Carbohydrate Metabolism (Ivanov) Flashcards
Caries is the progressive destruction of mineralized tissues of the teeth (enamel, dentin, and cementum) initiated by ______ activity on ______ dietary carbohydrates at the _______.
-Microbial -Fermentable -Tooth surface
Why is the molecular structure of carbohydrates important?
Structure determines whether it is fermentable
The only nutrients that can be absorbed directly.
-Water -Inorganic salts -Vitamins -Certain lipids
______ is the hydrolysis of complex foodstuffs to simpler components.
Digestion
______ is the process by which the products of digestion are transported from the lumen of the intestine into the intestinal epithelial cells (and ultimately the circulatory system).
Absorption
The pH of saliva is…
Close to neutral pH (6.4 - 7.3)
Saliva moistens food. Particularly important are _____ which are glycoproteins which are approximately 60% by weight carbohydrate; very viscous and help disperse the solid into a form that can be more readily digested.
Mucins
Saliva contains ______, which initiates the hydrolysis of glycogen and starches by catalyzing the hydrolysis of a-1,4 glycosidic bonds.
Amaylase
Why do carbohydrates play a dominant role (compared to other nutrients) in caries formation?
- Readily available (most of energy)
- Simple carbohydrates can be directly absorbed by bacteria in the mouth
- Amaylase helps to release mono- and disaccharides from complex polysaccharides
- Acid is released during carb. fermentation by mouth microbes
- Sucrose is used in the synthesis to exopolysaccharides, a key component of bacterial biofilms
Carbohydrate processing enzymes secreted by S. mutans
Movement down a concentration gradient; requires neither a membrane “transporter” nor a source of energy (such as ATP or an ion gradient)
Simple Diffusion
Movement down a concentration gradient; requires a membrane “transporter”, but not a source of energy (such as ATP or an ion gradient)
Facilitated Transport
Movement against a concentration gradient; requires both a membrane “transporter” and a source of energy (such as ATP or an ion gradient)
Active Transport
Can carbs be absorbed by simple diffusion?
No
Modes of active transport of sugars in S. mutans
Breakdown, capture “energy” in various biochemical intermediates or “carriers”
Catabolic Processes
Synthesis, expend “energy” in various biochemical intermediates or “carriers” to enable biosynthesis
Anabolic Processes
ATP synthesis ______ significant free energy; ATP hydrolysis ______ significant free energy. ATP is the universal short-term storage of chemical energy in biology.
-Requires -Yields
Reactions in which there is a net transfer of electrons from one species to another.
Reduction-Oxidation (Redox)
The species that gives up electrons
Reductant
The species that takes up electrons
Oxidant
Pyridine Nucleotides
NAD+/NADH NADP+/NADPH
Glycolysis pathway splits glucose into _______.
Two molecules of pyruvate
Pyruvate is converted to _______ by ______.
-Acetyl-CoA -Pyruvate dehydrogenase complex
In the Citric Acid Cycle the acetyl group of Acetyl-CoA is converted into ____ and the energy is harvested by converting ____ to ______.
-CO2 -NAD+ to NADH
The Electron Transfer Chain and the Oxidative Phosphorylation pathways pass electrons from ______ to _____ and use the energy to synthesize ATP.
NADH to oxygen
Glycolysis under anaerobic conditions
Pyruvate is converted to lactate which is excreted from cells as lactic acid
Phosphoglucoisomerase
-Reversible reaction (means that ΔGo´ is close to 0) -F-6-P is NOT irreversibly “committed” to the glycolytic pathway
Phosphofructokinase (PFK)
-Irreversible reaction; catalyzes the “committed” step in the pathway -Important regulatory enzyme; regulated allosterically in the following manner: -Stimulated by AMP and ADP -Inhibited by ATP and Citrate
Pyruvate Kinase
-Irreversible reaction (ΔGo´ = -7.5 kcal/mol). Thermodynamically this “pulls” the series of reactions from F-1,6-bisP to pyruvate -Regulates the pathway -Activated by AMP, ADP, F-1,6-bisP -Inhibited by ATP
Glucan synthesis by ______ is required for biofilm formation.
Glycosyltransferases
Secreted ftf and fruA enzymes may be used by S. mutans to ________ in the biofilm
Store carbohydrates
