Carbohydrates and Lipids Flashcards
what are some examples of carbohydrates?
starch, cellulose, sucrose, chitin
what are some functions of carbohdyrates?
- energy stores
- fuels
- metabolic intermediates
- structural backbone of RNA and DNA
what are monosaccharides? give some examples.
- simplest unit
- glucose, galactose and ribose
what are disiccharides? give some examples.
- 2 monosaccharides
- lactose, sucrose, maltose
what are polysaccharides? give some examples
- lots of monomers joined in a chain
- starch, glycogen, cellulose
what is a polysaccharides structural function?
- cell walss = cellulose
- extracellular matrix
- connective tissue
- lubrication of skeletal joints
what is a polysaccharides link to proteins and lipids?
- cell to cell recognition
- cell adhesion
- intracellular localisation tags on glycoproteins
- determine metabolic rate of glycojugates
what is an aldose?
has an aldehyde group
what is a ketose?
has an internal ketone group
what do carbohydrates contain?
- carbon backbone
- several hydroxyl groups
- either an aldehyde group or a ketone group
what is an isomer?
same chemcial formula but different arrangement
what is a chiral carbon?
carbon that is attached to 4 different groups
how does a chiral centre help to determine whether is a D or L form?
- optical isomers
- look at the penultimate carbon
- d form = OH on the right side of the chiral centre
- L form = OH on left side
which form (D or L) is predominate in living orgnisms?
D isomers
give some examples of D aldoses
Triose (3C) = D- Glyceraldehyde
Tetrose (4C) = D-erythrose, D-Threose
Pentose (5C) = D ribose
Hexose (6C) = D- Glucose, D - Mannose, D - Galactose
what are epimers?
isomers which differ at only one chiral centre
what are some examples of epimers?
- Galactose is a C4 epimer of glucose
- Mannose is a C2
give some examples of D-ketoses?
- Ribulose → pentose
- Fructose → hexose
how does a D-glucose go from being an open chain to a ring?
- OH on carbon 5
- Electrons can attack aldehyde group
- Form ring intermediate
- Can form one of 2 forms
what are the 2 forms of D-glucose (anomers) ?
- Alpha D glucose → 30%, Hydroxyl on Cl points down
- Beta D glucose → 70%, Hydroxyl on Cl points up
what is the most common form of glucose?
ring - the open chain is less than 1%
what is the structure of fructose?
Can form 5 or 6 membered rings
Look at the anomeric carbon (C2)
Alpha and beta
what are the different models of beta - D - glucose?
fischer, haworth, conformation, space filling model
describe ribose and deoxyribose
- pentoses
- Beta D-ribose → OH at carbon 2 → key difference in stability
- 2 deoxy - beta - ribose
how many possible structures are there of hexoses?
48 possible structures
what are the different structures of aldoses ketoses?
Aldoses: alpha - 8D, 8L, beta - 8D, 8L (32)
Ketoses: alpha - 4D, 4L, beta - 4D, 4L (16)
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
what bond joins disaccharides?
glycosidic bonds
describe maltose
2 glucose units Glc - alpha - 1,4 - Glc Glucose OH is below the ring 1,4 carbon lineage
describe sucrose
Glucose and fructose
alpha-D-Glc-1,2-beta-D-Fru
OH below
OH above
describe lactose
galactose and glucose
Gal-beta-1, 4 - Glc
Condensation reaction = loss of water
what are homopolysaccharides?
One monosaccharides
Branched
Linear
what are heteropolysaccharides?
More than one monomer type
Branched
Linear
what is glycogen?
storage polysaccharide in animals
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
what is starch?
storage in plants
made of amylose and amylopectin
what are the key features of starch?
Helical structure caused by branching
Allows enzymes to have access to cleave glucose
describe alpha-Amylose
–Glc - alpha - 1,4 - Glc –
describe amylopectin
– Glc - alpha-1, 4 - Glc –
Alpha-1,6 - branching, every 24-30 residues
what is cellulose?
carbohydrates found in plant cell walls
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
what is chitin?
- GlcNAc
- Structure similar to cellulose
- Can get hydrogen bonding between chains
what is peptidoglycan?
bacterial cell envelope
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
what do penicilins inhibit?
glycopeptide transpeptidase activity
describe penicilins process
B lactam ring Acts as a mimic Binds to enzyme Can’t catalyse this process Cell wall not formed
describe gram positive
Peptidoglycan
Lipid bilayer
Lipid molecules to anchor peptidoglycan layer
describe gram negative
Thinner peptidoglycan
Outer lipid membrane
Lipid bilayer
what is N linked?
- glycosidic linkage to asparagine → attaches to side chain
- GclNAc (sugar added)
what is O linked?
- glycosidic linkage to ser or threonine
- GalNAc (sugar added)
what modifications can be made to glycosylation?
Modification → add or removing sugars on the sugar chain → can get branching
where does glycosylation occur in the cell
- N = begins in RER → continues in golgi
- O = occurs in golgi
how does glycosylation work in the golgi?
different enzymes present in each compartment
describe the sugars of blood groups
- antigens glycoproteins
- different due to the sugars attached to the protein
- one sugar difference
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
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
what are glucosamine lycans?
