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Biochemistry 1 - Week 1

Terms in this set (143)

..., fatty acids and glycerol to acetyl CoA, a metabolic process that breaks down ingested fats into fatty acids and glycerol and then into simpler compounds that can be used by cells of the body, Triglycerides can be hydrolyzed to glycerol & fatty acids (can be run thru Kreb's), gylcerol is converted into pyruvate, which enters the kreb cycle, fatty acids are broken down into 2 C fragments by beta oxidation, then 2 C pieces enter the Kreb cycle, Most efficient form of storage: more cals per gram so good for storage. Fatty acids used to produce ATP or glucose. Ketones are produced when liver degrades fatty acids (too may=acidosis from starvation or lg amt of fat breakdown), Primarily energy foods. If cells have inadequaet glucoe from carb they use fats. Fats are converted to a form of glucose in this case and enters the citric acid cycle. Fats not needed for catabolism are stored as adipose (fat) tissue., Lipids are broken down in to fatty acids and glycerol. Fatty acids are further broken down via beta oxidation. These can enter Krebs cycle for further digestion producing NADH and FDHA2 to be processed through the electron transport chain, Liver is involved in this which includes hydrolysis of triglycerides using the glycerol for glycolysis and the fatty acids for beta-oxidation, synthesis of most lipoproteins, major site for converting excess carbs and proteins into FAs and TGs (exported and stored in adipose) and synthesis of large quantities of cholesterol and phospholipds some packaged as lipoproteins and made available to the rest of the body where as the rest are excreted in bile.
..., → Insulin is composed of two chains held together by disufide bonds. Insulin is synthesized in significant quantities only in beta cells in the pancreas. The insulin mRNA is translated as a single chain preproinsulin, and removal of its signal peptide during insertion into the endoplasmic reticulum generates precursor called proinsulin., high blood glucose leads to (3),
Insulin Release - Stimulated when blood glucose concentration becomes too high. As blood glucose level concentration falls, this release is inhibited, in respone to carbohydrates and proteins, inhibits Hunger Center and increases POMC release from the Satiety center., *High Blood glucose (main stimulus)

*High blood amino acids

*High blood fatty acid

*Glucose-dependant Insulinotropic peptide (GIP)
-A hormone released into the digestive system in response to glucose in the digestive tract, *Low blood glucose

*Low blood amino acids

*Low blood fatty acids

*Somastatin (released by the delta cells of the pancreas), Insulin inhibits glucagon secretion, especially if there's high glucose, (1) cephalic stage - sensory stimuli from food evoke conditioned release of insulin in anticipation of glucose arrival (2)digestive phase - food enters intestives which causes release of gut hormones which stimulate pancrease to produce insulin (3) absorbitive phase- glucose enters bloodstream and cells on liver called glucodetectors detect it and signal the pancreas to release insulin, Glucose enters the β-cells through the glucose transporter GLUT2
Glucose goes into glycolysis and the respiratory cycle, where multiple high-energy ATP molecules are produced by oxidation
Dependent on the ATP:ADP ratio, and hence blood glucose levels, the ATP-dependent potassium channels (K+) close and the cell membrane depolarizes
On depolarization, voltage controlled calcium channels (Ca2+) open and calcium flows into the cells
An increased calcium level causes activation of phospholipase C, which cleaves the membrane phospholipid phosphatidyl inositol 4,5-bisphosphate into inositol 1,4,5-triphosphate and diacylglycerol.
Inositol 1,4,5-triphosphate (IP3) binds to receptor proteins in the membrane of endoplasmic reticulum (ER). This allows the release of Ca2+ from the ER via IP3 gated channels, and further raises the cell concentration of calcium.
Significantly increased amounts of calcium in the cells causes release of previously synthesized insulin, which has been stored in secretory vesicles, most impt regulator - blood glucose

beta cells - glucose taken up (GLUT2) and used to make ATP
- ATP sensitive K channel: opens (hyperpolarizes) with low ATP, closes (depolarizes) with high ATP
- depolarizing cell - releases insulin, in response to HIGH glucose levels, the BETA cells in the pancreas stimulate the uptake of glucagon by the GLUT2 transporter producing a rise inf ATP:ADP ratio; causing the inactivation of the potassium channel that depolarizes the membrane allowing calcium to flow in causing release of insulin, Made in response to ATP from glucose metabolism- closes K+ channels and depolarizes cells- thus causing an influx of Ca and vesicle release

Starts as a long chain; C-peptide is removed from pro-insulin and the final structure is an alpha and beta chain connected by disulfide bonds
..., The formation of ketones from the excess products of lipid breakdown, formation of ketone bodies instead of acetyl CoA from fatty acids, This is the synthesis of ketone bodies from acetyl CoA, formation of ketone bodies from acetyl co-enzyme-A in liver; ketone bodies can be a secondary energy source for heart & kidneys, this pathway occurs in the liver yields an alternative fuel source for skeletal and cardiac muscle, brain, nerves, renal cortex. Generally only active under fasting conditions when acetyl CoA is in abundance due to FA metabolism. The abundance of acetyl CoA is converted to 3-hydroxybutyrate., stimulated by glucagon, Ketone body formation in liver, oxidation (removes electrons), making ketone bodies from acetyl coa when there is inadequate glucose in the cells, increased as a result of lypolysis in the liver, In liver. Acetyl Coa + Acetoacyl Coa > HMG CoA > acetoacetate + Acetyl Coa; acetoacetate (rdxn; NADH)> β-hydroxybutyrate; Some acetoacetate sponateously > acetone, Mitochondrial Matrix of Liver cells.
In response to low glucose levels in the blood, and after exhaustion of cellular carbohydrate stores, such as glycogen (e.g. Fasting, Diabetes Melitus)

The production of ketone bodies is then initiated to make available energy that is stored as fatty acids. Fatty acids are enzymatically broken down in β-oxidation to form acetyl-CoA.
Under normal conditions, acetyl-CoA is further oxidized in the citric acid cycle (TCA cycle).
However, if the amounts of acetyl-CoA generated in fatty-acid β-oxidation challenge the processing capacity of the TCA cycle or if activity in the TCA cycle is low due to low amounts of intermediates such as oxaloacetate, acetyl-CoA is then used instead in biosynthesis of ketone bodies via acetoacetyl-CoA and β-hydroxy-β-methylglutaryl-CoA (HMG-CoA).

