AP BIO UNIT 2 REVIEW (RAMOS)

WE WILL GET 100

Cell

A group of organelles and molecules working together to perform a specific task and help the organism maintain homeostasis.

Living Organisms

Must have at least one cell.

Two Categories of Cells

Prokaryotes and Eukaryotes.

Prokaryotic Characteristics

Include Bacteria and Archaea; are Single Celled ONLY; No Nucleus; No Membrane Bound Organelles; smaller and simpler cells; and are the oldest cells.

Eukaryotic Characteristics

Include Plants, Animals, Fungi, Protists; can be Single celled OR multicellular; have a nucleus; Have Membrane Bound Organelles; are larger and more complex cells; and Evolved from prokaryotic cells.

Shared Characteristics (Prokaryotes and Eukaryotes)

Both have Genetic Material (DNA/RNA), Cell Membrane, and Ribosomes. Some also have Cell Walls or Flagella. Both use cellular respiration to make ATP energy.

Typical Range of Cell Size

Anywhere from 10 micrometers to 1 mm.

Cell Size Constraint (Homeostasis)

Cells must be big enough to fit all the DNA and organelles, but small enough to efficiently exchange nutrients, oxygen, and waste with the extracellular environment to maintain homeostasis.

Factors Determining Cell Function

A cell's shape and the amount and types of organelles it has.

Non-Membrane Bound Organelles

Organelles that do not have their own membrane inside of the cell.

Examples of Non-Membrane Bound Organelles

Ribosomes, Cell Membrane, Cell Wall, Cytoplasm, Cytoskeleton, Centriole and Spindle Fibers, Flagella.

Membrane Bound Organelles

Organelles that have their own membrane inside of the cell.

Examples of Membrane Bound Organelles

Nucleus, Vacuole, Mitochondria, Chloroplast, Golgi, Endoplasmic Reticulum, Nucleolus, Smooth ER, Rough ER, Lysosome, Peroxisome.

Importance of Membrane Bound Organelles

They compartmentalize different areas of the cell, allowing those areas to have different conditions.

Benefit of Organelle Compartmentalization

Allows for specialization of different areas to do different jobs and concentrate enzymes and substrate in the same physical area.

Organelle Membrane Folding

Usually folded to increase surface area, providing more real estate for important reactions/enzymes without making the organelles too big.

Endosymbiotic Theory

Explains that Eukaryotic cells evolved after a large ancestral prokaryote ingested mitochondria and chloroplast-like proto-prokaryotes and formed a close mutual relationship with them.

Evidence of Endosymbiosis (Membranes)

Some organelles have double membranes (outer membrane may be vesicular in origin).

Evidence of Endosymbiosis (Ribosomes)

Organelles have ribosomes which are 70S in size (identical to prokaryotic ribosomes).

Evidence of Endosymbiosis (DNA)

Organelles have their own DNA which is naked and circular (like prokaryotic DNA structure).

Evidence of Endosymbiosis (Division)

Reproduction occurs via a fission-like process.

Cell Membrane / Plasma Membrane / Phospholipid Bilayer

Phospholipid bilayer that surrounds the entire cell; regulates what comes into and out of the cell; and protects the cell interior from the extracellular space.

Cell Wall

Rigid structure made of complex carbohydrates found in plants, fungi, and bacteria; provides structure to cells.

Ribosomes

Found in all living organisms; composed of protein and Ribosomal RNA (rRNA); "read" messenger RNA (mRNA) to synthesize proteins; can be attached to Rough ER or free-floating in the cytoplasm.

Cytoplasm

Liquid made of water, salt and other dissolved nutrients; site of many water-based metabolic chemical reactions; helps both pro and eukaryotic cells maintain cell shape.

Cytoskeleton

Helps maintain the shape of animal cells; parts (Actin, microtubules, actin filaments) help vesicles get transported around the cell.

Centrioles

Make spindle fibers during mitosis and meiosis.

Spindle Fibers

Help pull chromosomes apart during mitosis and meiosis.

Flagella

Longer than cilia; help move cells around; move like a propeller.

