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Biochem > Exam 1 SG > Flashcards

Exam 1 SG Flashcards

1
Q

How do the classes of biomolecule compare in terms of % w/i the human body

A
  • protein: 16%
  • lipids: 15%
  • carbohydrates: 1%
  • nucleic acids: 1%
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2
Q

Lipids

A
  • monomer: fatty acids
  • water insoluble molecules
  • amphipathic
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3
Q

Importance of lipids

A
  • form barriers
  • serve as stored fuel source
  • involved in signal transduction
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4
Q

Proteins

A
  • monomer: amino acids
  • can be soluble/insoluble depending on AA 3D structure
  • participate in essentially all cellular processes (workhorses)
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5
Q

Importance of proteins

A
  • serve as catalysts, enhancing rate of chemical reactions
  • serve as signaling molecules and receptors
  • maintain cell shape/structural support
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6
Q

Carbohydrates

A
  • monomer: monosaccharides
  • water soluble rich in hydroxyl groups
  • can be attached to proteins OR lipids
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7
Q

Importance of carbohydrates

A
  • primary fuel source for living creatures
  • serve as sites for cell-cell interaction
  • maintain shape/structure
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8
Q

Nucleic Acids

A
  • monomer: nucleotides
  • RNA and DNA
  • primarily found in phosphorylated form
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9
Q

Importance of nucleic acids

A
  • store and transfer genetic information
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10
Q

Major Elements

A

CHNOPS

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11
Q

Why is Carbon so versatile?

A
  • bond formation
  • affinity for oxygen
  • bond dissociation
  • electronegativity
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12
Q

Covalent vs Noncovalent

A
  • covalent: share electrons b/w pairs (strong)

- noncovalent: vary in electromagnetic interactions w/i or between molecules (weak)

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13
Q

Covalent vs noncovalent in H2O structure

A
  • covalent: bonds b/w hydrogen and oxygen

- noncovalent: b/w one water molecule and another

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14
Q

Why are lipids not considered true polymers?

A
  • they do not contain multiple polymers and they are not interlinked
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15
Q

Saturated FA

A
  • composed of carbon-carbon single bonds
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16
Q

Unsaturated FA

A
  • one or more c-c double or triple bonds
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17
Q

Omega-3 FA and Omega-6 FA

A
  • the location of the first c-c double bonds counting from the methyl group
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18
Q

What is X:X

A

total carbons: c-c double bonds

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19
Q

Why must humans obtain. most of their cis-polyunsaturated fatty acids from their diet?

A
  • our bodies do not make them because we cannot synthesize them
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20
Q

Four Classes of lipids

A
  1. Triacylglycerols
  2. Phospholipids
  3. Glycolipids
  4. Steroids
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21
Q

Classes that contain FA

A
  • triacylglycerols, phospholipids, glycolipids
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22
Q

Classes that are found in the membrane

A
  • phospholipids, glycolipids, steroids
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23
Q

Why is the plasma membrane important?

A
  • surrounds the outside of every prokaryotic and eukaryotic cells
  • composed of two layers and contains proteins and carbs
  • impermeable to MOST molecules
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24
Q

Attributes membranes share

A
  1. contain amphipathic phospholipids
  2. are asymmetric, non covalent assemblies
  3. are electrically polarized and fluid structures
  4. have specific proteins, which mediate distinct functions
25
Q

Why are membranes electrically polarized?

A
  • because of the electrical differences across the membrane
26
Q

What affects the rigidity of the membrane?

A
  • temperature. the lower the temperature, the more rigid, due to the degree of brownian motion and non-covalent interactions
27
Q

What type of proteins are transporters?

A
  • integral proteins
28
Q

Voltage-gated vs Ligand-gated channels

A
  • voltage-gated: open in response to changes in membrane potential
  • ligand-gated: open in response to signal molecule binding
29
Q

What powers a primary active pump?

A
  • hydrolyzed ATP
30
Q

What powers a secondary active pump?

A
  • electrochemical gradient
31
Q

How do signal transduction pathways operate?

A
  • A stimulus triggers release of a primary messenger
  • PM is recognized by a receptor
  • info is relayed to cells interior by SM
  • SM activate/inhibit effector molecule
  • signal cascade is terminated
32
Q

Why are lipid messengers synthesized on demand?

