Cell Metabolism and Energy Production

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Questions and Answers

What is the primary function of mitochondria in cells?

Protein synthesis

Energy storage

Cell signaling

Power generation through energy-generating pathways (correct)

What is the byproduct of energy release during metabolism?

Energy, water, and carbon dioxide (correct)

Water and ATP

Oxygen and carbon dioxide

Glucose and amino acids

What is the role of Stage 1 in catabolic pathways?

Energy storage in ATP

Oxidation of acetyl CoA

Conversion of building blocks to acetyl CoA

Hydrolysis of complex molecules to their component building blocks (correct)

What is a characteristic of anabolic pathways?

Endergonic reactions that require ATP Signup and view all the answers

What is the precursor molecule for energy-yielding nutrients from carbohydrates?

Glucose Signup and view all the answers

What is a key difference between catabolic and anabolic pathways?

Catabolic pathways involve complex to simple molecules, while anabolic pathways involve simple to complex molecules Signup and view all the answers

What is the net result of the ATP-ADP cycle in biological systems?

Energy is liberated from ATP molecules Signup and view all the answers

What is the primary function of oxidation in metabolic reactions?

Loss of hydrogen and oxygen Signup and view all the answers

Which of the following is an example of an intracellular signal?

Substrate availability Signup and view all the answers

What is the major metabolic fuel of most tissues?

Glucose Signup and view all the answers

What is the result of the electron transport chain in oxidative phosphorylation?

Pumping of hydrogen ions Signup and view all the answers

What is the effect of high ATP concentrations on phosphofructokinase enzyme?

It inhibits its activity Signup and view all the answers

What would be the result of the continuous release of energy from glucose when the cells do not need energy?

An extremely wasteful process Signup and view all the answers

What is the effect of citrate ion on phosphofructokinase enzyme?

It inhibits the enzyme Signup and view all the answers

What happens to ADP and AMP when they are used by the cell to energize physiological functions?

They are converted back to ATP almost instantly Signup and view all the answers

What is the role of ADP (and AMP) in energy metabolism?

It increases energy metabolism Signup and view all the answers

What is the function of anaerobic glycolysis in the body?

To provide energy for a short duration when oxygen is unavailable Signup and view all the answers

What is the normal blood glucose concentration in a person who has not eaten a meal within the past 3 to 4 hours?

90 mg/dl Signup and view all the answers

What is the significance of the pentose phosphate pathway?

It is an alternative pathway for energy metabolism when certain enzymatic abnormalities occur in cells Signup and view all the answers

What happens to lactic acid when oxygen becomes available again?

It is converted to pyruvic acid Signup and view all the answers

What is the regulation of blood glucose concentration related to?

The pancreatic hormones insulin and glucagon Signup and view all the answers

What is the maximum blood glucose concentration after a meal containing large amounts of carbohydrates in a normal person?

140 mg/dl Signup and view all the answers

What is the typical range of amino acid concentration in the blood?

35-65 mg/dl Signup and view all the answers

What happens to the amino acid concentration in the blood after a meal?

It increases by a few milligrams per deciliter Signup and view all the answers

What is the effect of growth hormone and insulin on protein formation?

They increase the formation of tissue proteins Signup and view all the answers

What is the effect of adrenocortical glucocorticoid hormones on amino acid concentration?

They increase the concentration of plasma amino acids Signup and view all the answers

What is the normal state of amino acids in the blood?

They exist in the ionized state Signup and view all the answers

What is the primary function of albumin in the plasma?

To provide colloid osmotic pressure in the plasma Signup and view all the answers

What is the role of globulins in the plasma?

To promote natural and acquired immunity of the body Signup and view all the answers

What is the function of fibrinogen in the plasma?

To form blood clots during blood coagulation Signup and view all the answers

What is the rate of plasma protein formation by the liver?

30 g/day Signup and view all the answers

What is the process involved in the removal of amino groups from amino acids?

Deamination Signup and view all the answers

What happens to proteins in the body when a person eats no proteins?

A certain proportion of body proteins is degraded into amino acids Signup and view all the answers

What is the effect of starvation on protein degradation?

Proteins in the tissues degrade rapidly, as much as 125 grams daily Signup and view all the answers

What is the amount of protein lost daily in the absence of dietary protein?

20 to 30 grams Signup and view all the answers

What happens to the amino acids formed from degraded proteins?

They are deaminated and oxidized Signup and view all the answers

What is the fate of urea in the body?

It is excreted by the kidneys Signup and view all the answers

What is the primary effect of growth hormone on protein metabolism?

