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Prokaryotic v. Eukaryotic Cells

Think About itWhat’s the smallest part of any living thing that still counts as being “alive?”

Can we just keep dividing living things into smaller and smaller parts, or is there a point at which what’s left is no longer alive?

The smallest living unit of any organism is the cell.

The Discovery of the CellThe cell theory states:

1.All living things are made up of cells.

2.Cells are the basic units of structure in living things.

3.New cells are produced from existing cells.

Exploring the Cell

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Prokaryotes and Eukaryotes

All cells:• Contains DNA (biological

information)• surrounded by a thin, flexible barrier

called a cell membrane• BUT………How are prokaryotic

and eukaryotic cells different?

• Eukaryotic cells - DNA in nucleus• (separates the genetic material

from the rest of the cell)• Eu = Nu

• Prokaryotic cells - DNA in cytoplasm• Pro = No

What is a Nucleus?• 2 categories of cells

• depending on whether they contain a nucleus. • Nucleus - large membrane-enclosed structure that

contains DNA (cell’s genetic material)• Controls many of the cell’s activities.

Prokaryotes • Prokaryotic cells

• Smaller/simpler than eukaryotic cells. • Grow, reproduce, and respond to the

environment• All characteristics of life

• Example: Bacteria

Eukaryotes

• Eukaryotic cells• Larger/ more complex than prokaryotic cells. • Dozens of structures and internal membranes.• Highly specialized. • Examples: plants, animals, fungi, protists

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Prokaryote or Eukaryote?

BACTERIA Escherichia coli

Prokaryote or Eukaryote?

Prokaryote or Eukaryote? Prokaryote or Eukaryote?

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Prokaryote or Eukaryote? Prokaryote or Eukaryote?

Prokaryote or Eukaryote? Prokaryote or Eukaryote?

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Prokaryote or Eukaryote? Prokaryote or Eukaryote?

Cell Structure

Cell Structure• At first glance, a factory is a puzzling place, and the sheer

diversity of activity can be confusing. • if you take your time and watch carefully, what might at first

seem like chaos begins to make sense.

• The same is true for the living cell.

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Cell Organization

• Organelles: “little organs”• Specialized cell structures• All have different jobs

•Cytoplasm: the fluid portion of the cell outside the nucleus

Here come the Organelles!!!!!!

The Nucleus • Control center of the cell• contains cell’s DNA • DNA - coded instructions for making proteins and

other important molecules

The Nucleus

• Nuclear envelope – has thousands of pores, which allow material in and out

• Chromosomes – genetic information passed from one generation to the next

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Cell Walls • Support and Protection• Not in all cells

• Have cell walls:• prokaryotes, plants, algae, fungi

• Do not have cells walls• Animals

• Outside the cell membrane• Allow water, oxygen, CO2,

and other substances to pass through easily

Cell Membranes

• IN ALL CELLS• Regulates what enters and leaves the cell• Protects and supports the cell• Has 2 layers called a lipid bilayer

Properties of Lipids • 2 parts to the Phospholipid

• Hydrophobic (water-hating) Tail• Hydrophilic (water-loving) Head

• In membrane, form lipid-bilayer• Tails facing in towards each

other• Heads facing out to watery

environment inside and outside the cell.

Fluid Mosaic Model • Fluid Mosaic Model: many different kinds of

molecules make up the cell membrane• proteins are embedded in the lipid bilayer • some of the proteins form channels (move materials

in/out of cell)• carb chains act as chemical ID cards allowing cells to

identify one another

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The Fluid Mosaic Model • Permeable – substances are able to cross a membrane• Impermeable – substances cannot pass across it • most biological membranes are semipermeable, meaning

that some substances can pass across and others cannot

Vacuoles• Vacuoles: large and saclike• structures that store materials

• H2O, NaCl, proteins, and carbs• Only in plant cells• Liquid-filled vacuole increases rigidity

