AP BIO UNIT 2 Flashcards
Cells
The basic structural and functional units of every organism
All Cells…
- Are bound by a plasma membrane
- Contain cytosol
- Contain chromosomes
- Contain ribosomes
Prokaryotes
Domains bacteria & archaea. DNA is in the nucleoid region. Generally smaller in size than eukaryotes.
Eukaryotes
Protists, fungi, animals, & plants. DNA is in the nucleus. Contain membrane bound organelles.
Organelles
Membrane bound structures in eukaryotes. Two classifications: endomembrane & energy.
Endomembrane Organelles
Nuclear Envelope
Endoplasmic Reticulum (ER)
Golgi Complex
Vesicles/Vacuoles
Lysosomes
Plasma Membrane
Energy Organelles
Mitochondria
Chloroplasts
Compartmentalization
Compartmentalization in organelles allows for different metabolic reactions to occur in different locations. It increases the surface area for reactions to occur on and prevents interfering reactions from occuring in the same location.
Unique Plant Cell Components
Chloroplasts, Central Vacuole, Cell Wall, and Plasmodesmata (holes in the cell wall)
Unique Animal Cell Components
Lysosomes, Centrosomes, Flagella
Nucleus
Contains chromosomes (genetic information). It is enclosed by the nuclear membrane which protects the nucleus. It has a double membrane and pores. The pores regulate the exit and entry of all materials from the cell. It contains a nucleolus.
Nucleolus
The dense region of the nucleus where ribosomal RNA (rRNA) is synthesized. rRNA is combined with proteins to form large & small subunits of ribosomes. Subunits exit via nuclear pores and assemble ribosomes. The ribosomes translate message found on mRNA into the primary structure of polypeptides.
Ribosomes
*Some texts do not classify ribosomes as organelles because they are not membrane bound. Ribosomes are comprised of ribosomal RNA and protein. Their function is to synthesize proteins. They can be found in cytosol or bound to the ER or nuclear envelope. Ribosomes found in the cytosol generally produce proteins that functions only within the cytosol (example: enzymes). They are known as “free ribosomes.” Ribosomes bound to the ER/nuclear envelope produce proteins that can be secreted from the cell and leave via transport vesicles.
Endoplasmic Reticulum
Synthesize membranes and compartmentalize the cell to keep proteins formed in the ER separate from those of free ribosomes.
Rough Endoplasmic Reticulum
Contains ribosomes bound to the ER membrane.
Smooth Endoplasmic Reticulum
Contains no ribosomes. Synthesizes lipids, metabolizes carbohydrates, and detoxifies the cell.
Golgi Complex
The “shipment center.” Contains flattened membranous sacs called cisternae. Separates the sacs from the cytosol and each cisternae is not connected. It has directionality with a “cis” and “trans” face. The “cis”face receives vesicles from the ER. The “trans” face sends vesicles back out into cytosol to other locations or to the plasma membrane for secretion. The golgi complex receives transport vesicles from the ER (vesicles with materials), modifies the materials, adds molecular tags, packages materials into new transport vesicles that exit the membrane via exocytosis.
Lysosomes
Membranous sac with hydrolytic enzymes. It hydrolyzes macromolecules within animal cells.
Autophagy
Lysosomes can recycle their own cell’s organic materials. This allows the cell to renew itself.
Peroxisomes
Similar to lysosomes. They are a membrane-bound metabolic compartment. They catalyze reactions that produce H2O2. Enzymes in peroxisomes then break down H2O2 into water.
Vacuoles
Large vesicles that stem from the ER and Golgi. They are selective in transport. There are several types including food, contractile, and central.
Food Vacuole
Form via phagocytosis (cell eating) and then are digested by lysosomes.
Contractile Vacuole
Maintain water levels in cells.
Central Vacuole
Found in plants. Contains inorganic ions and water. Important for turgor pressure.