Increases the synthesis of cellular proteins Signup and view all the answers

What is the primary function of insulin in relation to protein synthesis?

Accelerates the transport of some amino acids into cells Signup and view all the answers

What is the effect of glucocorticoids on protein metabolism?

Increases the breakdown of most tissue proteins Signup and view all the answers

What is the primary effect of testosterone on protein metabolism?

Increases protein deposition in tissues Signup and view all the answers

What is the indirect effect of thyroxine on protein metabolism?

Increases metabolism of cells, affecting protein metabolism Signup and view all the answers

Which type of lipoprotein contains high concentrations of triglycerides and moderate concentrations of both cholesterol and phospholipids?

Very low-density lipoproteins (VLDLs) Signup and view all the answers

What is the role of lipoprotein lipase in adipose tissue, skeletal muscle, and heart?

To break down triglycerides into free fatty acids Signup and view all the answers

How many free fatty acids are transported in the blood in combination with one albumin in normal conditions?

3 Signup and view all the answers

What is the percentage of protein in High-density lipoproteins (HDLs)?

50% Signup and view all the answers

Which type of lipoprotein is derived from Intermediate-density lipoproteins (IDLs) by the removal of almost all the triglycerides?

Low-density lipoproteins (LDLs) Signup and view all the answers

In what condition are 30 free fatty acids transported in the blood in combination with one albumin?

Both diabetes and starvation Signup and view all the answers

What is the primary function of adipose tissue?

To store triglycerides Signup and view all the answers

What is the liver's role in lipid metabolism?

To synthesize triglycerides, mainly from carbohydrates, but to a lesser extent from proteins as well Signup and view all the answers

Under which condition do large quantities of triglycerides appear in the liver?

During the early stages of starvation Signup and view all the answers

What is the role of the liver in lipodystrophy?

To store large amounts of lipids Signup and view all the answers

What is the primary function of adipose tissue besides storing triglycerides?

To synthesize hormones, such as leptin and adiponectin Signup and view all the answers

What is the result of the degradation of fatty acids to acetyl Coenzyme A by beta oxidation?

Formation of ATP Signup and view all the answers

What is the fate of part of the acetoacetic acid in the body?

It is converted into β-hydroxybutyric acid Signup and view all the answers

What is the primary function of the formation of adenosine triphosphate (ATP) from triglycerides?

To provide energy for the body's functions Signup and view all the answers

What is the result of the hydrolysis of triglycerides?

Formation of fatty acids and glycerol Signup and view all the answers

Where are the fatty acids transported in the blood after being released from triglycerides?

To other cells throughout the body Signup and view all the answers

Which hormones directly activate hormone-sensitive triglyceride lipase?

Epinephrine and norepinephrine Signup and view all the answers

What is the effect of corticotropin and glucocorticoids on fat metabolism?

They have a ketogenic effect Signup and view all the answers

Which hormone causes rapid mobilization of fat?

Thyroid hormone Signup and view all the answers

What is the effect of growth hormone on hormone-sensitive lipase?

It has a similar effect to corticotropin and glucocorticoids Signup and view all the answers

Which hormones have a ketogenic effect?

Corticotropin and glucocorticoids Signup and view all the answers

Study Notes

Metabolism

Human body releases energy from chemical bonds in nutrients, which breaks down to release energy
Energy, water, and carbon dioxide are released during metabolism

Cellular Structure

Cells are the work centers of metabolism, with similar structures
Cells have two basic parts: nucleus and cytoplasm
Mitochondria in cells are the power generators that contain energy-generating pathways

Energy-Yielding Nutrients

Glucose is derived from carbohydrates
Glycerol and fatty acids are derived from lipids (triglycerides)
Amino acids are derived from proteins

Catabolic Pathways

Stage 1: Hydrolysis of complex molecules to their component building blocks
Stage 2: Conversion of building blocks to acetyl CoA
Stage 3: Oxidation of acetyl CoA; oxidative phosphorylation
Catabolic pathways involve complex to simple molecules, exergonic reactions, oxidations, and require NAD+
Convergent process

Anabolic Pathways

Precursor molecules are converted to complex molecules
Endergonic reactions require ATP
Anabolic pathways involve simple to complex molecules, endergonic reactions, reductions, and require NADPH
Divergent process

Comparison of Catabolic and Anabolic Pathways

Key differences between catabolic and anabolic pathways:
- Direction of molecules (complex to simple vs simple to complex)
- Energy requirement (exergonic vs endergonic)
- Redox reactions (oxidations vs reductions)
- Co-factors required (NAD+ vs NADPH)
- Process type (convergent vs divergent)

Energy Currency and ATP-ADP Cycle

ATP (adenosine triphosphate) is the energy currency in biological systems.
ATP is broken down into ADP (adenosine diphosphate) and Pi (inorganic phosphate) through hydrolysis, releasing free energy to drive endergonic reactions.
ATP is formed from ADP and Pi when fuel molecules are oxidized, and this cycle is the fundamental mode of energy exchange in biological systems.

