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Questions and Answers
Which of the following lipoproteins is known as 'bad' lipids that deliver cholesterol to cells?
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.
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What is the primary function of high-density lipoproteins (HDLs)?
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Which process breaks down triglycerides into glycerol and fatty acids?
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Match the following lipoproteins with their primary role:
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What are the two types of amino acids based on how they are synthesized by the body?
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Catabolism refers to the building up of molecules in an organism.
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Proteins in the body are formed from a combination of 20 amino acids.
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What is the net gain of ATP from one molecule of glucose after complete processing?
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During cellular respiration, glucose is converted into carbon dioxide and ________.
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Match the following metabolic pathways with their correct description:
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What are the main products of glycolysis and their respective ATP yield?
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Triglycerides are the most abundant storage carbohydrates in the body.
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What is the primary function of the cardiovascular system in metabolism?
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The process of ________ turns glucose into glycogen for storage.
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How many ATP molecules can be produced from one 18-carbon fatty acid molecule through beta-oxidation?
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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.
