Biochem 8-9 Flashcards
Carbohydrate applications
-energy storing
-structural
-communication
-modular incorporation
WE CARE ABOUT D
Monosaccharide
-smallest unit of carbohydrate
1. polyhrdroxy aldehydes (aldoses)
2. polyhydroxy ketones (ketoses)
-must contain 3 carbon atoms
-suffix -ose used in nomenclature
aldose most oxidized is C-1
ketose most oxidized is C-2
Oligosaccharide
-polymers 2-20 monosaccharide residues
Polysaccharides
-polymers contain more than 20 residues
Trioses
- Glyceraldehyde
- Dihydroxyacetone
Cyclization of Aldoses and Ketoses
reaction of a hydroxyl with either the aldehyde or ketone results in hemiacetal or hemiketal (ketone)
furanose
5 membered ring
pyranose
6 membered ring
anomeric carbon
C-1 carbon
either alpha or beta
beta is best! OH on top
alpha is bottom
Cyclization of carbohydrate
carby C can either be attacked by C4 OH or by C5 OH
sugar phosphate
-one of the hydroxyls is converted to a phosphate ester
-numbered according to the carbon it is attached to
alpha-D-Ribose 5 phosphate
Deoxy sugars
-a hydrogen replaces the hydroxyl in the parent sugar
-loss of chiral center
beta-2-deoxy-D-ribose
Amino sugars
-amino group replaces the hydroxyl in parent
-often not numbered
alpha-D-glucosamine
Sugar alcohols
-the carbonyl of the parent sugar is reduced to an alcohol
-replace -ose with -itol
glycerol
sugar acids
Two choices:
oxidize the top to a carby from aldehyde
oxidize the bottom to a carby
Disaccharides
two monomers connected through a glycosidic bond at the anomeric carbon
-product is a glycoside!
reducing and non reducing sugars
-hemiacetals are reducing
-able to reduce metal ions and other friends.
-hemiketal cannot do this
glucose, maltose, cellobiose, lactose and more
polysaccharides
homoglycans–one kind of monomer
heterogylcans–several kinds of monomers
Homoglycans
starch, glycogen
Starches
amylose Glc alpha (1–>4)
amylopectin Glc alpha (1–>4) and branches every 25 residues (1–>6) (300-600 residues)
glycogen
Glc alpha (1-->4) and branches (1-->6) smaller and more frequently branches than amylopectin. every 8-12 residues branches (50,000 residues)
Structural homoglycans
cellulose
chitin
Cellulose
Glc beta (1-->4) cell walls. lots of H bonding
Chitin
GlcNAc (acetylglucosamine) beta (1–>4)
insects, fungi, red algae
fibrils of
Heteroglycans
Glycosaminoglycans
Hyaluronic Acid
Glycoconjugates
- polysaccharides covalently bound to proteins or peptides
- proteoglycans, glycoproteins, glycoconjugates
Proteoglycans
- complexes of proteins and glycosaminoglycans chains
- connective tissue
glycoproteins
- diverse!
- enzymes, hormones, structural proteins, transport proteins
- outer plasma membrane
- N linked or O linked ( alpha/beta position is stuck to an amine or to oxygen)
peptidoglycans
-polysaccharides linked to small peptides
-cell walls in bacteria
MurNAc-beta-(1–>4)-GlcNAc-beta-(1–>4)
Bacterial peptidoglycan
- nice bacteria net over the membrane
- D ala D ala needs a transpeptidase that attaches the pentaglycine portion. Penicillin inhibits this enzyme
Lipids
-water insoluble organic molecules
-hydrophobs or amphiphilic–polar and nonpolar regions
FOUR CLASSES:
1. fatty acids
2. phospholipids
3. glycosphingolipids
4. isoprenoids
Lipid nomenclature
-carby group is C1
-name main chain
-delta n for unsaturations
-shorthand is like this 18 : 1 delta 9
means 18 carbon chain, 1 unsaturation, at the 9 to 10 carbon
-hydrocarbon tail (C2) group begins with alpha.
