18 Questions
What is the term used to describe the state where the rate of protein synthesis equals the rate of breakdown and loss?
Nitrogen balance
Which group of hormones accelerates protein synthesis?
Anabolic hormones like GH and sex hormones
What happens when the rate of protein breakdown exceeds the rate of synthesis in the body?
Negative nitrogen balance
Which of the following amino acids is considered essential for infants?
Histidine
What is the main consequence of inadequate caloric intake with respect to protein use in the body?
Protein breakdown is accelerated
Which vitamins are synthesized in the body and are crucial for helping the body use nutrients effectively?
Vitamin K and B12
Which of the following is an essential function of proteins in the body?
Structural support in muscle proteins
What is the main role of amino acids in the body?
Forming enzymes and some hormones
Which type of proteins lack some essential amino acids?
Proteins derived from legumes and nuts
What are the essential fatty acids that must be ingested through diet?
Linoleic and linolenic acid
Which body cells primarily rely on glucose as their main fuel source to make ATP?
Hepatocytes and red blood cells
What is a major function of phospholipids in the body?
Forming myelin sheaths and cell membranes
What are the main functions of proteins in the body?
Structural and functional roles, such as serving as enzymes or hormones
Which of the following is NOT a product of the oxidative breakdown of nutrients in the mitochondria?
NH3
Why are essential amino acids important in the body?
They must be obtained from the diet as the body cannot produce them
Which of the following is a key factor in protein synthesis within tissue cells?
Availability of essential amino acids and ribosomes
What role do coenzymes like NAD+ and FAD play in cellular metabolism?
Act as hydrogen acceptors in redox reactions
Which process involves the incorporation of proteins into molecules and the breakdown of nutrients to form intermediates within tissue cells?
Anabolism within tissue cells
Study Notes
Protein Synthesis
- All amino acids must be present for protein synthesis to occur
- Insufficient carbohydrate or fat availability leads to protein being used as fuel
Nitrogen Balance
- State where protein synthesis rate equals protein breakdown and loss rate
- Positive nitrogen balance: synthesis exceeds breakdown (normal in children and tissue repair)
- Negative nitrogen balance: breakdown exceeds synthesis (e.g., stress, burns, infection, or injury)
Hormonal Controls
- Anabolic hormones (GH, sex hormones) accelerate protein synthesis
Essential Amino Acids
- Threonine, Leucine, Phenylalanine, Isoleucine, Lysine, Histidine (infants), Arginine (infants) are essential amino acids
- Valine and Methionine are also essential amino acids
- Tryptophan and Methionine are important amino acids
Vitamins
- Organic compounds crucial in helping the body use nutrients
- Most function as coenzymes
- Vitamins D, some B, and K are synthesized in the body
- Two types: water-soluble and fat-soluble
- Water-soluble vitamins: B complex and C, absorbed with water, not stored in the body
- Fat-soluble vitamins: Vitamins A, D, E, and K, require fat for absorption
Nutrients
- Major nutrients: Carbohydrates, Lipids, and Proteins
- Other nutrients: Vitamins, Minerals, and Water
- Energy (ATP) is derived from Carbohydrates, Lipids, and Proteins
Carbohydrates
- Dietary sources: Starch, Sugars, Insoluble fiber, Soluble fiber
- Uses: Glucose is the fuel used by cells to make ATP, neurons and RBCs rely on glucose
- Excess glucose is converted to glycogen or fat and stored
Lipids
- Dietary sources: Triglycerides, Saturated fats, Unsaturated fats, Cholesterol
- Essential fatty acids: Linoleic and linolenic acid, found in most vegetable oils
- Uses: Help absorb fat-soluble vitamins, major fuel of hepatocytes and skeletal muscle, phospholipids are essential in myelin sheaths and all cell membranes
- Functions of fatty deposits: Protective cushions, Insulating layer, Concentrated source of energy
- Regulatory functions of prostaglandins: Smooth muscle contraction, Control of blood pressure, Inflammation
- Functions of cholesterol: Stabilizes membranes, Precursor of bile salts and steroid hormones
Cellular Metabolic Processes
- Stage 1: Digestion, absorption, and transport to tissues
- Stage 2: Cellular processing, synthesis of lipids, proteins, and glycogen, or catabolism into intermediates
- Stage 3: Oxidative breakdown of intermediates into CO2, water, and ATP
Oxidation-Reduction (Redox) Reactions
- Oxidation: gain of oxygen or loss of hydrogen
- Reduced substances gain electrons and energy
- Coenzymes act as hydrogen (or electron) acceptors: NAD+, FAD
ATP Synthesis
- Two mechanisms: Substrate-level phosphorylation, Oxidative phosphorylation
Test your knowledge on protein synthesis, the all-or-none rule, adequacy of caloric intake, nitrogen balance, and hormonal controls. Understand how various factors can impact protein synthesis and breakdown.
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