Cell Structure & FunctionCell Structure & Function

Cells: the basic units of life. Cells: the basic units of life.

The cell theory, set forth in the 1850s, says that:All living things are composed of

cells.The cell is the smallest unit that

retains the properties of life.Under current conditions, all cells

come from preexisting cells.

QuestionQuestion

Which of the following statements is NOT part of the cell theory?

A. All living things are composed of cells.B. All cells are surrounded by an outer

membrane.C. The cell is the smallest unit that retains the

properties of life.D. Under current conditions, all cells come

from pre-existing cells.

All cells DO have an outer membrane (called the plasma membrane), but this observation is not considered part of the cell theory.

All cells DO have an outer membrane (called the plasma membrane), but this observation is not considered part of the cell theory.

Light Microscope(LM)

Light Microscope(LM)

Shows the entire cell and its interior

Scanning Electron Microscope (SEM)

Scanning Electron Microscope (SEM)

Shows a cell’s surface structure

Transmission Electron Microscope(TEM)

Transmission Electron Microscope(TEM)

Shows internal details of a preserved cell

QuestionQuestion

Biologists generally rely on the ________ microscope to study the surface structures of cells and the ________ microscope to study the internal structure of cells.

A. light; electron

B. light; transmission electron

C. scanning electron; transmission electron

D. transmission electron; scanning electron

Specimens for both types of electron microscopes must be killed and preserved before they can be examined. For this reason, light microscopes are still useful for observing living cells.

Specimens for both types of electron microscopes must be killed and preserved before they can be examined. For this reason, light microscopes are still useful for observing living cells.

Basic Cell StructureBasic Cell Structure

QuestionQuestion

1

2

3

Which of the following correctly labels the three major parts of the cell shown below?

A. 1-nucleus, 2-cytoplasm, 3-plasma membrane

B. 1-cytoplasm, 2-plasma membrane, 3-nucleus

C. 1-plasma membrane, 2-nucleus, 3-cytoplasm

D. 1-nucleus, 2-plasma membrane, 3-cytoplasm

The plasma membrane encloses the cytoplasm, and the cytoplasm surrounds the nucleus.

The plasma membrane encloses the cytoplasm, and the cytoplasm surrounds the nucleus.

Plasma membrane

Internal Cell StructuresInternal Cell StructuresCell membranes divide the cytoplasm of eukaryotic cells into functional compartments called organelles.

Organelle = “mini organs”

Plant Cell StructuresPlant Cell Structures

Animal Cell StructuresAnimal Cell Structures

Eukaryotic vs. ProkaryoticEukaryotic vs. Prokaryotic

Internal Cell MembranesInternal Cell Membranes

Organelle membranes physically separate important chemical reactions in the cytoplasm and allow them to take place in an orderly fashion.

Selective permeabilitySelective permeability

Cell membranes are said to be selectively permeable membranes, meaning that they allow some, but not all, materials to simply pass through them.

QuestionQuestionWhich of the following is NOT an accurate analogy for a cell membrane?

A. a window screen

B. the US – Mexico border

C. the Kansas – Colorado border

D. a university admissions department

The Kansas – Colorado border is a permeable barrier—anyone can cross the border at any time. All of the other barriers in the list are selectively permeable because they allow some things but not others to pass through.

The Kansas – Colorado border is a permeable barrier—anyone can cross the border at any time. All of the other barriers in the list are selectively permeable because they allow some things but not others to pass through.

Membrane CompositionMembrane CompositionA phospholipid bilayer forms the basic unit of the cell membrane.

QuestionQuestionWhere in this diagram of a cell membrane would you expect to find the FEWEST water molecules?

A

B

C

The fatty acid “tails” of the phospholipids are hydrophobic. They would repel any water molecules that came into that area of the membrane.

The fatty acid “tails” of the phospholipids are hydrophobic. They would repel any water molecules that came into that area of the membrane.

Membrane CompositionMembrane Composition

Proteins embedded in the bilayer help the cell transport materials in and out.

Carbohydrate chains attached to some membrane proteins help the cell communicate with other cells.

Structure of the Cell MembraneStructure of the Cell Membrane

QuestionQuestion

What type of membrane molecules are responsible for cell-to-cell communication?

A. lipids

B. proteins

C. phospholipids

D. carbohydrates

Carbohydrate chains act like “ID tags.” Different cell types have different kinds of carbohydrate chains on their surfaces.

Carbohydrate chains act like “ID tags.” Different cell types have different kinds of carbohydrate chains on their surfaces.

A “Fluid” MembraneA “Fluid” MembraneThe lipid molecules have hydrophilic (“water-loving”) heads and hydrophobic (“water-hating”) tails.

Therefore, if you puncture a membrane, it will come together and seal itself.

Cell Membrane AnalogyCell Membrane AnalogyThe cell membrane is similar to the walls that surround a house.

Both help protect the inside from the outside.

Both help protect the inside from the outside.

outside

inside

A house needs a way of receiving fuel and power from the outside.

Supply lines pass through the walls of the house to bring in

these materials.

A house needs a way of receiving fuel and power from the outside.

Supply lines pass through the walls of the house to bring in

these materials.

A cell receives fuel and power from the outside through protein

channels in the membrane.

A cell receives fuel and power from the outside through protein

channels in the membrane.

Doors are sometimes needed to bring in food and take out

the trash.

Doors are sometimes needed to bring in food and take out

the trash.

Channels in the membrane allow the cell to bring in food

and get rid of waste.

Channels in the membrane allow the cell to bring in food

and get rid of waste.

People in a house also need to communicate with the outside.People in a house also need to communicate with the outside.

Carbohydrates in the membrane allow the cell to

communicate with other cells.

Carbohydrates in the membrane allow the cell to

communicate with other cells.