Transcript Cells ppt

Cellular Structure and
Function
Chapter 7
7.1: Cell Discovery and
Theory
MAIN IDEA: The invention of the
microscope led to the discovery
of cells.
Types of Microscopes
 Light Microscopes
 Light waves pass through small
organisms, or thin slices of larger ones
 Simple – one set of lenses (magnifying
glass)
 Complex – more than one set of lenses
 Magnify up to 1500 times
 Dyes often used – kill/distort cells
Types of Microscopes cont’d
 Phase contrast microscope
 Type of light microscope
 Increases contrast – difference
btwn light/dark
 Cell structures more visible
 Can study living cells and
processes
Electron Microscopes
 Use electron beams instead of light
beams
 High magnification
 View image on screen: micrograph
 2 Types:
 Transmission electron microscope
(TEM) – electron beam passed
through thin slice of specimen; up
to 1 million X magnification
 Scanning electron microscope
(SEM) – views surface of specimen
2
1
3
4
1.Light
2.Phase
contrast
3.TEM
4.SEM
Compound Light Microscope
Early Scientists…
 1665 – Robert Hooke
 Also made microscopes
 Examined cork – discovered cells
 1600s – Anton von Leeuwenhoek
(Dutch lens maker) – made simple
microscopes
 Observed tiny organisms (bacteria,
insect structure, etc.)
 Scientists focused only on cell itself
Cell Theory Discovered!
 1700s – 1800s - 2 German
biologists: Matthias Schleiden and
Theodor Schwann discovered cell
theory
 Schwann emphasized contents of
cells, found similarities between
plant and animal cells
 1864 – Louis Pasteur disproved
spontaneous generation
 By 1880s – scientists could show
how cells divide
Cell Theory
1. All living things are made of
one or more cells.
2. Cells are the units of structure
and function in all organisms.
3. All cells come from preexisting cells.
Cells – Units of Life
 Cell – basic unit of life; in ALL
organisms:
 Unicellular (one-celled)
 Multicellular (many cells, some
with special functions)
 Complex organisms: cells  tissues
 organs  body systems 
organism
2 Main Cell Types
Prokaryotes
 “Pro-” = early
 Simple cells
 No nucleus
 No membranebound organelles
Eukaryotes
 “you”
 More complex
cells
 Have a nucleus
 May have other
organelles (other
membrane-bound
cell structures
w/specific jobs)
Prokaryotes
 Microscopic: .1 – 10 micrometers –
billions in a spoonful of soil, or in your
mouth!
 Can live in extreme environments
 Bacteria
 Has DNA, ribosomes, plasma membrane
 Some have cell walls, flagella
 Divide rapidly
 Will not form tissues
Prokaryote
Eukaryotes
 Larger – about 2-100 micrometers,
some even larger (neurons, frog eggs)
 Contain membran-bound organelles:
 structures for organization
 Allow for different reactions to occur
in cell at once b/c separate from each
other
 All have different functions
 Cells can form tissues
Eukaryote
7.2: The Plasma Membrane
MAIN IDEA: A cell’s plasma
membrane helps maintain
homeostasis.
Plasma Membrane
 Thin, flexible boundary between the
cell and its environment
 Allows nutrients into the cell
 Allows waste to leave the cell
Selective Permeability
 Ability of plasma membrane to
control which substances, and how
much of them, enter and leave a
cell
Composition of Membrane
 Made of phospholipids which form a
double layer (phospholipid bilayer)
One Phospholipid
Phospholipid Bilayer
Fluid Mosaic Model
 The phospholipid
bilayer allows
other molecules
to “float” in the
membrane.
 Proteins,
cholesterol,
carbohydrates
Proteins
 Transmit signals inside the cell
 Act as support structures
 Provide pathways for substances to
enter and leave the cell
Cholesterol
 Prevent fatty acid tails from sticking
together
Carbohydrates
 Identify chemical signals
7.3: Cell Structures and
Organelles
MAIN IDEA: The eukaryotic cell
contains organelles.
2 Main Eukaryotic Cell Types
 Animal and Plant cells
 Many of the same organelles,
but some different from each
other
Main Differences
Animal Cells
 Contain centrioles
 Contain lysosomes
 NO cell wall
 NO central
vacuole (only
small ones)
 NO chloroplasts
Plant Cells
 NO centrioles
 NO lysosomes
 Contain cell wall
 Contain central
vacuole
 Contain
chloroplasts
7.4 – Cellular Transport
MAIN IDEA: Cellular transport
moves substances within a cell,
and moves substances into and
out of cells.
Passive Transport
 Movement of particles across
cell membrane without using
energy
 3 Types:
 Diffusion
 Facilitated Diffusion
 Osmosis
Diffusion
 Movement of particles from an
area of high concentration to
an area of low concentration
Concentration
Gradient
Diffusion Controlled By…
 Temperature
 Concentration
 Pressure
 ALL of the above, when increased,
increase the amount of collisions
particles have with each other, so
diffusion occurs more rapidly.
Diffusion and Cells
 Diffusion allows for…
 Some substances to pass into and
out of cells
 Substances to spread out within
cells
 Dynamic Equilibrium
 Diffusion into cell = diffusion out of
cell
 Concentration on either side of
membrane is equal, although
movement of particles continues
Diffusion in a Cell
Facilitated Diffusion
 Movement of particles across a plasma
membrane using proteins
 Proteins are specific to certain particles
 Channel Proteins – span membrane so
particles do not come into contact with
nonpolar tails; effective for ion transport
 Carrier Proteins – physically bind
particles on one side of membrane, and
release them on other, changing shape;
used for ions, sugars, amino acids
Cellular Structure and Function
Facilitated Diffusion
Channel Proteins
Carrier Proteins
Osmosis
 Diffusion of WATER across
selectively permeable membrane,
from high concentration to low
concentration
Osmosis
3 Types of Solutions
 Isotonic
 Hypotonic
 Hypertonic
Isotonic Solution
 Water and dissolved substances
diffuse into and out of the cell at the
same rate.; concentrations equal; cell
size, pressure stays the same
Plant Cell
Blood Cell
Hypotonic Solution
 Solute concentration is higher inside the
cell than in the solution
 Water diffuses into the cell; cell swells
 Plant cells don’t burst (b/c of cell wall)
Plant Cell
Blood Cell
Hypertonic Solution
 Solute concentration is higher outside
the cell than in the solution
 Water diffuses out of the cell
(shrinks)
Plant Cell
Blood Cell
Active Transport
 Movement of substances AGAINST
the concentration gradient (____ to
_____ concentration)
 Requires energy
 Helps cell maintain homeostasis
 Uses carrier proteins called pumps
 Some move substances only one
way, some move them both ways
Active Transport and Proteins
Transport of Large Particles
 Endocytosis – cell surrounds
substance outside of cells, encloses
it in a sac/vesicle, and takes it into
the cell
 Exocytosis – vesicle with a
substance is released from the cell
Endocytosis
Exocytosis