Carbohydrates and Lipids Flashcards
(116 cards)
1
Q
what are some examples of carbohydrates?
A
starch, cellulose, sucrose, chitin
2
Q
what are some functions of carbohdyrates?
A
- energy stores
- fuels
- metabolic intermediates
- structural backbone of RNA and DNA
3
Q
what are monosaccharides? give some examples.
A
- simplest unit
- glucose, galactose and ribose
4
Q
what are disiccharides? give some examples.
A
- 2 monosaccharides
- lactose, sucrose, maltose
5
Q
what are polysaccharides? give some examples
A
- lots of monomers joined in a chain
- starch, glycogen, cellulose
6
Q
what is a polysaccharides structural function?
A
- cell walss = cellulose
- extracellular matrix
- connective tissue
- lubrication of skeletal joints
7
Q
what is a polysaccharides link to proteins and lipids?
A
- cell to cell recognition
- cell adhesion
- intracellular localisation tags on glycoproteins
- determine metabolic rate of glycojugates
8
Q
what is an aldose?
A
has an aldehyde group
9
Q
what is a ketose?
A
has an internal ketone group
10
Q
what do carbohydrates contain?
A
- carbon backbone
- several hydroxyl groups
- either an aldehyde group or a ketone group
11
Q
what is an isomer?
A
same chemcial formula but different arrangement
12
Q
what is a chiral carbon?
A
carbon that is attached to 4 different groups
13
Q
how does a chiral centre help to determine whether is a D or L form?
A
- optical isomers
- look at the penultimate carbon
- d form = OH on the right side of the chiral centre
- L form = OH on left side
14
Q
which form (D or L) is predominate in living orgnisms?
A
D isomers
15
Q
give some examples of D aldoses
A
Triose (3C) = D- Glyceraldehyde
Tetrose (4C) = D-erythrose, D-Threose
Pentose (5C) = D ribose
Hexose (6C) = D- Glucose, D - Mannose, D - Galactose
16
Q
what are epimers?
A
isomers which differ at only one chiral centre
17
Q
what are some examples of epimers?
A
- Galactose is a C4 epimer of glucose
- Mannose is a C2
18
Q
give some examples of D-ketoses?
A
- Ribulose → pentose
- Fructose → hexose
19
Q
how does a D-glucose go from being an open chain to a ring?
A
- OH on carbon 5
- Electrons can attack aldehyde group
- Form ring intermediate
- Can form one of 2 forms
20
Q
what are the 2 forms of D-glucose (anomers) ?
A
- Alpha D glucose → 30%, Hydroxyl on Cl points down
- Beta D glucose → 70%, Hydroxyl on Cl points up
21
Q
what is the most common form of glucose?
A
ring - the open chain is less than 1%
22
Q
what is the structure of fructose?
A
Can form 5 or 6 membered rings
Look at the anomeric carbon (C2)
Alpha and beta
23
Q
what are the different models of beta - D - glucose?
A
fischer, haworth, conformation, space filling model
24
Q
describe ribose and deoxyribose
A
- pentoses
- Beta D-ribose → OH at carbon 2 → key difference in stability
- 2 deoxy - beta - ribose
25
how many possible structures are there of hexoses?
48 possible structures
26
what are the different structures of aldoses ketoses?
Aldoses: alpha - 8D, 8L, beta - 8D, 8L (32)
Ketoses: alpha - 4D, 4L, beta - 4D, 4L (16)
27
what are the different sugar derivavtives?
Amine group added to glucose: D Glucosamine
Acetyl group added: N-Acetyl-D-glucosamine
Phosphorylated sugars: Key intermediates in energy generated and biogenesis, Glucose 6- phosphate, Dihydroxyacetone Phosphate
28
what bond joins disaccharides?
glycosidic bonds
29
describe maltose
```
2 glucose units
Glc - alpha - 1,4 - Glc
Glucose
OH is below the ring
1,4 carbon lineage
```
30
describe sucrose
Glucose and fructose
alpha-D-Glc-1,2-beta-D-Fru
OH below
OH above
31
describe lactose
galactose and glucose
Gal-beta-1, 4 - Glc
Condensation reaction = loss of water
32
what are homopolysaccharides?
One monosaccharides
Branched
Linear
33
what are heteropolysaccharides?
More than one monomer type
Branched
Linear
34
what is glycogen?
storage polysaccharide in animals
35
what are the key features of glycogen?
```
Skeletal muscle cells
Liver cells
Glycogen granules
Homopolysaccharide
-Glc alpha-1, 4 - Glc -
Also has alpha 1,6 bonds which results in branching
Non-reducing ends and reducings
Reducing end → free glucose so more can join
```
36
what is starch?
storage in plants
| made of amylose and amylopectin
37
what are the key features of starch?
