How Cell Obtain Energy from Food Flashcards
Why would cell need to carry out the oxidation of sugar in a stepwise manner?
To prevent a large amount of energy from being released all at once
What are the three stages of catabolism?
- Digestion
- Glycolysis
- Citric Acid Cycle and Oxidative Phosphorylation
What happens in digestion?
Enzymes convert the large polymeric molecules in food into simpler monomeric subunits, outside of the cell, inside the intestine
What happens in glycolysis?
Each molecule of glucose is split into two molecules of pyruvate.
Where does glycolysis occur?
Cytosol
What does glycolysis yield?
- 2 NADH per glucose
- 2 ATP
-2 Pyruvate per glucose
How does glycolysis work?
- Glucose is phosphorylated with ATP by hexokinase to form a new sugar (glucose 6-phosphate).
- Glucose will rearrange itself into fructose and is phosphorylated with ATP again with phosphofructokinase. At this point, glucose has two phosphate group
- The sugar is cleaved into two 3-carbon molecule (only the glycerldehyde 3-phosphate will proceed)
4.The aldehyde will oxidize to a carboxylic acid, releasing energy which some is stored in NADH and some is used to convert ADP to ATP. At this point, the sugar only has one phosphate group.
5.The remaining sugar is catalyzed by pyruvate kinase by extracting a phosphate group, forming ATP and pyruvate
What happens to pyruvate under anaerobic condition?
Under anaerobic condition, the pyruvate is converted into products through fermentation that are excreted into the cell:
- lactase in muscle cell or
- ethanol and CO2 in yeast cell
What is fermentation?
Energy-yielding pathways that break down sugar in the absence of oxygen
- Pyruvate breaks down to lactase in muscle cell
- Pyruvate breaks down to CO2 and ethanol in yeast cell
What happens to pyruvate under aerobic condition?
The pyruvate is pumped into the mitochondrial matrix where it is oxidized by the pyruvate dehydrogenase complex into acetyl CoA, CO2, and NADH.
What oxidizes pyruvate in aerobic condition?
pyruvate dehydrogenase complex
Where does pyruvate dehydrogenase complex oxidizes pyruvate?
Mitochondria
What does pyruvate dehydrogenase complex produce from oxidizing pyruvate?
acetyl CoA and CO2
What is a pyruvate dehydrogenase complex
a large 3-enzyme complex that oxidize pyruvate into CO2 and acetyl CoA
Besides the pyruvate dehydrogenase complex, how else are acetyl CoA formed?
Fatty acids and amino acids in the mitochondria
What does fatty acid breakdown yield?
1 Acetyl CoA
2 NADH
1 FADH2
If oxygen is not used in the kreb cycle, why is oxygen still needed?
Oxygen is the final electron acceptor, which allow for oxidative phosphorylation. Oxygen accepts electron which allows electron to be passed on, maintaining the hydrogen pumping that produces ATP.
What is an activated carrier?
Small organic molecules that contain one or more energy-rich covalent bonds. In a cell setting, cells used activated carrier to carry out unfavorable reaction.
How does GTP convert to ATP?
Nucleoside diphosphokinase
What is the citric acid cycle?
a chain of reactions occurring in the mitochondria, through which almost all living cells produce energy in aerobic respiration.
What happens in the citric acid cycle?
- Citrate Synthase
- Two carbons from acetyl CoA to oxaloacetate to form citrate. - Release of Carbon Dioxide
- Two molecules of CO2 are released; acetyl CoA oxidized into CO2 - Malate Dehydrogenase; Oxaloacetate is regenerated
- Malate molecule is oxidized into oxaloacetate and the produced oxaloacete will enter into the next cycle with the next acetyl coA
What does the citric acid cycle yield?
-1 GTP
-1 FADH2
-3 NADH
What is oxidative phosphorylation?
chemical energy captured by the activated carriers produced during glycolysis and the citric acid cycle is used to generate ATP
What is oxidative phosphorylation?
chemical energy captured by the activated carriers produced during glycolysis and the citric acid cycle is used to generate ATP
