Biology - Exam 2 Review

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Robert Hooke

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116 Terms

1

Robert Hooke

English scientist who, in 1665, observed plant cork cells and coined the term "cell”

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Matthias Schleiden

German botanist (1838) who proposed that all plant tissues are composed of cells, contributing to the Cell Theory

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Theodor Schwann

German zoologist (1839) who demonstrated that animal tissues are also made up of cells and proposed the Cell Theory

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Cell Theory

A scientific theory stating that all organisms are composed of one or more cells, cells are the smallest living things, and cells arise only by division of previously existing cells

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Microscopes

Instruments that enable the visualization of cells and their structures

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Resolution

The minimum distance between two points where they can still be distinguished as two separate points

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Compound Light Microscope

A microscope that uses two magnifying lenses to achieve high magnification and clarity but has limitations in observing cell structures

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Transmission Electron Microscope (TEM)

A microscope that transmits electrons through the specimen to create high-resolution images of thin sections

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Scanning Electron Microscope (SEM)

An electron microscope used to create 3D images of specimens by bombarding them with electrons

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Stains

Chemicals applied to specimens to bind specific molecules, making them more easily distinguishable under a microscope

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Cell Structures

Common components found in all cells, including genetic material, cytoplasm, plasma membrane, and ribosomes

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Genetic Material

The material (DNA) that carries genetic information and is housed in the nucleus in eukaryotic cells or the nucleoid in prokaryotes

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Cytoplasm

A semifluid matrix within cells that contains sugars, amino acids, and proteins and houses cell organelles

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Plasma Membrane

A phospholipid bilayer that surrounds the cell, acting as a gatekeeper and embedded with various proteins

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Ribosomes

Cellular structures composed of RNA and proteins that synthesize polypeptide chains using mRNA and tRNA

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Prokaryotes

The simplest organisms lacking a distinct nucleus and membrane-bound organelles; includes bacteria and archaea

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Prokaryote Cell Wall

A protective structure outside the plasma membrane in prokaryotic cells, often made of peptidoglycan

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Flagella

Long, threadlike structures that protrude from the surface of some cells, used for locomotion

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Eukaryotes

Cells with a membrane-bound nucleus and organelles, more complex than prokaryotes

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Endosymbiotic Theory

A theory explaining the origin of eukaryotic organelles through symbiotic relationships between different single-celled organisms

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Animals vs. Plants

Comparison of structures in animal and plant cells, including cell walls and chloroplasts unique to plant cells

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Nucleus

The organelle housing genetic information in eukaryotic cells, surrounded by the nuclear envelope and containing nuclear pores

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Endoplasmic Reticulum

An organelle involved in cell membrane and material synthesis, divided into rough and smooth ER

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Golgi Apparatus

A stack of membranes that receives, modifies, and directs materials synthesized in the cell

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Lysosomes

Membrane-bound vesicles produced by the Golgi Apparatus, involved in intracellular digestion and waste breakdown

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Peroxisomes

Membrane-enclosed vesicles containing enzymes for fatty acid breakdown, known for producing and breaking down hydrogen peroxide

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Vacuoles

Membrane-bound organelles used for storing nutrients, ions, pigments, or toxins, found in various sizes in different cells

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Chloroplasts

Organelles in plant cells that use sunlight to produce carbohydrates through photosynthesis

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Mitochondria

Organelles known as the powerhouse of the cell, producing ATP through cellular respiration

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Cytoskeleton

A network of protein fibers providing structural support and aiding in organelle movement within eukaryotic cells

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Microfilaments (Actin Filaments)

Thin protein fibers involved in cell movement, contractions, and support

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Microtubules

Large cytoskeletal fibers made of tubulin dimers, involved in cell movement, vesicle transport, and chromosome separation

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Intermediate Filaments

Stable cytoskeletal fibers providing mechanical strength to cells and tissues

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Cilia and Flagella

Structures used for cell movement, with cilia being short and flagella being longer, whip-like projections

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Centrosome

A cellular region organizing microtubules and aiding in cellular division, consisting of two centrioles

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Cell Wall

A rigid structure found in plant, fungal, and some protist cells, made of cellulose (plants) or chitin (fungi)

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Extracellular Matrix

Substance secreted by animal cells for structural support, communication, and protection, often containing collagen

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Junctions Between Cells

Specialized connections between adjacent cells, including adhesion junctions, tight junctions, gap junctions (animal cells), and plasmodesmata (plant cells)

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Phospholipid Bilayer

Two layers of phospholipids that form the foundation of cell membranes

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Fluid Mosaic Model

A model describing the structure of cell membranes, consisting of a fluid phospholipid bilayer with scattered proteins

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Membrane Components

Fundamental components found in eukaryotic cell membranes, including the phospholipid bilayer, transmembrane proteins, interior protein network, and cell surface markers

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Phospholipid Bilayer Structure

Composed of glycerol, two hydrophobic fatty acids, and a hydrophilic phosphate group

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Influence on Fluidity

Factors affecting the fluidity of the phospholipid bilayer include fatty acid saturation, temperature, and membrane composition

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Transmembrane Proteins

Proteins embedded within the lipid bilayer, serving various functions such as transport, enzymes, receptors, and adhesion

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Integral Membrane Proteins

Proteins that span the entire phospholipid bilayer with nonpolar regions embedded in the lipid core and polar regions protruding on both sides

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Interior Protein Network

Proteins providing structural support to cell membranes, contributing to their shape

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Cell Surface Markers

Proteins on the membrane surface used for communication, identification, and interactions with other cells

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Cell Transport

The movement of molecules across cell membranes, including passive transport (no energy required), active transport (energy required), and bulk transport

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Passive Transport

Movement of molecules from high to low concentration without energy, including diffusion and facilitated diffusion

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Diffusion

Passive movement of molecules from areas of high concentration to low concentration until equilibrium is reached

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Simple Diffusion

Movement of molecules directly through the phospholipid bilayer

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Facilitated Diffusion

Passive movement of molecules through channel or carrier proteins, selectively allowing certain molecules to pass

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Osmosis

Passive diffusion of water across a semipermeable membrane from high to low concentration

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Osmosis in Cells

The movement of water into or out of cells due to different solute concentrations, resulting in isotonic, hypotonic, or hypertonic solutions

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Maintaining Osmotic Balance

Strategies used by cells to regulate osmotic pressure, including extrusion, isosmotic regulation, and turgor

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Extrusion (Unicellular Eukaryotes)

Removal of excess water using contractile vacuoles

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Isosmotic Regulation (Animals)

Adjusting internal solute concentrations to match the surrounding environment

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Turgor (Plants)

Internal pressure in plant cells caused by a hypertonic environment, providing structural support

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Active Transport

Movement of molecules against their concentration gradient, requiring energy, transport proteins, and selectivity

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Types of Active Transport Carrier Proteins

Uniporters (one molecule), symporters (two molecules in the same direction), and antiporters (two molecules in opposite directions)

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Sodium-Potassium Pump

A crucial example of active transport, pumping sodium ions out and potassium ions into the cell against their concentration gradients, requiring ATP

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Bulk Transport

Transport of large molecules or particles that cannot pass through the phospholipid bilayer, including exocytosis and endocytosis

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Exocytosis

The process of transporting macromolecules out of the cell via secretory vesicles

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Endocytosis

The process of engulfing substances outside the cell into vesicles, including phagocytosis and pinocytosis

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Receptor-Mediated Endocytosis

A type of endocytosis where receptor proteins in coated pits selectively take in specific molecules from the extracellular space

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Energy

The capacity to do work

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Types of Energy

Includes potential energy (stored) and kinetic energy (in motion)

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Heat Measurement

Energy can be measured using heat, typically in calories

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Energy Flow

Energy captured by photosynthetic organisms is stored as potential energy in chemical bonds and used in cellular processes

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Redox Reactions

Reactions involving both oxidation (loss of electrons) and reduction (gain of electrons)