last carbon is omega
Fatty acid unsaturation
- create a kink in the hydrophobic chain
- don’t pack as tight, more fluid
- cis or trans
- usually every three bonds
triacylglycerols
-three fatty acids esterified with one molecule of glycerol
-highly hydrophobic
FATS long chain unsaturated fatty acids
OILS short chain unsaturated fatty acids
Metabolism of triacylglycerols
- lipases–enzymes that break down dietary lipids
- most fat is stored in adipose tissue
Glycerophospholipids
-compose the majority of membranes
-amphiphilic molecules: polar head and nonpolar tail
-several subclasses
phosphatidates
plasmalogens
Phosphatides
-glycerol backbone
-fatty acid at C1
-C2 is unsaturated
-phosphate at C3
other classes vary with what fxnal group is esterified to the other OH on the phosphate
Phospholipases
- class of enzymes that catalyze the cleavage of esters in phospholipids
- can be used to find the structure of a lipid by cutting it up!
Plasmalogens
C1 substituent is linked by a vinyl ester
CH=CH after the fatty acids linkage
Important in the central nervous system
Sphingolipids
-after glycophospholipids, most abundant in plants and animals
-CNS
-sphigosine backbone as you count across:
18 C chain, C2 amine C4-5 trans double bond
CERAMIDE fatty acid at C2, precursor for other sphingos
1. Sphingomyelins
2. Cerebrosides
3. Gangliosides
Sphingomyelins
- phosphocholine at C1 (otherwise same as the ceramide)
- major component of myelin sheath surrounding nerve cells
Cerebrosides
-a monsaccharide is attached through B- glycosidic bond
-abundant in nerve tissues and myelin sheaths (15%)
-different subclasses depending on ID of the sugar
galactocerebroside
glucocerebroside
Gangliosides
-linked to complex oligosaccharides
-containing NeuNAc
contains a carby acid, polar head is anionic
-protrudes into ECM, function as cell surface markers
Steroids
-third class of lipids
-isoprenoids
-four ring structure
-derived from squalene
-hydrophobs
essential role in mammalian biochemistry
Waxes
-nonpolar esters of long chain fatty acids and long chain monohydroxylic alcohols
Eicosanoids
-oxygenated derivatives of C20 polyunsaturated fatty acids
prostaglandins have a cyclopentane ring
Biological membranes
- essential component of cells and have a variety of functions
- separate cellular components
- generate and maintain ion and small molecule gradients
- biosynthesis and delivery of transmembrane proteins ER
Lipid bilayers
main structural component of biological membranes, proteins and carbohydrates
5-6 nm thick, two sheets together
Biological membrane composition
-lipid-protein ratio is 25-50% lipid 50-75% protein
Plasma membrane
- cholesterol with glycosphingolipids form lipid rafts
- lipid ocean, with protein ice bergs floating about
- oligosaccharide chains for recognition and signaling
Membrane fluidity
-Lateral diffusion and Transverse Diffusion
TWO ENZYMES:
-Flippase takes outside to inside
-Floppase takes inside to outside
Membrane Fluidity
Affected by:
1. increase in temp
2. unsaturation
3. amount of cholesterol (20-25% of animal membrane lipids)
-decrease fluid at high
-increase fluid at low
HELP organisms cope in vastly different environments
Liposomes
- synthetic vessels composed of lipid bilayers
- great method for drug delivery
Classes of membrane proteins
-Integral membrane proteins: spans the membrane completely
*includes pores and channels
-Peripheral proteins: associated with one face of the membrane through charge to charge interactions
-Lipid-Anchored Membrane proteins
tethered to a membrane through a covalent bond to a lipid anchor
Thermodynamics of Membrane Transport
- Concentration Gradient (doesnt apply to charged things)
2. Membrane potential CHARGE
Passive transport
movement of a solute down its concentration gradient without expenditure of energy
also called facilitated diffusion
Active transport
requires energy to move a molecule against the concentration gradient
typically uses ATP
1. Primary Active
2. Secondary Active
Primary Active
- different source of energy
- ATP or light
Secondary Active
- ion conc gradient
- coupled to something that is primary active transport
Endocytosis and Exocytosis
- large molecules like proteins cannot diffuse across membrane
- Endocytosis: macromolecule engulfed by plasma membrane and brought inside with lipid vesicle
- Exocytosis: lipid vesicle fuses to membrane, releasing contents to the outside of the cell
Blood Groups
H antigen -can be modded by A or B enzyme A adds a GalNAc B adds a Gal D Different oligosaccharides on cell surface!
