Chapter 9 Metabolism Flashcards
Definition of metabolism
Entire net work of chemical processes involved in maintaining life.
Metabolism pathway
A group of biomedical reactions that occur in the progression from beginning to end.
Intermediate
Compounds formed in the pathway.
Two categories of pathways
Anabolic(合成) and catabolic(分解)
What does metabolism do?
Releas new use energy from carb, alcohol, fat and protein. Synthesis new substances from another and prepare waste products for excretion.
The balance of anabolic and catabolic
Bodies strives to keep the balance. But sometimes one is more prominent than the other. Eg. During the growth, new compounds are synthesized(Anabolic), but during the weight loss or wasting disease(cancer), compounds are broken down(Catabolic).
Where is the energy initially come from?
Sun
adenosine triphosphate (ATP)
Body’s source of energy derived from catabolic reactions of macronutrients.
What can energy in ATP do?
Only the energy in ATP can directly use to synthesize new compounds, contract muscles, conduct nerve impulses, and pump ions across the membranes.
Structure of a ATP molecule
Consists of the organic compound adenosine bound to 3 phosphate groups.
High-energy phosphate bonds
The bonds between he phosphate groups contain energy.
Adenosine diphosphate (ADP)
To release the energy in ATP, cells break a high energy phosphate bonds and create a ADP plus Pi and a free phosphate group
Adenosine monophosphate (AMP)
Hydrolysis of ADP happens in the AMP.
Recycling of ATP
ATP is regenerated by adding phosphate back to AMP and ADP.
The recycling of ATP
A cell is constantly breaking down ATP for energy, then
rebuilding it to maintain a constant supply of fuel for the body .
Why the recycling of ATP is essential survival strategy?
Because the body contains only about 0.22 lb (100 g) of ATP at any given time, but a sedentary adult breaks down and resynthesizes about 88 lb (40 kg) of ATP each day. And an additional 66 lb (30 kg) of ATP are broken down and resynthesized when people do exercises.
Oxidation-Reduction Reactions氧化还原
Key Processes in Energy Metabolism.
Oxidized and Reduced
失电子是Oxidized，得电子是Reduced
If the compound gains oxygen or loses hydrogen, it has been oxidized.
If it loses oxygen or gains hydrogen, the compound has been reduced.
The synthesize of ATP from ADP and AMP
Involves the exchange of e-,(H+ from energy yielding compounds, fat, protein, carbs and alcohol) this process use Oxidation-Reduction reactions.
What controls OR reaction?
Enzymes.
Niacin and Riboflavin
Key Players in Energy Metabolism.
Two vitamin-Bs, assist dehydrogenase enzymes and play a role in transferring hydrogen ions from energy-yielding compounds to oxygen in the metabolic pathways of the cell.
Reaction between Pyruvate and Lactate
(Pyruvate)NAD+ —> NADH + H+ (Lactate)——> NAD+ (Pyruvate) Niacin plays as a coenzyme.
Role of riboflavin
Also as a coenzyme.
The ultimate driving force for life
The reduction of oxygen (O) to form water (H2O). Because it is vital to the way cells synthesize ATP.
Cellular respiration
ATP is generated through it. 细胞呼吸作用 The process oxidizes (removes electrons) food molecules to obtain energy(ATP).
Aerobic(厌氧的) and Anaerobic（需氧的）
When O2 is available, cellular respiration may be aerobic. When O2 is not present, CR is anaerobic.
Which is more efficient?
Aerobic respiration is far more efficient than anaerobic
metabolism at producing ATP. E.g. Aerobic R can gain 30-32 ATP from one glucose molecule, anaerobic can only gain 2 ATP.
4 stages for aerobic cellular respiration of glucose
Glycolysis. Transition reaction. Citric acid cycle. Electron transport chain.
Glycolysis
Glycolysis occurs in the cytosol of cells.
Transition reaction
Convert 3-carbon pyruvate to 2-carbon molecule acetyl CoA.
The transition reaction also produces NADH + H+ and releases carbon dioxide (CO2) as a waste product. These
molecules are transitioning from the cytosol into the mitochondria(线粒体) of cells where this reaction occurs.
Citric acid cycle
In this pathway, acetyl-CoA enters the citric acid cycle, resulting in the production of NADH + H+, FADH2, and ATP. Carbon dioxide is released as a waste product. Take place in mitochondria.
