Nutrition Lecture 2

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Questions and Answers

Which statement accurately describes the mechanical digestion process?

Includes physical actions like chewing and stomach churning. (correct)

Is primarily conducted in the small intestine.

Focuses solely on the enzymatic action in the stomach.

Involves enzymatic breakdown of carbohydrates into glucose.

What is the primary purpose of the respiration stage in digestion?

To absorb nutrients into the bloodstream.

To eliminate undigested food from the body.

To synthesize proteins from amino acids.

To produce energy through metabolic pathways. (correct)

Which enzyme initiates protein digestion in the stomach?

Lipase

Pepsin (correct)

Amylase

Trypsin

In which part of the digestive process does bile play a crucial role?

Chemical digestion of fats Signup and view all the answers

What occurs during the assimilation stage of digestion?

Absorbed nutrients are transported to cells for use. Signup and view all the answers

Which nutrient's digestion starts in the mouth and continues in the small intestine?

Carbohydrates Signup and view all the answers

What is the correct sequence of nutrient digestion according to the processes described?

Carbohydrates → Proteins → Fats Signup and view all the answers

Which statement about excretion during digestion is true?

Excretion includes both defecation and urination. Signup and view all the answers

Which of the following correctly describes a key product of pyruvate oxidation?

Acetyl-CoA Signup and view all the answers

What do NADH and FADH₂ primarily serve as in cellular respiration?

Electron carriers Signup and view all the answers

During the Krebs cycle, how many carbon dioxide molecules are produced per acetyl-CoA?

Two Signup and view all the answers

Which process occurs in the mitochondrial membrane and requires oxygen as the final electron acceptor?

Electron transport chain Signup and view all the answers

What is hypermetabolism primarily characterized by?

Increased metabolic rate Signup and view all the answers

Which statement is true regarding insulin resistance?

It is often caused by a sedentary lifestyle. Signup and view all the answers

What is the role of Coenzyme A in pyruvate oxidation?

To form acetyl-CoA Signup and view all the answers

Which metabolic condition is characterized by a decreased metabolic rate?

Hypometabolism Signup and view all the answers

What is produced during oxidative phosphorylation in the electron transport chain?

Water Signup and view all the answers

Which of the following best describes an anabolic process?

Synthesis of proteins from amino acids Signup and view all the answers

What is the primary purpose of food processing related to food safety?

To eliminate microbial and chemical hazards Signup and view all the answers

Which mechanical processing technique is most likely to cause nutrient loss due to heat generated by friction?

Grinding Signup and view all the answers

Which heat processing method preserves most nutrients due to its cooking mechanism?

Steaming Signup and view all the answers

How does frying affect the nutrient content of food?

Good retention of fat-soluble vitamins Signup and view all the answers

What is one of the main effects of pasteurization on food?

Kills pathogens while preserving nutritional quality Signup and view all the answers

Which factor does NOT affect nutrient retention during food processing?

Food presentation techniques Signup and view all the answers

What is the role of emulsifiers in food processing?

To create a uniform mixture of water and oil Signup and view all the answers

Which chemical food processing method is most associated with the preservation of proteins and minerals but can increase sodium content?

Curing and Salting Signup and view all the answers

What is a negative consequence of hydrogenation in food processing?

It produces trans fats that can raise cholesterol levels Signup and view all the answers

Which method of food processing is most effective for enhancing B-vitamin availability?

Fermentation Signup and view all the answers

What impact does blanching have on nutrient retention in food?

It reduces nutrient loss by limiting cooking time Signup and view all the answers

Which type of processing involves using salts or acids to preserve food?

Chemical Processing Signup and view all the answers

What is a common result of enzymatic browning in fruits and vegetables?

Browning due to oxidation of phenolic compounds Signup and view all the answers

Which factor does NOT influence Basal Metabolic Rate (BMR)?

Dietary Fiber Intake Signup and view all the answers

Which of the following is an accurate characteristic of low Glycemic Index (GI) foods?

They are high in fiber and digestion is slow. Signup and view all the answers

Which statement about the Harris-Benedict Equation is true?

It includes factors like age and weight. Signup and view all the answers

In the context of energy balance, which statement about negative energy balance is correct?

