Concept 6.1ALL

ORGANISMS ARE MADE OF

CELLS

THE CELL THEORY 1. All living things are composed of

cells.

2. Cells are the basic unit of structure

and function in living things.

3. All cells come from pre-existing cells.

CELL THEORY DEVELOPMENT

Prior to the development of microscopes, cells could not be seen in any detail

Two types are used Light microscope: first used around 1600 Electron microscope: developed in the

1950s

TYPES OF MICROSCOPES Light Microscopes:

Simplest type

Use visible light

Used to examine living cells

Magnify 1000 X

ELECTRON MICROSCOPES

Use electron beams Magnify 1,000,000 X All specimens must

be killed to view Two types: SEM – used view cell

surface TEM – used to view

internal structures

TYPES OF CELLS Two basic kinds of cells

Classification based on the presence or absence of organelles—parts of cells with specific functions

Prokaryotic cells: have no organelles

Eukaryotic cells: have organelles

PROKARYOTIC CELLS Most primitive cell type

Lack organelles—structures that perform specific functions in cells

First organisms to appear in fossil record

Domains Archaea and Bacteria

PROKARYOTIC CELL

EUKARYOTIC CELLS More advanced cell type

Contain organelles that perform specific functions for the cell

Domain Eukarya

Includes organisms in 4 Kingdoms: Plants Animals Protists Fungi

PROKARYOTIC vs. EUKARYOTIC CELLS

PLANT vs. ANIMAL CELLS

Both contain most organelles Plant cells have 3 structures not seen in

animal cells:

1. Cell wall: surrounds cell membrane

2. Chloroplast: photosynthesis occurs here

3. Central vacuole: large storage area

ANIMAL CELL

PLANT CELL

Concept 6.2MEMBRANES ORGANIZE A

CELL’S ACTIVITIES

MEMBRANE FUNCTIONS

Keeps cell organized

Partitions the cell

Controls movement of substances into and out of cell

Helps maintain chemical environment for cell

- homeostasis - balanced internal

condition of cells

MEMBRANE STRUCTURE

Bilayer structure:

Two layers of phospholipid molecules with protein molecules embedded

Phospholipids are similar to triglycerides—fat molecules

Allows membrane to separate watery inside of cell from watery outside of cell

MEMBRANE STRUCTURE

PHOSPHOLIPID STRUCTURE

Two part molecule:

Hydrophilic polar phosphate group head is attracted to water faces outward towards water

Hydrophobic non-polar fatty acids tails face inward toward each other—away from water

PHOSPHOLIPID MOLECULE

MEMBRANE PHOSPHOLIPIDS

CELL MEMBRANES

Package

PROTEINS PERFORM MOST MEMBRANE FUNCTIONS

Enzyme activity: catalyze reactions of nearby substrates

Cell-to-cell recognition: surface proteins of other cells are “recognized”

Cell signaling: chemical messengers bind to surface proteins causing change in shape relaying message inside cell

Transport of materials: provide channels for certain solutes

PROTEINS PERFORM MOST MEMBRANE FUNCTIONS

CELL MEMBRANE ACTIVITY

Package

Concept 6.3MEMBRANES

REGULATE THE TRAFFIC OF MOLECULES

TYPES OF MEMBRANES

Permeable membranes: allow particles freely pass through them

Selectively permeable membranes: allow some substances to cross more easily than others; block some completely

MEMBRANE TRANSPORT

Two main types of transport:

Passive transport: no energy is used by the cell in transporting material

Active Transport: cell must expend energy to move molecules or particles across the membrane

PASSIVE TRANSPORT Three types of passive transport:

Simple diffusion

Facilitated diffusion

Osmosis

DIFFUSION Diffusion: net movement of particles from

area where they are more concentrated to an area where they are less concentrated

Diffusion may occur with or without a membrane—the only requirement is that a concentration gradient must exist

Concentration gradient: difference in the concentration of a substance between one area and another

During diffusion, particles of a substance move through a space until the concentration of the substance is the same in all areas

When diffusion occurs a membrane, particles will continue to move across the membrane until the concentrations are equal on both sides of membrane balance or equilibrium is reached

DIFFUSION

CELL MEMBRANE TRANSPORT

Cell membranes are selectively permeable

O2 and CO2 pass freely

H2O must pass through protein channels

Other molecules pass only under specific conditions

Ions, hydrophilic molecules larger than water, proteins, & large molecules do not move through the membrane on their own.

