AP Biology Chapter 6 and 7

Tour of the Cell Membrane Transport

Eukaryotic cell’s genetic instructions Nucleus Nuclear envelope Nuclear lamina Chromosomes Nucleolus

Eukaryotic cell ribosomes Ribosomes

Free ribosomes Bound ribosomes

Endomembrane system Nuclear envelope ER Golgi apparatus Lysosomes Plasma membrane Vesicles Vacuoles

Endosymbiosis Theory

Mitochondria Mitochondria Cristae Mitochondrial matrix

Chloroplasts Thylakoids Granum Stroma plastids

Peroxisomes

Cytoskeleton Network of fibers extending throughout

the cytoplasm Roles of cytoskeleton

Mechanical support to cell shape Cell motility (movement) using motor

proteins

Cell junctions Tight junctions-

plasma membrane of other cells form a seal which prevents leakage

Cell Junction Desmosomes

(anchoring) Fasten cells together into strong sheets

Cell Junction Gap Junction-

provide cannels so cells can communicate with each other, and molecules can pass to and from

AP Biology- Quiz today Finishing extracellular components

Cell wall parts of plant Cell wall- protects and maintains shape Primary cell wall- thin flexible wall (young

plant) Secondary cell wall- hardened structure

between the plasma membrane and primary wall

Middle lamella- Thin layer with sticky polysaccharides (pectins) glues cells together

Plasmodesmata- communicating channel between plant cells

Chapter 7- Membranes The plasma membrane separates the

living cell from its surroundings Selectively permeable: some substances

cross more easily than others Membrane encloses a solution different

from the surrounding solution

Phospholipid bilayer Contains: lipids,

proteins, and carbohydrates

Most abundant lipid: phospholipid

Amphipathic molecule: hydrophilic and hydrophobic regions

Phospholipid Bilayer Fluid mosaic model: the membrane is a

fluid structure with various proteins embedded in or attached to the double layer

Phospholipid bilayer1. Not all membranes are like

Membranes with different functions differ in chemical composition and structure

2. Measurements showed that membrane proteins are not very soluble in water

Phospholipid bilayer Freeze fracture technique

Splits a membrane along the middle of the phospholipid bilayer

Found that: membranes are more mosaic than fluid, lipids appear to form defined regions

Phospholipid Bilayer Membrane molecules are held in place

by relatively weak interactions Most lipids and some proteins drift

laterally in the plane of the membrane but rarely flip-flop from one phospholipid layer to the other

Phospholipid bilayer Membrane fluidity is influenced by

temperature: As temperature cools, membranes switch

from a fluid state to a solid state Phospholipids pack together more closely

Phospholipid bilayer Steroid cholesterol is wedged between

phospholipid molecules in the plasma membrane of animal cells Warm temp: restrains movement (reduces

fluidity) Cold temp: maintains fluidity by

preventing tight packing Fluidity buffer

Proteins determine membrane’s function

Two major populations of membrane proteins: integral and peripheral

Membrane Proteins Integral-

Embedded in the bilayer

Penetrate hydrophobic interior of bilayer

Peripheral- Not embedded in

the bilayer Loosely bound to

surface of membrane

Major functions of membrane proteins1. Transport2. Enzymatic activity3. Signal transduction (relaying

messages)4. Cell-cell recognition5. Intercellular joining6. Attachment to cytoskeleton

Cell to cell recognition- ability of a cell to distinguish one type of neighboring cell from another

Membrane carbohydrates may be bonded to lipids or proteins making glycolipids or glycoproteins respectively

Selective permeability and structure:

1. Small molecules and ions move across the plasma membrane in both directions

Example: sugar, amino acids and other nutrients enter a

muscle cell and metabolic waste leave The muscle cell takes in oxygen and expels

carbon dioxide Muscle also regulates the concentrations of

inorganic ions, such as Na, K, Ca, Cl by shuttling them one way or the other across the membrane

Movement of molecule depends on the interaction of the molecule with the hydrophobic interior of membrane Nonpolar molecules can dissolve in the

lipid bilayer easily Polar molecules and water extremely

small can cross bilayer slowly Passage of water occurs via aquaporins Carrier proteins- bind to molecules and

change shape to shuttle them across membrane

Membrane Transport

Passive Transport

Diffusion Osmosis

Tonicity

Isotonic Hypertonic

Hypotonic

Facilitated Diffusion

Carrier proteins

Channel proteins

Active transport

Sodium-potassium

pumpCotransport

Vesicular Transport

Exocytosis Endocytosis

Pinocytosis Phagocytosis

Receptor-mediated

endocytosis

Water potential A property predicting the direction in

which water will flow

Formula: Ψ = ΨS + ΨP

Water Potential ΨS = -iCRT

i = ionization constant (1 for sucrose) C = osmotic molar concentration R = Pressure constant (R= 0.0831 liter bars/mole

°Kelvin T = temperature

Calculations: Calculate the osmotic potential using

the following data. Answer should be in bars.

C = 0.32 T =21 °C *must convert to Kelvin