10.2 Metabolism

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Questions and Answers

Which of the following lipoproteins is known as 'bad' lipids that deliver cholesterol to cells?

High-density lipoproteins (HDLs)

Low-density lipoproteins (LDLs) (correct)

Very low-density lipoproteins (VLDLs)

Chylomicrons

All lipids are soluble in water.

False

What is the process called that uses lipids to provide energy reserves?

lipid storage

The body synthesizes ____ essential amino acids that cannot be synthesized by itself.

10 Signup and view all the answers

What is the primary function of high-density lipoproteins (HDLs)?

Remove excess cholesterol and return it to the liver Signup and view all the answers

Which process breaks down triglycerides into glycerol and fatty acids?

Lipolysis Signup and view all the answers

Match the following lipoproteins with their primary role:

Chylomicrons = Transport dietary lipids VLDLs = Transport triglycerides LDLs = Deliver cholesterol to cells HDLs = Remove cholesterol from cells Signup and view all the answers

What are the two types of amino acids based on how they are synthesized by the body?

Essential and nonessential amino acids Signup and view all the answers

Catabolism refers to the building up of molecules in an organism.

False Signup and view all the answers

Proteins in the body are formed from a combination of 20 amino acids.

True Signup and view all the answers

What is the net gain of ATP from one molecule of glucose after complete processing?

36 Signup and view all the answers

During cellular respiration, glucose is converted into carbon dioxide and ________.

water Signup and view all the answers

Match the following metabolic pathways with their correct description:

Glycolysis = Breakdown of glucose to form ATP and pyruvate Citric Acid Cycle = Completes the oxidation of carbohydrates, fats, and proteins Oxidative Phosphorylation = Most ATP is generated through this stage Gluconeogenesis = Synthesis of glucose from non-carbohydrate sources Signup and view all the answers

What are the main products of glycolysis and their respective ATP yield?

2 ATP and 4 NADH Signup and view all the answers

Triglycerides are the most abundant storage carbohydrates in the body.

False Signup and view all the answers

What is the primary function of the cardiovascular system in metabolism?

Carries materials through the body Signup and view all the answers

The process of ________ turns glucose into glycogen for storage.

glycogenesis Signup and view all the answers

How many ATP molecules can be produced from one 18-carbon fatty acid molecule through beta-oxidation?

144 ATP Signup and view all the answers

Study Notes

Metabolism

Refers to all chemical reactions in an organism
- Anabolic is building up
- Catabolic is breaking down
- Both processes happen in cells
Cells must spend ATP to:
- perform routine maintenance
- remove and replace structures and components
Cells spend additional energy for vital functions:
- growth
- secretion
- contraction

Energy

Cells break down molecules to obtain energy:
- used to generate ATP
Most ATP production takes place in the mitochondria

Materials Transport

The cardiovascular system carries materials through the body
Materials diffuse from the bloodstream into cells

Organic Compounds

Glycogen: the most abundant storage carbohydrate in the body; a branched chain of glucose molecules
Triglycerides: the most abundant storage lipids; primarily composed of fatty acids
Proteins: the most abundant organic components in the body; perform many vital cellular functions

Nutrient Usage

Carbohydrate Metabolism: Generates ATP and other high-energy compounds by breaking down carbohydrates:
- Glucose + Oxygen → Carbon Dioxide + Water
- C6H12O6 + 6O2 → 6CO2 + 6H2O
The process happens in several parts:
- Glycolysis
- Citric acid cycle
- Oxidative phosphorylation

Glucose Breakdown

Occurs in small steps which release energy to convert ADP to ATP
Breaking down 1 molecule of glucose nets 36 molecules of ATP
For 1 glucose molecule processed, the cell gains 36 molecules of ATP:
- 2 from glycolysis
- 4 from NADH generated in glycolysis
- 2 from the Citric acid cycle (through GTP)
- 28 from Oxidative Phosphorylation

Glycolysis

The first stage of carbohydrate metabolism, where glucose is broken down into pyruvate
Occurs in the cytosol
Does not require oxygen (anaerobic)

