General Principles Week 1 Flashcards
1
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Nucleus:
A
Controls cellular activities and houses genetic material.
2
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Mitochondria:
A
Produce energy through ATP synthesis
3
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Endoplasmic Reticulum:
A
Rough ER synthesizes proteins; smooth ER synthesizes lipids.
4
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Golgi Apparatus:
A
Modifies, packages, and distributes cellular products.
5
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Lysosomes
A
Contain digestive enzymes for breaking down cellular waste.
6
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Peroxisomes
A
Involved in oxidation reactions, particularly fatty acid breakdown.
7
Q
Topic 1 - Cellular Structure and Function
TLO 1.1: Identify cellular organelles and describe each of their functions
Ribosomes
A
Site of protein synthesis.
8
Q
TLO 1.1: Identify cellular organelles and describe each of their functions
Vacuoles
A
Storage organelles for various substances.
9
Q
TLO 1.1: Identify cellular organelles and describe each of their functions
Chloroplasts (in plant cells):
A
Responsible for photosynthesis.
10
Q
TLO 1.1: Identify cellular organelles and describe each of their functions
Cell Membrane
A
Controls what enters and exits the cell.
11
Q
Topic 1 - Cellular Structure and Function
TLO 1.2: Explain the basis of the fluid mosaic model of biological membranes and relate the structure to its function
The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins. Key features:
Phospholipid bilayer
A
Forms the membrane’s basic structure.
12
Q
Topic 1 - Cellular Structure and Function
TLO 1.2: Explain the basis of the fluid mosaic model of biological membranes and relate the structure to its function
The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins. Key features:
Fluidity:
A
Allows lateral movement of membrane components.
13
Q
Topic 1 - Cellular Structure and Function
TLO 1.2: Explain the basis of the fluid mosaic model of biological membranes and relate the structure to its function
The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins. Key features:
Embedded proteins:
A
Perform various functions (e.g., transport, signaling).
14
Q
Topic 1 - Cellular Structure and Function
TLO 1.2: Explain the basis of the fluid mosaic model of biological membranes and relate the structure to its function
The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins. Key features:
Cholesterol
A
Regulates membrane fluidity and stability.
15
Q
Topic 1 - Cellular Structure and Function
TLO 1.2: Explain the basis of the fluid mosaic model of biological membranes and relate the structure to its function
The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins. Key features:
Glycoproteins and glycolipids
A
Form the glycocalyx for cell recognition.
16
Q
Topic 1 - Cellular Structure and Function
TLO 1.2: Explain the basis of the fluid mosaic model of biological membranes and relate the structure to its function
The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins. Key features:
A
This structure enables selective permeability, cell signaling, and maintenance of cell shape.
17
Q
Topic 2 – Molecules of Life
TLO 2.1: Identify the four major macromolecules in the human body and their sources
Proteins
A
Sourced from dietary amino acids.
18
Q
Topic 2 – Molecules of Life
TLO 2.1: Identify the four major macromolecules in the human body and their sources
Lipids
A
Sourced from dietary fatty acids and glycerol.
19
Q
Topic 2 – Molecules of Life
TLO 2.1: Identify the four major macromolecules in the human body and their sources
Carbohydrates
A
Sourced from dietary simple sugars.
20
Q
Topic 2 – Molecules of Life
TLO 2.1: Identify the four major macromolecules in the human body and their sources
Nucleic Acids
A
Sourced from nucleotides synthesized in the body or from diet.
