Chapter 25 - Metabolism and Nutrition Flashcards
What is Metabolic Reaction?
Metabolism:
All of the chemical reactions taking place in the body
Results from balance of Anabolic and Catabolic reactions
Catabolism:
Decomposition
Reactions that break down complex molecules into simpler one
Anabolism:
Synthesis
Reactions that combine simple molecules to make complex molecules
What is ATP?
Adenosine Triphosphate (ATP):
Energy molecule that couples the 2 types of reactions
How does Metabolic Reaction Work?
1- Simple molecules such as glucose, amino acids, glycerol, and fatty acids
2- Anabolic Reaction:
Transfer energy from ATP to complex molecules
Release Heat
ATP becomes ADP + Pi
3- Complex molecules such as glycogen, proteins, and triglycerides
4- Catabolic Reaction:
Transfer energy from complex molecules to ATP
Release Heat
ADP + Pi becomes ATP
What is Energy Transfer?
Oxidation-Reduction Reactions:
One category of reactions important in energy transfer
1- Oxidation
2- Reduction
What is Oxidation?
Oxidation:
Involves removal of electrons from an atom or molecule
ex:
Conversion of Lactic Acid to Pyruvic Acid
Remove 2H ( H+ and H- )
When a substance is oxidized, the liberated H atoms are transferred by 2 Coenzymes to another compound. These are:
1- Nicotinamide Adenine Dinucleotide (NAD)
NAD+ <—– NADH + H+ Oxidation
NAD+ —–> NADH + H+ Reduction
2- Flavin Adenine Dinucleotide (FAD)
FADH2 <—– FAD Oxidation
FADH2 —–> FAD Reduction
What is Reduction?
Reduction:
Involves addition of electrons to a molecule
ex:
Conversion of Pyruvic Acid to Lactic Acid
Add 2H ( H+ and H- )
What is Oxidation-Reduction (Redox Reaction)?
Oxidation and Reduction are always coupled so the 2 reactions are called Redox Reactions
ex:
The Oxidation of Lactic Acid to Pyruvic Acid and the associated Reduction of NAD+ may be written as:
Lactic Acid (Reduced) and NAD+ (Oxidized)
Pyruvic Acid (Oxidized) and NADH + H+ (Reduced)
Some of the energy released during Oxidation Reactions is captured when ATP is formed
Phosphorylation:
A Phosphate group is added to ADP along with energy to form ATP
ADP + Pi + Energy —–> ATP
What is Carbohydrate Metabolism?
Carbohydrate Metabolism:
Mostly Glucose metabolism
The body’s use of glucose depends on the needs of cells:
1- ATP production
2- Amino acid synthesis
3- Glycogen synthesis
4- Triglyceride synthesis
How does Glucose Metabolism Start?
Glucose must pass through plasma membrane to be used by cell
Facilitated Diffusion makes it happen:
In most body cells, GluT molecules perform this
Insulin increases insertion of GluT Transporters into the plasma membrane increasing the rate of Facilitated Diffusion
What is Cellular Respiration?
Cellular Respiration:
Oxidation of Glucose to produce ATP
4 Sets of reactions:
1- Glycolysis
2- Formation of Acetyl Coenzyme A
3- Krebs Cycle Reactions
4- Electron Transport Chain Reactions (ETC)
What is Glycolysis?
Glycolysis:
Process where a 6-Carbon Glucose molecule is split into 2 3-Carbon molecules of Pyruvic Acid
It involves 10 reactions:
1 Molecule of Glucose becomes 2 molecules of Pyruvic Acid
And releases 4 ATP and 2 NADH and 2 H+
What happens to Pyruvic Acid?
Depends on availability of oxygen
1- Anaerobic Condition:
Pyruvic Acid reduced by addition of 2H to form Lactic Acid
2- Aerobic Condition:
Most cells convert Pyruvic Acid to Acetyl Coenzyme A in Mitochondrial Matrix
What is Krebs Cycle?
