Human Nutrition - Lectures 6 to 10 Flashcards

A set of practice vocabulary flashcards covering human nutrition, microbiology of the gut, glucose and lipid metabolism, and protein catabolism/excretion.

Continuous stirred-tank reactor (CSTR)

A type of chemical reactor model used to describe sections of the digestive tract where contents are mixed.

Plug-flow reactor (PFR)

A chemical reactor model that characterizes the digestive tract's function where reactants flow through without mixing.

Bacteroides thetaiotaomicron

A microbe found in the large intestine that digests complex polysaccharides using fermentative pathways.

Bacteroides fragilis

An OTU (Operational Taxonomic Unit) that regulates human regulatory T-cells; a lack of this microbe can lead to autoimmune problems.

Polysaccharide A

A molecule that allows Bacteroides fragilis to hijack certain biological processes in the large intestine.

Firmicutes

A group of microbes efficient at digesting carbohydrates and generating short-chain fatty acids (SCFA).

Bacteroidetes:Firmicutes ratio

A microbial metric that is typically lower in obese humans and rats compared to control subjects.

Formyltetrahydrofolate synthetase (FTHFS)

An enzyme involved in microbial fermentative pathways in the large intestine for the production of acetate.

Butyryl CoA transferase (BCoAT)

An enzyme in the microbial fermentative pathway responsible for the conversion of Butyryl CoA to Butyrate.

Human milk oligosaccharides (HMOs)

A significant part of breast milk (4-11%) that the baby cannot digest endogenously but serves as a prebiotic for Bifidobacterium.

Mesentery

A structure associated with the gut that is described as a 'new' organ; HMOs increase blood flow to it by upregulating Nitric Oxide Synthase.

Lateral hypothalamus

The brain region that acts as the Feeding Center, receiving input from the cortex and various peptides.

Ventromedial hypothalamus

The brain region that acts as the Satiety Center.

Glucostatic Theory

The hypothesis that glucose concentrations, insulin, and glucagon regulate feeding and satiety centers.

Lipostatic Theory

The hypothesis that adipose storage levels affect feeding and satiety centers, with adipocytokines like leptin allowing the satiety center to dominate as storage increases.

Neuropeptide Y (NPY)

An important neuropeptide that works to increase feeding behavior.

Ghrelin

A peptide sourced from the stomach that stimulates appetite.

Islets of Langerhans

Clusters of endocrine cells in the pancreas containing alpha, beta, and delta cells.

Beta cells ($\beta$-cells)

Pancreatic cells that secrete insulin and amylin.

Hexokinase

An enzyme with a $K_m \text{-glucose}$ of $0.15\text{ mM}$ that converts glucose to glucose 6-phosphate.

Glucokinase

A specific hexokinase found in the liver with a high $K_m \text{-glucose}$ of $20.0\text{ mM}$.

Glycogenesis

The process of forming glycogen from glucose, which costs $2\text{ mol } ATP$ for each glucose unit added.

Ketogenesis

The formation of ketone bodies, which increases during catabolic or fasted states when glucose is low.

Glycogenolysis

The breakdown of glycogen into glucose 1-phosphate, activated by glucagon binding to a G-protein coupled receptor.

PVT TIM HALL

A mnemonic for the essential amino acids: Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, and Lysine.

Type I Diabetes

A condition where pancreatic $\beta$-cells are destroyed by an autoimmune response, leading to a lack of insulin.

Type II Diabetes

A condition where insulin receptors are no longer responsive to insulin, though insulin production may be normal.

Acylcarnitine transporter

The system involving CAT 1 and CAT 2 (carnitine acetyltransferase) that grants fatty acyl CoA access to the mitochondrial matrix.

$\beta$-oxidation

The process of fatty acid breakdown by the removal of 2-carbon units at a time, resulting in $106\text{ ATP}$ from one molecule of palmitic acid ($16C$).

Malonyl CoA

A molecule formed during fatty acid synthesis from Acetyl CoA and $CO_2$ in a reaction requiring $ATP$.

Pentose Phosphate Pathway

A pathway active in the liver that yields $NADPH$ needed for fatty acid synthesis.

VLDL (Very Low Density Lipoproteins)

Lipoproteins synthesized in the liver to transport lipids to tissues; their remnants or excess cholesterol can suppress receptor synthesis.

Biological Value (BV)

The proportion of protein absorbed from food that is retained in the body; a value of $0.9\text{-}1.0$ for egg and human milk.

Transamination

The transfer of an amine group ($NH_3$) from an amino acid to a keto-acid, a process that requires Vitamin $B_6$.

Urea cycle

The multienzyme process occurring in the liver that packages excess ammonia into urea for excretion, utilizing ornithine as a carrier.