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%
2
Q
Lipids
A
- monomer: fatty acids
- water insoluble molecules
- amphipathic
3
Q
Importance of lipids
A
- form barriers
- serve as stored fuel source
- involved in signal transduction
4
Q
Proteins
A
- monomer: amino acids
- can be soluble/insoluble depending on AA 3D structure
- participate in essentially all cellular processes (workhorses)
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
6
Q
Carbohydrates
A
- monomer: monosaccharides
- water soluble rich in hydroxyl groups
- can be attached to proteins OR lipids
7
Q
Importance of carbohydrates
A
- primary fuel source for living creatures
- serve as sites for cell-cell interaction
- maintain shape/structure
8
Q
Nucleic Acids
A
- monomer: nucleotides
- RNA and DNA
- primarily found in phosphorylated form
9
Q
Importance of nucleic acids
A
- store and transfer genetic information
10
Q
Major Elements
A
CHNOPS
11
Q
Why is Carbon so versatile?
A
- bond formation
- affinity for oxygen
- bond dissociation
- electronegativity
12
Q
Covalent vs Noncovalent
A
- covalent: share electrons b/w pairs (strong)
- noncovalent: vary in electromagnetic interactions w/i or between molecules (weak)
13
Q
Covalent vs noncovalent in H2O structure
A
- covalent: bonds b/w hydrogen and oxygen
- noncovalent: b/w one water molecule and another
14
Q
Why are lipids not considered true polymers?
A
- they do not contain multiple polymers and they are not interlinked
15
Q
Saturated FA
A
- composed of carbon-carbon single bonds
16
Q
Unsaturated FA
A
- one or more c-c double or triple bonds
17
Q
Omega-3 FA and Omega-6 FA
A
- the location of the first c-c double bonds counting from the methyl group
18
Q
What is X:X
A
total carbons: c-c double bonds
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
20
Q
Four Classes of lipids
A
- Triacylglycerols
- Phospholipids
- Glycolipids
- Steroids
21
Q
Classes that contain FA
A
- triacylglycerols, phospholipids, glycolipids
22
Q
Classes that are found in the membrane
A
- phospholipids, glycolipids, steroids
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
24
Q
Attributes membranes share
A
- contain amphipathic phospholipids
- are asymmetric, non covalent assemblies
- are electrically polarized and fluid structures
- have specific proteins, which mediate distinct functions
25
Why are membranes electrically polarized?
- because of the electrical differences across the membrane
26
What affects the rigidity of the membrane?
- temperature. the lower the temperature, the more rigid, due to the degree of brownian motion and non-covalent interactions
27
What type of proteins are transporters?
- integral proteins
28
Voltage-gated vs Ligand-gated channels
- voltage-gated: open in response to changes in membrane potential
- ligand-gated: open in response to signal molecule binding
29
What powers a primary active pump?
- hydrolyzed ATP
30
What powers a secondary active pump?
- electrochemical gradient
31
How do signal transduction pathways operate?
- 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
Why are lipid messengers synthesized on demand?
- diffuse through membranes as lipophilic; cannot be stored in vesicles
33
Where are lipid receptors?
- ligand lipids bind to extracellular and intracellular receptors
- seven-transmembrane-helix receptors
- nuclear hormone receptors
34
Why are seven-transmembrane-helix receptors also known as G protein coupled receptors?
- they are associated with guanyl nucleotide proteins
35
In the insulin transduction pathway, what does active protein kinase B (Akt) do?
- phosphorylates enzymes in cell
- leads to phosphorylation of GLUT4
- increase glucose intake
- glycogen synthesis
36
How is the insulin transduction pathway shut down?
- dephosphorylation
37
How are dietary triacylglycerols digested in the human body?
1. TAGs are mobilized from adipose tissue
2. FAs are activated and transported to mitochondria
3. FAs are oxidized into acetyl CoA
38
Does cholesterol cross the intestinal plasma membrane considering it is lipophilic?
- cholesterol is moved to the intestinal cells by a transporter, NPC1L1, after it has been cleaved by enzymes
39
What do chylomicrons transport? where does it go?
- 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
How is dietary cholesterol moved into intestinal cells?
- cholesterol esterase cleaves ester linkages in cholesterol esters
- NPC1L1 transports from there to intestinal cells
41
What is shared among metabolic pathways?
- intermediates
42
What is the rate limiting step in metabolism of TAGs
- transportation of FAs where they have to be attached to carnitine to cross the inner mitochondrial membrane
43
How are fatty acids synthesized in the human body?
1. acetyl CoA is transported to cytoplasm
2. acetyl CoA is activated and transferred
3. FAs are synthesized
44
What is the committed step of FA synthesis?
- activation of acetyl CoA
45
How is acetyl CoA transported out of the mitochondria?
- 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
What are the four repeating steps in FA synthesis?
1. condensation
2. reduction of the carbonyl group
3. dehydration
4. reduction of the double bonds
(synthesize saturated FA 2 at a time)
47
What molecule is used to synthesize even fatty acid chains?
Propionyl CoA (3-carbon molecule)
48
What molecule is used to synthesize odd fatty acid chains?
Propionyl CoA (3-carbon molecule)
49
What FA chain length can mitochondria synthesize?
- shorter chains
50
What FA chain length can ER synthesize
- longer chains
51
What two pathways can be used to synthesize TAGs in the intestine?
- monoacylglycerol (80%)
| - glycerol phosphate pathway
52
What starting material is used to synthesize TAGs in the liver?
- phosphatidate--precursor has two hydrocarbon chains and glycerol
53
Which lipids are synthesized from ceramide?
- sphingolipid (ceramide reacted with phosphatidylcholine; generates sphingomyelin)
54
Which lipids are synthesized from acetyl CoA
- steroids
55
How do statins reduce cholesterol?
- statins are an inhibitor
| - mimic enzymes substrates and steal the binding site
56
LDL
- transport cholesterol from liver to body
57
HDL
- transport cholesterol from body to liver
58
Regulation of lipid synthesis
- 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
Regulation of cholesterol synthesis
- 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
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