AP Biology Unit 2

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Cell Characteristics

-Cell Membrane

-Ribosomes

-Cytoplasm

-Chromosomes

Cell membrane

phospholipid bilayer with proteins

Chromosomes

Composed of DNA and proteins; Contains genetic material for cell

Nucleus

Where the eukaryotic cell’s genetic instructions are housed and carried out by the ribosomes; Contains DNA that codes for proteins

Free Ribosomes

Make proteins that stay in cytoplasm

Bound Ribosomes

Make proteins destined for cell membrane, lysosomes, that are secreted from the cell

Rough Endoplasmic Reticulum

Makes proteins for cell membrane, lysosomes, secreted from cell (has ribosomes)

Smooth Endoplasmic Reticulum

Makes lipids and complex carbs

Golgi Apparatus

Ships and receives proteins from Rough ER. Packages, modifies, and sorts them for their final destination.

Lysosomes

Sacs filled with digestive enzymes (comes from Rough ER). Involved in Apoptosis, and destruction of foreign invaders in white blood cells.

Vacuoles

Main purpose is for storage. Central one maintains turgidity of plant cells

Mitochondria

Site of ATP synthesis via aerobic respiration. Double membraned organelle where inner membrane is folded into cristae (for surface area).

Chloroplast

Double membraned organelle containing stacks of membrane sacs (thylakoids) (for surface area) called grana. Contain chlorophyll. Uses solar energy to make precursor to glucose.

Endomembrane System

Basically reason we have ER, Nucleus, Golgi is because a lot of infolding happened in prokaryotes. The infoldings pinched off the membrane and enclosed the nucleoid, which now becomes a nucleus.

Endosymbiont Theory

Reason we have mitochondria and chloroplasts is because Ancestral eukaryote engulfed prokaryotic aerobe followed by prokaryotic autotroph and they coexisted in symbiotic relationship. They have similarities with bacteria, ribosomes and DNA similar in size and structure to bacteria, same size, and divide independently from rest of cell

Small Cells

Living cells need to take in nutrients and eliminate waste. Surface area to volume ratio (SA/V) is important in how efficiently this is done. The larger the SA/V, the more efficiently cells can transport material All material must pass through the surface area of the cell. The bigger the radius (volume) the lower the SA/V ratio.

Membrane Folds

-The highly folded mitochondrial inner membrane

-The highly folded membrane of cells lining the

small intestine

These increase SA/V and allow more

-ATP to be made on inner membrane

-Nutrients to be absorbed by small intestine

Phospholipid Bilayer

Composed of two layers of phospholipids. Phospholipids are amphipathic, hydrophobic tails face in, polar heads face out. Prevents soluble material from passing across the membrane and allows for diffusion of small nonpolar molecules across the membrane

Membrane Fluidity

-Unsaturated fatty acids prevent tight packing enhancing membrane fluidity

-Saturated fatty acids allow tight packing, decreasing membrane fluidity

-Cholesterol prevent fluidity at high temperatures but enhances fluidity at lower temps

-Decreased temps decrease fluidity

-Many species that live where temps vary can

alter the lipid composition of their membranes

Selectively Permeable

-Membranes regulate what enters and leaves

-Hydrophobic molecules can easily slip thru the bilayer (gases, steroids)

-Polar molecules and large molecules can’t cross as easily (sugar, ions, proteins)

-Hydrophobic molecules slip thru bilayer

-Smaller hydrophilic molecules must pass thru

transport proteins

Passive Transport

High to low concentration, no energy required. Includes: Diffusion, Osmosis, Facilitated Diffusion

Diffusion

Movement of small nonpolar molecules across the phospholipid bilayer. Down the gradient, No energy. Ex: O2 in CO2 out

Facilitated Diffusion

Movement of slightly larger molecules through proteins. Down the gradient, No energy. As solute concentration increases, rate of transport increases till all transport proteins are saturated.

Osmosis

Movement of water across phospholipid bilayer through aquaporins. No energy, down the gradient.

Hypotonic

More water and less solute than hypertonic

Hypertonic

Less water and more solute than hypotonic

Water potential

Solute + Pressure potential. Tendency for water to move across a membrane from higher to lower ___. In living cell it is zero or negative. Equal to -iCRT.

Active Transport

Uses Energy. Movement of ions low to high through transport protein specific to ion. Energy changes shape of transport protein so that ions can be transported.

Endocytosis

Movement of material into cell

Exocytosis

movement of material out of cell