Redox Reactions

Oxidation: the loss of hydrogen and oxygen from a molecule.
Reduction: the gain of hydrogen and oxygen by a molecule.

Regulation of Metabolism

Intracellular signals that regulate metabolism include substrate availability, product inhibition, and allosteric activators.
Intercellular communication involves chemical signaling through hormones, which trigger second messengers such as cAMP, cGMP, and Ca/phosphatidylinositol.

Metabolic Fuels

Carbohydrates, lipids, and proteins are used as metabolic fuels, with glucose being the major metabolic fuel of most tissues.
Glucose, fatty acids, and amino acids are used as energy sources.

Oxidative Phosphorylation

The process involves the pumping of hydrogen ions into the outer chamber of the mitochondrion, driven by the electron transport chain.
The energy generated is used to form ATP through oxidative phosphorylation.

Energy Metabolism Control

Continual release of energy from glucose when cells don't need energy is a wasteful process.

ATP's Role in Glycolysis Control

ATP inhibits the enzyme phosphofructokinase, controlling energy metabolism.

ADP's Role in Glycolysis Control

ADP (and AMP) increases phosphofructokinase activity, having the opposite effect of ATP.
When ATP is used by the cell, newly formed ADP and AMP turn on energy processes again.

Citric Acid Cycle's Impact on Glycolysis

Citrate ion, formed in the citric acid cycle, strongly inhibits phosphofructokinase, preventing the glycolytic process.

ATP-ADP Cycle

ADP and AMP are almost instantly returned to the ATP state after energy processes are turned on.

Anaerobic Release of Energy

Anaerobic glycolysis is a lifesaving measure for up to a few minutes when oxygen becomes unavailable.
Formation of lactic acid during anaerobic glycolysis allows for the release of extra anaerobic energy.
Reconversion of lactic acid to pyruvic acid occurs when oxygen becomes available again.

Lactic Acid

Lactic acid is used by the heart for energy.
Lactic acid can be converted back to pyruvic acid when oxygen is available.

Pentose Phosphate Pathway

The pentose phosphate pathway provides energy independently of the citric acid cycle enzymes.
This pathway is an alternative for energy metabolism when certain enzymatic abnormalities occur in cells.

Blood Glucose

Normal blood glucose concentration is around 90 mg/dl after 3-4 hours of fasting.
Blood glucose levels rarely rise above 140 mg/dl after a meal containing carbohydrates, unless in cases of diabetes mellitus.
The regulation of blood glucose concentration is closely related to the pancreatic hormones insulin and glucagon.

Protein Structure

Amino acids combine into long chains through peptide linkages
Some protein molecules consist of multiple peptide chains linked by hydrogen bonding between CO and NH radicals

Blood Amino Acid Concentration

Normal concentration of amino acids in the blood: 35-65 mg/dl
Amino acids exist in the blood primarily in the ionized state due to their acidic nature

Post-Prandial Amino Acid Concentration

Amino acid concentration in the blood increases after a meal, but only by a few milligrams per deciliter

Amino Acid Regulation

Renal threshold for amino acids: regulates plasma amino acid concentration
Storage of amino acids as proteins in cells
Release of amino acids from cells to regulate plasma amino acid concentration

Hormonal Regulation

Growth hormone and insulin: increase formation of tissue proteins
Adrenocortical glucocorticoid hormones: increase plasma amino acid concentration

Types of Plasma Proteins

The three major types of protein present in the plasma are albumin, globulin, and fibrinogen.

Functions of Albumin

Albumin provides colloid osmotic pressure in the plasma, preventing plasma loss from capillaries.

Functions of Globulins

Globulins perform several enzymatic functions in the plasma.
Globulins are responsible for both natural and acquired immunity of the body against invading organisms.

Functions of Fibrinogen

Fibrinogen polymerizes into long fibrin threads during blood coagulation, forming blood clots that help repair leaks in the circulatory system.

Plasma Protein Formation

The liver can form plasma proteins at a rate of up to 30 g/day.

Plasma Proteins as a Source of Amino Acids

Plasma proteins serve as a source of amino acids for the tissues.