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Laws of Thermodynamics

  1. First Law: Energy cannot be created or destroyed, only changed in form.

  2. Second Law: Energy conversions result in the loss of usable energy as heat, leading to increased entropy (disorder)

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Energy of Activation

Extra energy required to initiate chemical reactions and break existing bonds

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Catalysts

Substances (e.g., enzymes) that lower activation energy, facilitating chemical reactions

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ATP

Adenosine triphosphate, a primary cellular energy currency

  • Composition: Ribose, adenine, and a chain of three phosphates

  • Energy Storage: Unstable phosphate bonds release energy when broken

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ATP for Short-Term Storage

ATP is not suitable for long-term energy storage due to unstable phosphate bonds

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ATP Cycle

ATP releases energy when a phosphate is removed, converting it to ADP and Pi. ADP can be regenerated back to ATP through processes like cellular respiration

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Enzymes

Biological catalysts, usually made of proteins, that speed up chemical reactions.

  • Example: Carbonic Anhydrase increases the rate of carbon dioxide and water conversion.

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Enzyme Binding

Enzymes have active sites that accommodate substrates and release products.

  • Model: Induced Fit model describes how the active site changes shape to fit the substrate.

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Multienzyme Complexes

Groups of enzyme subunits working together as a molecular machine to enhance reaction efficiency and control

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80

Environmental Factors and Enzymes

Temperature and pH affect enzyme activity

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Temperature

Effect: Increasing temperature initially speeds up reactions by increasing molecular movement. However, enzymes have an optimal temperature, and excessive heat can denature them

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pH

Effect: Enzymes have an optimal pH, and deviations can disrupt the bonds holding the protein's structure

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Enzyme Inhibition

Substances, apart from the substrate, can bind to enzymes and reduce their activity

  • Types: Competitive inhibitors compete for the active site, while noncompetitive inhibitors bind elsewhere

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Biochemical Pathways

Sequences of reactions where the product of one reaction serves as the substrate for the next enzyme in the pathway

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Feedback Inhibition

The product of a biochemical pathway inhibits an enzyme earlier in the pathway, preventing the overproduction of a particular substance

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Cell Theory

  • All living organisms are composed of cells

  • Cells are the basic structural and functional units of life

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Factors Limiting Cell Size

  • Surface area-to-volume ratio restricts cell size

  • Nutrient and waste exchange limitations impact cell size

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Structural and Functional Similarities in Cells

  • Cells have a cell membrane, cytoplasm, and genetic material

  • They carry out various metabolic processes

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Prokaryotic Cell Organization

  • Lack a true nucleus

  • DNA is located in the nucleoid region

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Bacterial and Archaeal Cell Types

  • Bacteria and Archaea are two domains of prokaryotes

  • They have distinct genetic and structural differences

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Eukaryotic vs. Prokaryotic Cell Organization

  • Eukaryotic cells have a true nucleus, while prokaryotic cells do not

  • Prokaryotic cells are generally smaller and simpler

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Role of the Nucleus in Eukaryotic Cells

  • The nucleus stores and protects genetic information

  • It controls gene expression and cell activities

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Role of Ribosomes in Protein Synthesis

  • Ribosomes are responsible for protein synthesis

  • They translate mRNA into amino acid sequences

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Endomembrane System Parts

  • Includes the endoplasmic reticulum, Golgi apparatus, and lysosomes

  • Involved in protein processing, modification, and transport

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Functions of Internal Membranes and Compartments:

  • Segregate cellular functions and protect sensitive processes

  • Enhance efficiency through compartmentalization

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Components of Biological Membranes

  • Phospholipid bilayer, proteins, and carbohydrates

  • These components form the structure of biological membranes

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Fluid Mosaic Model of Membrane Structure

  • Describes membranes as a dynamic, flexible mosaic of lipids and proteins

  • Allows for lateral movement of components

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Phospholipid Components

  • Consist of hydrophilic heads and hydrophobic tails

  • Form the basis of the lipid bilayer

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Membrane Spontaneous Formation

  • Membranes form due to the hydrophobic effect

  • Lipids self-assemble into bilayers in aqueous environments

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Factors Affecting Membrane Fluidity

  • Temperature and lipid composition impact fluidity

  • Unsaturated fatty acids increase fluidity

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