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
junctionsplasma membrane
of other cells form
a seal which
prevents leakage
Cell Junction
 Desmosomes
(anchoring) Fasten
cells together into
strong sheets
Cell Junction
 Gap
Junctionprovide 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
 Plasmodesmatacommunicating
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 bilayer
1.
Not all membranes are like

2.
Membranes with different functions differ in
chemical composition and structure
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
proteins
1.
2.
3.
4.
5.
6.
Transport
Enzymatic activity
Signal transduction (relaying messages)
Cell-cell recognition
Intercellular joining
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

1.
Selective permeability and structure:
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
Active
transport
Diffusion
Osmosis
Tonicity
Isotonic
Hypotonic
Facilitated
Diffusion
Carrier
proteins
Channel
proteins
Hypertonic
Sodiumpotassium
pump
Cotransport
Vesicular
Transport
Exocytosis
Endocytosis
Pinocytosis
Receptormediated
endocytosis
Phagocytosis
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