Carbohydrates, Lipids and Biological Membranes: every key term you need (+ practice quiz)
25 flashcard terms for Biochemistry Topic 5, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 8-question quiz — free, no account needed.
A single sugar unit classified by carbonyl type and carbon count. In solution most cyclize, and the resulting ring is what participates in linkage chemistry.
Anomeric carbon
The carbonyl carbon that becomes a new chiral centre on ring closure. Its configuration distinguishes the two anomers and determines glycosidic bond geometry.
Mutarotation
The spontaneous interconversion of anomers through the open-chain form, which is why a freshly dissolved pure anomer drifts to an equilibrium mixture.
Reducing sugar
A sugar with a free anomeric carbon that can open to an aldehyde and reduce an oxidizing reagent. Blocking that carbon in a glycosidic bond removes the property.
Glycosidic bond
The acetal linkage joining a sugar's anomeric carbon to another group. Its orientation and position define which enzymes can hydrolyse the polymer.
Starch
A plant storage polymer of glucose in one linkage orientation, made of a linear component and a branched one. Human digestive enzymes cleave both.
Glycogen
The animal storage polymer of glucose, more heavily branched than starch. Branching multiplies the non-reducing ends where degradation enzymes act, so mobilization is fast.
Cellulose
A structural glucose polymer whose alternate linkage orientation produces straight chains that hydrogen bond into rigid fibres and resist human digestive enzymes.
Glycoprotein
A protein carrying covalently attached sugar chains, usually added in the secretory pathway. The chains influence folding, stability, targeting and cell recognition.
Proteoglycan
A protein heavily substituted with long negatively charged sugar chains that hold water, giving cartilage and extracellular matrix their resistance to compression.
Fatty acid
A long hydrocarbon chain ending in a carboxyl group. Chain length and degree of unsaturation set melting point and therefore membrane fluidity.
Saturated versus unsaturated
Saturated chains pack tightly and raise melting point; each cis double bond puts a kink in the chain that disrupts packing and keeps the lipid fluid at lower temperature.
Triacylglycerol
Three fatty acids esterified to glycerol. Being fully reduced and anhydrous, it stores far more energy per gram than glycogen, which is stored hydrated.
Phospholipid
A glycerol or sphingosine backbone carrying two nonpolar tails and a phosphate-linked polar head. Its amphipathic shape drives spontaneous bilayer formation.
Sphingolipid
A membrane lipid built on sphingosine rather than glycerol. Its variants include the sugar-bearing lipids concentrated on the outer face of the plasma membrane.
Cholesterol
A rigid four-ring lipid that inserts between phospholipid tails. It broadens the phase transition, reducing fluidity at high temperature and preventing tight packing at low temperature.
Lipid bilayer
A two-layer sheet with tails inward and heads facing water. It self-seals and is essentially impermeable to ions and large polar molecules.
Fluid mosaic model
Describes the membrane as a two-dimensional fluid in which lipids and proteins diffuse laterally while flipping across the bilayer is rare without help.
Flippase
An enzyme that uses energy to move specific phospholipids between leaflets, maintaining the asymmetric distribution that marks a healthy cell.
Integral membrane protein
A protein embedded in the bilayer, usually through hydrophobic helices, and removable only with detergent that disrupts the membrane.
Peripheral membrane protein
A protein bound to the membrane surface by electrostatic or lipid-anchor interactions, released by changes in salt or pH without dissolving the bilayer.
Simple diffusion
Unassisted movement down a concentration gradient, restricted to small nonpolar molecules such as oxygen and carbon dioxide.
Facilitated diffusion
Protein-assisted movement down a gradient. It shows saturation and substrate specificity like an enzyme but consumes no energy.
Primary active transport
Moves a solute against its gradient using energy released directly by nucleotide hydrolysis, as the sodium-potassium pump does.
Secondary active transport
Moves one solute against its gradient by letting another run down the gradient built by a primary pump, coupling the two in the same or opposite direction.