Nutrition and Digestion: Enzymes, Macronutrients, and the Human Digestive System

Assignment Brief

Course Information

Course Title: Access to Higher Education Diploma – Nursing and Healthcare Professions
Unit Title: Nutrition and Digestion (Graded)
Unit Code: WJG335
Level: Three
Credit Value: 3
Tutor Name: [Insert Tutor Name]
Student Name: [Insert Student Name]
Task Number: 1
Task Title: Short answer questions (AC 1.1–1.3, 2.1–2.4 & 3.1–3.3)
Due Date: 12 March 2021

Student Declaration of Authenticity

I confirm that the assignment I have submitted is all my own work and that it has been appropriately referenced in line with the centre policy on referencing of submissions of academic work.

Signature of Student: ______________________
Date Submitted: __________________________

Work submitted after the deadline without an agreed extension two days before the due date or appropriate mitigation will be considered for pass only.

Unit Learning Outcomes

LO1: Understanding of Enzymes

• 1.1 Explain enzyme function with reference to the lock and key and induced fit models.
• 1.2 Describe the mechanisms of enzyme inhibitors and coenzymes.
• 1.3 Investigate factors that influence enzyme activity.

LO2: Understanding of Lipids, Carbohydrates and Proteins

• 2.1 Describe the structure and function of phospholipids and cholesterol; explain differences between saturated and polyunsaturated fatty acids.
• 2.2 Describe glycosidic bond formation and the structure and function of monosaccharides, disaccharides and polysaccharides.
• 2.3 Describe peptide bond formation and the four levels of protein structure.
• 2.4 Investigate biochemical tests for lipids, starch, reducing sugars and protein.

LO3: Understanding of the Human Digestive System

• 3.1 Relate the anatomy of the digestive tract to ingestion, digestion, absorption, assimilation, and egestion.
• 3.2 Identify the origin and function of a range of digestive secretions.
• 3.3 Explain the role of gut flora and factors that can affect it.

Assignment Feedback & Assessment Criteria

Level: 3
AC: 1.1, 1.2, 1.3, 2.1, 2.2, 2.3, 2.4, 3.1, 3.2, 3.3

Grade Descriptors:

Grade Profile Achieved for Assignment
Tutor Signature: __________________
Date: __________________
Assessed and Graded by: Mark Taylor, 07.01.2021
Internally Moderated by: [Name]
Date: [Date]

Grading Information

1. Understanding of the Subject

• Merit: Demonstrates a very good grasp of the relevant knowledge base.

• Distinction: Demonstrates an excellent grasp of the relevant knowledge base.

• Assignment implication (Merit): Very good understanding of nutrition and digestion, including the digestive system.

• Assignment implication (Distinction): Excellent understanding of nutrition and digestion, including the digestive system.

3. Application of Skills

• Merit: Very good command of skills, techniques, and methods with high confidence, consistency, creativity, precision, accuracy, and efficiency.

• Distinction: Excellent command of skills, techniques, and methods with excellent confidence, consistency, creativity, precision, accuracy, and efficiency.

• Assignment implication (Merit): Very good written presentation and interpretation of biochemical tests.

• Assignment implication (Distinction): Excellent written presentation and interpretation of biochemical tests.

4. Use of Information

• Merit: Generally appraises relevance and value of new information accurately.

• Distinction: Consistently appraises relevance and value of new information accurately.

• Assignment implication (Merit): Very good selection of information/data to support discussion.

• Assignment implication (Distinction): Excellent selection of information/data to support discussion.

7. Quality

• Merit: Structured logically and fluently, minor ambiguities, demonstrates a very good response to the brief.

• Distinction: Structured logically and fluently, arguments unambiguous, demonstrates an excellent response to the brief.

• Assignment implication (Merit): Very good response to assignment demands.

• Assignment implication (Distinction): Excellent response to assignment demands.

Sample Answer

Nutrition and Digestion: Enzymes, Macronutrients, and the Human Digestive System

Enzymes (LO1)

Enzymes are biological catalysts that accelerate chemical reactions without being consumed in the process. Their specificity arises from the shape of their active sites, which bind to substrates in a precise manner. The classical lock and key model, proposed by Fischer in 1894, suggests that the substrate fits exactly into the enzyme, much like a key fits a lock. However, the induced fit model, introduced by Koshland in 1958, provides a more dynamic view, describing how the enzyme’s active site slightly alters its shape upon substrate binding, enhancing the efficiency of catalysis. Both models illustrate the critical role of enzyme-substrate complementarity in biochemical reactions.

Enzyme function can be modulated by inhibitors and coenzymes. Competitive inhibitors bind directly to the active site, preventing substrate attachment, whereas non-competitive inhibitors attach elsewhere on the enzyme, causing a conformational change that reduces activity. Coenzymes, which are typically small non-protein molecules, assist enzymes in catalysis by transporting chemical groups between reactions. A common example is NAD⁺, which acts as an electron carrier in cellular respiration. The activity of enzymes is also influenced by external factors such as temperature, pH, and the concentrations of both substrate and enzyme. Deviations from an enzyme’s optimal temperature or pH can lead to denaturation or reduced catalytic efficiency, while higher substrate concentrations increase the reaction rate until the enzyme becomes saturated.

Lipids, Carbohydrates, and Proteins (LO2)

Lipids, carbohydrates, and proteins are essential macronutrients that perform diverse structural and functional roles in the body. Phospholipids, which consist of hydrophilic heads and hydrophobic tails, are fundamental components of cell membranes, forming bilayers that regulate molecular transport. Cholesterol is another critical lipid that stabilises membrane fluidity and serves as a precursor for steroid hormones. Fatty acids vary in structure, with saturated fatty acids containing no double bonds and being solid at room temperature, while polyunsaturated fatty acids contain multiple double bonds and remain liquid at room temperature. These structural differences influence their physical properties and biological roles.

Carbohydrates provide energy and structural support. Monosaccharides such as glucose and fructose serve as immediate energy sources. Disaccharides, including sucrose and lactose, are formed by glycosidic bonds in condensation reactions that release water molecules. Polysaccharides such as starch, glycogen, and cellulose consist of long chains of monosaccharide units and function in energy storage or structural support. Similarly, proteins are composed of amino acids linked by peptide bonds, which form through condensation reactions. The structure of proteins is hierarchical, encompassing primary sequences of amino acids, secondary formations such as α-helices and β-pleated sheets maintained by hydrogen bonds, tertiary folding into complex three-dimensional shapes, and quaternary structures arising from the assembly of multiple polypeptide chains. These structural levels determine protein functionality, ranging from enzymatic activity to structural support.

Biochemical testing allows the investigation of these macronutrients in laboratory settings. Lipids can be identified using the Sudan III test, starch with iodine solution, reducing sugars via Benedict’s test, and proteins through the Biuret test. Accurate interpretation of these tests underpins practical understanding of nutrition and digestion, providing evidence for the presence and behaviour of essential biomolecules.

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