Chapter 3: Cells: The Living Units Flashcards
Cells
Structural units of all living things
Describe Cell Theory
1) A cell is the BASIC structural and functional UNIT OF LIVING ORGANISMS
2) The ACTIVITY of an organism depends on both the individual and combined activities of its cells
3) BIOCHEMICAL ACTIVITIES of cells are dictated by their SHAPES or forms and the relative number of the sub cellular structures they contain
4) Cells come from OTHER CELLS
Generalized/ Composits Cell
All cells have the same basic parts and some common functions
What are the 3 main parts of a cell?
1) Plasma Membrane
2) Cytoplasm
3) Nucleus
Extracellular materials
Substances contributing to body mass that are found outside the cells
What are the classes of Extracellular materials?
- Body fluids
- Cellular secretions
- Extracellular matrix
Body Fluids (also called extracellular fluids)
Important transport and dissolving media
• Interstitial Fluid
• Blood Plasma
• Cerebrospinal Fluid
Interstitial Fluid
The fluid in tissues that bathes all of our cells and has major and endless roles to play
• Rich, nutritious “soup” (ingredients: amino acids, sugars, fatty acids, regulatory substances and wastes)
• Each cell must extract from this to stay healthy
Cellular Secretion
Substances that aid in digestion and some act as lubricants (saliva, mucus…)
Extracellular Matrix
• Most abundant extracellular material
• Universal Cell “glue”- holds body cells together
1) Body cells are in contact with proteins and polysaccharides (secreted by cells)
2) Molecules self-assemble into organized mesh
Describe the cell membrane
- Lipid Bilayer
* Protein molecules
What are the lipids of the membrane?
1) Phospholipids
2) Glycolipids
3) Cholesterol
Describe the phospholipids
- Polar head is charged and hydrophilic
* Non Polar tail has 2 fatty acid chains and is hydrophobic
Describe the movement of Phospholipids
Move freely side to side
Glycolipids
Lipids with attached sugar groups
- 5% of total membrane lipids
Cholesterol
- 20% of membrane
- Polar region: Hydroxyl
- Non polar: Fused ring system
• Stabilizes membrane
• Decreases mobility of phospholipids and fluids
Membrane Proteins Functions
• Allows cell to communicate w/ environment
- 1/2 plasma mass
• Specialized membrane functions
What are the 2 distinct populations of proteins?
1) Integral
2) Peripheral
Integral Proteins
- Firmly inserted in membrane
- Some protrude one side, Most protrude both (transmembrane proteins)
• Have Hydrophilic and Hydrophobic regions - Can interact with Non-Polar lipid tails and water in/out of cell
Transmembrane Proteins
• Protrude both sides of membrane
- Some transport and provide channels: Water-soluble molecules or ions pass
- Some carry: bind to substance and move through membrane
- Enzymes
- Receptors for hormones
Signal transduction
A process where chemical messengers relay messages to the cell interior
Peripheral Proteins
- Not embedded in membrane
- Attach loosely to integral proteins and can be easily removed
Glycocalyx
Consists of glycoproteins and glycolipids that form a fuzzy, sticky, carbohydrate-rich area at the cell surface
- enriched by glycolipids and glycoproteins secreted by the cell
- *Provides highly specific biological markers by which approaching cells recognize each other; Ex: Sperm recognizes an ovum
What 3 factors act to bind cells together?
1) Glycoproteins in the glyocalyx act an adhesive
2) Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion
3) Special cell junction form
What 3 junctions are important for factors in securing cells together?
1) Tight Junction
2) Desmosomes
3) Gap Junctions
Tight Junctions
A series of integral protein molecules in the plasma membrane of adjacent cells fuse together, forming an impermeable junction that encircles the cell
- Prevents molecules from passing through the extracellular space between adjacent cells
Desmosomes
Anchoring junctions that bind adjacent cells together act like molecular “Velcro” and also help form an internal tension-reducing network of fibers
- Plaque: is on the face of each plasma membrane
- Cadherins: Protein filaments that hold together adjacent cells that extend from the plaques
- Keratin: the extend from the cytoplasmic side if the plaque to anchor to the plaque on the cells opposite side
Distributes tension throughout a cellular sheet and reduces the chance of tear when under pulling force
- Ex: Skin, Heart muscle
Gap Junctions
Communicating junctions that allow ions and small molecules to pass are particularly important for communication in heart cells and embryonic cells
- adjacent plasma membranes are close connected by hollow cylinders (connezons), which are composed of transmembrane proteins
- Present in electrically excitable tissues where ion passage from cell to cell helps synchronize their electrical activity and contraction
Passive Processes
Substances cross the membrane without any energy input from the cell
Active Processes
The cell provides the metabolic energy (usually ATP) needed to move substances across the membrane
What are the 2 main types of Passive Transport?
