Chapter 6 and 7
AP Biology
• All living things are made of cells.
• Cells are the basic unit of structure and function in
living things.
• All cells come from pre-existing cells.
• Eukaryotic cells contain DNA in the nucleus.
Prokaryotic cells contain DNA in a concentrated region
called the nucleoid.
• Plasma Membrane- a
selective barrier
(semipermeable) that
allows passage of enough
oxygen, nutrients, and
wastes to and from the
cell.
• The plasma membrane is a
lipid bilayer embedded
with diverse proteins.
• As you ___________ the cell size, you ____________
the surface area to volume ratio, which ___________
the efficiency of transport across the cell membrane.
• Nucleus- contains cellular DNA
which includes most of the genes
in the cell. The nucleus is
surrounded by the nuclear
envelope.
• The nuclear envelope is a double
membrane made of 2 lipid
bilayers. Includes pore structures
that help regulate things entering
and exiting the nucleus.
• Nuclear Lamina- a net of protein
filaments that maintain shape of
nucleus and support nuclear
envelope.
• Chromosomes- structures that
carry genetic information (DNA).
Each chromosome contains one
long DNA molecule.
• Each eukaryotic species has a
distinct number of
chromosomes.
• Chromatin- the complex of DNA
and protein making up
chromosomes.
• Nucleolus- helps synthesize rRNA
(ribosomal RNA) and ribosomes.
• Ribosomes- made of rRNA and proteins- carry out
protein synthesis.
• Ribosomes exist as either free ribosomes (suspended in
cytosol) or bound ribosomes (attached to the Rough ER or
nuclear envelope)
• Endoplasmic Reticulum- consists of membranous
tubules, and sacs, called cisternae.
• Smooth ER- lacks ribosomes. Functions lipid synthesis,
detoxification, and storing calcium ions.
• Rough ER- has ribosomes on surface. Continuous with
the nuclear envelope. Synthesizes glycoproteins and
other secretory proteins.
• Golgi Apparatus- made of flattened membranous
sacs called cisternae. Has 2 sides the cis face
(receiving) and the trans face (shipping).
• Lysosome- contains hydrolytic enzymes used to digest
molecules.
• Phagocytosis- “cell eating”- lysosome digesting food
• Autophagy- lysosome breaking down damaged organelles.
• Vacuole- functions vary depending on cell type.
• Food Vacuole
• Contractile Vacuole
• Central Vacuole
• Mitochondria- site of cellular
respiration.
• Cellular Respiration- the process
that uses O2 to generate ATP by
extracting energy from sugars,
fats, and other fuels.
• Chloroplast- found in plants and algae- the site of
photosynthesis. Contain the green pigment chlorophyll.
• Is a member of the plastid family- a group of plant
organelles.
• Peroxisomes- contain enzymes that remove hydrogen
atoms and transfer them to oxygen, producing
hydrogen peroxide (H2O2).
• Cytoskeleton- a network of fibers extending
throughout the cytoplasm- plays a major role in
organizing the structure and activities of the cells.
• Motor Proteins- allows for cell movement.
• Microtubules- the thickest cytoskeletal fiber, provide
a track that organelles with motor proteins can move
along. Help separate chromosomes during mitosis.
Form flagella and cilia.
• Centrosome- region where microtubules are organized.
Contains a pair of centrioles. Only in animal cells.
• Microfilaments- the thinnest fiber. Actin and myosin
filaments help muscle cells contract. Aide in
pseudopodia movement by converting cytoplasm from
a liquid to a gel.
• Cytoplasmic Streaming- circular flow of cytoplasm within
cells. Speeds distribution of cell materials.
• Intermediate Filaments- more permanent fixtures, fix
the position of organelles and shape of the cell.
Include keratin proteins.
• Cell Wall- extracellular structure of plant cells. Protects the
cell, maintains its shape, and prevents excessive uptake of
water. Holds the plant up against gravity.
• Primary Cell Wall, Middle Lamella, Secondary Cell Wall
• Plasmodesmata-perforations in the plant cell wall that allows
cytoplasm to be continuous between neighboring plant cells.
• Extracellular Matrix (ECM)- glycoproteins, carbohydrates and
proteoglycans that form strong fibers outside of cells.