TYPES OF PASSIVE TRANSPORT

Simple diffusion: passage of substance directly through the membrane

O2, CO2

TYPES OF PASSIVE TRANSPORT

Facilitated diffusion Substances pass

through a channel in a transport protein in membrane

Sugars, H2O, some ions

PASSIVE TRANSPORT

DIFFUSION

Diffusion.url

OSMOSIS Osmosis: passive transport of H2O across

a selectively permeable membrane

Aqueous solutions: solutions in which water is the solvent

Aqueous solutions can be classified into 3 categories called osmotic solutions

TYPES OF OSMOTIC SOLUTIONS

Hypotonic: lower solute concentration outside cell than inside

Water moves into cell

Hypertonic: higher solute concentration outside cell than inside

Water moves out of cell

Isotonic: same solute concentration outside cell as inside cell

Water moves in equal amounts in and out

39

Cell in Hypotonic Solution

CELLCELL

10% NaCL90% H2O

20% NaCL

80% H2O

What is the direction of water movement?

40

Cell in Hypertonic Solution

CELLCELL

15% NaCL85% H2O

5% NaCL95% H2O

What is the direction of water movement?

ENVIRONMENTENVIRONMENT

41

Cell in Isotonic Solution

CELLCELL

10% NaCL90% H2O

10% NaCL

90% H2O

What is the direction of water movement?

The cell is at _______________.equilibrium

ENVIRONMENTENVIRONMENT

NO NET MOVEMENT

43

CYTOLYSIS & PLASMOLYSISCYTOLYSIS & PLASMOLYSIS

Cytolysis Plasmolysiscopyright cmassengale

44

Isotonic Solution

NO NET MOVEMENT OF H2O

(equal amounts entering & leaving)

Hypotonic Solution

CYTOLYSIS cell swells and bursts

Hypertonic Solution

PLASMOLYSIS cells shrink and shrivel

copyright cmassengale

OSMOSIS

Osmosis.url

OSMOSIS & PLANT CELLS

Hypotonic environment: plant cells are firmest and healthiest cell wall prevents membrane from bursting (CYTOLYSIS)

Isotonic environment: non-woody plants wilt

Hypertonic environment: membrane pulls away from cell wall (PLASMOLYSIS)

- kills the cell

ACTIVE TRANSPORT Two major types of active transport:

1. Solute ions are “pumped” across the membrane

2. Large particles are transported into or out of the cell

ACTIVE TRANSPORT

Requires energy or ATP

Moves materials from LOW to HIGH concentration

AGAINST concentration gradient

Specific transport protein pumps a solute across a membrane.

48

49

Sodium-Potassium Pump

3 Na+ pumped in for every 2 K+ pumped out

LARGE MOLECULE TRANSPORT

Some particles are too large to move through the membrane

Must be packaged in membrane sacs called vesicles

Particle fuses with plasma membrane and is moved either into (endocytosis) or out of (exocytosis) the cell

Both processes require energy

ENDOCYTOSIS Material is brought into the cell

TYPES OF ENDOCYTOSIS Phagocytosis: cell membrane engulfs and

takes in particle of solid material; - “cell eating”

Pinocytosis: cell membranes engulfs and takes in small droplet of liquid;

- “cell drinking”

EXOCYTOSIS Product of cell is exported

ENDOCYTOSIS & EXOCYTOSIS

05_09Endo_Exocytosis.swf

Concept 6.4THE CELL BUILDS

A DIVERSITY OF PRODUCTS

NUCLEUS Directs the activities of the cell

Contains most of cell’s DNA in the form of chromatin

Chromatin: long fibers of DNA;

- attached to proteins

- organized when cell divides

NUCLEUS Nuclear envelope:

double membrane surrounding nucleus

Membrane contains tiny nuclear pores

Substances made in nucleus exit through these pores

Contains nucleolus

NUCLEOLUS Nucleolus: round structure made of fibers

and granules inside nucleus

Produces ribosomes—tiny organelles involved in protein synthesis

RIBOSOMES Made of proteins and nucleic acids

NOT surrounded by a membrane

Produce all the proteins for the cell

Float free in cytoplasm or are attached to membrane network within the cytoplasm

ENDOPLASMIC RETICULUM

Network of membranes within cytoplasm

Connected to the nucleus One of the main manufacturing and

transportation facilities of the cell Two distinct regions:

