Cells Study Guide PDF

Microscopy Light Microscope ○ Uses visible light ○ Lower magnification, lower resolution ○ Living cells can be observed Scanning Electron Microscope (SEM) ○ Uses a focused beam...

Microscopy Light Microscope ○ Uses visible light ○ Lower magnification, lower resolution ○ Living cells can be observed Scanning Electron Microscope (SEM) ○ Uses a focused beam of electrons ○ Higher magnification, higher resolution ○ Produces 3D-like images of the cell surface ○ Cells must be dead and dehydrated Transmission Electron Microscope (TEM) ○ Uses a beam of electrons transmitted through the sample ○ Very high magnification and resolution ○ Shows internal cell structures ○ Cells must be dead, dehydrated, and stained with heavy metals Magnification vs. Resolving Power ○ Magnification: how much larger an image appears ○ Resolving Power: the minimum distance between two points where they can still be distinguished as separate ○ Increasing magnification does not always improve resolution Cell Theory Parts of Cell Theory 1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of life. 3. All cells arise from pre-existing cells. Cell Size Upper Limit ○ Diffusion is insufficient to meet the metabolic demands of large cells ○ Surface area to volume ratio decreases as cells get larger Lower Limit ○ Cells cannot be smaller than their critical components (e.g., DNA, ribosomes) Plasma Membrane Structure ○ Phospholipid bilayer (hydrophilic heads, hydrophobic tails) ○ Integral and peripheral proteins ○ Carbohydrates (glycoproteins, glycolipids) Functions ○ Regulates movement of substances in and out of the cell ○ Provides structural support and shape ○ Cell signaling and recognition Fluid Mosaic Model ○ Phospholipids form a fluid bilayer ○ Proteins are embedded or attached to the bilayer Prokaryotic vs. Eukaryotic Cells Prokaryotes ○ Smaller ○ Lack a true nucleus and membrane-bound organelles ○ Typically single-celled organisms (bacteria, archaea) Eukaryotes ○ Larger ○ Have a true nucleus and membrane-bound organelles ○ Include single-celled protists and multicellular plants and animals Compartmentalization Importance in Eukaryotes ○ Allows for specialization of function ○ Increases efficiency of cellular processes ○ Protects the cell from its own digestive enzymes Eukaryotic Compartments Nucleus ○ Contains most of the cell's genetic material ○ Site of transcription (DNA → RNA)  Mitochondria ○ Site of cellular respiration (energy production) ○ Have two membranes (outer, inner with cristae) Endoplasmic Reticulum (ER) ○ Rough ER: protein synthesis and transport ○ Smooth ER: lipid synthesis, detoxification Cytosol ○ Gel-like substance between organelles ○ Site of some metabolic reactions Plant vs. Animal Cells Plant Cells ○ Have a cell wall (cellulose, lignin) ○ Chloroplasts for photosynthesis ○ Central vacuole for storage and support Animal Cells ○ Lysosomes for digestion and recycling ○ Cilia (motility, sensing the environment) ○ Centrioles (only in animal cells, involved in cell division) Transport Across the Cell Membrane Passive Transport ○ Diffusion: movement from high to low concentration ○ Osmosis: diffusion of water ○ Facilitated Diffusion: assisted by transport proteins Active Transport ○ Against concentration gradients, requires energy (ATP) ○ Protein pumps, endocytosis, exocytosis Osmosis Solutions ○ Hypotonic Lower solute concentration, higher water concentration Water enters the cell Cells swell, may lyse (burst) ○ Isotonic Equal solute and water concentrations No net movement of water Cells maintain their shape and volume ○ Hypertonic Higher solute concentration, lower water concentration Water leaves the cell Cells shrink, may crenate (for animal cells) or undergo plasmolysis (for plant cells) Effects on Cells ○ Red Blood Cells: crenation (hypertonic), hemolysis (hypotonic) ○ Plant Cells: turgor pressure (hypotonic), plasmolysis (hypertonic) Important Terms Lipid Bilayer: the arrangement of phospholipids in the plasma membrane Concentration Gradient: a difference in the concentration of substances across a space ATP (Adenosine Triphosphate): the