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
What is Protein Metabolism?
Digested proteins broken down into amino acids
Amino acids not stored
Oxidized:
To produce ATP or synthesize new proteins
What is Protein Catabolism?
Protein broken down to amino acids, which are converted o other Amino acids, fatty acids, ketone bodies, or glucose
Cells oxidize Amino acids to generate ATP via Krebs Cycle
What is Protein Anabolism?
Synthesis of new proteins by bonding Amino acids together on Ribosomes
What is Glucose 6-Phosphate?
Involved in:
1- Synthesis of Glycogen
2- Release of Glucose into bloodstream
3- Synthesis of Nucleic acids
4- Glycolysis
What is Pyruvic Acid?
Involved in:
1- Production of Lactic Acid
2- Production of Alanine
3- Gluconeogenesis
What is Acetyl Coenzyme A?
Involved in:
1- Helping 2-Carbon Acetyl groups enter the Krebs Cycle
2- Synthesis of lipids
What is Glucose Catabolism?
Complete oxidation of Glucose (Cellular Respiration)
Chief source of ATP in cells
Consists of:
1- Glycolysis
2- Krebs Cycle
3- ETC
1 Glucose —–> 30 or 32 ATP
What is Glycolysis?
Conversion of Glucose into Pyruvic Acid
Some ATP produced
Anaerobic
What is Krebs Cycle?
Series of redox reactions
Coenzymes NAD+ and FAD pick H+ and OH- from oxidized org acids
Some ATP produced
CO2 and H2O byproducts
Aerobic
What is ETC?
Series of redox reactions
e- passed from carrier to next
Most ATP produced
Aerobic
What is Glucose Anabolism?
1- Glycogenesis:
Glucose —–> Glycogen
When not needed for ATP production
2- Glycogenolysis:
Glycogen —–> Glucose
3- Gluconeogenesis:
AA or Glycerol or Lactic Acids —–> Glucose
What is Triglyceride Catabolism?
Triglyceride —–> Glycerol + Fatty Acids
Glycerol can be converted to Glucose by Gluconeogenesis
Or catabolized by Glycolysis
Fatty Acids catabolized via Beta Oxidation to Acetyl CoA that enters Krebs Cycle
Or converted to Ketone Bodies (Ketogenesis)
What is Protein Catabolism?
Deamination then AA oxidized via Krebs Cycle
Ammonia resulting from Deamination is converted to Urea in Liver
AA may be converted to Glucose (Gluconeogenesis), fatty acids, or ketone bodies
What is Protein Anabolism?
DNA directs mRNA to synthesize Protein on Ribosomes
What Hormone assist in Regulation of Glucose and AA into cells, and Glycogenesis?
Insulin
For Facilitated Diffusion of Glucose and Active Transport of AA: in most cells
For Glycogenesis: in Hepatocytes
What Hormones Regulate Protein Synthesis?
1- Insulin
2- Thyroid Hormones
3- IGFs
What Hormone Regulate Lipogenesis?
Insulin
Location:
Adipose Cells and Hepatocytes
What is Main Hormone that Regulates Glycogenolysis?
1- Glucagon
2- Epinephrine
Location:
Hepatocytes
Skeletal muscles
What is Main Hormone that Regulates Lipolysis?
1- Epinephrine
2- Norepinephrine
3- Cortisol
4- IGFs
5- Thyroid Hormones
Location:
Adipocytes
What is Main Hormone that Regulates Protein Breakdown?
1- Cortisol
Location:
Most cells
Especially skeletal muscle fibers
What is Main Hormone that Regulates Gluconeogenesis?
1- Glucagon
2- Cortisol
Location:
Hepatocytes
Kidney Cortex Cells
What happens when Fasting or Starving?
Ketogenesis:
Production of Ketone Bodies as Catabolism of fatty acids increase
Ketone Bodies may be used for energy by all cells
What is Basal Metabolic Rate (BMR)?
BMR:
Metabolic Rate measured when body is resting and fasting state
Overall rate at which metabolic reactions use energy
What Factors affect Metabolic Rate?
1- Exercise
2- Hormones
3- Nervous System
4- Body Temperature
5- Ingestion of food
6- Age
7- Gender, climate, sleeping, malnutrition
How is Heat Transferred from Body to Environment?
1- Conduction
2- Convection
3- Radiation
4- Evaporation
What is Preoptic Area of Hypothalamus?
Body’s thermostat
Thermoreceptors:
Send info to Preoptic Area
Preoptic Area send signals to Heat-Losing Center and Heat-Promoting Center of Hypothalamus
Negative Feedback:
Conserve heat and increase heat production
What is Negative Feedback Loop of Body Temperature Decreasing?
1- Body temperature decreases
2- Thermoreceptors in Hypothalamus and Skin send nerve impulses to Preoptic Area, Heat-Promoting Center, and Neurosecretory Cells in Hypothalamus and Thyrotrophs in Anterior Pituitary
3- Nerve impulses and TSH
4- Vasoconstriction decrease heat loss through skin
Adrenal Medulla releases hormones that increase cellular metabolism
Skeletal muscles contract in repetitive cycle called Shivering
Thyroid Gland releases Thyroid Hormones that increase Metabolic Rate
5- Body Temp increases
What is Total Energy Expenditure?
BMR: 60%
Physical activity: 30-35%
Food-induced Thermogenesis: 5-10%
What Controls Hunger?
Arcuate Nucleus and Paraventricular Nucleus of Hypothalamus control hunger
Hormone Leptin:
Helps decrease Adiposity
Neuropeptide Y:
Stimulates food intake
Melanocortin:
Inhibits food intake
What is Minerals?
Inorganic elements
Important role in maintaining healthy body
What is Vitamins?
Nutrients required in small amounts
Maintain growth and normal metabolism
Most cannot be synthesized in body, must be consumed from food
What is Potassium?
Major Cation K+ in ICF
Needed for generation and conduction of Action Potentials in neurons and muscle fibers
What is Sodium?
Most abundant Cation Na+ in ECF
Affects distribution of water through Osmosis
Part of Bicarbonate buffer system
Functions in nerve and muscle Action Potential conduction
What is Anorexia Nervosa?
Chronic disorder characterized by self-induced wight loss
What is Fever?
Elevation of core temp caused by resetting of the Hypothalamus thermostat
What is Obesity?
Body weight more than 20% above desirable standard due to an excessive accumulation of Adipose tissue
