Energy Storage and use: Metabolism of Carbs, fats, and proteins Flashcards Preview

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Flashcards in Energy Storage and use: Metabolism of Carbs, fats, and proteins Deck (39):

What is the largest substrate storage in the body?



Types of Lipids. 3. What do each do. 

1. Simple Lipids: Acylglycerol

  • ( Unsaturated, Saturated)
    • Formed from one glycerol and free fatty acids
  • Mostly participate in energy production by entering into the Beta-oxidation cycle to produce acetyl-CoA, and ultimately, ATP

2. Complex Lipids: 

  • Phospholipids
  • glycolipids
  • lipoproteins
  • important role in cell functions as they constitute the major part of the cell barrier and are involved in signal transduction and lipid transport

3. Precursors and derived lipids.

  • Hormones
  • Ketone bodies 
  • Glycerol 
  • Steroids


Fatty acids are stored as what?



During fasting, what do fatty acids do

Enter Beta oxidation to produce acetyl Co-A


What is glycogen? What is it composed of?

Branched chain molecule found in animal cells. Similar to startch. Is composed of glucose molecules joined together to form polymere.



What is the first stage of fat breakdown? What is this? What happens to glycerol after this? What happens to fatty acids during this? 

Lypolysis. Seperation of fatty acids from glycerol molecule. Enters glycolysis pathway and then procedes to krebs cycle and oxidative phosphorylation. Fatty acids are catabolized to acetyl CoA by Beta Oxidation (mitochondrial Matrix)


Everytime fatty acids are converted to Acetyl CoA what happens?

Coenzymes are reduced to generate one NADH+H+ and one FADH2. The acetyl CoA then enters Kreb cycle and oxidative phosphorylation.


When fats are broken down for energy, what is waste product?

Ketones. Synthesized from Acetyl CoA


What is the significance of ketones? Why does this help?

Ketones can be utilized by the nervous system as partial alternative to glucose.  Helps conserve body's supply of glucose  if energy becomes limited.


What is synthesis of fat from nutrients?



Where does digestion of Triaglycerides occur? Facilatated by what?

•Bile salts (emulsification)
•Alkaline medium (pancreatic juice)


In Fed state, adipose tissue does what 

converts glucose via pyruvate and acetyl–CoA into fatty acids which are stored as fat globules of TG


In humans, FA synthesis occurs where? Adipocytes store FA's as?

•FA synthesis occurs in the liver – adipocytes store FAs arriving from liver as VLDL and directly from intestine


Explain Lipid Catabolism.

Two pathways: Broken into glycerol and 3FFA

  1. Glycerol heads towards fast glycolytic pathway to form one glycerole 3 phosphate via glycerole kinase. 
  2. 3 FFA enter beta-oxidation to form Acetyl CoA and later on ATP


What is one of the major mechanisms leading to fat storage?

The reversal of Acetyl-coA into fatty acids


In fasting state, what happens to TG in adipose tissue? This process is regulated by what?

TGs are hydrolysed by lipases to release free Fas, and are delivered through bloodstream to skeletal muscle and heart. 
•Adrenaline which stimulates activity of TG lipase
•Insulin which inhibits the activity of TG lipase


Walk through catabolism of triglycerol.

. First the TAG is broken by TAG lipase into one DAG and one free fatty acid. In the next step, the DAG is catabolized by the DAG lipase to form one MAG and one free fatty acid, and the last step will release with the action of the MAG lipase, the last free fatty acid and one glycerol.


Walk through the action of hormones on lypolysis 

when glucagon binds with it cell receptor it triggers the activation of the adenylyl cyclase with the addition of one ATP that in turn will activate the cAMP with the result of triggering lipase activity. These  enzymes will then catabolize the TAG into FFA  and one glycerol. Note that insulin will block the activity of the lipases.


During Lipid metabolism, what do the liver and muscle do? What are the two major fates of this fatty acid?

take up non-esterified fatty acids from plasma.