Endosymbiont Theory
The theory that explains the similarities mitochondria and chloroplasts have to a prokaryote. The theory states that an early eukaryotic cell engulfed a prokaryotic cell. The prokaryotic cell became an endosymbiont (cell that lives in another cell). It then became one functional organism. Evidence for the theory includes double membrane, ribosomes, circular DNA, and being capable of functioning on their own.
Mitochondria
Site of cellular respiration. Structure of the double membrane: outer membrane is smooth while the inner membrane has folds called cristae. These membranes divide the mitochondria into two internal compartments and increase surface area. The number of mitochondria in a cell correlates with metabolic activity. Cells with high metabolic activity have more mitochondria.
Intermembrane of Mitochondria
The space between the inner and outer membrane.
Mitochondrial Matrix
The location for the Krebs cycle. It contains enzymes that catalyze cellular respiration and produce ATP, mitochondrial DNA, and ribosomes.
Chloroplast
Specialized organelles in photosynthetic organisms. It is the site of photosynthesis and contains the green pigment, chlorophyll. Inside of its double membrane are thylakoids (membranous sacs that can organize into stacks called grana) and stroma (fluid around the thylakoids). Light dependent reactions occur in grana. Stroma is the location for the Calvin Cycle. They contain chloroplast DNA, ribosomes, and enzymes.
Thylakoids
Membranous sacs that can organize into stacks called grana. Light dependent reactions occur in grana.
Stroma
Fluid around the thylakoids. The location for the Calvin Cycle. It contains chloroplast DNA, ribosomes, and enzymes.
Cytoskeleton
(NOT an organelle). A network of fibers throughout the cytoplasm. They give structural support (especially for animal cells) and mechanical support. They anchor organelles and allow for movement of vesicles and organelles and/or the whole cell. Movement occurs when the cytoskeleton interacts with motor proteins. The three types of fibers in the cytoskeleton include microtubules, microfilaments, and intermediate filaments.
Microtubules
A fiber in the cytoskeleton. Hollow rod-like structures made form the protein tubulin. They grow from the centrosome and assist in microtubule assembly. They serve as structural support (kind of like tracks) for the movement of organelles that are interacting with motor proteins. They assist in the separation of chromosomes during cell division and assist in cell motility (example: cilia and flagella).
Microfilaments
Thin solid rods made of the protein actin. They maintain the cell shape and bear tension and assist in muscle contraction and cell motility. Actin works with another protein called myosin to cause a contraction. They also assist in the division of animal cells, causing the contractile ring of the cleavage furrow.
Intermediate Filament
Fibrous proteins made of varying subunits. Permanent structural elements of cells. They maintain cell shape, anchor the nucleus and organelles, and form the nuclear lamina which lines the nuclear envelope.
Cell Size
Cellular metabolism depends on cell size. Cellular waste must leave and thermal energy must dissipate. Nutrients and other resources/chemical materials must enter. At a certain size, it begins to be too difficult for a cell to regulate what comes in and what goes out of the plasma membrane.
Surface Area to Volume
The size of a cell will dictate the function. Cells need a high surface area-to-volume ratio to optimize the exchange of material through the plasma membrane.
Formulas for Cuboidal Cells
Total SA = height x width x # of sides x number of boxes
Total Volume = height x width x length x # of boxes
Formulas for Spherical Cells
SA = 4πr²
Total Volume = 4/3πr³
SA:V Overview
Cells tend to be small. Small cells have high SA: V ratios. This optimizes the exchange of materials through the plasma membrane. Larger cells have a lower SA: V ratio. Because of this, they lose efficiency exchanging materials. The cellular demand for resources increases and the rate of heat exchange decreases.
Plasma Membrane
Separates the internal cell environment from the external environment. Comprised primarily of phospholipids. Phospholipids are amphipathic (hydrophilic head and hydrophobic tails which form a bilayer). Plasma membranes have selective permeability that allows the membrane to regulate the substances that enter and exit the cell.
Hydrophilic Heads
Oriented TOWARDS aqueous environments
Hydrophobic Tails
Oriented inwards AWAY from aqueous environments
Fluid Mosaic Model
A model to describe the structure of cell membranes. Fluid: membrane is held together by weak hydrophobic interactions and can therefore move and shift. Temperature affects fluidity. Unsaturated hydrocarbon tails help maintain fluidity at low temperatures. The kinked tails prevent the tight packing of phospholipids. Mosaic: comprised of many macromolecules.