21
Q
Topic 2 – Molecules of Life
TLO 2.2: Describe the major roles of proteins in the human body
Proteins serve as:
A
- Structural components (e.g., collagen)
- Enzymes catalyzing biochemical reactions
- Transport molecules (e.g., hemoglobin)
- Hormones (e.g., insulin)
- Antibodies for immune function
- Cell signaling receptors
- Muscle contraction components (actin and myosin)
22
Q
Topic 2 – Molecules of Life
TLO 2.3: Describe the major roles of lipids in the human body
Lipids function as:
A
- Energy storage (triglycerides)
- Cell membrane components (phospholipids and cholesterol)
- Insulation (subcutaneous fat)
- Hormone precursors (steroid hormones)
- Facilitators of fat-soluble vitamin absorption
- Cell signaling molecules (lipid-based second messengers)
23
Q
Topic 2 – Molecules of Life
TLO 2.4: Describe the major roles of carbohydrates in the human body
Carbohydrates serve as:
A
- Primary energy source (glucose)
- Energy storage (glycogen)
- Structural components (e.g., ribose in nucleic acids)
- Cell recognition molecules (glycoproteins and glycolipids)
- Dietary fiber for digestion and gut health
24
Q
Topic 2 – Molecules of Life
TLO 2.5: Describe the major roles of nucleic acids in the human body
Nucleic acids (DNA and RNA) are crucial for:
A
- Genetic information storage (DNA)
- Protein synthesis (mRNA, tRNA, rRNA)
- Gene regulation (miRNA and other regulatory RNAs)
- Enzyme cofactors (e.g., NAD+ and FAD in metabolism)
25
Topic 2 – Molecules of Life
TLO 2.6: Discuss how dysfunction of macromolecules can result in disease
Macromolecule dysfunction can lead to various diseases:
Proteins
Misfolding (e.g., Alzheimer's) or enzyme deficiencies (e.g., Phenylketonuria)
26
Topic 2 – Molecules of Life
TLO 2.6: Discuss how dysfunction of macromolecules can result in disease
Macromolecule dysfunction can lead to various diseases:
Carbohydrates
Impaired glucose metabolism (diabetes) or glycogen storage diseases
27
Topic 2 – Molecules of Life
TLO 2.6: Discuss how dysfunction of macromolecules can result in disease
Macromolecule dysfunction can lead to various diseases:
Lipids
Cholesterol imbalance (atherosclerosis) or lipid storage disorders (e.g., Tay-Sachs)
28
Topic 2 – Molecules of Life
TLO 2.6: Discuss how dysfunction of macromolecules can result in disease
Macromolecule dysfunction can lead to various diseases:
Nucleic Acids
Genetic mutations (e.g., sickle cell anemia) or DNA repair defects (increased cancer risk)
29
Topic 3 – Cell Transport
TLO 3.1: Identify cellular transport mechanisms used by a cell to move substances across the membrane and discuss factors that determine the type of transport used
Transport mechanisms:
Passive transport
Simple diffusion, facilitated diffusion, osmosis
30
Topic 3 – Cell Transport
TLO 3.1: Identify cellular transport mechanisms used by a cell to move substances across the membrane and discuss factors that determine the type of transport used
Transport mechanisms:
Active transport
Primary active transport, secondary active transport
31
Topic 3 – Cell Transport
TLO 3.1: Identify cellular transport mechanisms used by a cell to move substances across the membrane and discuss factors that determine the type of transport used
Transport mechanisms:
Vesicular transport
Endocytosis, exocytosis
32
Topic 3 – Cell Transport
TLO 3.1: Identify cellular transport mechanisms used by a cell to move substances across the membrane and discuss factors that determine the type of transport used
Transport mechanisms:
Factors determining transport type
* Concentration gradient
* Molecule size and polarity
* Membrane permeability
* Energy requirements
* Presence of specific transport proteins
33
Topic 3 – Cell Transport
TLO 3.2: Explain the differences between passive and facilitated diffusion
Passive diffusion:
* Molecules move directly through the phospholipid bilayer
* No energy required
* Limited to small, nonpolar molecules
34
Topic 3 – Cell Transport
TLO 3.2: Explain the differences between passive and facilitated diffusion
Facilitated diffusion:
* Requires transport proteins (channels or carriers)
* No energy required
* Allows passage of larger or polar molecules
* Can be regulated by the cell
35
Topic 3 – Cell Transport
TLO 3.3: Explain the difference between primary and secondary active transport using relevant clinical examples
Secondary active transport
* Uses energy from electrochemical gradient created by primary active transport
