TLO week 1 Flashcards
Identify cellular organelles and describe each of their functions (10)
- Nucleus: controls cellular activities and houses genetic material
- Mitochondria: Produces energy through ATP cellular resp (power house)
- Enoplasmic Reticulum (ER)
Rough ER: Synthesizes proteins (ribbed with ribosomes)
Smooth ER: Synthesizes lipids, detox chemicals and stores calcium
- Golgi Appartaus: Modifies, sorts and packages proteins and lipids for transport
- Lysomes: Contains enzymes for digesting cellular waste and foreign materials
- Ribosomes: synthesizes proteins by translating mRNA
- Peroxisomes: Breaks down fatty acids and detox harmful substances
- Cytoskeleton: provides structural support, facilitates cell movement and intracellular transport
- Plasma membranes: Acts as a barrier
- Centrosomes and centrioles: Organising microtubules during cell division
Identify the 4 major macromolecules in human body and their sources
Proteins: From dietary amino acids
Lipids: From dietary fatty acids and glycerol
Carbohydrates: Dietary simple sugars
Nucleic Acids: Nucleotides synthesized in body or from diet
Explain basis of fluid mosaic model of biological membranes and relate the structure to its function
Fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins
Phospholipids bilayer: Forms membrane structure
Fluidity: allows movement of membranes components
Embedded proteins: Performs various functions (transport, signaling etc)
Cholesterol: Regulates membrane fluidity and stability
Glycoproteins and glycolipids: Form glycocalyx for cell recognitions.
Identify the four major macromolecules in the human body and their sources
- Proteins: Sourced from dietary amino acids.
- Lipids: Sourced from dietary fatty acids and glycerol.
- Carbohydrates: Sourced from dietary simple sugars.
- Nucleic Acids: Sourced from nucleotides synthesized in the body or from diet.
Describe the major roles of proteins in the human body Proteins serve as
- 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)
Describe the major roles of lipids in the human body Lipids function as:
- 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)
Describe the major roles of carbohydrates in the human body Carbohydrates serve as:
- 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
Describe the major roles of nucleic acids in the human body Nucleic acids (DNA and RNA) are crucial for
- 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)
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)
- Lipids: Cholesterol imbalance (atherosclerosis) or lipid storage disorders (e.g., Tay-
Sachs) - Carbohydrates: Impaired glucose metabolism (diabetes) or glycogen storage diseases
- Nucleic Acids: Genetic mutations (e.g., sickle cell anemia) or DNA repair defects
(increased cancer risk)
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
- Active transport: Primary active transport, secondary active transport
- Vesicular transport: Endocytosis, exocytosis
Factors determining transport type:
* Concentration gradient
* Molecule size and polarity
* Membrane permeability
* Energy requirements
* Presence of specific transport proteins
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
Facilitated diffusion:
* Requires transport proteins (channels or carriers)
* No energy required
* Allows passage of larger or polar molecules
* Can be regulated by the cell
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)
Secondary active transport:
* Uses energy from electrochemical gradient created by primary active transport
* Example: Glucose-sodium cotransporter (SGLT) in kidney tubules (glucose reabsorption)
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
- Mitotic phase:
Mitosis: Nuclear division
Cytokinesis: Cytoplasmic division - G0 phase: Quiescent or senescent state (optional)
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
- Metaphase: Chromosomes align at the metaphase plate
- Anaphase: Sister chromatids separate and move to opposite poles
- Telophase: Chromosomes decondense, nuclear envelopes reform, cytokinesis begins
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)
Pluripotent: Can form most cell types (e.g., embryonic stem cells)
Multipotent: Can form multiple cell types within a lineage (e.g., hematopoietic stem
cells)
Unipotent: Can form only one cell type (e.g., spermatogonial stem cells) Therapeutic potential: Regenerative medicine, tissue engineering, disease modeling, drug screening.
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
Describe the process of meiosis Meiosis consists of two divisions:
Meiosis I: Homologous chromosomes pair, crossover, and separate
Meiosis II: Sister chromatids separate
Results in four haploid gametes with genetic diversity.
Compare meiosis to mitosis
Similarities:
* Both involve DNA replication and cell division
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
Describe the major components that make up the human genome
- Nuclear DNA: 23 pairs of chromosomes
- Mitochondrial DNA: Circular DNA in mitochondria
- Genes: Protein-coding sequences
- Regulatory elements: Promoters, enhancers, silencers
- Non-coding DNA: Introns, repetitive sequences
- Telomeres: Protective end sequences of chromosomes
Identify the major enzymes involved in DNA replication and their functions
- DNA helicase: Unwinds the DNA double helix
- DNA primase: Synthesizes RNA primers
- DNA polymerase III: Main replicative enzyme, extends DNA strands
- DNA polymerase I: Removes RNA primers, fills gaps
- DNA ligase: Joins Okazaki fragments
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)
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
Explain the process of transcription and translation in a eukaryotic cell Transcription
- Initiation: RNA polymerase binds to promoter
- Elongation: RNA synthesis
- Termination: RNA release
- Post-transcriptional modifications: 5’ capping, 3’ polyadenylation, splicing
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
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:
- G protein-coupled receptors (GPCRs)
- Receptor tyrosine kinases (RTKs)
- Ion channel-linked receptors
- Enzyme-linked receptors
Identify and explain the roles of the major receptor types
- G protein-coupled receptors (GPCRs): Signal transduction through G proteins
- Receptor tyrosine kinases (RTKs): Phosphorylation of target proteins
- Ion channel-linked receptors: Direct ion flow across membranes
- Enzyme-linked receptors: Catalyze intracellular reactions
Explain the role of proteins in cell signaling and communication Proteins play crucial roles in cell signaling:
- Receptors: Detect and respond to signals
- Signal transducers: Relay and amplify signals
- Enzymes: Modify other proteins
- Scaffold proteins: Organize signaling complexes
- Transcription factors: Regulate gene expression
- Ion channels: Control ion flow and membrane potential
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.