• support for leaves and flowers

Vesicles •Vesicles: smaller storage structures

•move materials around the cell

Lysosomes • Lysosomes: filled with enzymes that function as

the cell’s cleanup crew• removes “junk” that clutter up the cell• breaks down fats, carbs, and proteins that can be

used by the rest of the cell• breaks down old organelles

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The Cytoskeleton • Cytoskeleton: network of filaments that give

cells shape and organization• help transport materials around the cell• two protein filaments that make up the

cytoskeleton• microfilaments (Smaller)• microtubules (Larger)

Ribosomes •Ribosomes: small particles of RNA (nucleic acid) and protein found throughout the cytoplasm in all cells

•make proteins by following instructions from DNA

Endoplasmic Reticulum

• Endoplasmic Reticulum: Builds many cell parts• cell membrane, proteins, lipids and carbs

Endoplasmic Reticulum

• Rough ER: has ribosomes on surface• Makes proteins

• Smooth ER: NO ribosomes on surface• Makes lipids and carbs

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Golgi Apparatus •Golgi apparatus: sorts and packages what the ER makes•Packages can be stored, or leave the cell

•How proteins and other materials are “shipped” to their final destination inside/outside the cell

•

Organelles That Capture and Release Energy• Chloroplasts (Plants only)• Mitochondria (Plants and Animals)All living things require a source of energy

Chloroplasts•Chloroplasts – capture the energy from sunlight and convert it into food in a process called photosynthesis •contain the green pigment chlorophyll

Mitochondria •Mitochondria: power plants of the cell that convert chemical energy•ALL eukaryotic cells, including plants, contain mitochondria•Take food and make it useable as energy in the body

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Different Types of Cells

• Different types of cells have different functions

• The structure of a cell is based on its function.• Cells differ in numbers of organelles• Cells differ in types of organelles Cell Transport

Passive Transport

• Passive transport- the movement of materials across the cell membrane without using energy

Passive Transport• Diffusion: the process by which solute

particles move from an area of high concentration to an area of lower concentration.• Solution Solute +

solvent • Concentration

amount of substance in a given volume

• Cytoplasm: A solution of many different substances (solutes) dissolve in water.

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Passive Transport• Diffusion

• Down concentration gradient• From higher concentration to lower concentration • Affected by size (more you have, the longer it takes)

• TYPES of diffusion:•Simple diffusion

•Diffusion through the lipid bilayer (small molecules like O2, CO2)

•Facilitated diffusion•Diffusion through a channel protein (small molecules)

•EXAMPLE : Osmosis •water molecules through aquaporins

Simple Diffusion

• Suppose a substance is present in unequal concentrations on either side of a cell membrane.

Simple Diffusion

• If the substance can cross the cell membrane, its particles will tend to move toward the area where it is less concentrated until it is evenly distributed.

Simple Diffusion • At that point, the concentration of the substance on both

sides of the cell membrane is the same, and equilibrium is reached.

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Simple Diffusion • Even when equilibrium is reached, particles of a solution

will continue to move across the membrane in both directions.

• Because almost equal numbers of particles move in each direction, there is no net change in the concentration on either side.

Facilitated Diffusion

• Cell membranes have proteins that act as channels!

• Facilitated diffusion: Molecules that cannot directly move across the membrane pass through special protein channels in a process.

Osmosis: An Example of Facilitated Diffusion

• OSMOSIS: the movement of water through cell membranesextremely important processmovement of water molecules from

an area of higher concentration to an area of lower concentration

The inside of a cell’s lipid bilayer is hydrophobic—or “water-hating.”(Water molecules struggle to get through!)

Aquaporins - water channel proteins

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How Osmosis Works• Isotonic: the concentrations of solutes is the same inside and outside the cell

• Hypotonic: the solution has a lower solute concentration than the cell

• Hypertonic: the solution has as higher solute concentration than the cell

Active Transport = NEED ENERGY

• Active transport- the movement of materials against a concentration difference• low concentration to high

concentration• Requires energy (ATP)• Carried out by transport proteins, or

protein “pumps”• Examples: endocytosis and exocytosis

Active Transport

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Endocytosis vs. Exocytosis

• Endocytosis: Taking material into cell by means of pockets through cell membrane

• Exocytosis: Many cells also release large amounts of material from the cell

• membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell.

Endocytosis

Exocytosis