* Example: Glucose-sodium cotransporter (SGLT) in kidney tubules (glucose reabsorption)
36
Topic 3 – Cell Transport
TLO 3.3: Explain the difference between primary and secondary active transport using relevant clinical examples
Primary active transport
* Directly uses ATP for energy
* Example: Na+/K+ ATPase pump in neurons (maintains resting membrane potential)
37
Topic 4 – Cell Cycle and Cell Division
TLO 4.1: Describe the stages of the cell cycle and the important functions that take place within each one
Interphase
* G1: Cell growth and preparation for DNA synthesis
* S: DNA replication
* G2: Preparation for mitosis
38
Topic 4 – Cell Cycle and Cell Division
TLO 4.1: Describe the stages of the cell cycle and the important functions that take place within each one
Mitotic phase
* Mitosis: Nuclear division
* Cytokinesis: Cytoplasmic division
39
Topic 4 – Cell Cycle and Cell Division
TLO 4.1: Describe the stages of the cell cycle and the important functions that take place within each one
G0 phase
Quiescent or senescent state (optional)
40
Topic 4 – Cell Cycle and Cell Division
TLO 4.2: Explain the process of mitosis and describe the important events that take place in each phase
Prophase
Chromatin condenses, nuclear envelope breaks down, spindle fibers form
41
Topic 4 – Cell Cycle and Cell Division
TLO 4.2: Explain the process of mitosis and describe the important events that take place in each phase
Metaphase
Chromosomes align at the metaphase plate
42
Topic 4 – Cell Cycle and Cell Division
TLO 4.2: Explain the process of mitosis and describe the important events that take place in each phase
Anaphase
Sister chromatids separate and move to opposite poles
43
Topic 4 – Cell Cycle and Cell Division
TLO 4.2: Explain the process of mitosis and describe the important events that take place in each phase
Telophase
Chromosomes decondense, nuclear envelopes reform, cytokinesis begins
44
Topic 4 – Cell Cycle and Cell Division
TLO 4.3: Identify the different types of stem cells in the human body and the structures they can potentially become (unipotent, pluripotent, multipotent and totipotent), and relate their function to therapeutic potential
Totipotent
Can form all cell types (e.g., zygote)
45
Topic 4 – Cell Cycle and Cell Division
TLO 4.3: Identify the different types of stem cells in the human body and the structures they can potentially become (unipotent, pluripotent, multipotent and totipotent), and relate their function to therapeutic potential
Pluripotent
Can form most cell types (e.g., embryonic stem cells)
46
Topic 4 – Cell Cycle and Cell Division
TLO 4.3: Identify the different types of stem cells in the human body and the structures they can potentially become (unipotent, pluripotent, multipotent and totipotent), and relate their function to therapeutic potential
Multipotent
Can form multiple cell types within a lineage (e.g., hematopoietic stem cells)
47
Topic 4 – Cell Cycle and Cell Division
TLO 4.3: Identify the different types of stem cells in the human body and the structures they can potentially become (unipotent, pluripotent, multipotent and totipotent), and relate their function to therapeutic potential
Unipotent
Can form only one cell type (e.g., spermatogonial stem cells)
48
Topic 4 – Cell Cycle and Cell Division
TLO 4.3: Identify the different types of stem cells in the human body and the structures they can potentially become (unipotent, pluripotent, multipotent and totipotent), and relate their function to therapeutic potential
Therapeutic potential
Regenerative medicine, tissue engineering, disease modeling, drug screening.
49
Topic 4 – Cell Cycle and Cell Division
TLO 4.4: Justify the importance of maintaining balance between cell division and apoptosis
Balancing cell division and apoptosis is crucial for:
* Tissue homeostasis
* Proper organ function
* Prevention of cancer and other diseases
* Embryonic development
* Immune system regulation
50
Topic 4 – Cell Cycle and Cell Division
TLO 4.5: Describe the process of meiosis
Meiosis consists of two divisions:
Meiosis I
Homologous chromosomes pair, crossover, and separate
51
Topic 4 – Cell Cycle and Cell Division
TLO 4.5: Describe the process of meiosis
Meiosis consists of two divisions:
Meiosis II
Sister chromatids separate
52
Topic 4 – Cell Cycle and Cell Division
TLO 4.5: Describe the process of meiosis
Meiosis consists of two divisions:
Results in four haploid gametes with genetic diversity.