Helical structure caused by branching
| Allows enzymes to have access to cleave glucose
38
describe alpha-Amylose
--Glc - alpha - 1,4 - Glc --
39
describe amylopectin
-- Glc - alpha-1, 4 - Glc --
| Alpha-1,6 - branching, every 24-30 residues
40
what is cellulose?
carbohydrates found in plant cell walls
41
what are the key features of cellulose?
- - Glc - beta -1,4 - Glc --
- Forms microfibril
- Homopolysaccharide
- Uses the beta anomer of glucose
- Between chains you can get hydrogen bonding → hydroxyl groups allow this
- Lots of hydrogen bonds = high tensile strength
- Beta and hydrogen bonds → more linear structure
42
what is chitin?
- - GlcNAc
- Structure similar to cellulose
- Can get hydrogen bonding between chains
43
what is peptidoglycan?
bacterial cell envelope
44
what are the main features of peptidoglycan?
- Heteropolysaccharide
- -MurNAc - beta - 1,4 GlcNAc --
- Between chains → peptides → short sequences of amino acids
- First line of defence → have lysozyme → cleaves/hydrolyses peptide → oligopeptides
45
what do penicilins inhibit?
glycopeptide transpeptidase activity
46
describe penicilins process
```
B lactam ring
Acts as a mimic
Binds to enzyme
Can’t catalyse this process
Cell wall not formed
```
47
describe gram positive
Peptidoglycan
Lipid bilayer
Lipid molecules to anchor peptidoglycan layer
48
describe gram negative
Thinner peptidoglycan
Outer lipid membrane
Lipid bilayer
49
what is N linked?
- glycosidic linkage to asparagine → attaches to side chain
| - GclNAc (sugar added)
50
what is O linked?
- glycosidic linkage to ser or threonine
| - GalNAc (sugar added)
51
what modifications can be made to glycosylation?
Modification → add or removing sugars on the sugar chain → can get branching
52
where does glycosylation occur in the cell
- N = begins in RER → continues in golgi
| - O = occurs in golgi
53
how does glycosylation work in the golgi?
different enzymes present in each compartment
54
describe the sugars of blood groups
- antigens glycoproteins
- different due to the sugars attached to the protein
- one sugar difference
55
describe carbohydrates as components of extracellular matrix
- gap between 2 cells shows there are protein and carbohydrate complexes
- cell adhesion protein → multiadhesive protein → collagen fibers
56
what are proteoglycans?
- Consist of protein and carbohydrates
- Protein a small component
- Lots of sugars
- proteins attached to glycosaminoglycans (~95% saccharide by weight)
- In cartilage
- Regulate movement of molecules in ECM
57
what are glucosamine lycans?
- components of the ECM
- Eg hyaluronic acid, chondroitin - 6 - sulfate, keratan sulfate
- Anionic polysaccharide chains made of repeating disaccharide units
58
what is the function of biological membranes?
- define inside and outside of cells
| - selectively permeable to small molecu;es
59
what is the structure of biological membranes?
- dynamic and fluid structures
- lipids and proteins
- spontaneuosly form
- self assembling
60
where do eukaryotic cells have internal membranes?
```
Mitochondria/chloroplasts
Nuclear envelope
RER
Golgi
Peroxisomes
Lysosomes
Vesicles
```
61
how does the chemical composition differ depending on function?
Myelin → lipids 79%, 18% protein
RBC → 49% lipid, protein 43% → around the same amount
Can get membranes with a high protein content eg chloroplast membrane
62
what are the common features of biological membranes?
Sheet like structures
Lipids → hydrophobic tails, hydrophilic head
Non-covalent structures → held together by many different interactions
Membranes = asymmetric (outer leaflet/inner leaflet)
Most are electrically polarised
63
what are the key components of lipids?
fatty acids
64
what do lipids form?
- bilayers due to hydrophobic properties
65
what do fatty acids form?
micelle
66
where do the hydrophobic properties come from in lipids?
fatty acid hydrocarbon tails
67
how are fatty acids classified?
Number of carbons
16 = saturated
18 carbons, 1 cis db = unsaturated
Double bond positions in fatty acid chain
68
what are the different isomerisms in unsaturated?
- positional
| - geometric
69
what is saturated?
no double bonds
70
what is unsaturated?
at least one double bond
71
what is trans fatty acids?
not produced in nature
72
what do double bonds cuase?
bends or kinks
73
what are short chain fatty acids?
- essential
| - needed in the diet
74
what is the melting point for different length chains?
Saturated → 16 palmitic → would be solid at body temperature → 63 degrees
Unsaturated → 16 palmitoleic → 0 degrees → would be liquid at body temperature
75
what do neutral lipids have?
no ampipathic properties
76
what are some examples of netrual lipids?