A
  • diffuse through membranes as lipophilic; cannot be stored in vesicles
33
Q

Where are lipid receptors?

A
  • ligand lipids bind to extracellular and intracellular receptors
  • seven-transmembrane-helix receptors
  • nuclear hormone receptors
34
Q

Why are seven-transmembrane-helix receptors also known as G protein coupled receptors?

A
  • they are associated with guanyl nucleotide proteins
35
Q

In the insulin transduction pathway, what does active protein kinase B (Akt) do?

A
  • phosphorylates enzymes in cell
  • leads to phosphorylation of GLUT4
  • increase glucose intake
  • glycogen synthesis
36
Q

How is the insulin transduction pathway shut down?

A
  • dephosphorylation
37
Q

How are dietary triacylglycerols digested in the human body?

A
  1. TAGs are mobilized from adipose tissue
  2. FAs are activated and transported to mitochondria
  3. FAs are oxidized into acetyl CoA
38
Q

Does cholesterol cross the intestinal plasma membrane considering it is lipophilic?

A
  • cholesterol is moved to the intestinal cells by a transporter, NPC1L1, after it has been cleaved by enzymes
39
Q

What do chylomicrons transport? where does it go?

A
  • they are released into the lymph system and then into the blood carrying fat absorbed from the diet as well as fat-soluble vitamins
40
Q

How is dietary cholesterol moved into intestinal cells?

A
  • cholesterol esterase cleaves ester linkages in cholesterol esters
  • NPC1L1 transports from there to intestinal cells
41
Q

What is shared among metabolic pathways?

A
  • intermediates
42
Q

What is the rate limiting step in metabolism of TAGs

A
  • transportation of FAs where they have to be attached to carnitine to cross the inner mitochondrial membrane
43
Q

How are fatty acids synthesized in the human body?

A
  1. acetyl CoA is transported to cytoplasm
  2. acetyl CoA is activated and transferred
  3. FAs are synthesized
44
Q

What is the committed step of FA synthesis?

A
  • activation of acetyl CoA
45
Q

How is acetyl CoA transported out of the mitochondria?

A
  • acetyl CoA is converted to citrate by oxaloacetate and then cleaved into the cytoplasm as citrate
  • two can be transported at a time for a given FA
46
Q

What are the four repeating steps in FA synthesis?

A
  1. condensation
  2. reduction of the carbonyl group
  3. dehydration
  4. reduction of the double bonds
    (synthesize saturated FA 2 at a time)
47
Q

What molecule is used to synthesize even fatty acid chains?

A

Propionyl CoA (3-carbon molecule)

48
Q

What molecule is used to synthesize odd fatty acid chains?

A

Propionyl CoA (3-carbon molecule)

49
Q

What FA chain length can mitochondria synthesize?

A
  • shorter chains
50
Q

What FA chain length can ER synthesize

A
  • longer chains
51
Q

What two pathways can be used to synthesize TAGs in the intestine?

A
  • monoacylglycerol (80%)

- glycerol phosphate pathway

52
Q

What starting material is used to synthesize TAGs in the liver?

A
  • phosphatidate–precursor has two hydrocarbon chains and glycerol
53
Q

Which lipids are synthesized from ceramide?

A
  • sphingolipid (ceramide reacted with phosphatidylcholine; generates sphingomyelin)
54
Q

Which lipids are synthesized from acetyl CoA

A
  • steroids
55
Q

How do statins reduce cholesterol?

A
  • statins are an inhibitor

- mimic enzymes substrates and steal the binding site

56
Q

LDL

A
  • transport cholesterol from liver to body
57
Q

HDL

A
  • transport cholesterol from body to liver
58
Q

Regulation of lipid synthesis

A
  • phosphatidic acid phosphatase plays a key role (PAP)
  • upregulated: by phosphatidylinositol and cardiolipin
  • serine palmitoyltransferase and ceramide play roles in sphingolipid and glycolipid synthesis
  • activity regulated by small ER proteins
59
Q

Regulation of cholesterol synthesis

A
  • controlled my HMG CoA reductase
  • has several levels:
    1. HMG CoA reductase gene expression
    2. Hormones (insulin and glucagon)
    3. oxygenated-cholesterol derivatives
    4. covalent modification of enzyme

Biochem (2 decks)

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