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Questions and Answers
What role does heterochromatin play in gene expression?
What role does heterochromatin play in gene expression?
Which component of RNA distinguishes it from DNA?
Which component of RNA distinguishes it from DNA?
What is the primary function of messenger RNAs (mRNAs)?
What is the primary function of messenger RNAs (mRNAs)?
Which activated carrier plays a central role in energy transfer during coupled reactions?
Which activated carrier plays a central role in energy transfer during coupled reactions?
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What does the presence of specific chromatin patterns indicate?
What does the presence of specific chromatin patterns indicate?
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Why might genes packaged into heterochromatin fail to be expressed?
Why might genes packaged into heterochromatin fail to be expressed?
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Which base is found in RNA but not in DNA?
Which base is found in RNA but not in DNA?
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How do enzymes contribute to biochemical reactions in cells?
How do enzymes contribute to biochemical reactions in cells?
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What function does alternative splicing serve in eukaryotic gene expression?
What function does alternative splicing serve in eukaryotic gene expression?
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Which statement correctly describes the activity of voltage-gated channels in resting cells?
Which statement correctly describes the activity of voltage-gated channels in resting cells?
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What role do potassium and sodium transporter proteins play in the cell?
What role do potassium and sodium transporter proteins play in the cell?
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Which of the following is a consequence of the intron-exon structure of genes?
Which of the following is a consequence of the intron-exon structure of genes?
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What is the primary purpose of chromatography in protein studies?
What is the primary purpose of chromatography in protein studies?
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Which type of protein is responsible for removing phosphate groups from proteins?
Which type of protein is responsible for removing phosphate groups from proteins?
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What happens during the initial phase of an action potential?
What happens during the initial phase of an action potential?
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In the context of enzymes, which of the following actions is NOT typically a way they encourage reactions?
In the context of enzymes, which of the following actions is NOT typically a way they encourage reactions?
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What defines the primary function of euchromatin in a cell?
What defines the primary function of euchromatin in a cell?
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Which type of chromatin is characterized as transcriptionally inactive?
Which type of chromatin is characterized as transcriptionally inactive?
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What is the role of tRNAs during protein synthesis?
What is the role of tRNAs during protein synthesis?
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Which DNA base pairing is stabilized by three hydrogen bonds?
Which DNA base pairing is stabilized by three hydrogen bonds?
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How many different codons can be generated using the four nucleotides present in RNA?
How many different codons can be generated using the four nucleotides present in RNA?
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What condition results in larger EEG signals?
What condition results in larger EEG signals?
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Which enzyme is responsible for attaching amino acids to their corresponding tRNAs?
Which enzyme is responsible for attaching amino acids to their corresponding tRNAs?
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What is the general concept behind codons in mRNA?
What is the general concept behind codons in mRNA?
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Study Notes
Chapter 1 – Cells: The Fundamental Units of Life
- Cells are the basic units of life, evolving from an ancestral cell over 3 billion years ago.
- All cells are enclosed by a plasma membrane, separating the cell's interior from its environment.
- Cells contain DNA for genetic information and direct RNA/protein synthesis.
- Differences exist in multicellular organisms, due to varying gene activation based on development and environmental cues.
- Animal and plant cells are typically 5-20 μm in diameter, visible through light microscopes, revealing some internal components.
- Electron microscopes reveal smaller organelles but require specimen preparation and aren't used for live samples.
- Specific molecules can be localized in cells using fluorescent microscopy (live or fixed).
- Prokaryotic cells are the simplest, lacking a nucleus and organelles, resembling the ancestral cell.
- Prokaryotes (bacteria and archaea) are diverse in chemical capabilities and environments.
- Eukaryotic cells have a nucleus and organelles and evolved from prokaryotic cells via engulfment (endosymbiosis).
Chapter 2 – Chemical Components of Cells
- Cells follow fundamental chemical and physical laws.
- Cells primarily consist of C, H, N, O, making up 96% of their mass.
