cycle)
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5
Q

Kerbs/citric acid cycle products

A
  • 2 ATP
  • 6 NADH
  • 2 FADH2
  • 4 CO2
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6
Q

Kerbs cycle process

A
  • CoA removed from Acetyl CoA
  • 2 carbon chain attaches to an existing 4 carbon chain
  • Chain partially broken down to produce CO2 (all carbon is used up by the end of the cycle)
  • Electrons captured to reduce NAD+ to NADH
  • ATP produced
  • FAD reduced to FADH2
  • Remaining 4 carbon chain attaches to new carbon from Acetyl CoA
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7
Q

Substrate phosphorylation

A

ATP generated by direct transfer of a phosphate group from a substrate to ADP

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8
Q

Oxidative phosphorylation

A
  • ATP generated from oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons
  • ATP synthase enzyme catalyses but no substrate needed
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9
Q

Electron transport chain products

A
  • 6 H2O

- high conc. Of H+ in intermembrane space

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10
Q

Chemiosis products

A

26 or 28 ATP

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11
Q

Diabetes mellitus

A

Impaired ability to produce or respond (unable to recognise) to hormone insulin (lack of functional insulin)

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12
Q

Result of diabetes (biological)

A

abnormal metabolism of carbohydrates and elevated levels of blood glucose ( ≥ 7 mmol/L fasting)

  • no glucose in cells
  • no ATP from glucose
  • no glycogen stored for harder times
  • altered volume and osmolarity of blood, with subsequent pathological consequences, due to built up blood glucose levels
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13
Q

Diabetes symptoms

A
  • significantly increased hunger

- significant weight loss

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14
Q

Local signalling

A

Signal acts on nearby target cells

  • paracrine (growth factors e.g fibroblast growth factor FGF1)
  • synaptic (via neurotransmitters e.g acetylcholine Ach)
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15
Q

Long distance signalling

A

Signals act from a distance

- hormones

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16
Q

Stages of signalling

A

1) reception
2) transduction
3) response

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17
Q

Types of receptors

A

1) intracellular
2) membrane-bound / cell surface
- G protein couple receptor GPCR
- ligand gated ion channels
- receptor tyrosine kinase

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18
Q

GPCR structure

A
  • Transmembrane proteins pass plasma membrane 7 times

- loops interact with molecules inside/outside cell

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19
Q

GPCR second messengers

A
  • cAMP

- calcium ions and IP3 signalling

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20
Q

Ligand gated ion channels components

A

Receptor, ligand, ion channel, ion channel receptor/ionotropic receptor

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21
Q

Most common signal transduction pathways

A

Phosphorylation cascade

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22
Q

Signal transduction pathways

A

Signals relayed from receptors to target molecules via a cascade of molecular interactions

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23
Q

Components of typical phosphorylation cascade

A

Protein kinase (phosphorylate), phosphatase (dephosphorylate), serine/threonine (residues that are typically phosphorylated)

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24
Q

Time period of signalling

A

Proteins should only be activated as needed so signalling is for a short period of time to ensure homeostatic equilibrium

  • All signals are for a limited time thus activation usually promotes the start of deactivation
  • This means the cell is ready to respond again if required
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25
Q

Cellular responses

A
  • Gene expression (start/stop): final effector is a transcription factor that activates gene expression in response to signalling by growth factor
  • Alter cellular biochemistry occurring in the cell
    • alteration of protein function to gain or lose an activity
    • opening or closing of an ion channel
    • alteration of cellular metabolism
    • regulation of cellular organelles or organisation
    • rearrangement/movement of cytoskeleton
  • blood glucose: final effector may be a muscle enzyme that breaks down glycogen in response to epinephrine (adrenalin) signalling
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26
Q

Need for so many steps

A
  • amplifies the response via multiple reactions (massive amplification)
  • provides multiple control points
  • allows for specificity of response (temporal/spatial control)
  • allows for coordination with other signalling pathways
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27
Q

Deceived receptors

A

Viruses (surface spike glycoprotein (S protein) on coronavirus)

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28
Q

Anabolic reactions

A

Consume energy to build up from simple to complex molecules

- energy from ATP to complex molecule

29
Q

Catabolic reactions

A

Release energy while breaking down complex molecules into simple molecules
- energy from complex molecule to ATP

30
Q

Respiration equation

A

Carb. + oxygen = carbon dioxide + water + energy

31
Q

Glycolysis location

A

Cytoplasm

32
Q

Glycolysis process

A
  • Glucose with 2 ATP splits in half
  • NAD+ picks up H and electrons to make NADH
  • ATP and pyruvic acid produced
33
Q

Pyruvate oxidation location

A

Matrix of mitochondria

34
Q

Pyruvate oxidation process

A
  • CO2 produced from 3 carbon pyruvate to form 2 carbon chain
  • Electrons stripped from 2 carbon chain to reduce NAD+ to NADH and H+
  • Coenzyme A attaches to 2 carbon fragment to produce Acetyl CoA
35
Q

