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Physiology > Principles Of Cellular Function > Flashcards

Principles Of Cellular Function Flashcards

1
Q

How is water distributed through the body compartments? How do age and gender affect total body water?

A
  1. Total body water (TBW) is 60% body weight
    - 2/3 (40%) ICF
    - 1/3 (20%) ECF -> 1/4 Plasma, 3/4 Interstitial
  2. Age
    - Body water decreases with age
  3. Gender
    - Body water higher in males
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2
Q

What are the buffer systems in the BLOOD?

A
  1. Carbonic acid/Bicarbonate system
    - Main buffer
  2. Plasma proteins
    - Free carboxyl and amino groups
  3. Haemoglobin
    - Imidazole groups of histidine residues
    - Deoxygenated Hb better than oxygenated Hb
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3
Q

Explain the carbonic acid/bicarbonate system

A
  1. H2CO3 H + HCO3
    - Reaction sped up in the presence of carbonic anhydrase found intracellularly
    - Increase acid/H in blood will shift the equilibrium to the left -> Forms more carbonic acid
    - Increase OH in blood will shift the equilibrium to the right -> To replace H used up with OH to form H20
  2. Buffering system linked to
    - Renal system -> Removes HCO3
    - Respiratory system -> Removes CO2
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4
Q

What are the major buffers in CELLS and how do they work?

A
  1. Hprotein H + Protein

2. H2PO4 H + HPO4

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5
Q

Describe the Henderson-Hasselbach equation

A

pH = pKa + log [A-]/[HA]

- Most effective when [A-]/[HA] = 1, so pH = pKa

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6
Q

Outline the different ways in which a substance can cross a cell membrane.

A
  1. Passive
    - Diffusion
    - Facilitated diffusion
  2. Active
    - Endocytosis -> Phagocytosis by leukocytes
    - Exocytosis -> Golgi apparatus to extracellular
    - Ion channels
    - Active transport via transport protein
    > Primary active transport - Na/K ATPase pump
    > Secondary active transport - Na/glucose transporter
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7
Q

Can you please explain the process of secondary active transport?

A
  • The movement of an ion down its electrochemical gradient provides energy to another substrate/ion to move against its electrochemical gradient
  • Eg. Na/glucose transporters, Na/amino acids transporters
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8
Q

Describe the Na/K pump

A
  • Energy-dependant pump requiring ATP to ADP as energy source
  • Transports 3Na out of cell + 2K into cell against its electrochemical gradient for each ATP molecule
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9
Q

Describe the synthesis and metabolism of cAMP. Discuss the function of cAMP.

A
  1. Cyclic adenosine monophosphate
    - Intracellular secondary messenger
    - Formed from ATP by adenyl cyclase into cAMP
    - Metabolised by Phosphodiesterase
  2. Functions
    - Intracellular secondary messenger
    - Stimulates protein synthesis
    - Activates cAMP-related element-binding protein (CREB) to alter transcription of genes
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10
Q

What are the major factors determining plasma glucose level? List the hormones which affect plasma glucose levels.

A
  1. Overall determined by intake/glucose entering blood stream vs output/glucose leaving blood stream
    - Dietary carbohydrate intake
    - Cells uptake of glucose
    - Liver glycogenolysis, gluconeogenesis, glycogenesis
    - Renal filtration and reabsorption of glucose
    - Hormonal effects -> insulin, glucagon, cortisol, thyroid hormone
  2. Hormones affecting glucose level
    - Reduce BSL -> Insulin, Insulin-like growth factor 1 and 2
    - Increase BSL -> Glucagon, Cortisol, Catecholamines
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11
Q

What are the potential pathways for glucose metabolism in the body.

A
  • Aerobic
  • Anaerobic
  • Glycogen
  • Pentoses
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12
Q

What are the types of immunoglobulin and clinical significance of each

A
  1. Immunoglobulin A
    - Found in mucous membranes
    - Important in mucous secretions
  2. Immunoglobulin D
    - Antigen recognition by B cells
  3. Immunoglobulin E
    - Anaphylaxis
    - Histamine release by mast cells and basophils
  4. Immunoglobulin G
    - Infection causing complement activation
    - Crosses the placenta and breast milk
  5. Immunoglobulin M
    - Infection causing complement activation
    - First to be produced
    - Largest immunoglobulin
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13
Q

Draw a typical immunoglobulin molecule and label the parts

A
  • Fab = Antigen-binding portion
  • Antigen-binding site
  • Fc = Effector portion
  • Hinge
  • Variable region
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14
Q

What are the features of innate vs acquired immunity?

A
  1. Innate immunity
    - Defence mechanism present even before infection
    - E.g: Phagocytes, NK cells, complements
    - Important in early phases of infection
    - Triggered by cellular receptors -> Toll-like receptors
  2. Acquired immunity
    - Defence mechanism against infection
    - Cellular mediated -> T cells -> Recognizes antigen on antigen-presenting cells (APC), major histocompatibility complex (MHC), human leukocyte antigen (HLA) -> Protects against intracellular microbes
    - Humoral mediated -> B cells -> Protects against extracellular microbes -> Releasing antibodies
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15
Q

How do cells communicate with one another?

A
  1. Cell-to-cell
    - Gap junctions
  2. Chemical mediators in the ECF
    - Neural -> Neurotransmitters in synapses
    - Autocrine -> Cell produces messenger that acts on itself
    - Paracrine -> Cell produces messenger that acts on neighbouring cells
    - Endocrine -> Hormone and growth factor secreted from another site and circulating in blood or lymph
    - Juxtacrine -> Molecules attached to receptor of membrane that attaches to another cell
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16
Q

How do receptors respond to variations in messenger?

A
  1. Upregulation of receptors
    - Deficient messenger causes increase in receptors
  2. Downregulation of receptors
    - Excess messenger causes decrease in receptors
17
Q

How do messengers act? What are the actions of second messengers?

A
  1. Open or close ion channels
  2. Produce cAMP
  3. Produce cGMP
  4. Increase activity of tyrosine kinase
  5. Activates phospholipase-C to produce intracellular IP3, DAG
  6. Increase serine, threonine
18
Q

Name the principal ketone bodies. How are ketone bodies produced and metabolised? In which clinical situation do they accumulate in the body?

A
  1. Principal ketone bodies are
    - Acetoacetate
    - Acetone
    - B-hydroxybutyrate
  2. Metabolism of ketone bodies
    - Produced in mitochondria of liver and all tissues
    - Substrate -> Fatty acids, AcetylCoA
    - Fatty acids undergo B-oxidation to form AcetylCoA -> Enters citric acid cycle -> Yields 11 ATP, 1 GTP
  3. Ketones accumulate in ketosis metabolic acidosis during
    - Starving/fasting
    - Diabetes (T1DM)
    - High fat low carbohydrate diet
19
Q

Describe the structure, mechanism of action and function of the Na/K pump

A
  1. Structure
    - Antiport
    - 2a + 2b subunits
    - a-subunit binds Na + ATP intracellularly and K extracellularly
    - b-subunit does not have Na or K binding site
  2. Mechanism of action
    - Na binds to a-subunit intracellularly
    - ATP also binds to a-subunit intracellularly
    - ATP converted to ADP
    - Causes change in protein configuration
    - Na expelled out of cell
    - K then binds to a-subunit extracellularly
    - Dephosphorylates a-subunit to return protein to original configuration
    - K released into cell
  3. Function of pump
    - Maintains electrochemical gradient -> Pumping 3 Na out, 2 K in
    - Co-transport of other molecules -> Glucose in small intestine
20
Q

What is normal serum osmolality? What substances contribute to serum osmolality? How does plasma differ in composition intracellularly vs extracellularly?

A
  1. Normal serum osmolality is 290mOsm/L
  2. Substances
    - Mainly ions (270mOsm) -> Na, K, Cl, HCO3
    - Rest (20mOsm) -> Other cations, anions, urea, glucose, protein
  3. Difference in plasma composition
    - Intracellularly -> High K, PO4, proteins
    - Extracellularly -> High Na, Cl
21
Q

What is the difference between diffusion and osmosis? Define tonicity.

A
  1. Diffusion is
    - Movement of solutes through semi-permeable membrane down its concentration gradient
    - Governed by Fick’s Law
  2. Osmosis is
    - Movement of SOLVENT/water molecules through membrane impermeable to solutes
    - Down its concentration gradient to area of high concentration of SOLUTES
  3. Tonicity is osmolality of a solution relative to plasma osmolality
    - Isotonic -> Same osmolality as plasma
    - Hypotonic -> Lower osmolality than plasma
    - Hypertonic -> Higher osmolality than plasma
22
Q

What is the genesis of the membrane potential?

A
  • Due to difference in concentration and electrochemical gradient of Na + K intracellularly and extracellularly
  • Maintained by Na/K pump
  • Pumps 3 Na out and 2 K in
23
Q

What are the phases of protein synthesis? Describe the process of protein secretion from cells.

A
  1. Protein synthesis has 2 phase
    - Transcription of DNA into mRNA in nucleus
    - Translation of mRNA into amino acid chain by ribosome with help of tRNA in cytoplasm
  2. Protein secretion has 2 pathways
    - Amino acid/polypeptide produced are cleaved and secreted out of cell by ATP-dependent membrane transporters
    - Amino acid/polypeptides are transporters into endoplasmic reticulum to be modified, packaged and secreted by exocytosis

Physiology (8 decks)

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