Applied Biochemistry – Unit 1: Carbohydrates

These vocabulary flashcards cover core definitions, key molecules, enzymes, hormonal regulators, metabolic pathways, disorders and diagnostic tests related to carbohydrate digestion, absorption, metabolism and associated clinical conditions presented in the lecture notes.

Carbohydrate

Most abundant biological macromolecule; polyhydroxy aldehyde or ketone with empirical formula (CH₂O)ₙ, serving as energy source, storage and structural component.

Monosaccharide

Simplest carbohydrate containing one sugar unit that cannot be hydrolyzed to smaller carbohydrates (e.g., glucose).

Disaccharide

Carbohydrate composed of two monosaccharide units joined by a glycosidic bond (e.g., sucrose).

Oligosaccharide

Carbohydrate containing 3–9 monosaccharide residues; examples include ABO blood group antigens.

Polysaccharide

Complex carbohydrate with ≥10 monosaccharide units arranged in linear or branched chains (e.g., starch, glycogen).

Glucose

Primary monosaccharide used by cells for energy; blood sugar regulated by insulin and glucagon.

Fructose

Fruit sugar; a ketohexose absorbed via GLUT5–mediated facilitated diffusion.

Galactose

Monosaccharide converted to glucose in the liver; component of lactose.

Sucrose

Table sugar; disaccharide of glucose + fructose hydrolyzed by sucrase.

Lactose

Milk sugar; disaccharide of glucose + galactose hydrolyzed by lactase.

Maltose

Disaccharide of two glucose units produced during starch digestion; hydrolyzed by maltase.

Raffinose

Trisaccharide (oligosaccharide) composed of galactose–glucose–fructose.

Stachyose

Tetrasaccharide oligosaccharide found in legumes; galactose–galactose–glucose–fructose.

Starch

Plant storage polysaccharide of amylose and amylopectin; first digested by amylases.

Glycogen

Highly branched animal storage polysaccharide; broken down by glycogenolysis.

Cellulose

Structural polysaccharide of β-1,4-linked glucose in plant cell walls; indigestible to humans.

Salivary α-amylase

Enzyme in saliva initiating starch digestion to maltose and dextrins in the mouth.

Pancreatic α-amylase

Enzyme secreted into small intestine that continues starch and glycogen digestion.

Sucrase

Intestinal disaccharidase that splits sucrose into glucose and fructose.

Maltase

Brush-border enzyme that hydrolyzes maltose into two glucose molecules.

Lactase

Intestinal enzyme that hydrolyzes lactose into glucose and galactose.

Active Transport

Energy-requiring movement of substances against concentration gradient; glucose & galactose uptake via SGLT1.

Facilitated Diffusion

Carrier-mediated transport down a concentration gradient; fructose uptake via GLUT5.

SGLT1

Sodium-glucose linked transporter 1; actively co-transports glucose/galactose with Na⁺ into enterocytes.

GLUT5

Facilitated fructose transporter on intestinal apical membrane.

Glycolysis

Cytoplasmic pathway converting glucose to pyruvate with net gain of 2 ATP and 2 NADH.

Citric Acid Cycle

Mitochondrial cycle oxidizing acetyl-CoA to CO₂, generating NADH, FADH₂ and GTP/ATP.

Glycogenesis

Synthesis of glycogen from excess glucose for storage in liver and muscle.

Glycogenolysis

Breakdown of glycogen to glucose-1-phosphate (and ultimately glucose) during fasting or exercise.

Gluconeogenesis

Formation of new glucose from non-carbohydrate precursors (e.g., amino acids, lactate) mainly in liver.

Lipogenesis

Conversion of excess glucose to fatty acids for triglyceride storage in adipose tissue.

Insulin

β-cell pancreatic hormone that lowers blood glucose by promoting uptake and glycogenesis.

Glucagon

α-cell pancreatic hormone that raises blood glucose via glycogenolysis and gluconeogenesis.

Epinephrine

Adrenal medulla hormone that stimulates glycogen breakdown and increases blood glucose during stress.

Hyperglycemia

Abnormally high blood glucose; characteristic of diabetes mellitus.

Hypoglycemia

Abnormally low blood glucose (<70 mg/dL) producing symptoms like tremor, hunger, sweating.

Diabetes Mellitus Type 1

Autoimmune destruction of β-cells leading to absolute insulin deficiency; requires insulin therapy.

Diabetes Mellitus Type 2

Insulin resistance and relative insulin deficiency; managed with lifestyle, oral agents, ± insulin.

Glucose Tolerance Test (GTT)

Assessment of body’s ability to handle glucose load; includes OGTT and IVGTT.

Oral Glucose Tolerance Test (OGTT)

Standard test where 75 g oral glucose is given and blood glucose measured over 2–3 h.

Intravenous GTT (IVGTT)

Glucose injected (0.5 g/kg) IV with rapid blood sampling to evaluate insulin sensitivity.

Glucose Challenge Test (Mini GTT)

50 g oral glucose screening for gestational diabetes with 1-hour post-load measurement.

HbA1c Test

Measures percentage of glycated hemoglobin reflecting average blood glucose over previous 3 months.

Renal Threshold for Glucose

Blood glucose level (~160–180 mg/dL) above which glucose begins to appear in urine.