BIOL 1720 Exam 1 Study Guide: Prokaryotes, Protists, Fungi, Animal Form & Function, Nervous System, and Muscles

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Prokaryotes: Bacteria and Archaea

Overview of Prokaryotes

Prokaryotes are unicellular organisms lacking a membrane-bound nucleus and organelles. They are classified into two domains: Bacteria and Archaea. Prokaryotes are found in diverse environments and play essential roles in ecological and biological processes.

Bacteria: Characterized by the presence of peptidoglycan in their cell walls.
Archaea: Lack peptidoglycan; often inhabit extreme environments.
Prokaryotic cell structure: Includes a cell wall, plasma membrane, nucleoid region, plasmids, and sometimes external structures like capsules, fimbriae, pili, and flagella.

Cell Wall Structure and Gram Staining

The cell wall provides structural support and protection. The Gram stain differentiates bacteria based on cell wall composition:

Gram-positive bacteria: Thick peptidoglycan layer; stain purple.
Gram-negative bacteria: Thin peptidoglycan layer and an outer membrane; stain pink/red.

External Structures

Capsule: Sticky layer outside the cell wall; aids in protection and adherence.
Fimbriae/Pili: Hair-like appendages for attachment and genetic exchange.
Flagella: Used for motility.
Endospore: Dormant, resistant structure for survival in harsh conditions.

Genetic Material and Reproduction

Nucleoid: Region containing the circular DNA.
Plasmid: Small, circular DNA molecules; often carry genes for antibiotic resistance.
Binary fission: Asexual reproduction; rapid population growth.

Genetic Recombination and Variation

Prokaryotes increase genetic diversity through:

Transformation: Uptake of DNA from the environment.
Transduction: DNA transfer via bacteriophages.
Conjugation: Direct transfer of DNA between cells via pili.

Metabolic Diversity

Prokaryotes exhibit diverse metabolic pathways: photosynthesis, chemosynthesis, fermentation, and respiration.
Extremophiles: Archaea adapted to extreme environments.
Thermophiles: Thrive in high temperatures.
Halophiles: Thrive in high salt concentrations.
Methanogens: Produce methane; often found in anaerobic environments.

Three-Domain System

Classification of life into Bacteria, Archaea, and Eukarya.

Example:

Escherichia coli is a Gram-negative bacterium commonly found in the intestines of animals.

Additional info:

Prokaryotes are essential for nutrient cycling, decomposition, and biotechnology.

Protists

Overview of Protists

Protists are a diverse group of mostly unicellular eukaryotes. They exhibit varied modes of nutrition and play key roles in aquatic ecosystems.

Photoautotrophs: Use light energy to synthesize organic compounds (e.g., diatoms, green algae).
Heterotrophs: Obtain energy by consuming other organisms (e.g., slime molds).
Mixotrophs: Combine photosynthesis and heterotrophy (e.g., dinoflagellates).

Endosymbiosis and Evolution

Endosymbiosis: Theory explaining the origin of mitochondria and plastids (chloroplasts) from engulfed prokaryotes.
Primary endosymbiosis: Eukaryote engulfs a prokaryote (e.g., mitochondria from alphaproteobacteria, chloroplasts from cyanobacteria).
Secondary endosymbiosis: Eukaryote engulfs another eukaryote with a plastid (e.g., brown algae).

Major Groups of Protists

Brown algae: Multicellular, marine, photosynthetic.
Red algae: Multicellular, marine, photosynthetic.
Green algae: Unicellular or multicellular; ancestors of land plants.
Diatoms: Unicellular, silica cell walls.
Dinoflagellates: Unicellular, some cause harmful algal blooms.
Slime molds: Heterotrophic, decomposers.

Example:

Plasmodium (a protist) causes malaria in humans.

Additional info:

Protists are important producers, decomposers, and symbionts in ecosystems.

Fungi

Overview of Fungi

Fungi are eukaryotic heterotrophs that absorb nutrients through external digestion using hydrolytic enzymes. They play roles as decomposers, parasites, and mutualists.