Cholesterol
Helps maintain fluidity at high and low temperatures. High temperature: reduces movement. Low temperature: reduces tight packing of phospholipids.
Integral Proteins
Proteins that are embedded into the lipid bilayer. (aka transmembrane proteins). Amphipathic.
Peripheral Proteins
Proteins that are not embedded into the lipid bilayer.
Membrane Carbohydrates
Important for cell-to-cell recognition.
Glycolipids
Carbohydrates bonded to lipids.
Glycoproteins
Carbohydrates bonded to proteins. Most abundant.
Plant Cells
Plants have a cell wall that cover their plasma membranes. Extracellular structure (not found in animal cells). Provides shape/structure, protection, and regulation of water intake. The cell wall is composed of cellulose. Thicker than plasma membranes and contains plasmodesmata (hole-like structures in the cell wall filled with cytosol that connects adjacent cells).
Selective Permeability
Some substances can cross the membrane more easily than others.
Easy Passage Across the Membrane
Small, nonpolar, hydrophobic molecules. (Examples: hydrocarbons, C2, O2, N2)
Difficult Passage or Protein Assisted Passage
Hydrophilic, polar molecules, large molecules, ions. (Examples: sugar, water)
Passive Transport
Transport of a molecule that does not require energy from the cell because a solutie is moving with its concentration or electrochemical gradient. Involved in the import of materials and export of waste. (Examples: diffusion, osmosis, facilitated diffusion.)
Diffusion
Spontaneous process resulting from the constant motion of molecules. Substances move from a high to a low concentration. Move DOWN the concentration gradient. Molecules diffuse directly across the membrane. Different rates of diffusion for different molecules. *Even with diffusion, the membrane is still selectively permeable.
Osmosis
The diffusion of water down its concentration gradient across a selectively permeable membrane.
Facilitated Diffusion
Diffusion of molecules through the membrane via transport proteins. Increases rate of diffusion for: small ion, water, and carbohydrates. Two categories of transport proteins: channel and carrier.
Channel Proteins
Provide a channel for molecules and ions to pass. The channel is hydrophilic. Many are gated channels. They only allow passage when there is a stimulus. (Example: aquaporins - a specific channel protein for water).
Carrier Proteins
Undergo conformational changes for substances to pass.
Active Transport
Transport of a molecule that requires energy because it moves a solute against its concentration gradient. Pumps, cotransport, exocytosis, and endocytosis are all types of active transport. Active transport requires energy.
ATP in Active Transport
Energy source used by cells. ATP can transfer the terminal phosphate group to the transport protein, which changes the shape of the transport protein to better move a substance (AKA a conformational change).
Pumps
Maintains membrane potential.
Membrane Potential
Unequal concentrations of ions across the membrane results in an electrical charge (electrochemical gradient). The cytoplasm is relatively negative in comparison to the extracellular fluid. Energy is stored in electrochemical gradients.
Electrogenic Pumps
Proteins that generate voltage across membranes which can be used later as an energy source for cellular processes.
Sodium Potassium Pump
Animal cells will regulate their relative concentrations of Na+ and K+. Animal cells have a relatively high concentration of K+ and low concentration Na+ inside the cell in comparison to outside the cell. When ATP phosphorylates the protein, a conformational change occurs. 3 sodium ions and a molecule of ATP are bound to the sodium-potassium pump. The ATP splits and creates energy to change the shape of the channel, driving the sodium out of the cell. The sodium is released outside the membrane and the new shape of the channel allows two potassium ions to bind. Release of the phosphate allows the channel to revert to its original form, releasing the potassium ions on the inside of the membrane. (3 Na+ out and 2 K+ in)
Proton Pump
Integral membrane protein that builds up a proton gradient across the membrane. Used by plants, fungi, and bacteria. Pumps H+ out of the cell.
