Cells • 2 Basic Cell Types:

• Prokaryotes • Eukaryotes

• Cell Organelles Structure and Function • The Cell Membrane

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 are produced from other cells.

Two Basic Cell Types:

Prokaryotic vs. Eukaryotic

Cells

Two Basic Types

• Remember….cells are the basic unit of life

for ALL living things.

• There are two basic types of cells:

1. Prokaryotic cells – found in bacteria

2. Eukaryotic cells – found in protists, fungi,

plants and animals

Characteristics Shared

• Perform the same basic functions

• Surrounded by plasma membrane to control

what enters and leaves the cell

• “Filled” with cytoplasm

• Contain ribosomes to make protein

• Contain DNA to give the general

instructions for the cell’s life

What Makes Eukaryotic Cells

Different?

• Much larger • Much more complex

• Contain a true nucleus to house the genetic material (DNA)

• Linear DNA packaged into chromatin found inside the nucleus

• Contains specialized structures in the cytoplasm called organelles to carry out various functions

• Not all have a cell wall

Eukaryotic Cells

What Makes Prokaryotic Cells

Different?

• Much smaller

• Less complex

• No true nucleus

• Circular DNA that is found in the cytoplasm

• No organelles found in the cytoplasm

• Surrounded by a cell wall

Prokaryotic Cell

What does size have to do with

it? • Prokaryotic cells are much smaller than

eukaryotic cells. Why?

– Smaller surface area to volume allows nutrients to

easily and quickly reach inner parts of the cell.

– Eukaryotic cells are larger and can not pass

nutrients as quickly. They require specialized

organelles to:

• carry out metabolism

• provide energy

• transport chemicals throughout the cell

Prokaryotic Cell

http://www.cellsalive.com/cells/bactcell.htm#top

Cell Organelles

Review

• No organelles in prokaryotic cells

• Both plants and animals are eukaryotic

cells!

Animal Cell

Plant Cell

Organelles Found in Plant and

Animal Cells

• Cell Membrane

• Nucleus

• Nucleolus

• Mitochondria

• Endoplasmic reticulum

• Ribosomes

• Golgi apparatus

• Vacuoles (small in animals; large in plants)

• Lysosomes

The Cell Membrane • Location: Around the outside of the cell

• Function: Controls what substances enter and

leave the cell

• Aka: “plasma membrane”

Nucleus • Location: In the cytoplasm

• Function: Directs all of the cell’s activities; stores

the chromatin

• Aka: “control center”

Nucleolus • Location: In the nucleus

• Function: Makes ribosomes

• Aka: “little nucleus”

Mitochondria

• Location: In the cytoplasm

• Function: Produces energy

• Aka: “Powerhouse” or “Mighty

Mitochondria”

Ribosomes • Location: In the cytoplasm and on the

rough ER

• Function: Makes protein

• Aka: “Protein packs”

Endoplasmic Reticulum (ER)

• Location: In the cytoplasm around the nucleus

• Function: Modifies materials needed in the cell

• Aka: “Fashion designers”

Rough ER (has ribosomes)

Smooth ER (no ribosomes)

Golgi Apparatus

• Location: In the cytoplasm

• Function: Sorts and ships materials to the correct

parts of the cell

• Aka: “the post office”

Vacuoles • Location: In the cytoplasm (large in plants;

small in animals)

• Function: Storage

• Aka: “the closet”

Animal Cell Vaculole = small Plant Cell Vaculole = large

Lysosome • Location: In the cytoplasm

• Function: Destroys worn out cell parts

• Aka: “the death chamber:

Cilia / Flagella

• (*animal cells only: not all cells have one of

these)

• Location: on the cell membrane

• Function: help the cell move

• AKA: the “motor”

Organelles Found in Only Plant

Cells

• Cell Wall

• Chloroplast

Cell Wall • Location: Around the cell membrane of

plant cells

• Function: Gives the cell shape and

protection

• Aka: “plant cell armor”

Chloroplast • Location: In the cytoplasm

• Function: Photosynthesis: Makes sugar

from sunlight (also takes in carbon dioxide

and gives off oxygen)

• Aka: “mean green sugar machine”

See the Cell in Action!

• http://www.youtube.com/watch?v=1Z9pqST72is

&feature=related (14 min.)

• Visit this link to see the cell in action, just click

on the various organelles to get a better idea of

how they work!

http://www.johnkyrk.com/CellIndex.html

http://www.cellsalive.com/cells/cell_model.htm

Plant Cell http://waynesword.palomar.edu/lmexer1a.htm

Animal Cell • http://waynesword.palomar.edu/lmexer1a.htm

Prokaryotic Cell

http://www.cellsalive.com/c

ells/bactcell.htm#top

Plant Cell http://waynesword.palomar.edu/lmexer1a.htm

Name_________________

Animal Cell • http://waynesword.palomar.edu/lmexer1a.htm

Name_________________

Prokaryotic Cell

http://www.cellsalive.com/c

ells/bactcell.htm#top

Name_________________

Movement Through

the Cell Membrane

http://programs.northlandcollege.edu/biology/biology1111/animations/passive1.swf

Selectively-Permeable Membranes

• A selectively-permeable membrane will allow

certain molecules to pass through it, but not

others.