Hyphae: Filamentous structures forming the body of fungi.
Mycelium: Network of hyphae; increases surface area for absorption.
Fruiting body: Spore-producing structure (e.g., mushroom).
Molds: Multicellular fungi with filamentous growth.
Yeasts: Unicellular fungi; reproduce by budding.

Fungal Life Cycle

Sexual reproduction: Involves plasmogamy (fusion of cytoplasm), heterokaryon stage (cells with two nuclei), karyogamy (fusion of nuclei), meiosis, and spore formation.
Asexual reproduction: Mitosis produces spores or budding in yeasts.

Fungal Symbioses

Mycorrhizae: Mutualistic association between fungi and plant roots.
Arbuscular mycorrhizal fungi: Penetrate plant root cells.
Ectomycorrhizal fungi: Surround plant root cells.
Lichens: Symbiotic association between a fungus and a photosynthetic partner (algae or cyanobacteria).
Soredia: Reproductive structures in lichens.

Example:

Penicillium (a mold) produces the antibiotic penicillin.

Additional info:

Fungi are crucial for nutrient cycling and biotechnology.

Animal Form and Function & Homeostasis

Overview of Animal Structure

Animal anatomy and physiology are closely linked, with form supporting function. Animals are organized into cells, tissues, organs, and organ systems.

Anatomy: Study of structure.
Physiology: Study of function.
Adaptation: Inherited traits enhancing survival.
Acclimatization: Short-term physiological adjustment.

Types of Animal Tissues

Epithelial tissue: Covers surfaces; protection, absorption.
Connective tissue: Supports and binds; includes bone, blood, cartilage.
Muscle tissue: Movement; includes skeletal, cardiac, and smooth muscle.
Nervous tissue: Communication; neurons and glial cells.

Homeostasis and Regulation

Homeostasis: Maintenance of internal stability.
Conformer: Internal conditions vary with environment.
Regulator: Maintains constant internal conditions.
Homeostatic system: Includes sensor, integrator, and effector.
Negative feedback: Reduces deviation from set point (e.g., temperature regulation).

Thermoregulation

Endothermic: Generates heat internally (e.g., mammals).
Ectothermic: Relies on external heat sources (e.g., reptiles).
Physical processes: Radiation, Evaporation, Convection, Conduction.
Vasodilation: Increases blood flow, releases heat.
Vasoconstriction: Reduces blood flow, conserves heat.
Countercurrent exchange: Efficient heat transfer between fluids.

Example:

Humans use sweating (evaporation) and shivering (muscle contraction) for thermoregulation.

Additional info:

Homeostasis is vital for enzyme function and survival.

Nervous System

Structure and Function of Neurons

The nervous system coordinates responses via specialized cells called neurons. Neurons transmit electrical and chemical signals.

Dendrite: Receives signals.
Axon: Transmits signals.
Synapse: Junction between neurons.
Neurotransmitter: Chemical messenger.
Glial cells: Support neurons.

Membrane Potential and Action Potential

Resting potential: Voltage across membrane at rest; maintained by sodium-potassium pump.
Action potential: Rapid change in membrane potential; involves depolarization, repolarization, and hyperpolarization.
Threshold: Minimum stimulus for action potential.
Voltage-gated ion channels: Open/close in response to voltage changes.
Refractory period: Time during which neuron cannot fire again.
Saltatory conduction: Rapid transmission in myelinated axons; jumps between nodes of Ranvier.

Synaptic Transmission

Chemical synapse: Neurotransmitter release.
Electrical synapse: Direct electrical connection.
Excitatory postsynaptic potential (EPSP): Increases likelihood of action potential.
Inhibitory postsynaptic potential (IPSP): Decreases likelihood.
Summation: Integration of multiple signals (spatial and temporal).

