AP Biology Unit 2 Cell Structure and Function

Prokaryotes

-Bacteria or protists

-No nucleus

-No membrane-bound organelles

-Have a flagellum, capsule, and a nucleoid

Eukaryotes

-Animals or plants

-Membrane-bound organelles

-Membrane-enclosed nucleus

Similarities between eukaryotes and prokaryotes

-DNA
-Ribosomes

-Cell Membrane

Endosymbiotic Theory

Idea that the mitochondria and the chloroplasts were at one point independent cells. 

-Inner membranes of both organelles have enzymes and transport systems that modern prokaryotes have

-Both organelles contain ribosomes and also replicate similarly to prokaryotes

Effect of surface area to volume ratios

Effects the exchange of materials between cells or organisms and the environment. A high surface area to volume ratio is vital because it facilitates the exchange of materials between a cell and it’s environment.

Plasma Mebrane

-Eukaryotes

-Controls what enters and exits the cell

Nucleus

-Eukaryotes

-Stores DNA and controls cell activities

Ribosomes

-Eukaryotes

-makes proteins

Rough Endoplasmic Reticulum

-Eukaryotes

-Folds and modifies proteins

Smooth Endoplasmic Reticulum

-Eukaryotes

-Synthesizes lipids

Golgi

-Eukaryotes

-Modifies, stores, and packages proteins

Mitochondria

-Eukaryotes

-Change energy from one form to another

Cytoskeleton

-Eukaryotes

-Provides support and cell shape

Centrosomes

-Eukaryotes

-Helps organize microtubules

Lysosomes

-Animal

-Break down waste

Centrioles

-Animal

-Cell division

Flagella

-Animal

-Movement and locomotion

Cilia

-Animal

-Move substances across the cell surface

Extracellular Matrix

-Animal

-Support and signaling

Tight Junctions

-Animal

-Seal cells together

Demosones

-Animal

-Anchor cells

Gap Junctions

-Animal

-Transport between cells

Central Vaculoles

-Plant

-Storage of waste and nutrients

Chloroplast

-Plant

-Photosynthesis

Cell Wall

-Plant

-Protection and shape

Plasmodesmata

-Plant

-Transport and communication

Parts of the Cytoskeletan

1. Microtubules: Tracks for organelle movement, hollow tubes. 

2. Microfilaments: Movement and muscle contractions, thin fibers. 

3. Intermediate Filaments: Provide structure and stabilize, medium size.

Eukaryotic Cell Types and Cell Walls

1. Animal: No cell wall

2. Plant: Cellulose cell wall

3. Funghi: Chitin cell wall

4. Protists: Some have cell walls

What makes up the Cell Membrane

1. Phospholipids: Phosphate head and 2 fatty acid tails. Tails are hydrophobic and non-polar. Heads are polar and hydrophilic. 

2. Made of proteins: Integral proteins and peripheral proteins

3. Made of carbs that are used in cell-to-cell recognition

Fluid Mosaic Model

Cell Membrane: Proteins and carbs are held together in the membrane by weak interactions=fluidity. Made of multiple different macromolecules=mosaic.

Osmolarity

Measure of the number of dissolved solute particles, (osmoles), in a given volume of a solution. 

Water Potential

Water potential equals pressure potential plus solute potential. 

-As solute is added, water potential of a solution drops, water will move into the solution. Water moves from high to low concentration. 

-As pressure potential increases, the water potential will increase. 

Why water movement into a plant cell will stop even if solute concentration isn’t equal

Water movement into a plant cell will stop even if solute concentration is not equal when the water potential inside the cell equals the water potential outside the cell.

Transpiration

Drives the transport of water and minerals from roots to shoots via the xylem. 

Factors that affect transpiration

-Light Intensity: Higher light intensity increases transpiration. 

-Temp: Higher temp increases transpiration. 

-Humidity: High humidity decreases transpiration.

-Wind Speed: Increased wind removes humid air, increasing transpiration rates. 

Stomata

Stomata regulates gas exchange by taking in carbon dioxide for photosynthesis, releasing oxygen and water vapor through transpiration. 

Guard Cells

Surround each stomata and control opening and closing in response to environmental factors. Critical for plants to balance their need for CO2 with the risk of losing water.

Selective Permeability

When membranes only let certain molecules through without channels. They are called selectively permeable because they have a phospholipid bilayer structure. Allows small, nonpolar, molecules to pass through easily. Blocks most water-soluable substances, but allows water to pass through easily. 

Factors affecting rate of diffusion

Increase the rate of diffusion:

-high Surface area to volume ratio

-high temperature

- large Concentration Gradient

Simple Diffusion

-no energy required

-moves down the concentration gradient

-moves from high to low concentration

-small particles

Facilitated Diffusion

-Ions and molecules that are nonpolar

-pass through transport proteins

-transport proteins provide a hydrophilic channel or bind loosely to molecules

Passive Transport

Can be simple diffusion, facilitated diffusion, or osmosis. 

Active Transport

-movement of solute across a membrane against the concentration gradient

-low to high concentration

-needs energy

Cotransport

-happens after pumping H+ against the gradient

-H+ can do work when they move with the gradient across the membrane

Bulk Transport (endocytosis)

-Large molecules move across the membrane

-cell takes in materials from it’s surroundings by engulfing them

-forms a vesicle

Bulk Transport (exocytosis)

-process where a cell releases molecules and substances out of the cell into the extracellular fluid

-vesicles fuses with the cell’s plasma membrane

Osmosis

-Movement of water

-Water moves across a semi-permeable membrane

-Moves from a region of lower solute concentration to a region of higher solute concentration (high to low water potential)

-Affected by concentration gradient, temp, pressure, and surface area of the membrane. 

Movement of water: Hypertonic Solution

In a hypertonic solution, water moves out of the cell.

Movement of water: hypotonic solution

In a hypotonic solution, water moves into the cell.

Movement of Water: Isotonic Solution

Water will not move; solute=H2O

Osmoregulation

The process by which animals control solute concentration in the interstitial fluid and balance water gain and loss.

Water Potential and Excretory System

Water potential is the driving force behind the excretory system’s ability to regulate water and solute concentrations in the body.

Excretion

Helps regulate water potential by removing waste and controlling how much water and solute the body keeps or loses. When water potential is too low, less water is excreted and vice versa. 

Aldosterone

Hormone that promotes re-absorption of sodium and water by the body, which increases blood volume and pressure. 

Angiotensin II

Hormone that promotes feelings of thirst when your body needs more water and increases blood pressure. 

ADH

ADH makes walls of the distal tubule and collecting ducts more permeable to water. More water is absorbed by the body and urine becomes more concentrated in response to the osmolarity of the blood.