Biology - Exam 2 Review

Robert Hooke

Robert Hooke

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

Matthias Schleiden

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

Theodor Schwann

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

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

Microscopes

Instruments that enable the visualization of cells and their structures

Resolution

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

Compound Light Microscope

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

Transmission Electron Microscope (TEM)

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

Scanning Electron Microscope (SEM)

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

Stains

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

Cell Structures

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

Genetic Material

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

Cytoplasm

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

Plasma Membrane

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

Ribosomes

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

Prokaryotes

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

Prokaryote Cell Wall

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

Flagella

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

Eukaryotes

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

Endosymbiotic Theory

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

Animals vs. Plants

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

Nucleus

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

Endoplasmic Reticulum

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

Golgi Apparatus

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

Lysosomes

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

Peroxisomes

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

Vacuoles

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

Chloroplasts

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

Mitochondria

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

Cytoskeleton

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

Microfilaments (Actin Filaments)

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

Microtubules

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

Intermediate Filaments

Stable cytoskeletal fibers providing mechanical strength to cells and tissues

Cilia and Flagella

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

Centrosome

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

Cell Wall

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

Extracellular Matrix

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

Junctions Between Cells

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

Phospholipid Bilayer

Two layers of phospholipids that form the foundation of cell membranes

Fluid Mosaic Model

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

Membrane Components

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

Phospholipid Bilayer Structure

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

Influence on Fluidity

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

Transmembrane Proteins

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

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

Interior Protein Network

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

Cell Surface Markers

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

Cell Transport

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

Passive Transport

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

Diffusion

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

Simple Diffusion

Movement of molecules directly through the phospholipid bilayer

Facilitated Diffusion

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

Osmosis

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

Osmosis in Cells

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

Maintaining Osmotic Balance

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

Extrusion (Unicellular Eukaryotes)

Removal of excess water using contractile vacuoles

Isosmotic Regulation (Animals)

Adjusting internal solute concentrations to match the surrounding environment

Turgor (Plants)

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

Active Transport

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

Types of Active Transport Carrier Proteins

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

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

Bulk Transport

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

Exocytosis

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

Endocytosis

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

Receptor-Mediated Endocytosis

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

Energy

The capacity to do work

Types of Energy

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

Heat Measurement

Energy can be measured using heat, typically in calories

Energy Flow

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

Redox Reactions

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

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)

Energy of Activation

Extra energy required to initiate chemical reactions and break existing bonds

Catalysts

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

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

ATP for Short-Term Storage

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

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

Enzymes

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

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

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.

Multienzyme Complexes

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

Environmental Factors and Enzymes

Temperature and pH affect enzyme activity

Temperature

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

pH

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

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

Biochemical Pathways

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

Feedback Inhibition

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

Cell Theory

• All living organisms are composed of cells

• Cells are the basic structural and functional units of life

Factors Limiting Cell Size

• Surface area-to-volume ratio restricts cell size

• Nutrient and waste exchange limitations impact cell size

Structural and Functional Similarities in Cells

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

• They carry out various metabolic processes

Prokaryotic Cell Organization

• Lack a true nucleus

• DNA is located in the nucleoid region

Bacterial and Archaeal Cell Types

• Bacteria and Archaea are two domains of prokaryotes

• They have distinct genetic and structural differences

Eukaryotic vs. Prokaryotic Cell Organization

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

• Prokaryotic cells are generally smaller and simpler

Role of the Nucleus in Eukaryotic Cells

• The nucleus stores and protects genetic information

• It controls gene expression and cell activities

Role of Ribosomes in Protein Synthesis

• Ribosomes are responsible for protein synthesis

• They translate mRNA into amino acid sequences

Endomembrane System Parts

• Includes the endoplasmic reticulum, Golgi apparatus, and lysosomes

• Involved in protein processing, modification, and transport

Functions of Internal Membranes and Compartments:

• Segregate cellular functions and protect sensitive processes

• Enhance efficiency through compartmentalization

Components of Biological Membranes

• Phospholipid bilayer, proteins, and carbohydrates

• These components form the structure of biological membranes

Fluid Mosaic Model of Membrane Structure

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

• Allows for lateral movement of components

Phospholipid Components

• Consist of hydrophilic heads and hydrophobic tails

• Form the basis of the lipid bilayer

Membrane Spontaneous Formation

• Membranes form due to the hydrophobic effect

• Lipids self-assemble into bilayers in aqueous environments

Factors Affecting Membrane Fluidity

• Temperature and lipid composition impact fluidity

• Unsaturated fatty acids increase fluidity