Organization of the Nervous System

Central nervous system (CNS): Brain and spinal cord.
Peripheral nervous system (PNS): Nerves outside CNS.
Sensory neurons: Detect stimuli.
Interneurons: Process information.
Motor neurons: Cause responses.

Brain Structure and Function

Forebrain: Includes cerebrum, thalamus, hypothalamus.
Midbrain: Processes sensory information.
Hindbrain: Includes cerebellum, medulla oblongata, pons.
Cerebral cortex: Higher functions; divided into regions.
Limbic system: Emotion and memory; includes amygdala and hippocampus.

Autonomic Nervous System

Sympathetic division: "Fight or flight" responses.
Parasympathetic division: "Rest and digest" responses.
Enteric division: Controls digestive tract.

Example:

During stress, the sympathetic division increases heart rate and respiration.

Additional info:

Neurotransmitters include acetylcholine, dopamine, serotonin, and neuropeptides.

Muscles

Types of Muscle Tissue

Muscle tissue enables movement and force generation. There are three main types:

Skeletal muscle: Voluntary, striated, attached to bones.
Cardiac muscle: Involuntary, striated, found in heart.
Smooth muscle: Involuntary, non-striated, found in organs.

Muscle Structure

Muscle fiber: Single muscle cell.
Myofibril: Bundles of contractile proteins.
Sarcomere: Functional unit; contains actin (thin) and myosin (thick) filaments.
Z line: Boundary of sarcomere.
M line: Center of sarcomere.

Sliding Filament Model

Muscle contraction occurs when myosin heads bind to actin and pull, shortening the sarcomere.

Tropomyosin and troponin complex: Regulate actin-myosin interaction.
Sarcoplasmic reticulum (SR): Stores and releases calcium ions (Ca2+).
Transverse tubules (T-tubules): Conduct action potentials into muscle fiber.

Muscle Contraction Process

Action potential from motor neuron releases acetylcholine at neuromuscular junction.
Ca2+ released from SR binds to troponin, exposing actin binding sites.
ATP provides energy for myosin movement and detachment.

Muscle Fiber Types

Slow-twitch fibers: Endurance, aerobic metabolism.
Fast-twitch fibers: Rapid contraction, anaerobic metabolism.

Motor Units and Recruitment

Motor unit: Motor neuron and all muscle fibers it controls.
Recruitment: Activation of more motor units increases force.
Tetanus: Sustained contraction from rapid stimulation.

Example:

Running a marathon uses slow-twitch fibers; sprinting uses fast-twitch fibers.

Additional info:

Muscle contraction is regulated by calcium ions and ATP.

Comparison Table: Prokaryotes, Protists, Fungi, Animal Tissues, Muscle Types

Feature	Prokaryotes	Protists	Fungi	Animal Tissues	Muscle Types
Cell Type	Unicellular, no nucleus	Unicellular/multicellular, nucleus	Multicellular, nucleus	Specialized cells	Skeletal, cardiac, smooth
Reproduction	Binary fission, recombination	Asexual/sexual	Asexual/sexual	Varies by tissue	Contraction, relaxation
Metabolism	Diverse (extremophiles)	Photoautotroph, heterotroph, mixotroph	Heterotroph	Depends on tissue	Aerobic/anaerobic
Key Structures	Cell wall, capsule, flagella	Plastids, cilia, flagella	Hyphae, mycelium, spores	Cells, tissues, organs	Myofibrils, sarcomeres
Example	E. coli	Plasmodium	Penicillium	Muscle, nervous tissue	Slow/fast-twitch fibers
Additional info	Three-domain system	Endosymbiosis	Mycorrhizae, lichens	Homeostasis	ATP, Ca2+ regulation

Key Equations and Concepts

Resting Membrane Potential (Nervous System)

The resting membrane potential is maintained by the sodium-potassium pump:

Sliding Filament Model (Muscle Contraction)

Muscle contraction is powered by ATP hydrolysis:

Negative Feedback (Homeostasis)

Negative feedback reduces deviation from a set point: