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Medicine - Year 1 > Pharmacology, therapeutics and patient safety - Biochemistry > Flashcards

Pharmacology, therapeutics and patient safety - Biochemistry Flashcards

1
Q

Describe the function of lipids

A
  • Key components of cell membranes
  • They are the major form of energy storae
  • They play important roles in cell signalling
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2
Q

What are the 5 classes of lipids?

A
  1. Fatty acids
  2. Triacyglycerols (fats and oils)
  3. Glycerolphospholipids (membranes)
  4. Sphingolipids (membrane lipids)
  5. Cholesterol
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3
Q

Describe the structure of fatty acids

A
  • Fatty acids are hydrocarbon chains, with a carboxy group at one end (α-carbon) and a methyl group (CH3) at the other (the ω-carbon)
  • Ubranched
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4
Q

What are saturated and unsaturated fatty acids. Provide an example for each

A

Saturated - single bonds only between carbon atoms e.g., lauric, palmitic acid, stearic acid and arachidic acid

Unsaturated - contains one or more double bonds between the carbon atoms e.g., linoleic acid and arachidonic acid

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5
Q
A
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6
Q

Draw out the general structure of a fatty acid

A
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7
Q

Describe the relationship between saturated fatty acids and melting points

A

Melting point increases with the length of the chain

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8
Q

Compare the relationship between melting points of saturated and unsaturated fatty acids

A

Unsaturated fatty acids have lower melting points that saturated fatty acids of the same length

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9
Q

Describe the relationship between the melting point and the number of double bonds

A

The melting point decreases with the number of double bonds

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10
Q

What are 2 main essential fatty acids?

A
  • Omega-3
  • Omega-6
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11
Q

a) Describe the 3 main omega-3 fatty acids and how they can be synthesised
b) Name sources of omega-3 fatty acids

A

a)

  1. Alpha-linoleic acid (vitamin F) - human body cannot synthesise this fatty acid so it is supplied in diet
  2. Icosapentaenoic acid (EPA) and 3. docosahexaenoic acid (DHA) are not regarded as essential fatty acids and can be synthesised from alpha-linolenic acid

b) Omega-3 fatty acids are present in fish, shellfish, vegetable oil (e.g., olive and sunflower) and few vegetables

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12
Q

a) Describe the two Omega-6 acids and where they can be synthesised from
b) Name sources of omega-6

A

a)

  1. Linoelic acid (vitamin F) - supplied from diet
  2. Arachidonic acid not regarded as fatty aids and be synthesised from linoleic acid

b)

Omega-6 fatty acids are present in vegetable oilds seeds, soybean oil, canola oil and fish oil (particularly salmon and sardines)

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13
Q

What are fatty acid precursors of?

A

Fatty acids are precursors for prostaglandins, thromboxanes and leukotrienes (infammatory mediators)

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14
Q

a) What are triacylglycerols?
b) Describe their structure
c) What are the sources of triacylglycerols

A

a) Triacyglycerols are esters of glycerol and fatty acid. They are storage form of lipids
b) Composed of short-chain fatty acids/unsaturated fatty acids
c) Found in vegetable oils and animal fats

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15
Q

Describe the state of triacyglycerols at room temperature

A
  • Triacylglycerols are liquid at room temperature
  • Triacylglycerols that contain more saturated fats and longer fatty acids chains are solid at room temperature e.g., butter
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16
Q

Describe the transport and storage of triacylglycerols

A
  1. Triacylglycerols are transported by lipoproteins and stored in adipocytes
  2. Triacylglycerols from the liver are transported by very low density lipoproteins (VLDL) to adipocytes (fat cells)
  3. Triacylglycerols cannot be absorbed whole into adipocytes, as they are too big so they are broken down into glycerol and fatty acids by lipoprotein-lipase
  4. Fatty acids are taken up by adipocytes and form acyl-CoA
  5. Glucose enters the cell and is metabolised into glycerol-3-P, this joins to acyl-CoA to form on molecule of triacylglycerol
  6. When energy is needed triacylglycerol can be broken down by hrmone-sensitve lipase into glycerol and fatty acids. The fatty acids then travel in the blood as fatty acid-albumin complex
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17
Q

a) What are glycerophospholipids formed from?
b) Describe the structure of glycerophospholipids
c) What are they the main component of?

A

a) Formed from phosphatidic acid

b)

  • Composed of 2 fatty acids chains, glycerol, phosphate and alcohol
  • Fatty acid chains = hydrophobic
  • Phosphate and alcohol (head) = hydrophilic

b) Cell membrane

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18
Q

Describe the cleavage and resorption of glycerophospholipids

A
  • Glycerophospholipids are emulsified with bile and then are cleaved by phospholipases of the pancrease
  • Glycerophospholipids are broken down into glycerol, fatty acid and phosphate and their alcohols
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19
Q

a) Name the 3 main types of sphingolipids
b) Describe the function of sphingolipids

A

a)

  1. Sphingomyelin
  2. Glycosphingolipid - cerebroside and ganglioside
  3. Ceramide

b)

  • Components of cell membranes
  • Contribute to the structure of blood group substances
  • Phosphorylated sphingosine is a signalling molecule.
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20
Q

a) What type of lipid is sphingomylein?
b) Describe its structure

A

a) Sphingolipid
b) Fatty acid (hydrophobic) linked to sphingosome which is linked to phosphate and choline (polar head group)

21
Q

a) What type of lipid is glycosphingolipid?
b) Describe its structure

A

a) Sphingolipid
b) Fatty acid (hydrophobic) linked to sphingosome which is linked to sugar (polar head group)

22
Q

a) What type of lipid is ceramide?
b) Describe its structure

A

a) Sphingolipid
b) Molecule containing sphingosine linked to a fatty acid (hydroxyl group is not esterified)

23
Q

a) What type of lipid is cerebroside?
b) Describe its structure
c) Provide 2 common examples

A

a) Glycosphingolipid which is a sphingolipid
b) Ceramide joined with a single sugar (hydroxyl group esterified to sugar) - (glycosphingolipid)
c) Glucose cerebroside and galactose cerebroside

24
Q

a) What type of lipid is ganglioside?
b) Describe its structure

A

a) Glycosphingolipid which is a sphingolipid
b) Glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids linked on the sugar chain (hydroxyl group is esterified to sialic acid)

25
Q

Certain sphingolipds are abundant in cell membranes of nerve tissue ane the brain. Name the sphingolipids

A
  • Sphingomyelin
  • Cerebrosides
  • Gangliosides
26
Q

Defects in the degradation of cerebrosides and gangliosides result in several rare clinical disorders known as lysomal storage disease. Provide an example of a lysomal storage disease

A

Tay-Sachs disease

27
Q

a) Describe the structure of cholesterol
b) Describe its properties
c) Describe the sources of intakes of cholesterol and the daily intake

A

a) Consists of 4-ring system which is the the steroid ring system

b)

  • Weakly amphiphilc
  • Whole molecule is hydrophobic excep polar OH group

c) Ditary intake e.g., egg, steak: 300mg/day

Endogenous sysnthesis: 1000 mg/day

28
Q

Describe the role of cholesterol in membranes

A

Decreases the fluiduity of membranes

29
Q

Where do cholesterol synthesis take place?

A

All cells- liver and intestine major sites

30
Q

Cholesterol is an important precursor for a range of biologically important molecules. Provide 4 examples of this

A
  1. Bile acids e.g., glycocholate
  2. Mineralocorticoids - increase resporption of sodium, chloride and bicarbonate in the kidneys
  3. Vitamin D
  4. Steroid hormones: androgens (e.g., testosterone), prosteogens (e.g.,progesterone), oestrogens (e.g., estrone)
31
Q

Describe the role of fatty acid in lipid metabolism

A
  • Triacylglycerols (fat) and glycerophospholipids are broken down to glycerol and phospholipids
  • Glycerol is broken down into glucose in gluconeogenesos
  • Fatty acid broken down into acetyl-CoA (building blocks of cholesterol) in the process of beta oxidation
  • Sphingolipids are broken into ceramides and ceramides can be broken down into fatty acids
32
Q

Describe what a hormone is

A
  • A hormone is a chemical messenger which is a substance that controls and regulates biological functions
  • Hormones act by binding to a specific receptor, either on the cell surface or within the target cells
33
Q

Describe the 3 methods of hormone transport and provide examples

A

Autocrine

  • Local cell-cell diffusion
  • Act on neighbouring cells of the same type
  • E.g., prostglandins released by msucle cell and various tissue

Paracrine

  • Local cell-tissue diffusion
  • Act on differenct cells in the same tissue
  • E.g., histamine released by cells in various tissue

Endocrine

  • Distributed by blood
  • Act on distant targer cells
  • E.g., insulin, growth hormone
34
Q

Name the 5 types of hormones

A
  • Peptide hromones
  • Amino-acid derived hromones
  • Steroid and sterol hormones
  • Lipid hormones
  • Gaseous hormones
35
Q

Describe peptide hormones and provide examples

A
  • Encoded by genes
  • Usually synthesised as pre-propeptides by ribosomes
  • Pre-propeptides hormone is transformed into the biologically active peptide hormone by proteolytic processing
  • E.g., insuling, glucagon, growth hormone (GH), insulin-like growth factors (IGF), parathyroid hormone (PTH), follicle stimulating hormone (FSH), leptin, gastrin
36
Q

Describe amino-acid derived hormones and provide examples

A
  • Not directly encoded by genes but indirectly encoded by genes of the enzymes which enzymatically produce these hormones using certain amino acids
  • E.g., adrenaline, dopamine, melatonin, serotonin
37
Q

Describe steroid and sterol hormones and include examples

A
  • Not directly encoded by genes but indirectly encoded by the genes of the enzyes which synthesis these hormones from cholesterol
  • E.g., aldosterone, crotisol, progesterone, testosterone
38
Q

Describe lipid hormones and provide examples

A
  • Synthesized from fatty acids by specific enzymes
  • E.g., leukotrienes, prostacyclin, prostaglandins
39
Q

Describe gaseous hormones and provide examples

A
  • Produced from animo acid arginine and oxygen
  • E.g,, nitric oxide (NO) - the only gaseous hormone
40
Q

Name the ways a hormone receptor can transduce an extracellular ligand response into a cellular response

A
  • Ion channels
  • G-coupled receptors
  • Activation of protein kinases
  • Activation when receptor is a kinase
  • Intracellular receptors
41
Q

a) Describe how ion channel receptors transduce an extracellular hormone response into a cellular response
b) Provide two examples of hormones that enter the cell via an ion channel

A

a)

  1. Hormone binds to a receptor, which is an ion channel
  2. This causes a confromational change in the ion channel
  3. This allows ions to move frome extracellular sitte of cell to intracellular site of cell
  4. This causes membrane depolarisation

b) e.g., serotonin, GABA

42
Q

a) Describe how G protein-coupled receptors transduce an extracellular hormone response into a cellular response
b) Provide 2 examples of hormones that enters a cell via G protein-coupled receptors

A

a)

  1. Hormone binds to a receptor causign a confrmational change
  2. This causes GDP to be swapped for GTP on the alpha subunit of the G protien
  3. This exchange leads to a dissociation of the alpha subunit from the beta and gamma subunit of the G protien
  4. The alpha subunit then binds to another effector protein (e.g., Ca channel)
  5. The channel then opens and allows calcium ions to move into the cell, leading to an increase in intracellular mediators
  6. Eventually GTP then gets hydrolysed back into GDP, leadng to dissociation of the alpha subunit from the Ca channel
  7. The Ca channel closes, and no more calcium ions are moved from the extracellular side to the intracellular side
  8. The alpha subunit reassociates to the beta and gamma subunits of the G protein so the cycle can restart

b) Adrenaline, glucagon

43
Q

a) What type of receptor is involved in the adenyl cyclase pathway
b) Describe the adenyl cyclase pathway and provide one example of a hormone involved

A

a) G protein-coupled receptors

b)

  1. Hormone e.g. glucagon binds to alpha sub-unit,GDP is exhanged for GTP leading to dissociation of the alpha-subunit
  2. The alpha-subunit can bind with adenyl cyclase
  3. The enzyme activates the catalysation of ATP to cAMP
  4. cAMP is a secondar messenger that activates protein kinases
44
Q

a) What type of receptor is involved in the phospholipase C pathway
b) Describe the phsopholipase C pathway and provide one example of a hormone involved

A

a) G protein-coupled receptor

b)

  1. Hormone ee.g., adrenaline binds to alpha sub-unit, GDP is exchanged for GTP leading dissociation of the alpha-subunit
  2. The alpha subunit, can bind with phospholipase C to catalyse the conversion of PIP2 to IP3 and DAG, which regulates enzyme activity
  3. IP3 releases calcium ions from endoplasmic reticulum and opens calcium channels in the plasma membrane
  4. DAG activates protein kinase C which phosphorylates and activates other proteins
45
Q

a) Describe how hormones activate protein kinases to transduce an extracellular hormone response into a cellular response
b) Describe an example of a hormone that activates protein kinases

A

a)

  1. Binding of the hormone e.g., to a receptor causes confromational change of the receptor
  2. This activates kinase to phosphorylate proteins using ATP

b)

  1. Atrial-natriuretic hormone binds to a receptor that is linked to guanyl cyclase
  2. Guanyl cyclase is activated
  3. Guanylyl cyclase converts GTP to cGMP
  4. cGMP actiavtes protein kinases which phospholates other proteins, activating them too
46
Q

a) Describe how a kinase hormone receptor can transduce an extracellular hormone response into a cellular response
b) Provide an example of a hormone that enters the cell this way

A

a)

  1. Hormone binds to receptor and conformational change triggers the intrinsic kinase activity of the receptor
  2. The receptor phosphorylates specific proteins using ATP
  3. THe phosphorylation can either lead to an activation or to and inhibition of proteins

b) Insulin

47
Q

Describe the 2 types of pathways of intracellular receptors that can transuce extracellular ligand response into a cellular response and provde an example for each pathway

A

Pathway 1 - e.g., glucocorticoid

  1. Hormone diffuses into the cytoplasm where it binds to its intracellular receptor
  2. The hormone receptor complex locates the nucleus
  3. The hormone receptor complex binds to hormone response elements on the DNA and acts as transcription factor turning gene expression on or off

Pathway 2 - estrogens, androgens and thryoid hormone

  1. The hormone diffuses into the cytoplasm and into the nucleus where it binds to its nuclear located receptor
  2. Hormone receptor complex binds to hormone response elements on the DNA and acts as transcription factors turining gene expression on or off
48
Q

List the locations where you’ll find endocrine glands

A
  • Pineal body
  • Hypothalamus
  • Pituitary
  • Parathyroids
  • Thyroid gland
  • Thymus gland
  • Adrenal gland
  • Pancreas
  • Ovaries
  • Testicles

Medicine - Year 1 (61 decks)

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