1. Rough ER

2. Smooth ER

ENDOPLASMIC RETICULUM

ROUGH ER Has ribosomes attached

Ribosomes produce proteins and insert them into or through ER membrane

Some proteins are packaged in vesicles and exported

Cells that secrete many proteins are rich in rough ER

SMOOTH ER No attached ribosomes functions:

Lipid synthesis

Detoxification

Carbohydrate metabolism

Cells of ovaries and testes (produce sex hormones) are rich in smooth ER

GOLGI APPARATUS Series of flattened

sacs receive chemical products in vesicles

Modifies, stores, and repackages cell products in vesicles

Routes repackaged vesicles with chemical products to their destinations

LYSOSOMES Membrane-bound

sacs containing digestive enzymes

SEVERAL FUNCTIONS:

Fuse with food vacuoles and digest them

Digest harmful bacteria Recycle material from

damaged organelles

LYSOSOMES

Lysosomes (492.0K).url

VACUOLES Membrane-bound sacs having different

functions in different organisms:

Storage vacuole: stores food or wastes

Contractile vacuole: pumps out excess water in unicellular freshwater organisms

Central vacuole: large vacuole found in plants

CENTRAL VACUOLE Found in plant cells

and algae

Contribute to growth by absorbing water and causing cells to expand

Contain pigments in flower cells that attract insects

Concept 6.5CHLOROPLASTS

AND MITOCHONDRIA

ENERGIZE CELLS

CHLOROPLASTS Most living organisms run on energy

provided by photosynthesis

Photosynthesis: process of converting light energy to chemical energy

Chloroplasts: organelle in cells of plants and algae where photosynthesis occurs

CHLOROPLAST STRUCTURE

Enclosed by two membranes

Inner membrane divides chloroplast into two compartments

CHLOROPLAST STRUCTURE

One compartment is fluid-filled stroma

Other compartment contains thylakoids

- membrane-bound disks that trap light energy and convert it to chemical energy

MITOCHONDRIA “Powerhouse of the cell” site of

cellular respiration

Cellular respiration: process used to access energy from food by organisms

Releases energy from food and uses it to form another organic molecule—ATP

ATP (adenosine triphosphate): main energy molecule used by cells

STRUCTURE OF MITOCHONDRIA

Enclosed by two folded membranes

Folds greatly increase number of sites where cellular respiration can occur

Inner membrane—aerobic cellular respiration occurs here

Concept 6.6AN INTERNAL

SKELETON SUPPORTS THE CELL AND

ENABLES MOVEMENT

CYTOSKELETON Network of protein

fibers that extend throughout cell

Structural pattern changes constantly

Made up of 2 main types of fibers: microtubules and microfilaments

MICROTUBULES Straight, hollow tubes of proteins

Give rigidity and shape to cell

Provide “tracks” along which other organelles can move

MICROFILAMENTS Thinner, solid rods made of protein

Enable cell to move or change shape

Contribute to oozing movements of some cells—amoeba and white blood cells

FLAGELLA

Long, thin, whip-like structures projecting from cell

Wave in “S” shaped motion

Enable some cells to move around in their environment

Made up of microtubules

CILIA Hair-like structures projecting from cell

Shorter and more numerous than flagella

Composed of microtubules

Have a back-and-forth motion—like oars on a rowboat

Move a cell through its surroundings or move substances over cell surface

THE CELL FUNCTIONS AS A COORDINATED UNIT Each membrane-bound organelle

performs its own unique function

However, no organelle works alone

The cooperation of organelles makes the cell a living unit that is greater than the sum of its parts

THE END

ORGANELLE REVIEW

Cell Structure and Function.url

Origin of Organelles

The Evolution of Cellular Organelles.url

05_03Passive_diffusion.swf

05_03Diffusion.swf

ENDOCYTOSIS & EXOCYTOSIS

Endocytosis and Exocytosis (720.0K).url

SODIUM-POTASSIUM PUMP

Sodium-Potassium Exchange Pump (682.0K).url