• Generally, small

particles can pass

through…

Partially permeable

membrane

…but large

particles

cannot

Structure of the Plasma/Cell

Membrane

• Plasma Membranes consist of 2 types of

molecules – phospholipids and proteins

Diagram of a Phospholipid

Phospholipids have 2 regions:

• Polar head region:

– attracts water molecules (hydrophilic)

– Phosphorous group

• Non-polar tail region:

– nonpolar tails repel water molecules

(hydrophobic).

– Made of long carbon chains (fatty acids)

Phospholipid bilayer

• Due to the hydrophobic and hydrophilic nature of the

phospholipid, a double layer is formed where the heads

protect the tails from the water. This is called the

phospholipid bilayer. The bilayer is fluid, not a hard shell.

Proteins are Embedded Within the Bilayer

• Proteins act as passageways for nonpolar

(hydrophobic) molecules to pass through.

• Without proteins embedded in the bilayer, essential

molecules needed for communication, energy, etc.,

would not reach the interior of the cell.

• Carbohydrates are attached to the proteins.

– Allow for cell recognition and communication.

Proteins are Embedded Within the

Bilayer (continued)

• The model of the lipid bilayer with embedded

proteins is called the Fluid Mosaic Model.

TWO Types of Transport Through a

Cell Membrane

1. Active Transport – the movement of molecules

through a cell membrane using energy

2. Passive Transport – the movement of molecules

through a cell membrane without the expenditure

of energy

3 Types of Passive Transport

1. Diffusion - Movement of molecules from areas

of high concentration to low concentration

2. Osmosis - Diffusion of water molecules from

higher concentration of water to lower

concentration of water

3. Facilitated Diffusion - Diffusion through pores

or channel proteins

DIFFUSION

• Molecules tend to move from areas where there is more

of them to where there is less

high concentration low concentration

– This is called moving WITH the concentration gradient.

• Diffusion continues until equilibrium is reached, or

where molecules are equally distributed.

– Some solutes will be able to move through when others will

not.

Diffusion (continued)

OSMOSIS

• Water passes through cell membranes rapidly.

• Osmosis is a specialized form of diffusion that moves water molecules through membranes.

• Osmotic pressure – when more water molecules accumulate inside a cell, pressure increases. This pressure is called osmotic pressure.

– when osmotic pressure is high inside the cell, water will want to leave the cell.

OSMOSIS

3 Types of Solutions

hypertonic solution -solute concentration is HIGHER in

the solution than in the cell.

• Water will move out of the cell- cell will shrivel

hypotonic solution - solute concentration is LOWER in

the solution than in the cell.

• Water will move into the cell- cell will swell

isotonic solution - EQUAL solute concentrations in the

solution and in the cell.

• Water will move in and out of the cell at equal rates.

FACILITATED DIFFUSION

– some molecules cannot diffuse through on their own

(membrane is impermeable to them), and will need

assistance (facilitate).

– Passive transport aided by proteins. Each are very

specific to the size/shape/polarity of solute.

-transport proteins

-channel proteins

*aquaporins- facilitated diffusion of water

*ion channels- open and close in

response to a stimulus (gated channels)

Active Transport

• Some molecules exist in low amounts on one side of a

membrane and need to be moved to areas of high

amounts

• active transport- the use of energy to move molecules

from LOW concentration to HIGH concentration

(against or opposite the concentration gradient)

• Cell membranes have mechanisms to move these

molecules against their concentration gradients:

1. ion/molecular pumps

2. endocytosis

3. exocytosis

Types of Active Transport

1. ion/molecular pumps

-Molecules can be moved through the membrane by specific proteins embedded in the membrane

-Na, K, Ca ions are transported in this manner

-sodium-potassium pump is the major pump of animal cells

-proton pump is main pump of plants, fungi, and bacteria

2. endocytosis- process of cells engulfing large particles by forming a vesicle around them

-different names for different sizes of particles:

pinocytosis (cell drinking)

-occurs if the particles have been partially broken down into a liquid of tiny dissolved molecules

phagocytosis (cell eating)

- If the particles are cell fragments or organic matter

3. exocytosis -process by which wastes or secretions (hormones) are brought to the cell membrane, packaged into vesicles and sent out of the cell

– the reverse of endocytosis

Unicellular vs. Multicellular

• Unicellular organisms – single celled.

• Include both prokaryotes and eukaryotes.

• Maintain homeostasis by growing, responding to the environment, transforming energy, and reproducing.

• Multicellular organisms – many cells working together to create an organism.

• Cells are specialized – different cell types play different roles.

• Ex. Move, respond, communicate, substance production.

• Cells communicate with one another to maintain homeostasis for the organism.

• The organization allows them to divide labor in order to maintain homeostasis.

Cellular communication

• Cells in large organisms must communicate with one another in order to work together to maintain homeostasis!

• Occurs via chemical signals that influence the behavior of the cells receiving the signals.

• Receptors are often found on the outside of cells where they bind chemical signaling molecules and influence cellular activity.