- triglyceride
- diglyceride
- monoglyceride
77
what is a condensation reaction in lipids?
- between fatty acids and glycerol
- ester bond
- glycerol will have 3 OH
- OH and H lost
- forms water
78
what are cholesterol esters?
- cholesterol anomatic
| - OH group linked
79
what are membrane lipids?
amphipathic molecules - part hydrophilic and part hydrophobic
80
what are the 3 types of membrane lipids?
1. phospholippids
2. glycolipids
3. cholesterol
81
what are phosphpolipids?
- glycerol backbone
- 2 fatty acids, hydrophobic
- phosphate group, alcohol, hydrophilic
- can also have on with sphingosine
82
what is sphingosine?
phosphate, alcohol and one fatty acid
83
what are glycolipids?
Glycerol, 2 fatty acids, phosphate-sugar
| Sphingosine; 1 fatty acid, phosphate-sugar
84
what is cholesterol?
OH is intact
Hydrophobic part
Polar hydroxyl group
85
what are neutral lipids used for?
energy storage
86
what is amphipathic lipids used for?
in membranes
87
describe alcohols linked to phosphoglycerides
```
Serine → amino acid → OH attached
Ethanolamine
Choline
Glycerol
Inositol
```
88
what alcohol group does serine have?
- phosphate, +NH3, -COO
| Overall charge = -1
89
what alcohol group does phosphatidylcholine have?
- phosphate, + N
| Charge = 0 → neutral
90
what is sphingomyelin?
Phospholipid with sphingosine
Amide linkage → sphingosine and fatty acid
P-, +N
Ceramides contain sphingosine with an amide linked fatty acid
91
what is cerebroside?
Glycolipid with sphingosine
Amide linkage
glucose/galactose unit
Gangliosides contain branched polysaccharide chains with up to 7 sugars
92
where is lipoteichoic acid found?
gram positive
93
where is lipopolysaccharide found?
outer membrane of gram negative bacteria
94
what are the properties of phospholopids and glycolipids?
form membranes in water
Fatty acids → van der waals → in the interior
Polar part → outside → hydrophilic → face outwards aqueous environment
95
what is a liposome?
- lipid vesicle
- spontaneously form
- bilayers of phospholipids
96
what would a solution of fatty acids spontaneuosly form?
```
a micelle
Small polar group
Form a monolayer
Hydrophilic → face out
Tails → hydrophobic → inwards
```
97
what are the different types of types of phsopholipids?
- PC = phosphphocholine, head group larger than PE, equally distributed in both leaflets
- PE = wedge, inner leaflet
- PS = phosphoserine, cylindrical, inner leaflet
98
what does molecular shape determine?
- properties
- want curvature or connected with endo/exocytosis
- curved regions of membrane = different distributions on the types
99
how is membrane bilayer asymmetry maintained?
phospholipid flip flop occurs extremely slowly
100
why does phospholipid flip flop occur slowly
hard to flip between leaflets as they'd have to go through the hydrophobic section
101
what are the proteins that help with flip flop?
1. Flippases → outer to inner
2. Floppases → inner to outer
3. Scramblases → both directions
102
describe the affect of changing the temperature on lipid ilayers?
Gel/solid → fluid like : increase
Have different melting points
Body usually at constant temperature 37 degrees → not so much a factor
103
describe the effect of increased cholesterol content
makes it more solid/gel like
Becomes more rigid
Cholesterol is bulky
104
describe the effect of fatty acid content?
- Saturated → increase → more gel like
| - Unsaturated → creates kink → take up more space → becomes more fluid
105
what happens if you decrease the length of the fatty acid chain?
membrane becomes more fluid
106
what are the 4 factors that effect the lipid bilayer?
1. Temperature
2. Cholesterol
3. Fatty acid content
4. Fatty acid chain length
107
what can pass through the membrane?
```
Gases → O2, CO2, N2 → can pass freely
Small polar and uncharged
- Urea and ethanol
- OH group = polar
- Can pass through
```
108
how does water pass through the membrane?
Do have aquaporins to help transport water through
109
what can't pass through the membrane?
Polar, large, uncharged → glucose → too big
| Polar and uncharged → can't move through
110
what can ketose and aldose sugars do?
interconvert between open chain and cyclic forms in solution
111
what are enantiomers?
pair of molecules that are mirror images of each other
112
what is an alpha anomer?
The –OH of C1 points down
113
what is a beta anomer?
The –OH of C1 points up
114
what are some examples of glycosaminoglycans?
Hyaluronic acid, chondroitin 6 sulfate, keratan sulfate
115
what is mainly found in the outer leaflet?
spingomyelin. phosphatidycholine. some phosphatidylethanolamine
116
what is mainly found in the inner leaflet?
phosphatidylethanolamine. phosphatidylserine. phosphatidylinositol
