CHAPTER 7

The invention of the microscope led to the discovery of cells
.
7.1 CELL DISCOVERY AND THEORY

MICROSCOPE
• Compound Light Microscope
• Series of glass lenses
• Uses visible light to produce a magnified image
• Electron Microscope
• Uses magnets to aim a beam of electrons at thin slices of cells
• Transmission Electron Microscope – TEM, electrons are transmitted through a specimen to a fluorescent screen
• Scanning Electron Microscope – SEM, directs electrons over the surface of a specimen to produce a 3D image

CELL THEORY
• The advances in microscope technology allowed the formulation of the cell theory
• Three main beliefs of the cell theory:
• 1. All known living things are made up of cells
• 2. The cell is the basic unit of structure and function in all living things
• 3. Cells only come from preciously existing cells, with cells passing copies of their genetic material on to their daughter cells

BASIC CELL TYPES
• Contains a nucleus
• The nucleus holds all the cell’s genetic information in the form of DNA
• Contains membrane-bound organelles which enable cell functions to take place
• Found in multicellular organisms
• Called eukaryotes
• No nucleus
• No membrane-bound organelles
• Found in unicellular organisms such as bacteria
• Called prokaryotes

BASIC CELL TYPES
• Cells differ based on their function
• ALL cells have a plasma membrane – special boundary that helps control what enters and leave the cell
• ALL cells break down molecules to generate energy for metabolism
• Eukaryotic cells are generally one to one hundred times larger than prokaryotic cells
• Scientists believe that eukaryotic cells evolved from prokaryotic cells

Bill Nye Presents

The plasma membrane helps to maintain a cell’s homeostasis
7.2 THE PLASMA MEMBRANE

REVIEW
• Homeostasis: regulation of an organism’s internal environment to maintain conditions needed for life

THE PLASMA MEMBRANE
• Thin flexible boundary between cell and its environment
• Responsible for homeostasis in the cell
• Allows nutrients in and wastes out
• Controls HOW MUCH of the substance is going in and out
- SELECTIVE
PERMEABILITY

STRUCTURE OF THE PLASMA MEMBRANE
• Composed of phospholipid bilayer
• Phospholipids are diagrammed as a head and two tails
• 2 layers of phospholipids are arranged tail to tail
• The head is polar and attracted to water
• The fatty tails are nonpolar and repel it
• The two layers create a “sandwich” and separate the environment inside the cell from the outside of the cell

PROTEINS
• There are also cholesterol, proteins, and carbohydrates moving among the phospholipids in the plasma membrane
• Proteins on the outside of the cell transmit signals to the inside of the cell
• Proteins on the inside anchor the membrane to the cell and give it shape, and some create tunnels through which certain substances can enter and leave the cell –
TRANSPORT PROTEINS

CHOLESTEROL & CARBOHYDRATES
• Cholesterol helps prevent the tails of the phospholipids from sticking together, creates fluidity. Also, important to structure of the membrane and maintaining homeostasis
• Carbohydrates attach to the outer proteins and help identify chemical signals

PLASMA MEMBRANE

FLUID MOSAIC MODEL
• The phospholipid bilayer creates a “sea” in which other molecules can float
• Since there are different substances in the membrane, a pattern, or mosaic, is created on the surface
• These components are in constant motion, sliding past one another

Eukaryotic cells contain organelles that allow the specialization and the separation of functions within the cell.
7.3 STRUCTURE AND ORGANELLES

ANIMAL VS. PLANT

ORGANELLE TRADING CARDS
• Trading card materials are located at the front of the class
• You get ONE sheet of colored pictures so use them wisely!
• The rubric is attached to your packet, when you are finished have me or Mr. Klein check your work
• These are due at the end of the period!
• When you finish, begin 7.3 Study Guide and Cell City worksheet

HALF SHEET OF PAPER: NAME THAT
ORGANELLE

Cellular transport moves substances within the cell and moves substances into and out of the cell.
7.4 CELLULAR TRANSPORT

REVIEW
• ION: an atom or group of atoms with a positive or negative electron charge

CELLULAR TRANSPORT
• Three kinds:
• Diffusion
• Osmosis
• Active Transport

DIFFUSION
• In Da Club
• Diffusion – the net movement of particles form an area where there are many particles of the substance to an area where there are fewer particles of the substance
• HIGH CONCENTRATION to LOW CONCENTRATION
• Concentration – the amount of substance in a particular area
• Diffusion does not require additional energy input since the particles are already in motion, this is an example of
PASSIVE TRANSPORT

DIFFUSION
• Once an equal concentration is reached, the particles will continue to move, but there is no overall change –
DYNAMIC EQUILIBRIUM
• Concentration, temperature, and pressure affect the rate of diffusion
• Concentration is high = diffusion occurs more quickly
• Temperature increase = diffusion occurs more quickly
• Pressure increase = diffusion occurs more quickly

DIFFUSION

FACILITATED DIFFUSION
• Diffusion happens in water, but also in cells
• Most substances cannot diffuse across the plasma membrane
• Facilitated Diffusion - uses transport proteins to move ions and other molecules across the plasma membrane
• A channel or carrier protein opens and closes to allow the substances into the cell

FACILITATED DIFFUSION

OSMOSIS: DIFFUSION OF WATER
• In diffusion, no membrane is necessary
• Osmosis involves the diffusion of water across a selectively permeable membrane
• The regulation of water movement across the plasma membrane is important for maintaining homeostasis in the cell

OSMOSIS
• Review – substance called solutes are dissolved in solvents
• Water is the solvent in a cell
• The concentration of a solution decreases when the amount of solvent increases

OSMOSIS
• For example, sugar water.
Sugar is the solute and water is the solvent
• What happens if the water can pass through the membrane, but the sugar cannot?

OSMOSIS
• The water molecules will diffuse towards the side with greater sugar concentration
• It will continue to diffuse until dynamic equilibrium occurs
• OSMOSIS

COMPARE AND CONTRAST

ISOTONIC SOLUTIONS
• ISO – equal
• If a cell is in a solution that has the same concentration of water and solutes
• The cell is in equilibrium and maintains its shape

HYPOTONIC SOLUTION
• HYPO – under
• Solute concentration is higher INSIDE the cell
• Osmosis causes water to diffuse into the cell, pressure increases

HYPERTONIC SOLUTION
• HYPER – above
• Solute concentration is higher OUTSIDE of the cell
• Osmosis causes water to diffuse out of the cell, pressure decreases

ACTIVE TRANSPORT
• Passive transport – requires no additional energy input, movement from high concentration to low
• Active transport – substances moving from lower concentration to higher, requires energy
• Occurs with the aid of carrier proteins, commonly called pumps
• Some pumps move substances in only one direction, other move substances back and forth
• Helps maintain homeostasis

ACTIVE TRANSPORT

TRANSPORT PUMPS
• Na + /K + ATPase Pump
• Sodium-potassium
ATPase pump
• Found in the plasma membrane of animal cells
• Moves three Na + ions out of the cell and two
K + ions into the cell

ACTIVE VS. PASSIVE

LARGE PARTICLES
• Some substances are too large to move through the membrane by diffusion or transport proteins
• Endocytosis – the process by which a cell surrounds a substance and encloses it in the plasma membrane
• Exocytosis – secretion of materials at the plasma membrane, used to expel wastes
• Both require energy