Explain the basic principles of enzyme function Enzymes are biological catalysts that:
- Lower activation energy of reactions
- Exhibit substrate specificity
- Remain unchanged after catalysis
- Function optimally under specific conditions (pH, temperature)
- Can be regulated by various factors
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
Describe the different classifications of enzymes and their relative function Enzyme classifications
- Oxidoreductases: Catalyze oxidation-reduction reactions
- Transferases: Transfer functional groups between molecules
- Hydrolases: Catalyze hydrolysis reactions
- Lyases: Add or remove groups without hydrolysis
- Isomerases: Catalyze intramolecular rearrangements
- Ligases: Join two molecules using ATP hydrolysis
Identify key enzyme inhibitors and their clinical relevance
- Competitive inhibitors: Compete with substrate for active site (e.g., statins inhibiting HMG-CoA reductase)
- Non-competitive inhibitors: Bind to allosteric site (e.g., aspirin inhibiting
cyclooxygenase) - Irreversible inhibitors: Permanently modify enzyme (e.g., penicillin inhibiting bacterial cell wall synthesis)
- Suicide inhibitors: Enzyme converts inhibitor to reactive form (e.g., acyclovir inhibiting viral DNA polymerase)
Justify the use of glucose as the body’s primary energy source
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
Identify the locations of bioenergetic reactions in the cell
- Cytoplasm: Glycolysis
- Mitochondrial matrix: Krebs cycle, fatty acid oxidation
- Inner mitochondrial membrane: Electron transport chain, oxidative phosphorylation
- Endoplasmic reticulum: Lipid synthesis
- Peroxisomes: Fatty acid oxidation (very long-chain fatty acids)
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 exerci
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
Identify the key enzymes and steps in glycogen metabolism Key enzymes in glycogen metabolism
- Glycogen synthase: Adds glucose units to glycogen
- Glycogen phosphorylase: Breaks down glycogen to glucose-1-phosphate
- Branching enzyme: Creates branch points in glycogen
- Debranching enzyme: Removes branch points during glycogen breakdown
Steps: - Glycogenesis: Glucose → Glucose-6-phosphate → Glucose-1-phosphate → UDP- glucose → Glycogen
- Glycogenolysis: Glycogen → Glucose-1-phosphate → Glucose-6-phosphate → Glucose (in liver) or pyruvate (in muscle)
Provide clinical examples of metabolism disorders
- Diabetes mellitus: Impaired glucose metabolism
- Phenylketonuria: Phenylalanine metabolism disorder
- Glycogen storage diseases: Impaired glycogen metabolism
- Fatty acid oxidation disorders: e.g., Medium-chain acyl-CoA dehydrogenase deficiency
- Urea cycle disorders: e.g., Ornithine transcarbamylase deficiency
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
- Transport into mitochondria via carnitine shuttle
- β-oxidation cycle:
a. Dehydrogenation (FAD → FADH2) b. Hydration
c. Dehydrogenation (NAD+ → NADH) d. Thiolysis (CoA-SH)
- Acetyl-CoA enters Krebs cycle
Regulation:
* Inhibited by high levels of acetyl-CoA and NADH
* Stimulated by glucagon and epinephrine
* Inhibited by insulin
Describe the pathway for activation and transport of fatty acids to the mitochondrion for catabolism
- Activation: Fatty acid + CoA + ATP → Fatty acyl-CoA + AMP + PPi
- 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 - Fatty acyl-CoA enters β-oxidation cycle
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
- Acetoacetyl-CoA + Acetyl-CoA → HMG-CoA
- HMG-CoA → Acetoacetate
- Acetoacetate → β-hydroxybutyrate or Acetone
Major intermediates: Acetoacetyl-CoA, HMG-CoA
Major products: Acetoacetate, β-hydroxybutyrate, Acetone (ketone bodies)
Describe the three mechanisms used by humans for removal of nitrogen from amino acids before the metabolism of their carbon skeleton
- Transamination: Transfer of amino group to α-ketoglutarate, forming glutamate
- Oxidative deamination: Removal of amino group as ammonia by glutamate
dehydrogenase - Urea cycle: Conversion of ammonia to urea for excretion
Outline the sequence of reactions in the urea cycle including key regulatory steps Urea cycle steps
- Carbamoyl phosphate synthesis
- Citrulline formation
- Argininosuccinate synthesis
- Argininosuccinate cleavage
- Arginine cleavage to urea
Key regulatory steps:
* Carbamoyl phosphate synthetase I (rate-limiting)
* N-acetylglutamate (allosteric activator)
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)
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.
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, V aline
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)
Cells placed in an isotonic solution will?
Remain the same size
Enzymes work by?
Decreasing the activation energy
Base pairing events, which formation is the strongest bond
Cytosine bound to Guanine
Are lipids hydrophobic and phosphates hydrophilic?
Yes
Which organelle is essential for cells to replicate?
Nucleus
Homoeostasis can be described as?
The maintenance of a relatively stable internal environment
Protein coding region of a gene begins with?
The first AUG or start codon encountered by the ribosome
Form of cell death involving pyknosis, chromatin condensation and fragmentation as well as engulfment by resident phagocytes
Apoptosis
How many chromosomes are found in the human oocyte
23
For fatty acids synthesis to occur
Pyruvate dehydrogenase must be inactivated
The demand for nucleotide biosynthesis is high during which stage in the cell cycle?
S- phase
The enzyme responsible for the synthesis of mRNA during the transcription
RNA Polymerase
Proteins are made up of
Amino acids