53
Topic 4 – Cell Cycle and Cell Division
TLO 4.6: Compare meiosis to mitosis
Similarities:
* Both involve DNA replication and cell division
54
Topic 4 – Cell Cycle and Cell Division
TLO 4.6: Compare meiosis to mitosis
Differences
* Meiosis produces haploid gametes; mitosis produces identical diploid cells
* Meiosis involves two rounds of division; mitosis involves one
* Meiosis includes genetic recombination; mitosis does not
* Meiosis occurs only in germ cells; mitosis occurs in somatic cells
55
Topic 5 – Introduction to the Genome
TLO 5.1: Describe the major components that make up the human genome
Nuclear DNA
23 pairs of chromosomes
56
Topic 5 – Introduction to the Genome
TLO 5.1: Describe the major components that make up the human genome
Mitochondrial DNA
Circular DNA in mitochondria
57
Topic 5 – Introduction to the Genome
TLO 5.1: Describe the major components that make up the human genome
Genes
Protein-coding sequences
58
Topic 5 – Introduction to the Genome
TLO 5.1: Describe the major components that make up the human genome
Regulatory elements
Promoters, enhancers, silencers
59
Topic 5 – Introduction to the Genome
TLO 5.1: Describe the major components that make up the human genome
Non-coding DNA
Introns, repetitive sequences
60
Topic 5 – Introduction to the Genome
TLO 5.1: Describe the major components that make up the human genome
Telomeres
Protective end sequences of chromosomes
61
Topic 5 – Introduction to the Genome
TLO 5.2: Identify the major enzymes involved in DNA replication and their functions
DNA helicase
Unwinds the DNA double helix
62
DNA primase
Synthesizes RNA primers
63
DNA polymerase III
Main replicative enzyme, extends DNA strands
64
DNA polymerase I
Removes RNA primers, fills gaps
65
DNA ligase
Joins Okazaki fragments
66
Topic 5 – Introduction to the Genome
TLO 5.3: Compare and contrast the process of DNA replication in eukaryotic and prokaryotic cells
Differences
* Eukaryotic replication is slower and more complex
* Eukaryotes have multiple origins of replication; prokaryotes have one
* Eukaryotes replicate linear chromosomes; prokaryotes replicate circular DNA
* Eukaryotes have telomere maintenance; prokaryotes do not
67
Topic 5 – Introduction to the Genome
TLO 5.3: Compare and contrast the process of DNA replication in eukaryotic and prokaryotic cells
Similarities
* Both use semiconservative replication
* Both require similar enzymes (helicases, polymerases, ligases)
68
Topic 5 – Introduction to the Genome
TLO 5.4: Explain the process of transcription and translation in a eukaryotic cell
Transcription:
1. Initiation: RNA polymerase binds to promoter
2. Elongation: RNA synthesis
3. Termination: RNA release
4. Post-transcriptional modifications: 5' capping, 3' polyadenylation, splicing
69
Topic 5 – Introduction to the Genome
TLO 5.4: Explain the process of transcription and translation in a eukaryotic cell
Translation:
1. Initiation: Ribosome assembly on mRNA
2. Elongation: Amino acid chain formation
3. Termination: Release of completed protein
4. Post-translational modifications: Folding, chemical modifications
70
Topic 6 – Cell Signaling and Communication
TLO 6.1: Define the term receptor and identify the different membrane proteins that can act as receptors
A receptor is a protein that binds to a specific signaling molecule, triggering a cellular response. Membrane proteins acting as receptors:
1. G protein-coupled receptors (GPCRs)
2. Receptor tyrosine kinases (RTKs)
3. Ion channel-linked receptors
4. Enzyme-linked receptors
71
Topic 6 – Cell Signaling and Communication
TLO 6.2: Identify and explain the roles of the major receptor types
1. G protein-coupled receptors (GPCRs): Signal transduction through G proteins
2. Receptor tyrosine kinases (RTKs): Phosphorylation of target proteins
3. Ion channel-linked receptors: Direct ion flow across membranes
4. Enzyme-linked receptors: Catalyze intracellular reactions
72
Topic 6 – Cell Signaling and Communication
TLO 6.3: Explain the role of proteins in cell signaling and communication
Proteins play crucial roles in cell signaling:
1. Receptors: Detect and respond to signals
2. Signal transducers: Relay and amplify signals
3. Enzymes: Modify other proteins
4. Scaffold proteins: Organize signaling complexes
5. Transcription factors: Regulate gene expression
6. Ion channels: Control ion flow and membrane potential
73
Topic 6 – Cell Signaling and Communication
TLO 6.4: Distinguish between endocrine, paracrine and autocrine signaling mechanisms and the types of transduction pathways that can be activated
Endocrine signaling: Long-distance communication via bloodstream
Paracrine signaling: Short-distance communication between nearby cells
Autocrine signaling: Cell signals to itself. Transduction pathways:
1. cAMP pathway
2. Phosphoinositide pathway
3. JAK-STAT pathway
4. MAP kinase pathway
Each signaling mechanism can activate various transduction pathways depending on the specific receptor and ligand involved.
