3.5 Physiology of the GI Tract- Cell Metabolism Flashcards
Metabolism
a set of chemical reactions that are essential for the body to sustain life
Anabolism
the set of reactions in which smaller molecules are combined to make larger, more complex molecules
Catabolism
the set of reactions in which larger molecules are broken down to be used as energy sources for the body
Adenosine triphosphate (ATP)
Most widely used form of energy in the cells
- ATP has energy to donate
Adenosine diphosphate (ADP)
- one less phosphate group than ATP
- ADP can accept energy (phosphate group) to become ATP
Cellular respiration
the process by which cells generate ATP
Aerobic respiration
- function that most organisms carry out
- requires oxygen and a fuel (glucose)
- releases carbon dioxide, water, and ATP
Carbohydrates
- main source of energy for cells with the body
- digests carbohydrates into glucose
Glucose metabolism
- used by the body primarily during high energy demands
- glucose is one of the most abundant biomolecules
- the catabolism of glucose is an important metabolic pathway used by microorganisms for ATP production
- complete catabolism of a single molecule of glucose (C6H12O6) yields up to 38 ATP with three distinct transitions:
- glycolysis
- cellular respiration
- the electron transport chain
Glycolysis
- process of breaking down a 6-carbon molecule of glucose into two 3-carbon molecules of pyruvate
- process yields 2 molecules of ATP per molecule of glucose
Cellular respiration
- an aerobic process (oxygen must be present)
- used by cells to produce energy
Tricarboxylic acid (TCA cycle)
- also known as the Krebs Cycle or the citric acid cycle
- central pathway of respiration
- pyruvic acid (product of glycolysis) is converted to carbon dioxide forming 2 ATP
- (one ATP for each pyruvate processed) and an abundance of electron carriers: NADH and FADH2
- primary function of TCA cycle is the production of NADH & FADH2
- transfer of NADH & FADH2 will fuel the generation of ATP via the electron transport system
Mitochondria
Respiration takes places in and around this double sided organelle
Fermentation
Takes place in the absence of oxygen
Electron transport chain
continuation of cellular respiration
Complete catabolism of glucose
yields 2 ATP from glycolysis, 2 ATP from the TCA cycle and 34 ATP from the electron transport system, for a total of 38 ATP from a single glucose molecule
Proton motive force
- drives H+ back through the ATP synthase complex
- located in the membrane
- production of up to 34 molecules of ATP
Lipid metabolism
- occurs in the liver by a process known as beta-oxidation
- used by the body primarily during low energy activities
- yields twice the amount of ATP than when a carbohydrate or protein is broken down
Protein metabolism
- only takes place when carbohydrates and fats are unavailable to the body
- proteins are the building blocks for the cells
- saved as a last resort
Ammonia
Product formed when protein is used for ATP as the amino group is removed from the protein
- harmful to the body and must be converted into a different form
- usually combined with CO2 in the liver to create urea
Urea
- ammonia + carbon dioxide combined in the liver
- excreted from the body in the urine
