Carbohydrate Structure and Metabolism Overview

Carbohydrates

Primary energy source and structural components.

Cellulose

Structural carbohydrate in plant cell walls.

Glycoconjugates

Carbohydrates involved in cell signaling.

Carbonyl Group

Functional group determining ketose or aldose.

Fructose

Ketose form of glucose, an aldose.

Furanose

Five-ring structure of carbohydrates.

Pyranose

Six-ring structure of carbohydrates.

Ribose

Five-carbon sugar, a type of furanose.

D-Form

Most common enantiomer of carbohydrates.

Mutarotation

Interconversion between alpha and beta forms.

Alpha Anomer

Trans configuration of anomeric hydroxyl group.

Beta Anomer

Cis configuration of anomeric hydroxyl group.

Glycosidic Bond

Linkage between two sugar monomers.

Chiral Center

Carbon atom bonded to four different groups.

Hemiketals

Formed from cyclic ketoses.

Hemiacetals

Formed from cyclic aldoses.

Fischer Projection

2D representation showing chirality of sugars.

Haworth Projection

3D representation of cyclic carbohydrate structures.

Epimers

Diastereomers differing at one chiral center.

Mannose

Epimer of glucose differing at C2.

Galactose

Epimer of glucose differing at C4.

Lactose

Disaccharide of glucose and galactose.

Sucrose

Disaccharide of glucose and fructose.

Maltose

Disaccharide of two glucose units.

Dehydration Synthesis

Process linking sugar monomers by removing water.

Reducing End

End of sugar chain with free anomeric carbon.

Nonreducing End

End of sugar chain without free anomeric carbon.

Acetal

Formed from fusion of two monomers.

Polysaccharides

Carbohydrates made of multiple sugar units.

Homo- vs. Heteropolysaccharides

Consistency of monomer types in polysaccharides.

Linear vs. Branched Polysaccharides

Classification based on bonding patterns.

Branched polysaccharides

Contain C1-C4 and C1-C6 bonds.

Cellulose

Linear homopolysaccharide in plant cell walls.

Glycogen

Main energy storage molecule in plants.

Starch

Energy storage combining amylose and amylopectin.

Chitin

Homopolysaccharide in insect exoskeletons.

Glycoconjugates

Carbohydrates linked to macromolecules for functions.

Proteoglycans

Oligosaccharides linked to proteins for immune support.

Glycolipids

Carbohydrate-lipid complexes with specialized functions.

Lipopolysaccharides (LPS)

Glycolipids on gram-negative bacteria surfaces.

Gangliosides

Lipids with saccharide polar heads, blood-type determinants.

Glycoproteins

Proteins with carbohydrate attachments for various functions.

Peptidoglycans

Targets for antibiotics, found in bacterial cell walls.

Glycolysis

Process converting glucose to pyruvate, ten steps.

Energy investment phase

Initial phase of glycolysis consuming ATP.

Energy payoff phase

Phase producing 2 net ATP in glycolysis.

PFK-1

Enzyme phosphorylating F6P to form fructose-1,6-biphosphate. At this point, the product is committed in glycolysis to form pyruvate.

Cori cycle

Recycles lactate to glucose in the liver.

Anaerobic conditions

Lactic acid fermentation reduces pyruvate to lactate.

TCA cycle

Oxidizes pyruvate to CO2, generating NADH and FADH2.

Pyruvate dehydrogenase complex (PDC)

Converts pyruvate to acetyl-CoA for TCA cycle.

Acetyl-CoA

Not an intermediate, generated from pyruvate.

Pentose Phosphate Pathway

Generates NADPH and ribose-5-phosphate for nucleotides.

Glycogen metabolism

More complex for synthesis than for breakdown.

Glycogen synthase

Inhibited by phosphorylation, activated by insulin.

Acetyl-CoA

Coenzyme linked to acetyl group via thioester.

TCA Cycle

Series of reactions generating energy through oxidation.

NAD+/NADH

Two-electron carrier; fully reduced in reactions.

FAD+/FADH2

Two-electron carrier; can donate one electron.

Cofactors

Derived from vitamin B2 (riboflavin) and B3 (niacin).

Anaplerotic Reactions

Regenerate TCA cycle intermediates from precursors.

Pyruvate

Precursor that forms oxaloacetate and malate.

Pyruvate Dehydrogenase Complex

Activated by calcium, AMP/ADP; inhibited by ATP.

Citrate Formation

Activated by acetyl-CoA; inhibited by citrate.

Succinate Dehydrogenase Complex

Activated by succinate; inhibited by succinyl-CoA.

Mitochondrion Structure

Double-membraned organelle with inner and outer membranes.

Cristae

Folds of the inner mitochondrial membrane.

Proton Gradient

Created between mitochondrial matrix and intermembrane space.

Electron Transport Chain (ETC)

Four-complex chain creating a proton gradient.

Complex V (ATP Synthase)

Uses proton gradient to synthesize ATP.

Electron Carriers

Include NADH, FMN, FADH2, and ubiquinone.

Ubiquinone

Analogous to FAD+; can donate one electron.

Cytochromes

Heme-containing structures mobilizing electrons in ETC.

Iron-Sulfur Clusters

Rapidly transport electrons and protons in ETC.

Complexes I-IV

Donate 12 protons to intermembrane space.

Final Electron Acceptor

Oxygen reduces to water in Complex IV.

Oxidative Phosphorylation

Activated by oxygen and ADP; inhibited by ATP.

Coenzyme Q Deficiency

Reduces combined activity of Complexes I+III and II+III.

Hypoxia

Lack of oxygen causing reactive oxygen species formation.

Superoxide Dismutase

Converts superoxide radicals into hydrogen peroxide.

Catalase

Degrades hydrogen peroxide into oxygen and water.