Besides its role in the synthesis of ketone bodies, HMG-CoA is also an intermediate in the synthesis of cholesterol.
..., another name for cellular respiration, Body's preferred energy source=glucose. most tissues/organs able to use other forms of ATP production (except brain/NS bc it cannot use fats/proteins to make ATP and cant store glucose), Body uses both glucose (MAIN fuel) and fats (between meals) for fuel. Brain can't burn fats, so constant glucose needed there. Glucagon is released from pancreas to initiate secretion of glycogen from liver and convert to glucose. Epinephrine also has glucagon-like effect and causes further release of glycogen from liver., Adipose & muscle cells possess insulin receptors on the cell membrane that bind to insulin & activate glucose transporters. These transporters facilitate the diffusion of glucose. The presence of insulin stimulates the diffusion of glucose into adipose & muscle tissue., Glycolysis- converts glucose to pyruvate (10 steps)


Three possible fates for pyruvate
- With oxygen --> aerobic oxidation
- Without oxygen --> anaerobic homolactic fermentation
-Without oxygen in yeast -->anaerobic alcoholic fermentation

****Energy is captured at different specific steps, increase uptake of glucose,
increase glycolysis
increase gluconeogenesis
increase glucose absorption, Yields 2NADPH and 1 ATP per Glucose., • After a meal, glucose is taken up from the portal venous blood by the liver and converted into glycogen, which is stored in the hepatocytes
• Subsequently, the glycogen is converted back to glucose (glycogenolysis) and released as needed into the bloodstream to maintain normal levels of blod glucose, 1. Crosses cell membrane and is absorbed via facilitated diffusion
2. Glycolysis—hexokinase (enzyme) converts glucose into G-6-P; now it cannot cross back over the cell membrane. It is trapped
3. Glycolysis continues—phosphoglucoisomerase (enzyme) converts G-6-P to fructose -6-P. Not it can be released from the cell
..., a metabolic process that breaks down ingested fats into fatty acids and glycerol and then into simpler compounds that can be used by cells of the body, liver is responsible for this; fat storage (manufactures cholesterol), primarily energy foods, catabolized for energy. catabolized if glucose supplies inadequate., Triglycerides can be hydrolyzed to glycerol & fatty acids (can be run thru Kreb's), gylcerol is converted into pyruvate, which enters the kreb cycle, fatty acids are broken down into 2 C fragments by beta oxidation, then 2 C pieces enter the Kreb cycle, Most efficient form of storage: more cals per gram so good for storage. Fatty acids used to produce ATP or glucose. Ketones are produced when liver degrades fatty acids (too may=acidosis from starvation or lg amt of fat breakdown), are primarily an energy food converted to glucose by catabolism.
exceso is anabolized by adipose tissue.
LIPASE enzyme digests LIPID., Fat is found in muscle and in adipose tissue
Fat is also available in lipoproteins (VLDL and Chylomicrons)
HSL stimulated via epinephrine, norepinephrine and glucagon
Fatty acids are transported across mitochondrial inner membrane via carnitine involved transport system
, liver cells use fats to make ATP for their own cells use. some to make thromboplastin ( clotting protein). some to make cholesterol. then releases in bloodstream, Liver is a major storage of lipids
Myelin sheath
Phospholipids for cell membrane
Cholesterol makes vitamin D, Advantages
- Unlimited supply of fat in the body (for energy, vitamin storage, hormone production and transport, temperature regulation, etc.)
- Not associated with production of lactic acid

Disadvantages
- Requires sufficient oxygen, can only be metabolized using the aerobic energy system
- Cannot be tapped into w/o the presence of sufficient carbohydrate to get the "aerobic factory" working (you need glucose to tap into Fat)
..., The liver is involved in this, which includes synthesis of proteins, synthesis of non-essential amino acids, deamination and transamination of amino acids an removal of ammonia from body by urea synthesis., Synthesized proteins are actively transported across cell membranes, Proteins comprised of amino acids, limited storage of AAs (excess converted to fatty acids, ketones, glucose). Generally NOT used for energy production (only when other sources are not available), The liver is involved in this, which includes synthesis of proteins, synthesis of non-essential amino acids, deamination and transamination of amino acids an removal of ammonia from body by urea synthesis., proteins are broken down in to amino acids which then are converted to organic acids by means of deamination, decarboxylation or dehydrogenation., amino acids are either oxidized to produce ATP or used to synthesize new proteins. Excess dietary amino acids are not excreted but converted into glucose (gluconeogenesis) or triglycerides (lipogenesis), STEP 1:Proteolysis (make AAs) -> to liver for function (or energy if starving)
-excess to fatty acids/energy (TG)
STEP 2: deamination (Nitrogen made into urea)
STEP 3: enter TCA (pyruvate, oxaloacetate, acetyl CoA, deamination of amino acids-amino acids stripped of nitrogen-containing amino acid group resulting in ammonia and keto acid-keto acids create non-essential amino acids, used to make non essential amino acids, used to make other compounds like hormones, enzymes, neurotransmitters, lipoproteins, used for energy, deanimation, gluconeogenesis