74
Topic 7 – Enzyme Function and Classification
TLO 7.1: Explain the basic principles of enzyme function
Enzymes are biological catalysts that:
1. Lower activation energy of reactions
2. Exhibit substrate specificity
3. Remain unchanged after catalysis
4. Function optimally under specific conditions (pH, temperature)
5. Can be regulated by various factors
75
Topic 7 – Enzyme Function and Classification
TLO 7.2: Describe the properties of enzyme kinetics
Key properties of enzyme kinetics include:
1. Michaelis-Menten kinetics
2. Km (Michaelis constant) and Vmax (maximum velocity)
3. Lineweaver-Burk plot for determining kinetic parameters
4. Effects of substrate concentration on reaction rate
5. Enzyme saturation
76
Topic 7 – Enzyme Function and Classification
TLO 7.3: Describe the different classifications of enzymes and their relative function
Enzyme classifications:
1. Oxidoreductases: Catalyze oxidation-reduction reactions
2. Transferases: Transfer functional groups between molecules
3. Hydrolases: Catalyze hydrolysis reactions
4. Lyases: Add or remove groups without hydrolysis
5. Isomerases: Catalyze intramolecular rearrangements
6. Ligases: Join two molecules using ATP hydrolysis
77
Topic 7 – Enzyme Function and Classification
TLO 7.4: Identify key enzyme inhibitors and their clinical relevance
1. Competitive inhibitors: Compete with substrate for active site (e.g., statins inhibiting HMG-CoA reductase)
2. Non-competitive inhibitors: Bind to allosteric site (e.g., aspirin inhibiting cyclooxygenase)
3. Irreversible inhibitors: Permanently modify enzyme (e.g., penicillin inhibiting bacterial cell wall synthesis)
4. Suicide inhibitors: Enzyme converts inhibitor to reactive form (e.g., acyclovir inhibiting viral DNA polymerase)
78
Topic 8 - Cellular Biochemistry
TLO 8.1: Justify the use of glucose as the body's primary energy source
Glucose is the primary energy source because:
Glucose is the primary energy source because:
1. It's readily available from carbohydrate digestion
2. It can be quickly metabolized for energy
3. All cells can use it
4. It can be stored as glycogen for later use
5. It's essential for brain function
79
TLO 8.2: Identify the locations of bioenergetic reactions in the cell
1. Cytoplasm: Glycolysis
2. Mitochondrial matrix: Krebs cycle, fatty acid oxidation
3. Inner mitochondrial membrane: Electron transport chain, oxidative phosphorylation
4. Endoplasmic reticulum: Lipid synthesis
5. Peroxisomes: Fatty acid oxidation (very long-chain fatty acids)
80
TLO 8.3: Define aerobic and anaerobic metabolism and provide bioenergetic examples of each
Aerobic metabolism: Requires oxygen for complete oxidation of substrates
Example: Complete glucose oxidation through glycolysis, Krebs cycle, and electron transport chain.
Anaerobic metabolism: Occurs without oxygen
Example: Lactic acid fermentation during intense exercise
81
TLO 8.4: Explain the major steps and products of glycolysis, Krebs cycle and the Electron Transport Chain (ECT)
Glycolysis:
1. Glucose → 2 Pyruvate
2. Net production: 2 ATP, 2 NADH
Krebs cycle:
1. Acetyl-CoA → 2 CO2
2. Per cycle: 3 NADH, 1 FADH2, 1 GTP
Electron Transport Chain:
1. NADH and FADH2
82
TLO 8.5: Identify the key enzymes and steps in glycogen metabolism
Key enzymes in glycogen metabolism:
1. Glycogen synthase: Adds glucose units to glycogen
2. Glycogen phosphorylase: Breaks down glycogen to glucose-1-phosphate
3. Branching enzyme: Creates branch points in glycogen
4. Debranching enzyme: Removes branch points during glycogen breakdown
Steps:
1. Glycogenesis: Glucose → Glucose-6-phosphate → Glucose-1-phosphate → UDP-glucose → Glycogen
2. Glycogenolysis: Glycogen → Glucose-1-phosphate → Glucose-6-phosphate → Glucose (in liver) or pyruvate (in muscle)
83
TLO 8.6: Provide clinical examples of metabolism disorders
1. Diabetes mellitus: Impaired glucose metabolism
2. Phenylketonuria: Phenylalanine metabolism disorder
3. Glycogen storage diseases: Impaired glycogen metabolism