Krebs Cycle (Citric Acid Cycle):
Occurs in the Matrix of Mitochondria
Consists of 8 reactions
(happens twice)
(makes ATP)
(sends NADH and FADH2 to ETC)
What is Electron Transport Chain (ETC)?
ETC:
Series of electron carriers in the Inner Mitochondrial Membrane
Each carrier in the chain is reduced as it picks up e- and oxidized as it gives up e-
Exergonic Reactions:
Release energy used to form ATP
This mechanism links chemical reactions with the pumping of H+ and is known as Chemiosmosis
ETC includes e- carriers:
Flavin Mononucleotide (FMN)
Cytochromes
Iron-Sulfur Centers
Copper atoms
Coenzyme Q
What Happens inside ETC?
Inside the Inner Mitochondrial Membrane, the carriers are clustered into 3 complexes, each acting as a Proton Pump that expels H+:
1- NADH Dehydrogenase Complex:
FMN and 5 Fe-S Centers
2- Cytochrome b-c1 Complex:
Cyt b - Cyt c1, and an Fe-S Center
3- Cytochrome Oxidase Complex:
Cyt a, Cyt a3, and 2Cu
What does Cellular Respiration Generate?
Cellular Respiration:
Generates either 30 or 32 ATP molecules for each molecule of glucose catabolized
Reaction:
C6H12O6 + 6O2 + 30-32 ADPs + 30 or 32 Pi -> 6CO2 + 6H2O + 30-32 ATPs
Glucose + Oxygen + ADP + Pi —–> Carbon Dioxide + Water + ATP
What Happens to Glucose not Needed Immediately?
In Liver:
1- Glycogenesis:
Process of storing Glucose as Glycogen
Uses Hexokinase
Stimulated by Insulin
2- Glycogenolysis:
When ATP is needed for body activities, stored Glycogen is broken down to Glucose
Uses Phosphorylase and Phosphatase
Stimulated by Glucagon and Epinephrine
What is Gluconeogenesis?
Gluconeogenesis:
Glucose may be formed from:
Proteins
Glycerol portion of Triglycerides
Lactic Acid
Certain Amino Acids
Hormones that stimulate Gluconeogenesis:
Cortisol
Glucagon
Thyroid hormones
What is Lipid Metabolism?
Lipids:
Most are Nonpolar (hydrophobic)
Lipoproteins:
Blood Plasma is over 90% water, so lipids must be transported combined with proteins produced by Liver and Intestines
What are the 4 Classes of Lipoproteins?
1- Chylomicrons:
Transport dietary lipids to Adipose Tissue
2- Very-Low-Density Lipoproteins (VLDLs):
Transport triglycerides from Hepatocytes to Adipocytes
3- Low-Density Lipoprotein (LDLs):
Carry about 75% of the total Cholesterol in blood and deliver it to cells
4- High-Density Lipoprotein (HDLs):
Remove excess Cholesterol from body cells and the blood and transport it to the Liver for elimination
What is Cholesterol in Metabolism?
Cholesterol:
Comes from foods (eggs, dairy, organ meats)
Most synthesized by Hepatocytes
Increase in total Cholesterol levels associated with greater risk of Coronary Artery Disease
Exercise, diet, and certain drugs used to reduce high Cholesterol levels
What is Oxidation of Lipids?
Lipids may be oxidized to produce ATP
If body does not need lipids, they are stored in Adipose Tissue
Some is used as structural molecules or to synthesize other essential substances
What is Lipid Catabolism?
Adipose Tissue is used to remove Triglycerides from Chylomicrons and VLDL
VLDL Triglycerides constitute 98% of all body energy reserves
Lipid Catabolism:
Lipolysis
Split Triglycerides into fatty acids and Glycerol
What is Lipid Anabolism?
Lipogenesis:
Synthesize lipids from glucose or amino acids
Occurs when consume more calories than needed