• What are the three components of the cytoskeleton?
• Which cytoskeletal component provides tracks for
motor proteins to move along within the cell?
• Which cytoskeletal structure helps muscles contract?
• Which cytoskeletal component helps form cilia and
flagella?
• Fluid Mosaic Model- membrane is a fluid structure with a
“mosaic” of various proteins embedded in or attached to a
phospholipid bilayer. (lipids and proteins are amphipathic)
• Integral Proteins- penetrate the hydrophobic interior of he lipid
bilayer. (Ex: integrins)
• Most of these are transmembrane proteins which span the entire
membrane.
• Peripheral Proteins- loosely bound to the surface of the
membrane. Not embedded at all.
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Transport
Enzymatic Activity
Signal Transduction
Cell to Cell Recognition
Intercellular Joining
Attachment to Cytoskeleton
and ECM
• Membranes are held together by weak hydrophobic
interactions.
• Membrane remains fluid as temperature decreases, until
phospholipids pack so closely together that the membrane
solidifies.
• Cholesterol reduces membrane fluidity at high temperatures by
reducing movement. It also prevents packing, slowing
solidification at low temperatures.
• Transport Proteins
• Channel Proteins- provide a channel for hydrophilic
molecules to move through.
• Aquaporins- allow water to pass through the cell
membrane quickly.
• Carrier Proteins- bind to molecules and shuttle them across
the membrane.
• Diffusion- movement of molecules of any substance until they
spread out evenly in the available space. (equilibrium).
• Diffusion is a spontaneous process, needing no energy input.
• Rule of Diffusion: in the absence of a force, a substance will
diffuse from high concentration to low concentration.
• A substance diffuses down its own concentration gradient,
unaffected by the concentration of other substances.
• Diffusion is a form of passive transport- movement that does not
require the cell to use energy.
• Osmosis- the diffusion of
water. Water diffuses from
the region of lower solute
concentration (higher free
water concentration) to the
area of higher solute
concentration (lower free
water concentration)- until
equilibrium is reached.
• Osmosis is a method of
passive transport
• Tonicity- the ability of a surrounding solution to cause a cell to
gain or lose water.
• Hypertonic- concentration of solution is more than the cell. Cell will
lose water, shrivel, and probably die.
• Hypotonic- concentration of solution is less than the cell. Water
will enter the cell and the cell will swell and lyse (burst).
• Isotonic- concentration of solutions is the same on both sides of the
membrane. No net movement of water = stable volume.
• Osmoregulation- the control of solute concentrations and water
balance.
• Less permeable membrane, contractile vacuole, etc.
• Facilitated Diffusion- passive transport aided by proteins.
• Frequently involves polar molecules.
• Ion Channels- channel proteins that transport ions down the
concentration gradient. No energy required.
• Gated Channels- open or close in response to a stimulus.
• Active Transport- moves solute from low to high concentration.
Requires energy (usually ATP). Uses carrier proteins.
• Active transport allows a cell to have an internal concentration
different from its surroundings.
• Sodium-Potassium Pump- an example of active transport that
exchanges Na+ for K+ across the plasma membrane.
• Membrane Potential – the difference in voltage across the cell
membrane. (ranges from -50 to -200 mV)
• The inside of the cell is negative relative to the outside.
• This favors transport of cations into the cell and anions out of the
cell.
• Electrochemical Gradient- the combination of the membrane
potential (electrical force) and concentration gradient (chemical
force).
• Ions diffuse not only down their concentration gradient, but down its
electrochemical gradient.
• Electrogenic Pump- a transport protein that generates voltages
across a cell membrane by maintaining a membrane potential.
• Ex. Sodium-potassium pump in animals and proton pump in plants,
fungi and bacteria
• Cotransport- active transport driven by a concentration
gradient.
• Exocytosis- the secretion
of large molecules by the
fusion of vesicles with the
plasma membrane.
Requires energy.
• Endocytosis- cell takes in
molecules by forming new
vesicles from the plasma
membrane.
• Phagocytosis- cell eating
• Pinocytosis- cell drinking
• Receptor-Mediated
Endocytosis