1) Diffusion
2) Filtration/ Facilitated
Diffusion
The tendency of molecules or ions to move from an area where they are in higher concentration to an area where they in lower concentration (on the concentration gradient)
Describe the barrier of the plasma membrane?
It allows some substances to pass while excluding others
It allows nutrients to enter to cell, but keeps many undesirable substances out
- Keeps valuable cell proteins in
- Allows waste to exit
What molecules or ions are allowed to through the membrane?
1) Lipid soluble
2) Small enough to pass through membrane channels, or
3) Assisted by a carrier molecule
Simple Diffusion
The unassisted diffusion of lipid-soluble or very small particles; nonpolar and lipid-soluble substances diffuse directly through the lipid bilayer
- Lipid-soluble: Oxygen, Carbon Dioxide and fat-soluble vitamins
Osmosis
The diffusion of a solvent (usually water) through a membrane
Describe oxygen concentration
Higher in blood than in tissue cells so oxygen continuously diffuses from the blood into the cells
Describe carbon dioxide concentration
Higher in concentration within cells, so it diffuses from tissue cells into the blood
Facilitated Diffusion
The transported substance either (1) binds to protein carriers in the membrane and is ferried across or (2) moves through water-filled protein channels
Osmolarity
Measure of total concentration of solute particles
Tonicity
Ability of a solution to change the shape or tone of cells by altering the cells internal water volume
Isotonic
Solution has same osmolarity as inside the cell, so volume remains unchanged
Hypertonic
Solution has higher osmolarity than inside cell, so water flows out the cell, resulting in cell shrinking
Hypotonic
Solution has lower osmolarity than inside cell, resulting in cell swelling
Carrier-mediated Facilitated Diffusion
Transmembrane Integral proteins that transport specific polar molecules that are too large for membrane channels
- Binding to molecule causes carrier to change shape, moving molecule in process
Channel-mediated Facilitated Diffusion
- Channels with aqueous-filled cores are formed by transmembrane proteins
Transport molecules down their concentration gradient
1) Leakage Channels (always open)
2) Gated Channels (controlled by signals)
What are the 2 major active membrane transport processes?
1) Active Transport
2) Vesicular Transport
- Both require ATP
Active Transport
• Require carrier proteins - Anti porters - Symporters • Moves solutes against their concentration gradient (low-high) - Requires ATP
What are the types of Active Transport?
1) Primary Active Transport
2) Secondary Active Transport
Primary Active Transport
• Energy from hydrolysis of ATP causes change in shape of transport protein
- Shape change causes solutes (ions) bound to protein to be pumped across membrane
- Ex: Calcium, Hydrogen (proton), Na+ -K+ pumps
Sodium-Potassium Pump
Enzyme (Na+-K+ ATPase) that pumps sodium out of cell and potassium back into cell
- Leakage channels
- Antiporter
• Maintains electrochemical gradients, which involve both concentration and electrical charge of ions
Secondary Active Transport
Moves a lot of molecules to one side of a membrane, they will want to diffuse back.
When they diffuse, they may drag other molecules with them
• Symporters
Vesicular Transport
Involves transport of large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles
• Requires cellular energy (usually ATP)
Endocytosis
- Involves formation of protein-coated vesicles
Once vesicle is pulled inside cell, it may:
1) Fuse with lysosomes or
2) Undergo transcytosis (travel through the cell)
Phagocytosis
Type of endocytosis that is referred to as “cell eating”
- Membrane projections called pseudopods form and flow around solid particles that are being engulfed, forming a vesicle which is pulled into cell
• Vesicle formed is called a phagosome
- used by macrophages and certain white blood cells
Cytoplasm
All cellular material that is located between the plasma membrane and the nucleus
* citizens/ people
What is cytoplasm composed of?
1) Cytosol
2) Inclusions
3) Organelles
Cytosol
Gel-like solution made up of water and soluble molecules such as proteins, salts, sugars, etc.
