Metabolism Flashcards
(32 cards)
What is the conversion of glycogen to glucose called
glycogenolysis
From glucose to three carbon chain (pyruvate)?
Glycolysis
From 3-C chain (pyruvate) to glucose?
gluconeogenesis
From glucose to glycogen?
Glycogenesis
Fatty acids are stored as?
triglycerides
Triglycerides can be broken down into?
fatty acids and glygerol
What do we get when we break down a fatty acid?
An acetyl Co-A (2 C chain) that can enter the citric acid cycle
A two carbon chain also be made into what (instead of entering the citric acid cycle)?
Fatty acid synthesis begins with acetyl-Co A. Because acetyl-Co A is the common intermediary for all aerobic catabolic pathways, fatty acids can be synthesized from excess carbohydrates or amino acids.
What is the primary use of amino acids in the body?
Synthesis of proteins. These are rarely used if other energy sources are available, only in starvation.
Which events occur at the mitochondria?
The citric acid cycle, which produces Coenzymes for the electron transport chain, also in the mitochondria. This process is aerobic (consuming oxygen and producing carbon dioxide).
In one sentence, what does the citric acid cycle do?
It transfers hydrogen atoms to coenzymes.
What feeds into the citric acid cycle?
Pyruvate. It gets cleaved into acetate, which gets converted into acetyl-CoA. Acetyl-CoA is what directly enters the citric acid cycle. We generate Coenzymes with Hydrogens that are ready to be fed into the electron transport chain.
Describe the events of the electron transport chain.
Coenzymes. 2 molecules of NADH or 1 molecule of FADH2. The hydrogen atoms are delivered to Coenzyme Q, which releases the H+’s but keeps the electrons to feed them into the cytochrome line up. Oxygen accepts the low energy electrons and with hydrogen ions, forms water. The entire purpose here is to create a concentration gradient of protons on the inter membrane space. When hydrogens flow down their gradient into the mitochondrial space, they power an ATP synthase.
Where are the cytochromes physically located?
Embedded in the inner membrane space of the mitochondrion.
What is the preferred substrate for catabolism and ATP production under resting conditions?
Carbohydrates
What are the first steps in the breakdown of carbohydrates?
Salivary amylase breaks down complex carbohydrates into di and trisaccharides. This form of amylase breaks down by the time it hits the stomach acid. When chyme arrives at the duodenum, secretin stimulates the release of buffers that shift the pH up. CCK gets released and this triggers the secretion of pancreatic enzymes, including pancreatic alpha-amylase, which is not as wimpy.
What happens to the disaccharides in the chyme as they enter the duodenum/jejunum?
They trigger the release of GIP, which stimulates insulin release by the pancreas. The cells at the jejunum finish the digestion of carbs. Those cells utilize the enzymes maltase, sucrase, and lactase to convert the disaccharides into monosaccharides. The sugars then diffuse into the capillaries for transport to the liver.
What happens when the simple sugars reach the liver?
They are absorbed here and if needed, converted into glucose. The glucose is released into the blood to maintain normal glucose levels of about 90. Excess is stored as glycogen or used in other ways.
How does glucose enter cells for catabolism?
It requires a carrier protein which must be stimulated by insulin. Inside the cell, the glucose can be converted into ribose, if needed. For energy, it is broken down into pyruvate through glycolysis.
What is the first step of glucose metabolism in the cell?
Glycolysis.
Describe glycolysis.
We start with 6 carbon glucose. It gets split in the process. We generate some coenzymes along the way. Glycolysis uses energy to make energy, but at the end of glycolysis proper, we net 2 ATP. However, after the products from glycolysis go through the citric acid cycle and oxidative phosphorylation, the we net 36 ATP per glucose molecule.
In one sentence, how do lipids reach the bloodstream?
Lipid reach the bloodstream in chylomicrons; the cholesterol is then extracted and released as lipoproteins
What are the very first steps in digesting lipids?
Our saliva contains lingual lipase. This breaks triglycerides into monoglycerides and fatty acids. Sadly, the mixing of chyme in the stomach creates large drops containing a variety of lipids. Lipase can only act on the surface of the drops. Only 20% get broken down by the time we leave the stomach.
How does fat get processed at the level of the duodenum?
When chyme reaches the duodenum, CCK is released, triggering the secretion of pancreatic enzymes, including pancreatic lipase and stimulation gallbladder contraction and ejection of bile into the duodenum. Now bile salts from the bile break the large lipid drops into tiny droplets (emulsification). Pancreatic lipase can now more effectively break apart the triglycerides to form a mixture of fatty acids, monoglycerides, and glycerol. They form little lipid bile salt complexes called micelles.
