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ap bio 5
Unit 2: Cell Structure and Function
Cell Structure
Prokaryotic Cells: Simpler, lack a nucleus and membrane-bound organelles.
Bacteria and Archaea.
Eukaryotic Cells: More complex, have a nucleus and membrane-bound organelles.
Protists, fungi, plants, and animals.
Organelles:
Nucleus: Contains DNA, controls cell activities.
Ribosomes: Synthesize proteins.
Endoplasmic Reticulum (ER): Transports and modifies proteins and lipids.
Rough ER: Has ribosomes, modifies proteins.
Smooth ER: Synthesizes lipids, detoxifies.
Golgi Apparatus: Processes and packages proteins and lipids.
Lysosomes: Digest cellular waste.
Mitochondria: Generate ATP through cellular respiration.
Chloroplasts (in plants): Conduct photosynthesis.
Vacuoles: Store water, nutrients, and waste.
Cell Membrane: Phospholipid bilayer with embedded proteins.
Functions: Controls the movement of substances in and out of the cell.
Structure: Amphipathic (hydrophilic heads, hydrophobic tails).
Cell Wall: Plants, bacteria and fungi
Membrane Transport
Passive Transport: No energy required.
Diffusion: Movement of molecules from high to low concentration.
Osmosis: Diffusion of water across a membrane.
Hypotonic: Lower solute concentration outside the cell; water moves in.
Hypertonic: Higher solute concentration outside the cell; water moves out.
Isotonic: Equal solute concentration; no net water movement.
Facilitated Diffusion: Movement of molecules with the help of transport proteins.
Active Transport: Energy (ATP) required.
Pumps: Move molecules against the concentration gradient.
Sodium-Potassium Pump: Maintains ion balance.
Bulk Transport: Movement of large molecules.
Endocytosis: Cell takes in substances.
Phagocytosis: Cell eating.
Pinocytosis: Cell drinking.
Exocytosis: Cell releases substances.
Cell Communication
Types of Signals: Chemical and electrical signals.
Reception: Signal binds to a receptor protein.
Intracellular Receptors: Located inside the cell.
Membrane Receptors: Located on the cell surface.
G protein-coupled receptors (GPCRs): Activate G proteins.
Receptor tyrosine kinases (RTKs): Phosphorylate proteins.
Ion channel receptors: Open ion channels.
Signal Transduction: Signal is converted into a cellular response.
Phosphorylation Cascade: Series of protein phosphorylations.
Second Messengers: relay signals from receptors to target molecules in the cell
cAMP: Activates protein kinases.
Calcium Ions Ca^{2+}: Activate proteins.
Response: Cellular activity is altered.
Gene expression: Activates transcription factors.
Enzyme Activity: Activates signaling pathways.
Termination: The signal is turned off; important so that cells can respond to new signals. Often involves phosphatases.
Cell Cycle
Interphase: Cell grows and prepares for division.
G1 Phase: Cell growth and normal functions.
S Phase: DNA replication.
G2 Phase: Preparation for mitosis.
Mitotic Phase (M Phase): Cell division.
Mitosis: Division of the nucleus.
Prophase: Chromosomes condense.
Metaphase: Chromosomes align at the metaphase plate.
Anaphase: Sister chromatids separate.
Telophase: Nuclear envelope reforms.
Cytokinesis: Division of the cytoplasm.
Animal Cells: Cleavage furrow forms.
Plant Cells: Cell plate forms.
Regulation of the Cell Cycle: Controlled by checkpoints.
G1 Checkpoint: Checks for DNA damage.
G2 Checkpoint: Checks for DNA replication.
M Checkpoint: Checks for chromosome alignment.
Apoptosis: Programmed cell death.
Unit 3: Cellular Energetics
Enzymes
Function: Biological catalysts that speed up reactions by lowering activation energy (E_a).
Structure: Proteins with an active site.
Mechanism: Enzymes bind to substrates, forming an enzyme-substrate complex.
Factors Affecting Enzyme Activity:
Temperature: Optimal temperature for activity.
pH: Optimal pH for activity.
Substrate Concentration: Increases reaction rate up to a saturation point.
Inhibitors:
Competitive Inhibitors: Bind to the active site.
Noncompetitive Inhibitors: Bind to another site, changing the enzyme's shape.