primary energy currency of the cell Solute: the dissolved substance in a solution Solvent: the substance doing the dissolving in a solution Solution: a homogeneous mixture of a solute and solvent Water Potential: the potential energy of water due to concentration and pressure differences Organic Molecules Proteins ○ Long chains of amino acids ○ Involved in structure, enzymes, transport, signaling Carbohydrates ○ Sugars, starches, cellulose ○ Energy storage and structural roles Lipids ○ Fats, oils, phospholipids, steroids  ○ Energy storage, structural roles Nucleic Acids ○ DNA (genetic information), RNA (transcription, translation) Endosymbiosis Theory ○ Mitochondria and chloroplasts evolved from engulfed bacteria ○ Evidence: structure, DNA, mode of division Cytoskeleton Components ○ Microfilaments (actin): movement, shape ○ Microtubules (tubulin): support, shape, movement ○ Intermediate Filaments: support, shape Functions ○ Cell division (mitosis, cytokinesis) ○ Movement (cilia, flagella, muscle contraction) ○ Maintains cell shape and organization Cell Junctions Types ○ Tight Junctions: impermeable seals between cells ○ Anchoring Junctions: mechanically attach cells ○ Gap Junctions: allow direct communication between cells ○ Plasmodesmata: channels through plant cell walls Enzymes Definition ○ Biological catalysts, usually proteins ○ Increase reaction rates without being consumed Active Site ○ Region where the substrate binds Denaturation ○ Loss of enzyme function due to structural changes Organelles Nucleus Functions ○ Contains most of the cell's genetic material (DNA) ○ Site of transcription (DNA → RNA) Found in: Both plant and animal cells Nucleolus Functions ○ Site of ribosome synthesis Found in: Both plant and animal cells Plasma Membrane Functions ○ Regulates movement of substances in and out of the cell ○ Provides structural support and shape ○ Cell signaling and recognition Found in: Both plant and animal cells Ribosomes Functions ○ Site of protein synthesis (translation) Found in: Both plant and animal cells Endoplasmic Reticulum (ER) Rough ER ○ Functions: protein synthesis, protein transport  ○ Found in: Both plant and animal cells Smooth ER ○ Functions: lipid synthesis, detoxification ○ Found in: Both plant and animal cells Golgi Apparatus Functions ○ Protein modification, sorting, and transport ○ Lipid synthesis and transport Found in: Both plant and animal cells Lysosomes Functions ○ Digestion and recycling of cellular waste and foreign substances Found in: Animal cells Vacuoles Functions ○ Storage, waste removal, maintaining osmotic balance ○ Found in: Both plant and animal cells Plant Cells: ○ Central vacuole: supports cell growth, maintains turgor pressure Animal Cells: ○ Food vacuoles: digestion of ingested food ○ Contractile vacuoles: removal of excess water Mitochondria Functions ○ Site of cellular respiration (energy production) Found in: Both plant and animal cells Chloroplasts Functions ○ Site of photosynthesis (light-dependent reactions and the Calvin cycle) Found in: Plant cells and some protists Cytosol Functions ○ Gel-like substance between organelles ○ Site of some metabolic reactions Found in: Both plant and animal cells Cytoskeleton Microfilaments (Actin) ○ Functions: movement, shape ○ Found in: Both plant and animal cells Microtubules (Tubulin) ○ Functions: support, shape, movement ○ Found in: Both plant and animal cells Intermediate Filaments ○ Functions: support, shape ○ Found in: Animal cells Centrioles Functions ○ Involved in the formation of cilia, flagella, and the spindle fibers during cell division Found in: Animal cells Cell Wall Functions ○ Provides structural support and protection ○ Maintains cell shape Found in: Plant cells, some protists, and fungi Peroxisomes Functions ○ Breakdown of fatty acids and amino acids Found in: Both plant and animal cells Plasmodesmata Functions ○ Channels for direct communication between plant cells Found in: Plant cells Cilia and Flagella Functions ○ Movement of cells or movement of substances along the cell surface Found in: Some cells of both plants and animals