  1. oxidation (energy source for liver –production of ketone bodies; for muscle – production of Acetyl-CoA)
  2. triacylglycerol formation (local store in the liver and muscle for energy needs)


Once in the cell cytosol, fatty acid forms fatty acetyl CoA and what two paths can it take? (during Fasting and then during post meal)

  1. in the fasting state or energy deficit, through the action of CPT-1 the fatty acyl CoA enters into the b-oxidation cycle to form acetyl-CoA and ketone bodies. 
  2. in postprandial state or energy surplus, the fatty acyl CoA forms new triacylglycerol that will be stored in the cel


What effect does glucacon have on fatty acid metabolism? What about insulin?

The glucagon promotes fatty acyl CoA oxidation by activation of CPT-1 while Insulin will promote glucose as prime substrate leading to a higher formation of Malonyl-CoA, an intermediate that inhibits CPT-1


Explain mechanism to form fatty Acetyl-CoA

Carnitine transports long-chain acyl groups from fatty acids into the mitochondrial matrix, so they can be broken down through β-oxidation to acetyl CoA to obtain usable energy via the citric acid cycle. It requires to shuttle an acyl and carnitine from the matrix to the cytosol under the action of the CTP I and II.



What happens when the fatty acid is a long chain?

The long chain fatty acid must pass through an additional biochemical step before being shuttle to the mitochondria. The fatty acids longer than 20 carbon enter into the peroxisomes to form two components; the acetylcarnitine and octanoylcarnitine that will be released in the cytosol and picked up by the mitochondria. So, the structure of fatty acids play a role in the cascade of biochemical steps that leads to the formation of ATP


Beta oxidation breaks fats down into what? and these are used for what?

–Acetyl coenzyme A --> Krebs Cycle
–FADH2 --> Oxidative Phosphorylation
–NADH --> Oxidative Phosphorylation


Steps of beta oxidation.

  1. The first reaction is driven by the acyl-CoA dehydrogenase to produce beta-enoyl-CoA. It oxidizes simple Carbon bond into double bond, reason why it is called beta-oxidation
  2. The second biochemical reaction involves enoyl-CoA hydratase that forms a b-hydroxy product. 

  3. The third step of the cycle oxidizes a secondary alcohol to form a ketone and produce a NADH

  4. The final biochemical reaction of the cycle uses another co-Enzyme A through its reaction with the thiolase that produces one acetyl-CoA for the Kreb cycle and releases one Acyl-CoA for the next b-oxidation cycl


How much ATP is yielded from beta oxidation?



What is the most abundent fatty acid in our diets? How much ATP is yielded in the oxidation of this?

Palmatic Acid. 107.


Function of adipocytes.

fat cell makes up and stores the fat in postprandial state and breaks it down and releases it in fasting state as well as during and after exercise


What is proteolysis?

Proteins broken down into amino acids.


After proteolysis, what occurs? What happens to the substance that is produced?

Amino acids are then deaminated (amino group removed). This process produces amonia NH3 and is toxic. Carried by the bloodstream to the liver where is converted to Urea.



After amino group is removed from protein, what occurs to the remainder of the molecule?

Either converted to pyruvate, acetyl CoA(which goes to the krebs cycle) or converted to intermediate which directly enters the krebs cycle.


Which tissue provide glucose for other tissues?

Liver and kidneys


What is gluconeogenesis? What are the sources? Occurs where?

Formation of new glucose.Glycerol(produced by breaking down triglycerides), lactate, amino acids. Occurs in liver


What is glycogenesis?

Covalent bond formation between glucose molecules. When glucose is abundent in supply, stored as glycogen.



In cytosol, how is fatty acid produced? In Smooth endoplasmic reticulum how is trigliceride produced?

  • Acetyl CoA+Acetyl CoA+.........--->Fatty acid

•Glycerol + 3 Fatty Acids à Triglyceride


Where is cholesterol synthesized from?

Most comes from diet, some synthesized in smooth ER from acetyl CoA.


What is the role of creatine?

Acts as a buffer store of ATP. 

  1. during heavy activity phosphocreatine is converted to creatine and ATP
  2. during recovery period the reverse reaction generates phosphocreatine