It results in weight loss. Signup and view all the answers

Which hormone is primarily responsible for signaling satiety?

Leptin Signup and view all the answers

What is the primary role of non-exercise activity thermogenesis (NEAT)?

Accounts for energy burned through everyday activities. Signup and view all the answers

Which statement correctly describes glycolysis?

It is an anaerobic process that produces ATP and NADH. Signup and view all the answers

Which of the following best defines the concept of energy balance?

When caloric intake equals caloric expenditure. Signup and view all the answers

Which of the following is a consequence of a prolonged positive energy balance?

Obesity Signup and view all the answers

What are the components of Total Daily Energy Expenditure (TDEE)?

BMR, TEF, PAL, and NEAT Signup and view all the answers

Which compounds are primarily responsible for rapid increases in blood sugar when consumed?

High GI Foods Signup and view all the answers

What is NOT a characteristic of metabolic syndrome?

Low physical activity Signup and view all the answers

Which method is used for calculating the Glycemic Index (GI) of a food?

Evaluating blood glucose levels against a reference food. Signup and view all the answers

Which nutrient breakdown process occurs in the cytosol and is anaerobic?

Glycolysis Signup and view all the answers

Study Notes

Digestion, Absorption, Metabolism, and Energy Balance

Digestion is the process of converting ingested nutrients into absorbable forms. It involves mechanical (e.g., chewing) and chemical (enzymatic) processes.
Stages of feeding:
- Ingestion: Consumption of food.
- Digestion: Mechanical (chewing, churning) and chemical (enzymatic breakdown).
  - Carbohydrates: Broken down by amylase.
  - Proteins: Broken down by proteases (e.g., pepsin).
  - Fats: Broken down by lipases into fatty acids and glycerol.
- Absorption: Nutrients enter the bloodstream/lymphatic system.
- Assimilation: Nutrients used for energy, growth, and repair.
- Respiration: Metabolic pathways like glycolysis, Krebs cycle.
- Excretion/Egestion: Removal of waste and undigested matter.
Digestion of Nutrients:
- Carbohydrates: Digestion begins in the mouth with salivary amylase; further breakdown in the small intestine by pancreatic amylase.
- Proteins: Begins in the stomach with pepsin and HCl; further breakdown in the small intestine with enzymes like trypsin and chymotrypsin.
- Lipids (Fats): Begins in the small intestine; bile emulsifies fats, lipase breaks them down.
Food Processing:
- Methods to transform raw ingredients into consumable products.
- Reasons: Food safety, enhanced quality, increased convenience.

Categories of Food Processing

Mechanical: Grinding, chopping, mixing.
Thermal: Baking, frying, boiling, steaming.
Chemical: Preservatives, colorants, flavor enhancers.
Biological: Fermentation, enzymatic reactions.

Impact of Processing on Nutrient Content

Nutrient retention depends on chemical stability, extent of processing, environmental conditions, and food form (fresh, frozen, canned).

Heat Processing Techniques

Baking (Dry Heat): Loss of heat-sensitive vitamins (thiamin, vitamin C).
Microwaving: Retains some vitamins and minerals.
Frying: May lose water-soluble vitamins but retains fat-soluble ones.
Grilling: Moderate loss of water-soluble vitamins.
Boiling: Significant loss of water-soluble vitamins.
Steaming: Preserves most nutrients.
Blanching: Reduces nutrient loss by limiting cooking time.
Pasteurization: Kills pathogens while preserving nutritional quality.

Mechanical Food Processing

Grinding: Reduces particle size, increases surface area, may cause some nutrient loss (depending on refinement).
Chopping: Breaks food into smaller pieces; minimal nutrient loss unless oxidation occurs.
Blending: Liquefies/purees food; may degrade heat-sensitive vitamins; increases some nutrient bioavailability (like carotenoids).

Chemical Food Processing Techniques

Uses additives to preserve, enhance, and modify food.
- Preservatives: Prevent spoilage (e.g., sodium benzoate).
- Antioxidants: Prevent oxidation (e.g., vitamin C).
- Flavor Enhancers: Enhance taste.
- Color Additives: Restore or enhance color.
- Sweeteners: Provide sweetness.
- Emulsifiers: Combine incompatible ingredients.
- Thickeners/Stabilizers: Improve texture.
- pH Control Agents: Maintain desired acidity/alkalinity.
- Anti-Caking Agents: Prevent clumping.
- Leavening Agents: Cause gases for light texture.