- Atoms have a nucleus (+ charge) surrounded by electrons (- charge).
- Chemical properties depend on electron arrangement.
- Covalent bonds share electron pairs; double bonds share two pairs.
- Molecules are clusters of atoms held by covalent bonds.
- Ionic bonds form from electron transfer, creating oppositely charged ions.
- Cells have a set of carbon-based (organic) molecules.
- Main categories are sugars, fatty acids, amino acids, and nucleotides.
- Sugars provide energy; polysaccharides and oligosaccharides are formed from joined sugars.
- Fatty acids store energy and form lipid cell membranes.
- Macromolecules (polysaccharides, proteins, nucleic acids) are polymers of sugars, amino acids, or nucleotides.
- Proteins are the most diverse, composed of 20 amino acids linked by peptide bonds.
- Nucleotides transfer energy and form information-carrying RNA and DNA.
- Protein, RNA, and DNA functions depend on the sequence of their subunits.
- Four weak noncovalent bonds (hydrogen bonds, electrostatic attractions, van der Waals attractions, and hydrophobic interactions) allow macromolecular binding.
Chapter 3 – Energy, Catalysis and Biosynthesis
- Living organisms require energy input.
- Solar energy is the ultimate source for most life, used by plants and photosynthetic bacteria to create organic molecules.
- Animals obtain energy from plants or other animals.
- Every chemical reaction in a cell is catalyzed by an enzyme.
- Metabolic pathways are sequences of reactions.
- Catabolic reactions break down molecules, releasing energy (oxidative pathways).
- Anabolic reactions build complex molecules, requiring energy input.
- Enzymes lower activation energy needed for reactions.
- Reaction rate depends on substrate encounter and product release.
- Spontaneous reactions increase total disorder (entropy); measured by ΔG (free-energy change).
- ΔG depends on reactant concentrations and the equilibrium constant (K) or standard free-energy change (ΔG°).
- Equilibrium constants regulate molecule interactions.
- Coupled reactions combine favorable and unfavorable reactions.
- Activated carriers (ATP, NADH, NADPH) are crucial in coupled reactions.
Chapter 4 – Protein Structure and Function
- Proteins are linear chains of amino acids linked by peptide bonds.
- Protein function depends on its amino acid sequence and 3D shape.
- Folding stabilized by multiple noncovalent interactions.
- Regular folding patterns (α helices and β sheets) form from hydrogen bonds.
- Proteins can have smaller globular regions (domains).
- Protein function depends on its surface chemistry and ligand binding.
- Enzymes catalyze reactions by binding substrates at the active site.
- Enzyme shape changes in response to ligand binding (allosteric regulation).
- Allosteric enzymes' activity is controlled by ligands.
- Feedback inhibition regulates metabolic pathways by product binding to initial enzymes.
- Protein activity regulated by phosphorylation/dephosphorylation cycles.
- GTP-binding proteins function as molecular switches, turning on or off by hydrolyzing GTP to GDP.
- Motor proteins produce movement through ATP hydrolysis.
- Protein machines are assemblies of allosteric proteins performing complex functions.
- Covalent modifications control protein location and function.
- Obtaining purified proteins and determining their structure includes chromatography and spectroscopic techniques.
Chapter 5 – DNA and Chromosomes
- Life depends on stable storage and inheritance of genetic information encoded in DNA.
- DNA is a double helix of complementary nucleotide strands (A-T, C-G).
- Eukaryotic genetic material is in chromosomes (single very long DNA molecule containing genes).
- Gene expression involves transcribing DNA into RNA and translating RNA into proteins.
- Nucleotides consist of nitrogenous base, five-carbon sugar (deoxyribose for DNA, ribose for RNA), and phosphate.
- DNA sequences on chromosomes for replication, segregation (centromere), and stability (telomeres).
- DNA is tightly folded by binding to histone and nonhistone proteins (chromatin).