Inclusions
Insoluble molecules; vary with cell type
- Ex: Glycogen granules, pigments, lipid droplets, vacuoles, crystals
Organelles
Metabolic machinery structures of cell; each with specialized function; either membranous or non membranous
What organelles are membranous?
- Cytosol
- ER
- Golgi Apparatus
- Peroxisomes
- Lysosomes
What organelles are non membranous?
- Ribosomes
- Cytoskeleton
- Centrioles
Mitochondria
- “Power house” of cell
- Produces cells ATP via cellular respiration
- Double layer/ many folds= cristae
Ribosomes
• Site of protein synthesis
- Made up of protein and ribosomal RNA (rRNA)
What are the 2 forms of ribosomes found in the cell?
1) Free ribosomes
2) Membrane-bound ribosomes
Free Ribosomes
Free floating ribosomes in cytosol
Membrane-bound Ribosomes
Attached to membrane of ER
Endoplasmic Reticulum
Consists of series of parallel, interconnected cisterns- flattened membranous tubes that encloses fluid-filled interiors
Rough ER
Surface studded with ribosomes
• Site of synthesis of proteins that will be secreted from cell & of many plasma membrane proteins
1) Makes and modifies proteins
2) Final protein is enclosed in vesicle and sent to Golgi Apparatus for further processing
Smooth ER
Network of looped tubules continuous with Rough ER
- Enzymes found in its plasma membrane (integral proteins) function in:
• Lipid metabolism; cholesterol and steroid-based hormone synthesis; making lipids for lipoproteins
• Absorption, synthesis, and transport of fat
Golgi Apparatus
Stacked and flattened membranous cistern sacs
• Modifies, concentrates and packages proteins and lipids received from Rough ER
- Golgi is “traffic director” controlling which of 3 pathways final products will take as new transport vesicles pinch off trans (outer) face
Peroxisomes
Membranous sacs containing powerful detoxifying substances that neutralize toxins
- Free Radicals
1) Oxidase uses oxygen to convert toxins to hydrogen peroxide
2) Catalase converts hydrogen peroxide to harmless water
• Plays a role in breakdown and synthesis of fatty acids
Lysosomes
Spherical membranous bags containing digestive enzymes (acid hydrolases)
• Isolate potentially harmful intracellular digestion from rest of cell
- digest ingested bacteria, viruses and toxins
• Degrade nonfunctional organelles
• Involved in metabolism of glycogen and fatty acids
Free Radicals
Toxic, highly reactive molecules that are natural by-products of cellular metabolism; can cause havoc to cell if not detoxified
Endomembrane System
Consists of membranous organelles as well as the nuclear and plasma membranes
- Membranes and organelles work together to:
• Produce, degrade, store and export biological molecules
• Degrade potentially harmful substances
Cytoskeleton
Elaborate network of rods that run throughout cytosol
- Hundreds of different info of proteins link rods to other cell structures
• Also act as cells “bones, ligaments and muscles” by playing a role in movement of cell components
What are the 3 types of cytoskeleton?
1) Microfilaments
2) Intermediate filaments
3) Microtubules
Centrosome
Is a microtubule organizing center, consisting of a granular matrix and centrioles, located near the nucleus
• Some aid in cell division and some form cytoskeletal track system
Centrioles
A pair of barrel-shaped micro-tubular organelles that lie at right angles to each other
• Form basis of cilia and flagella
What are the 2 cellular extensions?
1) Cilia and flagella
2) Microvilli
Cilia and Flagella
Aid in movement of the cell or of materials across the surface of the cell
• Both made up of microtubules synthesized by centrioles
Microvilli
Minute finger like projections of plasma membrane that extends from the surface of select cells to increase surface area for absorption
- Ex: Intestinal and kidney tubule cells
• Have a core of actin microfilaments that is used for stiffening of projections
Cilia
Whiplike, motile extensions on surfaces of certain cells (Ex: Respiratory cells)
- Thousands work together in sweeping motion to move substances across cell surfaces in one direction (Ex: mucus)
Flagella
Longer extensions that propel the whole cell (Ex: tail of sperm)
Nucleus
Largest organelle; contains the genetic library of blueprints for synthesis of nearly all cellular proteins
• Responds to signals that dictate the kinds and amounts of proteins that needs to be synthesized
What are the 3 main parts of the nucleus?
1) Nuclear envelope
2) Nucleoli
3) Chrimatin