Deamination and Transamination

Deamination is the removal of amino groups from amino acids.
Transamination is promoted by several enzymes, including aminotransferases, which are derivatives of pyridoxine (Vitamin B6).

Protein Metabolism

Urea diffuses from liver cells into body fluids and is excreted by the kidneys.

Protein Degradation

20-30 grams of protein are degraded daily, even when no proteins are consumed, known as obligatory loss of proteins.
This degradation process involves deamination and oxidation of amino acids.

Effect of Starvation on Protein Degradation

Proteins in tissues degrade rapidly, up to 125 grams daily, during starvation.
As a result, cellular functions deteriorate rapidly.

Hormonal Regulation of Protein Metabolism

Growth hormone stimulates protein synthesis by increasing transcription, leading to the creation of new cellular proteins.
Insulin facilitates protein synthesis by accelerating the transport of specific amino acids into cells, which serves as a stimulus for protein synthesis.

Effects of Glucocorticoids on Protein Metabolism

Glucocorticoids increase the breakdown of most tissue proteins, except in the liver, by enhancing the rate of extrahepatic protein degradation.

Effects of Testosterone on Protein Metabolism

Testosterone promotes protein deposition in tissues, particularly in muscles, where it increases the deposition of contractile proteins.

Effects of Thyroxine on Protein Metabolism

Thyroxine indirectly affects protein metabolism by increasing the overall metabolic rate of cells, leading to a subsequent impact on protein synthesis and breakdown.

Lipid Metabolism

Triglycerides and other lipids are transported from the gastrointestinal tract to adipose tissue, skeletal muscle, and heart through lymph via chylomicrons.
Lipoprotein lipase is synthesized in adipose tissue, skeletal muscle, and heart.

Transport of Free Fatty Acids

Free fatty acids are transported in the blood in combination with albumin.
Normally, 3 free fatty acids combine with 1 albumin.
In diabetes and starvation, 30 free fatty acids combine with 1 albumin.

Types of Lipoproteins

Very low density lipoproteins (VLDLs): • High concentrations of triglycerides. • Moderate concentrations of cholesterol and phospholipids.
Intermediate-density lipoproteins (IDLs): • Derived from VLDLs with removed triglycerides. • Increased concentrations of cholesterol and phospholipids.
Low-density lipoproteins (LDLs): • Derived from IDLs with almost all triglycerides removed. • High concentration of cholesterol. • Moderately high concentration of phospholipids.
High-density lipoproteins (HDLs): • High concentration of protein (about 50%). • Low concentrations of cholesterol and phospholipids.

Fat Deposits

Two major tissues in the body store large quantities of fat: adipose tissue and the liver.

Adipose Tissue Functions

Stores triglycerides
Provides heat insulation for the body
Secretes hormones, such as leptin and adiponectin

Liver Functions in Lipid Metabolism

Degrades fatty acids into small compounds for energy
Synthesizes triglycerides from carbohydrates and proteins
Synthesizes other lipids, including cholesterol and phospholipids, from fatty acids

Triglyceride Accumulation in the Liver

Occurs during early stages of starvation
Occurs in diabetes mellitus
Occurs in conditions where fat is used for energy instead of carbohydrates
Also occurs in lipodystrophy, where large amounts of lipids are stored

Triglycerides for Energy: ATP Formation

Triglycerides are broken down into fatty acids and glycerol through hydrolysis.
Fatty acids enter the mitochondria to undergo further degradation.
Beta-oxidation degrades fatty acids into acetyl-CoA, which is then oxidized.
The oxidation of fatty acids yields large amounts of ATP.

Acetyl-CoA Conversion and Transportation

Two acetyl-CoA molecules condense to form one molecule of acetoacetic acid.
Acetoacetic acid is transported in the blood to cells throughout the body for energy production.
Part of the acetoacetic acid is converted into β-hydroxybutyric acid.
Minute quantities of acetoacetic acid are converted into acetone.

Hormonal Regulation of Fat Utilization

Epinephrine and norepinephrine directly activate hormone-sensitive triglyceride lipase, stimulating fat utilization.
Corticotropin and glucocorticoids have a ketogenic effect, promoting the breakdown of fat for energy production.
Growth hormone has a similar, but weaker, effect compared to corticotropin and glucocorticoids in activating hormone-sensitive lipase.
Thyroid hormone triggers rapid mobilization of fat, facilitating its utilization for energy purposes.

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This quiz covers the process of metabolism, the role of cells, and energy-yielding nutrients. Learn about the structure of cells, mitochondria, and how the body releases energy from chemical bonds.