- components of the ECM
- Eg hyaluronic acid, chondroitin - 6 - sulfate, keratan sulfate
- Anionic polysaccharide chains made of repeating disaccharide units
what is the function of biological membranes?
- define inside and outside of cells
- selectively permeable to small molecu;es
what is the structure of biological membranes?
- dynamic and fluid structures
- lipids and proteins
- spontaneuosly form
- self assembling
where do eukaryotic cells have internal membranes?
Mitochondria/chloroplasts Nuclear envelope RER Golgi Peroxisomes Lysosomes Vesicles
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
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
what are the key components of lipids?
fatty acids
what do lipids form?
- bilayers due to hydrophobic properties
what do fatty acids form?
micelle
where do the hydrophobic properties come from in lipids?
fatty acid hydrocarbon tails
how are fatty acids classified?
Number of carbons
16 = saturated
18 carbons, 1 cis db = unsaturated
Double bond positions in fatty acid chain
what are the different isomerisms in unsaturated?
- positional
- geometric
what is saturated?
no double bonds
what is unsaturated?
at least one double bond
what is trans fatty acids?
not produced in nature
what do double bonds cuase?
bends or kinks
what are short chain fatty acids?
- essential
- needed in the diet
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
what do neutral lipids have?
no ampipathic properties
what are some examples of netrual lipids?
- triglyceride
- diglyceride
- monoglyceride
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
what are cholesterol esters?
- cholesterol anomatic
- OH group linked
what are membrane lipids?
amphipathic molecules - part hydrophilic and part hydrophobic
what are the 3 types of membrane lipids?
- phospholippids
- glycolipids
- cholesterol
what are phosphpolipids?
- glycerol backbone
- 2 fatty acids, hydrophobic
- phosphate group, alcohol, hydrophilic
- can also have on with sphingosine
what is sphingosine?
phosphate, alcohol and one fatty acid
what are glycolipids?
Glycerol, 2 fatty acids, phosphate-sugar
Sphingosine; 1 fatty acid, phosphate-sugar
what is cholesterol?
OH is intact
Hydrophobic part
Polar hydroxyl group
what are neutral lipids used for?
energy storage
what is amphipathic lipids used for?
in membranes
describe alcohols linked to phosphoglycerides
Serine → amino acid → OH attached Ethanolamine Choline Glycerol Inositol
what alcohol group does serine have?
- phosphate, +NH3, -COO
Overall charge = -1
what alcohol group does phosphatidylcholine have?
- phosphate, + N
Charge = 0 → neutral
what is sphingomyelin?
Phospholipid with sphingosine
Amide linkage → sphingosine and fatty acid
P-, +N
Ceramides contain sphingosine with an amide linked fatty acid
what is cerebroside?
Glycolipid with sphingosine
Amide linkage
glucose/galactose unit
Gangliosides contain branched polysaccharide chains with up to 7 sugars
where is lipoteichoic acid found?
gram positive
where is lipopolysaccharide found?
outer membrane of gram negative bacteria
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
what is a liposome?
- lipid vesicle
- spontaneously form
- bilayers of phospholipids
what would a solution of fatty acids spontaneuosly form?
a micelle Small polar group Form a monolayer Hydrophilic → face out Tails → hydrophobic → inwards
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
what does molecular shape determine?
- properties
- want curvature or connected with endo/exocytosis
- curved regions of membrane = different distributions on the types
how is membrane bilayer asymmetry maintained?
phospholipid flip flop occurs extremely slowly
why does phospholipid flip flop occur slowly
hard to flip between leaflets as they’d have to go through the hydrophobic section
what are the proteins that help with flip flop?
- Flippases → outer to inner
- Floppases → inner to outer
- Scramblases → both directions
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
describe the effect of increased cholesterol content
makes it more solid/gel like
Becomes more rigid
Cholesterol is bulky
describe the effect of fatty acid content?
- Saturated → increase → more gel like
- Unsaturated → creates kink → take up more space → becomes more fluid
what happens if you decrease the length of the fatty acid chain?
membrane becomes more fluid
what are the 4 factors that effect the lipid bilayer?
- Temperature
- Cholesterol
- Fatty acid content
- Fatty acid chain length
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
how does water pass through the membrane?
Do have aquaporins to help transport water through
what can’t pass through the membrane?
Polar, large, uncharged → glucose → too big
Polar and uncharged → can’t move through
what can ketose and aldose sugars do?
interconvert between open chain and cyclic forms in solution
what are enantiomers?
pair of molecules that are mirror images of each other
what is an alpha anomer?
The –OH of C1 points down
what is a beta anomer?
The –OH of C1 points up
what are some examples of glycosaminoglycans?
Hyaluronic acid, chondroitin 6 sulfate, keratan sulfate
what is mainly found in the outer leaflet?
spingomyelin. phosphatidycholine. some phosphatidylethanolamine
what is mainly found in the inner leaflet?
phosphatidylethanolamine. phosphatidylserine. phosphatidylinositol