4. Fatty acid oxidation disorders: e.g., Medium-chain acyl-CoA dehydrogenase deficiency
5. Urea cycle disorders: e.g., Ornithine transcarbamylase deficiency
84
TLO 8.7: Describe the sequence of reactions involved in the oxidation of fatty acids in the mitochondrion and its regulation
Fatty acid oxidation (β-oxidation):
1. Activation: Fatty acid → Fatty acyl-CoA
2. Transport into mitochondria via carnitine shuttle
3. β-oxidation cycle:
a. Dehydrogenation (FAD → FADH2)
b. Hydration
c. Dehydrogenation (NAD+ → NADH)
d. Thiolysis (CoA-SH)
4. Acetyl-CoA enters Krebs cycle
85
TLO 8.7: Describe the sequence of reactions involved in the oxidation of fatty acids in the mitochondrion and its regulation
Regulation:
* Inhibited by high levels of acetyl-CoA and NADH
* Stimulated by glucagon and epinephrine
* Inhibited by insulin
86
TLO 8.8: Describe the pathway for activation and transport of fatty acids to the mitochondrion for catabolism
1. Activation: Fatty acid + CoA + ATP → Fatty acyl-CoA + AMP + PPi
2. Carnitine shuttle:
a. Fatty acyl-CoA + Carnitine → Fatty acyl-carnitine + CoA
b. Transport across inner mitochondrial membrane
c. Fatty acyl-carnitine + CoA → Fatty acyl-CoA + Carnitine
3. Fatty acyl-CoA enters β-oxidation cycle
87
TLO 8.9: Explain the rationale for the pathway of ketogenesis and identify the major intermediates and products of this pathway
Rationale: Ketogenesis occurs when glucose is scarce and fatty acid oxidation is high, providing alternative fuel for the brain.
Pathway:
1. Acetyl-CoA → Acetoacetyl-CoA
2. Acetoacetyl-CoA + Acetyl-CoA → HMG-CoA
3. HMG-CoA → Acetoacetate
4. Acetoacetate → β-hydroxybutyrate or Acetone
Major intermediates: Acetoacetyl-CoA, HMG-CoA
Major products: Acetoacetate, β-hydroxybutyrate, Acetone (ketone bodies)
88
TLO 8.10: Describe the three mechanisms used by humans for removal of nitrogen from amino acids before the metabolism of their carbon skeletons
1. Transamination: Transfer of amino group to α-ketoglutarate, forming glutamate
2. Oxidative deamination: Removal of amino group as ammonia by glutamate dehydrogenase
3. Urea cycle: Conversion of ammonia to urea for excretion
89
TLO 8.11: Outline the sequence of reactions in the urea cycle including key regulatory steps
Urea cycle steps:
1. Carbamoyl phosphate synthesis
2. Citrulline formation
3. Argininosuccinate synthesis
4. Argininosuccinate cleavage
5. Arginine cleavage to urea
Key regulatory steps:
* Carbamoyl phosphate synthetase I (rate-limiting)
* N-acetylglutamate (allosteric activator)
90
TLO 8.12: Define the terms and give examples of glucogenic and ketogenic amino acids
Glucogenic amino acids: Can be converted to glucose
Examples: Alanine, Aspartate, Glutamate
Ketogenic amino acids: Can be converted to ketone bodies
Examples: Leucine, Lysine
Some amino acids are both glucogenic and ketogenic (e.g., Phenylalanine, Tyrosine)
91
TLO 8.13: Summarise the sources and use of ammonia in animals, and explain the concept of nitrogen balance
Sources of ammonia:
1. Amino acid deamination
2. Bacterial action in the gut
3. Glutamine breakdown in the kidney
Uses of ammonia:
1. Urea synthesis
2. Glutamine synthesis
3. Nucleotide synthesis
Nitrogen balance: The state where nitrogen intake equals nitrogen excretion. Positive balance indicates growth or tissue repair, while negative balance suggests catabolism or inadequate protein intake.
92
TLO 8.14: Identify the essential amino acids and the metabolic sources of the nonessential amino acids
Essential amino acids (cannot be synthesized by humans):
Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
Nonessential amino acids
(can be synthesized):
Alanine, Arginine, Asparagine, Aspartate, Cysteine, Glutamate, Glutamine, Glycine, Proline, Serine, Tyrosine
Metabolic sources of nonessential amino acids:
1. Transamination of keto acids
2. Conversion from other amino acids
3. Synthesis from metabolic intermediates (e.g., 3-phosphoglycerate for serine)