Common Chemical Processing Methods

Curing/Salting: Draws out moisture; preserves protein and minerals; increased sodium content.
Pickling: Preserves food by acidity; may reduce water-soluble vitamins.
Emulsification: Mixes ingredients with emulsifiers.
Hydrogenation: Converts unsaturated fats to solid fats (unhealthy trans fats).
Acidification: Lowers pH to inhibit bacterial growth.

Biological Food Processing Techniques

Fermentation: Uses microorganisms to convert sugars; enhances B-vitamins and probiotics.
Enzymatic Browning: A reaction causing fruits/vegetables to brown due to oxidation; prevent by controlling pH, temperature, or using antioxidants.

Energy Balance

Basal Metabolic Rate (BMR): Minimum energy for basic functions (60-75% daily expenditure).
Factors affecting BMR: Age, gender, body composition, genetics, hormones, temperature.
BMR Calculation: Harris-Benedict Equation (men/women); simplified estimate (24 kcal/kg/day).
Glycemic Index (GI): Ranking of carbohydrates based on blood glucose rise.
- Low GI: Gradual rise (e.g., oats).
- Medium GI: Moderate rise (e.g., brown rice).
- High GI: Rapid rise (e.g., white bread).

Glycemic Index Calculation

50g of available carbohydrates are given to participants.
Blood glucose measured over 2 hours.
Compared to a reference food (glucose/white bread).
Average blood glucose response determines GI score.

Energy Balance Concepts

Energy Balance: Calories consumed = calories burned; crucial for weight maintenance.
Positive Energy Balance: More calories in than out; weight gain.
Negative Energy Balance: More calories out than in; weight loss.
Total Daily Energy Expenditure (TDEE): Components: BMR, TEF (Thermic Effect of Food), PAL (Physical Activity Level), NEAT (Non-Exercise Activity Thermogenesis).

Factors influencing Energy Balance

Diet composition: High protein increases TEF.
Physical activity: Boosts calorie expenditure and muscle mass.
Metabolic Rate: Varies with factors mentioned earlier.
Genetics: Influences metabolism.

Regulation of Energy Balance

Hormonal Regulation: (e.g., insulin, glucagon, leptin, ghrelin)
Neurological Signals: Hypothalamus controls hunger and satiety.

Nutritional and Metabolic Disorders

Obesity: Prolonged positive energy balance; associated risks.
Underweight/Malnutrition: Chronic negative energy balance; associated risks.
Metabolic Syndrome: Cluster of conditions (insulin resistance, high blood pressure).
Eating Disorders: Anorexia nervosa, bulimia, binge-eating disorder.

Key Metabolic Processes

Glycolysis: Breakdown of glucose to pyruvate; ATP and NADH produced.
Pyruvate Oxidation: Pyruvate to Acetyl-CoA; CO2, NADH, and Acetyl-CoA produced.
Krebs Cycle: Cyclic reactions producing ATP, NADH, and FADH₂ from Acetyl-CoA.
Electron Transport Chain (ETC): Transferring electrons for ATP generation; oxygen as final electron acceptor.

Energy Balance and Metabolic Disorders

Hypermetabolism: Increased metabolic rate leading to weight loss.
Hypometabolism: Decreased metabolic rate causing weight gain.
Insulin Resistance: Cells not responding to insulin leading to high blood sugar.

Key Definitions and Medical Terms

Metabolism: All chemical reactions in the body.
Anabolism: Building complex molecules.
Catabolism: Breaking down complex molecules.
Homeostasis: Maintaining stable internal conditions.
Enzyme: Protein speeding up reactions.
ATP: Primary energy carrier.
Gluconeogenesis: Creating glucose from non-carbohydrates.
Lipolysis: Breakdown of fats.
Ketosis: Using fat-derived ketones for energy.

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Description

Explore the intricate processes of digestion, absorption, and metabolism of nutrients. Understand the stages from ingestion to excretion, including the roles of different enzymes and metabolic pathways. Test your knowledge on how nutrients are processed and utilized by the body.