Cilia

Much shorter than flagella; help move cells around; move in a back and forth-beating motion.

Nucleus

Surrounded by a double nuclear membrane that houses and protects DNA from denaturation; site of transcription (DNA transcribed into mRNA); also responsible for synthesis of ribosomal RNA (rRNA).

Nucleolus

Site of ribosome synthesis in the cell.

Smooth Endoplasmic Reticulum (Smooth ER)

Responsible for lipid/hormone synthesis and detoxification of cell wastes. Synthesized lipid polymers and hormones get sent to the Golgi apparatus.

Rough Endoplasmic Reticulum (Rough ER)

Highly folded organelle contiguous with the nucleus and has ribosomes attached; responsible for packaging proteins and sending them to the Golgi apparatus.

Golgi Apparatus

Similar to a post office; responsible for helping fold and modify proteins, packaging proteins/lipids into vesicles, and sending these vesicles to their intended destination.

Protein Secretion Pathway Acronym (REGVC)

R- Ribosomes synthesize proteins, E- Rough ER folds proteins, G- Golgi packages proteins, V- Vesicles transport to cell membrane, C- Vesicles fuse with membrane for secretion.

Peroxisome

Responsible for lipid hydrolysis and also using catalase (an enzyme) to break down hydrogen peroxide (toxic to the cell). Lipids are broken down into fatty acid monomers, which are sent to the mitochondrion to help generate ATP.

Lysosome

Lipid bubble full of hydrolytic enzymes that break down cell waste and denatured proteins into their monomers; also involved in apoptosis (programmed cell death).

Vacuole

Responsible for storing and releasing fluids/biomolecules; very large in plants (maintaining turgor pressure) but usually very small in animals.

Mitochondrion

Has two membranes for compartmentalization; inner membrane folding (cristae) increases surface area for ATP production; synthesizes ATP via Citric Acid Cycle and Oxidative phosphorylation.

Chloroplast

Has two membranes for compartmentalization; internal anatomy arranged in stacks of thylakoid membranes (grana); multiple thylakoids increases surface area so more reactions can occur.

Phospholipid Head Group

Contains phosphate, choline and glycerol; is Polar and Hydrophilic; interacts with water.

Phospholipid Fatty Acid (FA) Tails

Contains saturated and unsaturated fatty acid; is Non-polar and Hydrophobic; avoids water. Unsaturated FA is bent, which allows for membrane fluidity.

Formation of Phospholipid Bilayer

Hydrophobic tails form the dense hydrophobic core of the membrane because it is energetically unfavorable for them to be exposed to water; hydrophilic head groups face the aqueous cell interior and exterior.

Fluid Mosaic Model

The membrane is frequently referred to as a fluid mosaic, meaning it is made of many components that can move laterally in the membrane.

Cholesterol (in membrane)

Regulates membrane fluidity in response to temperature changes.

Glycolipids

Carbohydrate attached to a phospholipid; facilitate cell-to-cell adhesion and recognition.

Glycoproteins

Carbohydrate attached to a protein; allow cross linking of cells, giving strength to tissues.

Peripheral Proteins

Found attached to the inside or outside surface of the cell membrane; usually used for cell signaling.

Integral Proteins

Fully OR Partially embedded in the membrane; usually used for cell signaling.

Transmembrane Proteins

Integral Proteins that go all the way through the membrane; usually function as channel proteins that move polar/large molecules.

Channel Protein

Transmembrane proteins with a channel through the middle; used for transport of large, polar, or charged molecules across the membrane.

Receptor Protein

Transmembrane or peripheral proteins that do not have a channel through the middle; used for cell signaling where ligands bind to the receptor.

Selective Permeability

The membrane only lets small, non-polar molecules diffuse freely through the spaces between the phospholipids (e.g., oxygen, carbon dioxide, and small amounts of water). 

Why charged/polar molecules can't diffuse freely

It is energetically unfavorable for large, charged, polar molecules to interact with the hydrophobic fatty acid tails at the core of the membrane.

Surface Area to Volume Ratio

Cells need to have a large surface area to volume ratio to be efficient at transport.

