Chapter 6 and 7
AP Biology
• Cells are the basic unit of structural and functional unit
of living things.
• English scientist named Robert Hooke made a simple
microscope. He observed small, box-shaped structures,
called cellulae (meaning small room)
• All living things are made of one or more cells.
• Cells are the basic unit of structure and function in the
organization of 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.
• Based on 1 of 2 types of cells
• Prokaryotic
• ‘pro’ =before
• ‘karyon’ = kernel
• Eukaryotic
• ‘eu’ = true
• ‘karyon’ = kernel
• Based on 1 of 2 types of cells
• Prokaryotic
• Only exist in domains of Bacteria or Archaea
• Eukaryotic
• Protists, fungi, animals, and plants
• Bound by selective barrier (plasma membrane)
• Have cytosol (jellylike substance)
• Where organelles and other components are found
• Contain chromosomes
• Carry genes in the form of DNA
• Have ribosomes
• Location of DNA
• Eukaryotes
• Most DNA is in nucleus
• Nucleus is bound by double membrane
• “true kernel”
• Prokaryotes
• DNA is concentrated in region not membrane-enclosed
• Nucleoid
• Cytoplasm
• Eukaryotes
• Region between the nucleus and plasma membrane
• Contains a variety of organelles of specialized form and function
• Prokaryotes
• Interior of prokaryotic cell
• Organelles
• Eukaryotes
• Membrane- bound organelles are Present
• Specialized form and function
• Prokaryotes
• Absence of organelles
• Size
• Eukaryotes
• Generally Larger than prokaryotes
• Size relates to function
• 10 – 100um in diameter
• Metabolic requirements limit size practicality of cells
• Prokaryotes
• Smallest cells known
• 1 – 5 um in diameter
• Acts as a selective barrier
• Allows sufficient passage of oxygen, nutrients, and wastes to
service entire cell
• 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.
• 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)
• Nucleus- contains cellular DNA
which includes most of the genes
in the cell. The nucleus is
surrounded by the 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.
• Passive Transport- moves solute from high to low concentration.
DO NOT requires energy.
• 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.
• 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