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Question: What invention revolutionized the discovery of cells and these organelles?
THE DISCOVERY OF CELLS
The invention of the microscopes made it possible for scientists to view and study cells.
Cells — basic units of all living organisms.
The Cell Theory
1. All living things are made of one or more cells.
2. Cells are the basic units of structure and function in living things.
3. All cells come from other cells.
Microscopes have helped scientists learn more about cells:
Electron microscopes — allow objects to be magnified up to 500,000 x using beam of
electrons instead of light
Scanning electron microscope (SEM) — can help scientists see a cells three-dimensional
shape
Transmission electron microscope (TEM) — allows scientists to see structures inside a
cell
Scanning probe microscopes — produce images by tracing surfaces of cells or structures
with a probe
All cells contain small structures called organelles. Each organelle has a specific function
in the cell.
Two Major Classes of Cells:
PROKARYOTIC CELL
EUKARYOTIC CELL
 lacks a nucleus and most
 has nucleus surrounded by
other organelles
membrane and other
membrane-bound organelles
Ex. bacteria and archaea
Ex. protists, fungi, plants and
animals
Question:
Question: How
Whatistwo
a plasma
organelles
membrane
do plant
like
cells
a window
have that
screen?
animal cells do not?
EUKARYOTIC
THE PLASMA
CELL
MEMBRANE
STRUCTURE
(aka protists, fungi, plant and animal cells)
Plasma
membraneOrganelle
— flexible boundary of a cell that separates
a cell from its
Function
Description
surroundings.
BOUNDARY Cell Wall
rigid wall outside plasma membrane giving extra
support – not found in animal cells
The plasma membrane regulates what enters and leaves the cell and also provides
protection and support. This is called selective permeability.
Nucleus
directs activity of cells organelles
NUCLEUS
Nuclear
surrounds nucleus and has thousands of pores allowing
AND
Envelope
material in
and
out ofto
nucleus
Selective permeability
— some molecules
are
allowed
pass through plasma membrane
CELL
at anytime - other molecules are only allowed at certain times or in limited amounts.
CONTROL
Chromatin
strands of DNA located throughout the nucleus
Some molecules
are never allowed.
Chromosomes condensed chromatin that contain genetic information
Structure
of Plasma
Membrane
passed on
to offspring
Nucleolus
makes ribosomes inside nucleus
Phospholipid bilayer — double-layered sheet that makes up nearly all plasma
Ribosomes
where proteins are assembled according to the DNA
membranes.
directions
Phospholipid —Cytoplasm
made up of glycerol,
fatty
acids,
and a phosphate
group
thicktwo
fluid
outside
nucleus
throughout
the cell
Endoplasmic
site where lipids for membrane are assembled along
Carbohydrate
chain
Reticulum
with proteins-two
types:
rough and smooth
OUTSIDE CELL
ASSEMBLY, Golgi
sorts and packages proteins and materials into
phosphate
TRANSPORT apparatuscell structures called vesicles then “shipped” out
fattyAND
acid
membrane
STORAGE
Vacuole
saclike structure used for storage (water, food and
chains
enzymes) - large single one in plant cells
INSIDE CELL
Proteins
Lysosomes
remove wastes using digestive enzymes
Protein
Mitochondria transform chemical energy from food into useful energy
for both channel
Chloroplasts
found in green plant cells and some protists capturing
Plasma membranes contain protein
are embedded
in the phospholipid
sun molecules
energy andthat
converting
it to chemical
energy
bilayer. Carbohydrate molecules are attached to many of the proteins. The organization
of all these structures is called the fluid mosaic model.
Function
SUPPORT
AND
LOCOMOTION
Organelle
Description
Cytoskeleton
network of protein filaments that help cell keep its shape
and helps with movement of protein filaments called
microtubules or microfilaments
Centrioles
made of microtubules and help with cell division
Cilia
short hair-like projections that wave to help move cell
Flagella
long whip-like projections that aid in movement – usually
just one or two
Question: What cell appeared earlier in history — eukaryotic or prokaryotic?
PROKARYOTIC CELL STRUCTURE
(aka Bacteria)
Prokaryotes — bacteria that are unicellular organisms that do not have a nucleus or
membrane—bound organelles
Plasmid — genes separate from chromosome which can carry antibiotic-resistant genes.
Capsule (slime layer) — sticky capsule around cell wall that enhances some bacteria to
cause disease
Chromosome — single DNA molecule not enclosed in nucleus; contains most of bacteria’s
genes
Flagellum — some bacteria have long whip-like projections that enable them to move
(flagella-plural)
Ribosomes — site of protein synthesis
Food molecule
Pilus — extensions of plasma membrane – helps bacteria stick to a surface and also acts as
a bridge where two bacteria can exchange DNA (pili-plural)
Plasma membrane — surrounds cell and regulates what enters and leaves cell
Cell wall — surrounds the plasma membrane-gives cell its shape and prevents osmosis
(water entering) from bursting cell
Question: Does a cell use passive transport or active transplant to move molecules?
CELLULAR TRANSPORT
Every living cell exists in a liquid environment that it needs to survive. The plasma
membrane is selectively permeable, meaning only certain molecules are allowed in and
out of cells.
Diffusion — particles tend to move from an area where they are more concentrated to an
area less concentrated.
— In cells substances can diffuse across membranes WITHOUT requiring use of energy —
passive transport
Osmosis — diffusion of water across a selectively permeable membrane — enables cell
membrane to regulate cells internal environment — this is called homeostasis
*Osmosis effects cells depending on the type of solution they are placed in: isotonic,
hypertonic or hypotonic.
Facilitated diffusion — molecules that cannot diffuse on their own, moves through
protein channels in membrane
Active transport — transport protein (carrier) protein requires ENERGY to help move
particles across the membrane against a force (concentration gradient)
Endocytosis
large particles are engulfed,
then enclosed by cell
membrane — moves into cell
vs
Exocytosis
large particles are released from
cell by secreting them or
expelling them out