C H A P T E R 7

Cell Structure and Function

EQ: What Scientists and inventions helped aid in creating Cell Theory?

7.1 Cell Theory (Cells and Living Things)

Cells are the basic building block of all life

Cells are small & cannot be seen with the unaided eye

Advances in cell biology were not made until the microscope was invented

Robert Hooke (1665) discovered cells in cork and named them

Anton van Leeuwenhoek (1700) observed living creatures and pond water

Named them animalcules

Cell Theory

Developed by many scientists over a period two centuries

Schleiden, Schwann, Virchow

Cell Theory (statements)

All living things are composed of cells

Cells are the basic unit of structure and function of living things

Cells are produced from pre-existing cells

Overview of Cell Parts

4 major types of cell Structures

Cell or Plasma Membrane (all cells)

Regulates what enters and leaves the cell

Cytosol (all cells)

Fluid region inside cell membrane

Nucleus (some cells)

Controls cell activities, contains DNA

Organelles (varies by type of cell)

Carry out various functions in cells

Provide energy, breakdown wastes, expel wastes, etc.

Prokaryotic vs. Eukaryotic

Two types of cells:

Prokaryotic Cell – cells that lack a nucleus and most other organelles

Usually smaller than eukaryotic cells

Eukaryotic Cell – cells that have a nucleus and other membrane bound organelles

Prokaryotes Eukaryotes

Very small in size

Single chromosome present

Nucleolus absent

Membrane bound cell organelles are absent

Cell division by fission or budding (no mitosis)

Fairly large in size

More than one chromosome present

Nucleolus present

Membrane bound cell organelles are present

Cell division by mitosis or meiosis

Prokaryote vs. Eukaryote

Compare and Contrast these Cells

Plant Cells: Animal Cells:

Have nucleus, cell membrane & cytoplasm

Have chloroplasts

Do photosynthesis

Have a cell wall

Protects cell & keeps its shape

One large vacuole

Have nucleus, cell membrane, & cytoplasm

Many of the same organelles as plants

Have lysosomes, many small vacuoles, & centrioles

Plant vs. Animal Cells

Different types of Plant cells

Leaf Cells

Different types of Plant cells cont.

Flower Cells

Different types of Plant cells cont.

Root Cells

Different types of Animal Cells

Epithelial Cells

Different types of Animal Cells cont.

Cardiac Cells

Different types of Animal Cells cont.

Nerve Cells

Light Microscope

Scanning power objective lens

Low power objective lens

EQ: What is the cell membrane and why is it important for a cell to

have?

8.1 Cell (Plasma) Membrane

Separates cell interior from the surroundings outside of the cell

Very Thin Stack 8,000 together to = paper thickness!

Regulates movement of chemicals and substances in and out of the cell.

Composed of a Phospholipid & some proteins

Cell Membrane

-(Phospholipid Bilayer)

2 layers of phospholipids Phosphate end faces out Lipid ends in middle Water will be on either side,

but not in middle Allows for non-polar

molecules to pass easy Polar molecules have a harder

time moving 3 Main parts of the cell

membrane: • Lipid Bilayer• Membrane proteins• Carbohydrates

cell membrane

protein

cholesterol

proteincarbohydrate

chain

protein channel

Plasma Membrane

Plasma Protein Functions

Many types of proteins are embedded with in the plasma membrane bilayer

4 major functions of the proteins

Enzyme Activity

Cell-to-Cell recognition

Cell signaling

Transport of Materials

EQ: What is the difference between diffusion and osmosis?

8.2 Cellular Traffic

Materials such as water, nutrients, dissolved gases, ions, and wastes must be able to move in and/or out of cells through the cell membrane

Diffusion – movement of particles from an area of high concentration to an area of low concentration

Diffusion occurs until equilibrium

Equilibrium = when particles are balanced through out

Passive Transport

Selectively permeable membrane – allows some substances to pass through while keeping other things from passing Cell membrane is selectively permeable

Passive transport – movement across a membrane with no energy used by the cell

Facilitated Diffusion – transport of larger molecules by use of transport proteins

as a pathway

Osmosis

Passive transport of water across a selectively permeable membrane Type of diffusion

through a membrane

Movement of water

Osmosis cont.

Isotonic – solution in which concentrations of a solute are equal

Hypertonic – solution with a higher concentration of a solute

Hypotonic – solution with a lower concentration of solute

Active Transport

Movement of molecules of ions across a membrane involving the use of the cells energy

Usually done against the concentration gradient – moving from low to high concentration

Transport of Large Molecules

Large molecules need to be packaged in vesicles

Small membrane sacs that move products into and out of cells

Fuse with the cell membrane and empty

Exocytosis – movement of molecules out of the cell through a vesicle

Endocytosis – movement of molecules into a cell through a vesicle

Exocytosis (above left) expels molecules from the cell

that are too large to pass through the plasma membrane.

Endocytosis (below left) brings large molecules into the

cell and packages them in vesicles.