Krebs/citric acid cycle location

A

Matrix of mitochondria

36
Q

Intermediates of Krebs/citric acid cycle

A

Feed into other biochemical pathways

37
Q

Series of reactions

A

Product of one reaction is the substrate for the next

38
Q

ETC + chemiosis location

A

Proteins within inner membrane of mitochondria

39
Q

ETC process

A
  • NADH and FADH2 (from glycolysis and citric acid cycle) are oxidised to donate 1 or 2 electrons to a series of electron carriers in the transport chain
  • Electrons transfer from protein to protein along the chain in a series of redox reactions
    • at each transfer, each electrons gives up a small amount of energy
    • this energy is used to pump H+ into the intermembrane space which establishes a proton gradient (storing energy as a proton-motive force)
  • Oxygen “pulls” the electrons down the chain and is the final electron acceptor where it is reduced to water
40
Q

Proteins in ETC

A
  • 1,3,4 are transmembrane proteins

- 2 is a peripheral protein

41
Q

Chemiosis process

A
  • H+ in intermembrane space rush down concentration gradient through ATP synthase
  • Turbine within ATP synthase is turned as a result
  • Rotation of ATP synthase turbine enables phosphorylation of ADP to ATP
42
Q

Homeostasis

A

Maintenance of relatively constant conditions within physiologically tolerable limits

43
Q

Type 1 diabetes

A
  • No insulin production due to destroyed beta cells often caused by autoimmune, genetic or environmental factors
  • Affects 5-10% of diabetics (less common) and onset usually occurs in children/adolescents
  • Requires insulin replacement
44
Q

Type 2 diabetes

A
  • Non-functional receptors (insulin resistance) despite insulin production
  • Most (>90%) diabetics and are usually adults over age of 40
  • Can be linked to other pathologies and obesity (but unsure how/why)
45
Q

Importance of cell communication

A

need to be able to respond as an individual cell, and as part of a whole tissue

46
Q

Signals

A

inside the body are often small molecules or chemical (but it can also be light - receptors in eyes, taste/smell - also chemical)
- these are what cells respond to

47
Q

Ways of communication

A
  • direct contact (via cell junctions - gap junctions or cell-cell recognition: diffusion of signalling molecules through cell-cell channels)
  • secretion of signalling molecules (ligand) which are recognised by specific receptors in the plasma membrane of target cells
48
Q

Cyanide in chemiosis

A

Blocks passage of electrons to O2 thus results in cell death

49
Q

Specificity of receptors

A

Only target receptor on target cell interacts with ligands (shape determined function)
- allows exquisite control

50
Q

Intracellular receptors

A
  • primary messenger generally hydrophobic and small (can enter cell)
  • least common method of signalling
51
Q

Membrane-bound/cell surface receptors

A
  • primary messenger generally hydrophilic and/or large

- most common method of signalling

52
Q

GPCR function

A

Diverse: development, sensory reception (vision, taste, smell) etc.

53
Q

Adenylyl/adenylate cyclase

A

Enzyme that converts ATP to cAMP which activates downstream protein
- pathway disrupted by cholera toxin
(can also be activated by things other than G proteins e.g Ca2+)

54
Q

Phosphodiesterase

A

Breaks down cAMP (action blocked by caffeine)

55
Q

Phospholipase C

A

Cleaves PIP2 into DAG and IP3 (both act as second messengers)

56
Q

IP3

A

Second messenger that diffuses through cytosol and binds to gated channel in ER

57
Q

Ca2+ action

A

Flows out of ER down concentration gradient and activate other proteins towards cellular response

58
Q

Ligand gated channel example

A

Neurotransmission in nervous system

  • released neurotransmitters bind as ligands which cause the ligand-gated ion channels to open in the postsynaptic membrane resulting in an influx of sodium ions and localised depolarisation
  • electrical signal (action potentials) are propagated/transmitted to the next neuron in this way
59
Q

Protein kinases

A
  • Enzymes that phosphorylate (transfer a phosphate group from ATP to another specific protein)
  • Typically this activates the protein
  • A series of protein kinases in a row (with different names) each add a phosphate to the next kinase
60
Q

Phosphatase

A
  • Enzymes that dephosphorylate (remove the phosphate group from activated proteins)
  • This renders the protein inactive, but recyclable/available for reuse
    (While ligand is bound, the protein kinases can still be reactivated)
61
Q

Serine / threonine

A

Amino acids/the residues that are typically phosphorylated
- DNA level mutations affecting these residues (causing them to become something else) will thus affect their
ability to be phosphorylated which could be detrimental

62
Q

second messengers

A

small molecule that is not a protein and is involved at the beginning of the cascade

63
Q

Normal blood glucose level

A

70-110 mg/dL (5 mmol/L)

64
Q

Advantage of cell amplification

A

Individual signalling reaction (one ligand) can produce a large no. Products

65
Q

GPCR signalling process

A

1) At rest:
- receptor unbound, G protein bound to GDP, enzyme inactive
2) Ligand binds:
- conformational change in receptor
3) G protein binds to receptor:
- GTP displaces GDP, G protein activated (while ligand bound), enzyme inactive
4) Activated G protein dissociates from receptor
- G protein binds to enzyme, enzyme activated

66
Q

G protein inactivation

A

GTPase activity in G protein (hydrolysis of GTP to GDP and P) promoting G protein to release from enzyme and revert back to resting state

67
Q

Ca2+ background info

A

high conc. outside cell, lumen of ER and matrix of mitochondria

  • maintenance of conc. via calcium pumps needed as Ca2+ toxic to cells
  • also means cell response strongly to Ca2+ = powerful signalling
68
Q

Ligand gated ion channel/receptor process

A

ligand binds - elicit shape change - gate opens - specific ions flow into cell - ligand dissociates - gate closes - back to resting

BIOSCI 107 (15 decks)

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