Electron transport chain
Most ATP is produced in the electron transport chain; thus, the mitochondria are the cell’s major energy-producing organelles.
2 roles of glycolysis
To break down carbohydrates to generate energy. To provide building blocks for synthesizing
other needed compounds.
During the glycolysis, how is the convert of glucose?
Glucose convert to 2 unit of 3-carbon compound called pyruvate.
The result of glycolysis
It need 2 ATP, but generates 4 ATP. Thus, yielding a net of 2 ATP.
Transition Reaction
When oxygen is present, the pyruvate dehydrogenase enzyme complex converts pyruvate into a 2-carbon compound called acetyl-CoA. The overall reaction is irreversible.
What happened during the transition reaction if someone is deficiency in pyruvate dehydrogenase?
This condition causes lactic acidosis, which causes many tissues, including the central nervous system, to malfunction.
What vitamins are involved in transition reaction?
Glycolysis only need B-vitamins. Transition reaction requires 4 B-vitamins: thiamin, riboflavin, niacin, and pantothenic acid.
Citric acid cycle
Also named as tricarboxylic acid cycle. (TCA cycle)
The citric acid cycle is a series of chemical reactions that cells use to convert the carbons of an
acetyl group to carbon dioxide while harvesting energy to produce ATP.
How many turns of CAC are needed to produce one glucose molecule?
2 turns. Because one glucose molecule need two acetyl-CoA to form.
What is the result of each complete turn of CAC?
Each complete turn of the citric acid cycle produces 2 molecules of CO2 and 1 potential ATP in the form of 1 molecule of guanosine triphosphate (GTP), as well as 3 molecules of NADH + H+ and 1 molecule of FADH2.
No oxygen participate.
Electron Transport chain
The final pathway aerobic respiration.
Cells need a lot of ATP has thousands of mitochondria, like muscle cells. But that need very little ATP, such as adipose cells, have fewer mitochondria. Almost 90% of the ATP produced from the catabolism of glucose is produced by the electron transport chain.
Oxidative phosphorylation
The way in which energy derived from the NADH + H+ and FADH2 is transferred to ADP + Pi to form ATP.
Copper and Iron in electron transport chain
Copper is a component of an enzyme, iron is a component of cytochromes in the electron transport chain.
Why we cannot live without oxygen?
it is a final acceptor of the electrons and hydrogen ions generated from the breakdown of energy-yielding nutrients. Without oxygen, most of our cells are unable to extract enough energy from energy-yielding nutrients to sustain life.
Anaerobic metabolism
Cells with mitochondria are capable of turning to anaerobic metabolism when oxygen is lacking.
Why anaerobic metabolism is not as efficiency as aerobic metabolism?
Because it converts only about 5% of the energy in a molecule of glucose to energy stored in the highenergy
phosphate bonds of ATP.
Anaerobic glycolysis pathway encompasses
Glycolysis and the conversion of pyruvate to lactate.
1-step reaction of anaerobic glycolysis pathway
Catalyzed by the enzyme pyruvate dehydrogenase, involves a simple transfer of a hydrogen from NADH + H+ to pyruvate to form lactate and NAD+.
The function of the reaction of anaerobic glycolysis pathway
Pyruvate + NADH + H+ → Lactate + NAD+
Which cells’s only way to form ATP is anaerobic glycolysis pathway?
For cells that lack mitochondria and therefore cannot use the electron transport chain and oxidative phosphorylation pathways
The final part of the anaerobic glycolysis pathway?
The NAD+ concentration falls too low to permit glycolysis to
continue.5 The anaerobic glycolysis pathway produces lactate to regenerate NAD+. The lactate produced by the
red blood cell is then released into the bloodstream, picked
up primarily by the liver, and used to synthesize pyruvate, glucose, or some other intermediate in aerobic respiration.
Cori cycle
During high-intensively exercises, they heavily rely on anaerobic glycolysis pathway to quickly supply ATP. Anaerobic glycolysis causes lactate accumulations and NAD1 regeneration, both of which allow anaerobic glycolysis to continue in the muscle. The lactate generated
is transported from the muscles to the liver, where it is converted to glucose, which can then be returned to the muscles. This process is known as the Cori cycle.
ATP production from fat
Fat is dense of energy. Also happens in mitochondria.
ATP production from fat is promoted by
Glucagon, growth hormone, and epinephrine.
Energy from fat and glucose
9kcal/g and 4kcal/g