Photosynthesis
Overview: Conversion of light energy into chemical energy.
Equation: 6CO2 + 6H2O + Light \rightarrow C6H{12}O6 + 6O2
Light-Dependent Reactions (in thylakoid):
Photosystems: Capture light energy.
Photosystem II (PSII): Splits H2O, releases O2, and produces ATP.
Photosystem I (PSI): Reduces NADP+ to NADPH.
Electron Transport Chain (ETC): Transfers electrons, creating a proton gradient to produce ATP.
Photophosphorylation
Light-Independent Reactions (Calvin Cycle) (in stroma):
Carbon Fixation: CO_2 is incorporated into organic molecules.
Reduction: ATP and NADPH are used to convert CO_2 into glucose.
Regeneration: RuBP is regenerated to continue the cycle.
Cellular Respiration
Overview: Breakdown of glucose to generate ATP.
Equation: C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + ATP
Glycolysis (in cytoplasm): Glucose is broken down into pyruvate.
Products: 2 ATP, 2 NADH, 2 Pyruvate.
Pyruvate Oxidation (in mitochondrial matrix): Pyruvate is converted to acetyl CoA.
Products: Acetyl CoA, CO_2, NADH.
Citric Acid Cycle (Krebs Cycle) (in mitochondrial matrix): Acetyl CoA is oxidized.
Products: ATP, NADH, FADH2, CO_2.
Oxidative Phosphorylation (in inner mitochondrial membrane): Electron transport chain and chemiosmosis.
Electron Transport Chain (ETC): Electrons are passed down, creating a proton gradient.
Chemiosmosis: ATP synthase uses the proton gradient to generate ATP.
Products: ATP, H_2O.
Fermentation (if no oxygen): regenerates NAD+ so glycosis can continue
Alcohol fermentation: Pyruvate is converted to ethanol.
Lactic acid fermentation: Pyruvate is converted to lactate.
Unit 7: Natural Selection
Genetic Variation
Mutations: Random changes in DNA.
Point Mutations: Single base changes.
Frameshift Mutations: Insertions or deletions.
Sexual Reproduction: Creates new combinations of genes.
Crossing Over: Exchange of genetic material during meiosis.
Independent Assortment: Random alignment of chromosomes during meiosis.
Random Fertilization: Any sperm can fertilize any egg.
Evidence for Evolution
Fossil Record: Shows the history of life on Earth.
Comparative Anatomy: Similar structures in different species.
Homologous Structures: Similar structure, different function.
Analogous Structures: Different structure, similar function.
Comparative Embryology: Similarities in early development.
Molecular Biology: Similarities in DNA and protein sequences.
Biogeography: Geographic distribution of species.
Mechanisms of Evolution
Natural Selection: Differential survival and reproduction based on heritable traits.
Conditions: Variation, inheritance, differential survival.
Types: Directional, disruptive, stabilizing.
Genetic Drift: Random changes in allele frequencies.
Bottleneck Effect: Population size is reduced due to a random event.
Founder Effect: Small group colonizes a new area.
Gene Flow: Movement of genes between populations.
Mutation: Introduces new alleles.
Nonrandom Mating: Individuals choose mates based on certain traits.
Speciation
Definition: Process by which new species arise.
Reproductive Isolation: Barriers that prevent interbreeding.
Prezygotic Barriers: Prevent mating or fertilization.
Habitat Isolation: Different habitats.
Temporal Isolation: Different breeding times.
Behavioral Isolation: Different courtship rituals.
Mechanical Isolation: Incompatible reproductive structures.
Gametic Isolation: Incompatible eggs and sperm.
Postzygotic Barriers: Reduce viability or fertility of hybrids.
Reduced Hybrid Viability: Hybrids do not survive.
Reduced Hybrid Fertility: Hybrids are infertile.
Hybrid Breakdown: Hybrids are fertile but subsequent generations are not.
Types of Speciation:
Allopatric Speciation: Geographic isolation.
Sympatric Speciation: No geographic isolation.
Phylogeny
Definition: Evolutionary history of a species or group of species.
Phylogenetic Tree: Diagram showing evolutionary relationships.
Rooted Tree: Includes a common ancestor.
Unrooted Tree: Does not include a common ancestor.
Taxonomy: Science of classifying organisms.
Hierarchical Classification: Domain, Kingdom, Ph