carbs and lipids

What is an aldose?

A monosaccharide containing an aldehyde group, usually at C1.

What is a ketose?

A monosaccharide containing a ketone group, usually at C2.

What is the difference between D and L sugars?

In a Fischer projection, look at the OH on the highest-numbered chiral carbon: right = D; left = L.

enantiomers

different at each chiral center

diastereomers

differ at more than one chiral center

epimers

Diastereomers that differ at exactly one chiral carbon, excluding differences solely at the anomeric carbon

What are anomers?

Sugars that differ only in configuration at the anomeric carbon.

What is the anomeric carbon?

The former carbonyl carbon that becomes a new chiral center when a sugar cyclizes.

How do you identify α and β in a D-sugar Haworth projection?

α: the anomeric OH is opposite the CH₂OH group. β: they are on the same side.

What is a hemiacetal?

A carbon bonded to both an OH and an OR group, formed when an aldehyde reacts with an alcohol.

What is a hemiketal?

A carbon bonded to an OH and an OR group, formed when a ketone reacts with an alcohol.

What is a glycosidic bond?

A covalent bond connecting the anomeric carbon of a sugar to another group, often another sugar.

What does α(1→4) mean?

The α-anomeric C1 of one sugar is linked to C4 of another sugar.

What makes a sugar reducing?

It has a free anomeric carbon that can open into a carbonyl-containing form.

What is mutarotation?

Interconversion between α and β anomers through the open-chain form.

amylose

startch- a(1—> 4)

unbranched

storage

amylopectin

a (1—>4) chains

branches at a (1—>6) every 12-30 residues

storage

Glycogen

a (1—>4)

branches at a (1—>6) every 8-12 residues

animal storage

cellulose

B (1—>4)

can fully extend

H bonding, strong fibers

structural

chitin

•Similar to cellulose, but C-2s are N-acetyl (N-acetylglucosamine)

•Chitin can form multiple hydrogen bonds

homopolysaccharide

A polysaccharide made of one type of monosaccharide.

heteropolysaccharide

A polysaccharide containing more than one type of monosaccharide.

Why is glycogen's branching useful?

It creates many nonreducing ends, allowing glucose to be released rapidly.

What are glycosaminoglycans (GAGs)?

•Linear chain of repeating disaccharides: one unit is always an amino sugar

•Contains at least one negative charge: one or both units are negatively charged (COO⁻ or SO₄²⁻ AKA carboxylate and sulfate groups)

Why do GAGs attract water?

Their negatively charged sulfate and carboxylate groups attract ions and water.

Why are GAGs useful in cartilage?

They retain water and help the tissue resist compression.

What is a glycoprotein?

A protein with covalently attached carbohydrate chains, typically relatively short and branched.

extended “bristle brush“ conformation

What is a proteoglycan?

•A core protein attached to glycosaminoglycan (GAG) chains

what are the two ways sugars attach to protein

N-linked: Attachment of a carbohydrate to the nitrogen of an asparagine (Asn) residue.

O-linked: Attachment of a carbohydrate to the oxygen of a serine (Ser) or threonine (Thr) residue.

 what gives glycosaminoglycans their properties in the matrix.

their high negative charge density, strong attraction to water (hydrophilicity), and unbranched, linear structure, resistance to compresion

What is a fatty acid?

A long hydrocarbon chain with a carboxyl group.

What is a saturated fatty acid?

A fatty acid with no carbon–carbon double bonds.

What is an unsaturated fatty acid?

A fatty acid with at least one carbon–carbon double bond.

What does Δ numbering indicate?

Double-bond positions counted from the carboxyl carbon.

What does ω-3 mean? ω-6?

The first double bond is at the third carbon from the methyl end.

The first double bond is at the 6th carbon from the methyl end.

What happens when fatty acid chain length increases?

Van der Waals interactions increase, so melting point generally increases and fluidity decreases.

What happens when cis double bonds increase?

Kinks disrupt packing, generally lowering melting point and increasing fluidity.

Why do saturated fats tend to be more solid?

Their straight chains pack tightly, strengthening van der Waals interactions.

Why do cis-unsaturated fats tend to be more liquid?

Their bent chains cannot pack as tightly.

What is a triacylglycerol (TAG)?

A glycerol molecule esterified to three fatty acids.

3 carbon glycerol backbone

What is the main function of TAGs?

Long-term energy storage.

Why are TAGs energy-dense?

Their reduced hydrocarbon chains release substantial energy when oxidized, and their hydrophobic storage requires little associated water(u can store them without having to store hella water so its more compact).

What is a wax?

•Insoluble esters of long-chain alcohols with long-chain fatty acids

•Plant & animal outer layers coated in wax to be water-repellent

glycerophospholipid

•Phosphate group + additional head group (hydrophilic)

•Glycerol backbone

•Two fatty acid chains (hydrophobic)

sphingolipid

sphingosine back bone (SUPER LONG)

steroid

Four fused carbon rings: three six-membered rings and one five-membered ring.

Ceramides

•a fatty acid joined to sphingosine in amide linkage

the core structure of many sphingolipids.

how does cholestrol helps regulate membrane fluidity.

high temps: restricts FA chain movement to make it more rigid

low temps: prevents packing to make membrane more fluid

What is cholesterol a precursor of?

Steroid hormones, bile acids and vitamin D.

What builds terpenes

•Lipids built from repeating isoprene units (5 carbon unit)

all steroids come from terpenes

GAG chains of proteoglycans are typically attached to the core protein through what residues

serine

lipid rafts are enriched in? what does this make them?

are enriched in sphingolipids, cholesterol, and saturated fatty acids, making them less fluid

Mannose

C2 epimer of glucose

Galactose

C4 epimer of glucose

sucrose

C1 of glucose and C2 of fructose

Glucose and galactose are

c epimers

D-Glucose: C4 OH points RIGHT
D-Galactose: C4 OH points LEFT

Fructose

ketohexose

D-mannose and D-galactose

differ at two (C-2 and C-4), so they are diastereomers

glucose exists predominantly as

cyclic anomers, not the open chain.

D in Haworth projection

CH₂OH group points up

L in hawroth projection

CH₂OH group points down

monosaccharide naming

prefiex: ado/keto

root: #, tri, tetra, pent, hex

suffix: ose

sphingomyelin

@C1- O carries a phosphate head group with choline

gangliosides

FA + sphingosine+ sialic acid and other sugars

glycerolphospholipid

sphingosine + phatty acid + phosphate head group