- Chromatin condenses into nucleosomes.
- Chromatin structure is regulated for gene expression via changes in compaction.
- Heterochromatin is highly condensed, often inactive chromatin.
- Histone modifications (e.g., acetylation, methylation) regulate chromatin structure and serve as binding sites for regulatory proteins.
Chapter 6 – DNA Replication, Repair and Recombination
- Cells replicate DNA to prepare for division.
- Each strand of DNA serves as a template for replication, producing two identical DNA molecules.
- Replication forks open DNA at replication origins, and DNA polymerases synthesize new strands.
- DNA polymerase has high fidelity, correcting most errors.
- The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously (Okazaki fragments).
- RNA primers initiate DNA synthesis, which are later replaced with DNA.
- DNA replication machine involves multiple proteins for efficient copying.
- Telomerase replicates chromosome ends.
- Mismatch repair proteins further refine replication accuracy.
- DNA damage is repaired by enzymatic removal and replacement of damaged segments.
- Double-strand breaks can be repaired by non-homologous end joining or homologous recombination.
- Accurate replication and repair protect against uncontrolled cell growth.
Chapter 7 – From DNA to Protein: How cells read the genome
- Genetic information flows from DNA to RNA to protein (central dogma).
- Transcription converts DNA to RNA (RNA polymerase).
- RNA is a single-stranded polymer of ribonucleotides and has a similar structure to DNA but with ribose and uracil.
- Different types of RNA (mRNA, rRNA, tRNA) have different roles.
- mRNA carries protein-coding instructions.
- Ribosomes are protein-RNA complexes translating mRNA into proteins.
- Codons are sets of three nucleotides in mRNA corresponding to amino acids.
- tRNAs act as adaptors, bringing appropriate amino acids to ribosomes.
- Protein synthesis starts at an initiation codon (AUG) and stops at a stop codon.
- rRNA catalyzes peptide bond formation.
- Protein concentration depends on synthesis and degradation rates.
Chapter 8 & 9 – Control of gene expression and How genes and genomes evolve
- Cells regulate gene expression to respond to external signals.
- Different cell types respond to the same signals in different ways.
- Combinatorial control of transcription factors regulates cell type development (e.g., myocytes, fibroblasts).
- Genes can be reprogrammed to change cell types using transcription factors.
- Pluripotent stem cells (ES and iPS) can generate diverse cell types in the body for research and potential treatments.
- Heritability of complex traits is influenced by multiple genes and environmental factors.
- Epigenetic factors (e.g., methylation, acetylation) can influence gene expression without changing the DNA sequence.
- Cell membranes have amphipathic lipids (hydrophilic heads and hydrophobic tails).
- Membrane structure is influenced by aqueous environment.
- Passive transport occurs via diffusion, facilitated diffusion and osmosis; whilst active transport moves against a gradient.
- Ion concentration differences across the cell membrane create an electrochemical gradient, influencing ion movement.
- Na+/K+ pumps maintain gradients, important for cell function.
- Action potential occurs when membrane potential reaches threshold.
- Myosin and actin filaments interact causing muscle contraction via action potentials.
Additional Topics (from exam questions)
- Model organisms (e.g., E. coli, yeast, etc.) are used for research due to their simple genetics
- Understanding molecular mechanisms behind processes like cellular respiration, protein synthesis, or DNA replication.
- Different types of microscopy techniques (light, fluorescence, electron, confocal).
- Important elements and molecules in cells (carbon, hydrogen, oxygen, nitrogen; sugars, lipids, proteins, nucleic acids).
- Basic mechanisms in DNA damage detection and repair.
- Cell and organismal functions (e.g., muscle contraction, nerve signaling, brain wave activity).
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Description
Explore the fundamental units of life with this quiz on cells from Biology Chapter 1. Learn about cell structure, functions, and differences between prokaryotic and eukaryotic cells. Test your knowledge on how cells have evolved and their role in complex organisms.
