Lecture 18: Metabolism & Nutrition Flashcards

Question

describe the electron transport chain (ETC)

Answer 1

-Made up of protein complexes in inner mitochondrial membrane *Where key reactions of oxidative phosphorylation occur -Protein complexes act as series of electron carriers from NADH and FADH2 *Each carrier is reduced by picking up electrons, and oxidized as it gives up electrons -ETC does not generate ATP directly *It breaks the large free-energy transferred from NADH and FADH2 to O2 into smaller steps that release energy in manageable amounts

Answer 2

-Chemiosmosis involves the use of energy in a proton (H+)gradient to drive cellular work -Energy released through ETC is used to pump proton (H+) from the mitochondrial matrix to the intermembrane space, generating a gradient→ proton-motive force -H+ then flow down their concentration gradient back across the inner membrane, through ATP Synthase synthase -ATP is generated using kinetic energy of passing hydrogen ions

Answer 3

-Flavin mononucleotide (FMN) – derivative of riboflavin (vit B2) -Cytochromes – heme group. Include cyt b, cyt c1, cyt c, cyt a, cyt a3 -Iron-sulfur centers -Copper atoms -Coenzyme Q

Answer 4

Inside the inner mitochondrial membrane, the carriers are clustered into 3 complexes, each acting as a proton pump that expels H+

Answer 5

-formation of glycogen from glucose -stored in skeletal muscle fibers and hepatocytes -stimulated by insulin scereted by pancreatic β-cells

Answer 6

-Breakdown of glycogen to reform glucose -In times of glucose deprivation – strenuous exercise, etc. -Stimulated by glucagon secreted by pancreatic alpha cells

Answer 7

-Formation of glucose from non-CHO sources – proteins, triglycerides, lactic acid and some amino acids -In time of glycogen depletion: prolonged starvation/fasting -Stimulated by cortisol, glucagon, and thyroid hormones

Answer 8

-Contain carbon, hydrogen, and oxygen -Triglycerides – most abundant lipid in the body -Most are nonpolar and hydrophobic -Blood plasma is > 90% H2O, thus, lipids must be transported combined with proteins produced by the liver and intestines → lipoproteins

Answer 9

-Function: Deliver lipids to cells, and clearance from blood of lipids -Inner core: mostly triglycerides -Outer shell: proteins, phospholipids, cholesterol -Outer shell proteins: apoproteins (A,B,C,D,E)

Answer 10

1. chylomicrons 2. very-low-density lipoproteins (VLDLs) 3. low-density lipoproteins (LDLs) 4. high-density lipoproteins (HDLs)

Answer 11

transport dietary (ingested) lipids to adipose tissue

Answer 12

transport triglycerides from hepatocytes to adipocytes

Answer 13

carry about 75% of total cholesterol in blood, deliver it to cells excessive LDL-> fatty plaque-> CAD; "LDL cholesterol = bad cholesterol"

Answer 14

remove excess cholesterol from body cells and blood, transport it to the liver for elimination low risk of CAD-> "good cholesterol"

Answer 15

1. Triglycerides (neutral fats) – most abundant form; Found in: * Saturated fats – meat, dairy foods, tropical oils, or hydrogenated oils (trans fats) * Unsaturated fats – seeds, nuts, olive oil, and most vegetable oils 2. Cholesterol – found in egg yolk, meats, organ meats, shellfish, and milk products, * Hepatocytes makes ~85% cholesterol. * Increase in total cholesterol levels are associated with a greater risk of CAD * Exercise, diet, and certain drugs are used to reduce high cholesterol levels

Answer 16

if no immediate need, stored in adipose tissue -oxidized to produce ATP when need arises

Answer 17

-Provides important energy reserves -Can provide large amounts of ATP, but slowly -Difficult for water-soluble enzymes to reach

Answer 18

-Cells require lipids to maintain plasma membranes -Steroid hormones must reach target cells in many different tissues

Answer 19

1. michelles are absorbed into intestinal mucosa where they are converted to chylomicrons 2. intestinal cells secrete chylomicrons, which are absorbed into lacteals 3. from the lacteals, the chylomicrons proceed within the lymphatic vessels and into the thoracic duct, and from there are distributed throughout the body 4. lipoprotein lipase in the capillary endothelium breaks down the chylomicrons and releases fatty acids and monoglycerides into the interstitial fluid 5. resting skeletal muscles absorb fatty acids and break then down for ATP production or storage as glycogen. adipocytes absorb fatty acids and use them to synthesize triglycerides for storage

Answer 20

6. the liver absorbs chylomicrons and creates LDLs and VLDLs. to make LDLs, triglycerides are removed from the chylomicrons, cholesterol is added, and the surface proteins are altered. VLDLs contain triglycerides manufactured by the liver, plus small amounts of phospholipids and cholesterol. some of the cholesterol is used. by the liver to synthesize bile salts; excess cholesterol is excreted in the bile 7. VLDLs transport triglycerides from the liver to muscle and adipose tissue 8. the LDLs enter the bloodstream and are delivered to peripheral tissues 9. once in peripheral tissues, the LDLs are absorbed 10. the cells exract the cholesterol and uses it in various ways 11. the cholesterol not used by the cells re-enters the bloodstream. there it gets absorbed by high-density lipoproteins (HDLs) 12. the HDLs return ot cholesterol to the liver, where it is extracted and packaged in new LDLs or excreted with bile salts in bile

Answer 21

-A sequence of reactions inside mitochondria that breaks fatty acid molecules into 2-carbon fragments that generates acetyl CoA -FAD and NAD+ are reduced -Each step: * Generates molecules of acetyl-CoA, NADH, and FADH2 * Leaves a shorter carbon chain bound to CoA

Answer 22

1. lysosomal enzymes break down triglycerides molecules into 1 glycerol molecule and 3 fatty acids 2. in the cytosol, the glycerol is converted to pyruvate through the glycolysis pathway 3. fatty acids are absorbed into the mitochondria 4. an enzyme reaction then breaks off the first 2 carbons as acetyl-CoA while leaving a shorter fatty acid bound to the second molecule of coenzyme A

Answer 23

* Formation of lipids in the body (glucose, aa). Cells can: 1. Use almost any organic substrate * because lipids, amino acids, and CHOs can be converted to acetyl-CoA 2. Glycerol * Synthesized from dihydroxyacetone phosphate (DHAP) * An intermediate product of glycolysis and gluconeogenesis * Nonessential fatty acids and steroids – synthesized from acetyl-CoA * Essential fatty acids – cannot be synthesized in the body * Must be consumed