Cotransport
The coupling of a favorable movement of one substance with an unfavorable movement of another substance. Uses the energy stored in electrochemical gradients (generated by pumps) to move substance against their concentration gradient. Plants use cotransport for sugars and amino acids. Example: sugar-H+ cotransporter.
Favorable Movement
Downhill diffusion
Unfavorable Movement
Uphill transport
Plants & Cotransport
Plants use contransport for sugars and amino acids. (Example: sucrose - H+ cotransporter. Sucrose can travel into a plant cell against its concentration gradient ONLY if it’s coupled with H+ that is diffusing down its electrochemical gradient).
Exocytosis
The secretion of molecules via vesicles that fuse to the plasma membrane. Vesicles can fuse to the membrane by forming a bilayer. Once fused, the contents of the vesicle are released to the extracellular fluid. (Example: nerve cells releasing neurotransmitter).
Endocytosis
The uptake of molecules from vesicles fused from the plasma membrane (opposite of exocytosis). Phagocytosis, pinocytosis, receptor-mediated.
Phagocytosis
When a cell engulfs particles to be later digested by lysosomes. Cell surround particle with pseudopodia. Packages particles into a food vacuole. Food vacuole fuses with a lysosome to be digested.
Pinocytosis
Nonspecific uptake of extracellular fluid containing dissolved molecules. Cell takes in dissolved molecules in a protein coated vesicle. Protein coat helps to mediate the transport of molecules.
Receptor-Mediated Endocytosis
Specific uptake of molecules via solute binding to receptors on the plasma membrane. Allows the cell to take up large quantities of a specific substance. When solutes bind to the receptors, they cluster in a coated vesicle to be taken into the cell.
Tonicity
The ability of an extracellular solution to cause a cell to gain or lose water. Depends on the concentration of solutes that cannot pass through the cell membrane.
Osmoregulation
Cells must be able to regulate their solute concentrations and maintain water balance. Animal cells will react differently than cells with cell walls, like plants, fungi, & some protists.
Isotonic Solutions
Cells immersed in an isotonic solution have no net movement of water. The concentration of nonpenetrating solutes inside the cell is equal to that outside the cell. Water diffuses into the cell at the same rate water moves outside the cell.
Hypertonic Solutions
Cells immersed in a hypertonic solution lose water to their extracellular surroundings. The concentration of nonpenetrating solutes is higher outside of the cell. Water will move to the extracellular fluid. Cells shrivel and die. Plasmolysis will occur in plant cells: vacuole shrinks and the plasma membrane pulls away from the cell wall.
Plasmolysis
Vacuole shrinks and the plasma membrane pulls away from the cell wall.
Hypotonic Solutions
Cells immersed in a hypotonic solution gain water. the concentration of nonpenetrating solutes is lower outside of the cell. the cell will gain water. Animals cells swell and lyse (burst). Plant cells work optimally (the cell wall maintains turgor pressure).
Water Potential
A physical property that predicts the direction water will flow. Includes the effects of solute concentration and physical pressure. Greek letter “psi” represents water potential. Measured in megapascals (mPa) or bars. 1 mPa = 10 bars
Water Will Flow From Areas of…
- High water potential to areas of low water potential.
- Low solute concentration to high solute concentration.
- High pressure to low pressure.
Water Potential Formula
Ψ = ΨS + ΨP
Solute Potential
Also known as osmotic potential. An increase in solutes causes binding to more free water. This reduces water potential. Expressed as a negative #. Pure water is 0 mPa.
Pressure Potential
The physical pressure on a solution. Can be + or - relative to atmospheric pressure. “Open air” = 0 mPa.
Solute Potential Formula
ΨS = -iCRT
Ionization Constant (-i)
Number of particles formed. If no ions are formed, the ionization constant is 1. Example: sucrose.
Molar Concentration (C)
Represented as C
Pressure Constant (R)
Pressure Constant
0.0831 liter bars/mol-K
0.00831 liter mPA/mol-K
Temperature in K (T)
K = 273 + C
273 + degrees in Celsius