Citric Acid Cycle (Krebs Cycle)

The second stage of carbohydrate metabolism, where pyruvate is broken down into carbon dioxide, water, and ATP
Occurs in the mitochondria
Requires oxygen (aerobic)

Oxidative Phosphorylation

The final stage of carbohydrate metabolism
Takes place in the mitochondria
Involves the electron transport chain and chemiosmosis
Produces the majority of ATP from glucose breakdown

Anabolism

Reversing the direction of catabolism is not directly possible due to enzymatic processes
Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate precursors, such as:
- Lactic acid
- Glycerol
- Amino acids
Glucose is stored as glycogen in the liver and skeletal muscle

Glycogenesis

The second stage of replenishing glycogen supplies
The formation of glycogen from glucose
Occurs slowly

Glycogenolysis

The breakdown of glycogen
Occurs quickly
Involves a single enzymatic step
Allows access to energy by muscle when needed

Lipid Metabolism

Lipid molecules contain carbon, hydrogen, and oxygen in different proportions than carbohydrates
Triglycerides are the most abundant lipid in the body

Lipid Catabolism

Also called lipolysis, breaks lipids down into smaller pieces
Hydrolysis splits a triglyceride into:
- 1 molecule of glycerol
- 3 fatty acid molecules
Important as energy reserves
Can provide large amounts of ATP, but slowly
Saves space, but hard for water-soluble enzymes to reach

Beta-Oxidation

Fatty acid breakdown
The cell can gain 144 ATP molecules from one 18-carbon fatty acid molecule
Breakdown yields about 1.5 times the energy of glucose breakdown

Lipid Usage

Lipid Synthesis (Lipogenesis): can use almost any organic substrate
Lipid Storage: Important energy reserves, providing large amounts of ATP, but slowly
- Saves space, but hard for water-soluble enzymes to reach

Lipid Transport

Cells require lipids to maintain membranes
Steroid hormones must reach target cells in many different tissues
Most lipids are not soluble in water and need special transport mechanisms
Most lipids circulate through the bloodstream as lipoproteins
Free fatty acids make up a fraction of the total circulating lipids

Lipoproteins

Are lipid-protein complexes
Contain large insoluble glycerides and cholesterol
5 classes:
- Chylomicrons
- Very low-density lipoproteins (VLDLs)
- Intermediate-density lipoproteins (IDLs)
- Low-density lipoproteins (LDLs)
- High-density lipoproteins (HDLs)

Role of LDL and HDL

LDL (Low-density lipoprotein) delivers cholesterol to cells; sometimes called “bad” lipids
HDL (High-density lipoprotein) removes excess cholesterol and returns it to the liver; sometimes called “good” lipids

Proteins

The body synthesizes 100,000 to 140,000 proteins, each with different form, function, and structure
All proteins are built from the 20 amino acids
10 essential amino acids:
- 8 that are not synthesized by the body: isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, and methionine
- 2 that are insufficiently synthesized: arginine and histidine

Protein Synthesis

The body synthesizes half of the amino acids needed to build proteins
Nonessential amino acids can be made by the body on demand

Protein Catabolism

Cellular proteins are recycled in the cytosol: peptide bonds are broken, and free amino acids are used in new proteins
If other energy sources are inadequate, the mitochondria generate ATP by breaking down amino acids in the TCA cycle

Summary

Metabolism is the sum of all chemical reactions in an organism.
Energy is obtained by breaking down molecules, primarily through respiration.
Carbohydrate Metabolism is broken down into three stages: glycolysis, citric acid cycle, and oxidative phosphorylation.
Lipid Metabolism involves the storage, breakdown (lipolysis), and transport (lipoproteins) of lipids.
Protein Metabolism involves synthesis, degradation (catabolism), and recycling of proteins.

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Description

Explore the fundamental concepts of metabolism, energy production, and material transport in biological systems. This quiz covers anabolic and catabolic processes, ATP generation, and the role of organic compounds in sustaining cellular functions. Test your knowledge about how these processes maintain life at the cellular level.