Projections (Villi)

Increase the surface area to volume ratio, making transport more efficient.

Concentration Gradient

The difference in concentration of molecules across a space (one area has a higher concentration than the other).

Net Movement

The overall direction that MOST of the molecules move, generally following the concentration gradient.

Passive Transport

Net movement with the concentration gradient until dynamic equilibrium is reached; relies on inherent energy and Does not require metabolic energy (ATP).

Active Transport

Net movement against the concentration gradient; requires a net input of metabolic energy (hydrolysis of ATP) to occur; the system will not reach dynamic equilibrium.

Dynamic Equilibrium (in transport)

Occurs when molecules moving with the concentration gradient reach the same net concentration on both sides of the membrane; molecules are still moving, but net movement is zero. Cells will remain in dynamic equilibrium unless work (using ATP energy) is done to reset the concentration gradient.

Three Processes of Passive Transport

Simple Diffusion, Facilitated Diffusion, Osmosis.

Simple Diffusion

Net movement of small, non-polar molecules with the concentration gradient without the aid of a channel protein. Only occurs with O₂, N₂, CO₂, and small amounts of water.

Facilitated Diffusion

Net movement of molecules with the concentration gradient that requires the use of a channel protein to occur (used for large, polar, or charged molecules).

Facilitated Diffusion Example (Water)

Large quantities of water require the help of special membrane proteins called aquaporins to cross the cell membrane because water is very polar and hydrophilic. Small quantities of water can still osmose though.

Active Transport Example (Ions)

Sodium-Potassium Pump: responsible for maintaining the concentration gradients of Na+ and K+ ions across neuron membranes for electrochemical signaling.

Membrane Potential

Separation of charge across the membrane (acting like a battery); when ions change concentrations, the membrane can become polarized and fire an electrical signal.

Endocytosis

Process by which cells take in molecules into the intracellular space. Requires formation of a vesicle for bulk import of substances and input of metabolic energy (ATP).

Exocytosis

Process by which cells release molecules into the extracellular space. Requires formation of a vesicle for bulk export of substances and input of metabolic energy (ATP).

Osmoregulation

Maintains water balance and allows organisms to control their internal solute composition/water potential.

Osmosis

Diffusion of water across a semipermeable membrane from high water concentration to low water concentration.

Tonicity

The way we describe how much solute is dissolved in the solvent.

Hypotonic Solution

Lower solute concentration outside the cell (Hypo = Less, Tonic = Stuff). Water will move inside the cell, causing it to swell and possibly burst.

Isotonic Solution

Same solute concentration inside and outside the cell (Iso = Same, Tonic = Stuff). There is no net movement of water because the cell is at dynamic equilibrium.

Hypertonic Solution

Higher solute concentration outside the cell (Hyper = More, Tonic = Stuff). Water will move out of the cell, causing it to shrink/crenation.

Water Movement Rule (Water Concentration)

Water moves from high concentration of water to low concentration of water.

Water Movement Rule (Water Potential)

Water moves from areas of high water potential to areas of low water potential.

Water Movement Rule (Solute Concentration)

Water moves from areas of low solute concentration to areas of high solute concentration.

Turgor Pressure

The pressure the water exerts back on the cell wall (important for maintaining plant cell shape).

Water Potential Equation

trident = trident p + trident s (Water Potential = Pressure Potential + Solute Potential). Used to quantify water potential and determine where water will move.

Water Potential (trident p) of pure (distilled) water

Always 0.

Pressure Potential ($\Psi_p$) (AP Bio standard)

How much pressure is exerted on the cell/solution. For AP Bio calculations, this is usually set equal to zero UNLESS specified otherwise.

Solute Potential (Trident s)

AKA Osmotic potential. It is given a negative value because adding solute to a solution always decreases the overall water potential.

Solute Potential Calculation

trident s = -iCRT.

$i$ (Ionization Constant) for covalent molecules (like sugars)

$i$ = 1 because they do not ionize in water.

$i$ (Ionization Constant) for ionic molecules (like NaCl)

$i$ is equal to the number of ions the compound breaks into