Cells

By the end of this class you should understand:

• The three major parts of all cells• The primary structures found in prokaryotic

and eukaryotic cells• The major organelles found in all living things• The basic functions of membrane-bound

organelles found in eukaryotes

Parts of a Cell

• There are two major types of cells– Prokaryotic cell– Eukaryotic cell

• All cells have three parts:– Cell membrane– Genetic information– Cytoplasm

Prokaryotic Cells

• Prokaryotic cells are cells without a nucleus– All genetic info is bundled

but not separated from cytoplasm

• All known prokaryotes are single-celled bacteria– Prokaryotic cells are tiny!

Eukaryotic Cells• If every cell was a

company:– Prokaryotic cells are a 1-

man startup in a garage– Eukaryotic cells are a large

corporation

• Eukaryotic cells have organelles which each perform separate jobs

• Genetic info stored in nucleus

Eukaryotes

• Some eukaryotes are single celled organisms– One eukaryotic cell performs

all functions of life

• Some eukaryotes are multicellular– The different cells specialize in

different tasks– Each cell is still individually

alive!

Key Parts of Eukaryotic Cells

• Nucleus– Stores genetic information

• Cytoplasm– Composed of a liquid called

cytosol– Filled with various membrane-

bound organelles

• Cell Membrane– Often referred to as plasma

membrane

Key Parts of Prokaryotic Cells

• Cell membrane, nucleic acids, and cytoplasm– Same as eukaryotes

• Cytoplasm is much simpler– Prokaryotes have NO

membrane-bound organelles– They do have a cytoskeleton

and ribosomes!

Cell Membrane

• The cell membrane is a flexible, selectively permeable (or semipermeable) barrier

• Boundary of cell, visible under microscope only as border of cell

• NOT the same as a cell wall– Cell wall is rigid

Cell Membrane Structure• The cell membrane is

composed of phospholipids– Hydrophilic head,

hydrophobic tail

• The nonpolar tails orient themselves into a hydrophobic zone surrounding the cell– Essentially a thin bubble of oil

Cell Membrane Structure

Cell Membrane Proteins

• Proteins are macromolecules constructed from many linked amino acids

• Some amino acids are hydrophobic and so mix with the inside of the cell membrane

• These proteins sit inside the cell membrane

Membrane Protein Functions

• Cell membrane proteins serve many vital functions:– Markers– Receptors– Channels

• Transporting things in and out of cells is a key function of life!– Will cover this more

tomorrow

Parts of the Eukaryotic Cell(organelles)

Nucleus Cell membrane Cytoskeleton Cytoplasm Mitochondria Ribosome Endoplasmic Reticulum Golgi Apparatus

Nucleus: The Library

The nucleus stores all the cell's genetic information in massive molecules of DNA

The DNA molecules are packed into many pairs of chromosomes

When a protein is needed, signals enter the nucleus and cause copies of the appropriate genes to be made with RNA

Key Nucleus Facts:

Every complete human cell has one nucleus Exception: red blood cells have no nucleus (also

have no other membrane-bound organelles) Exception: muscle cells are many cell fused

together and so have many nuclei Every nucleus has the complete human genome The nucleus has its own envelope to keep

unwanted things out

Cytoskeleton: The City Streets Every cell has long strands

of different kinds of proteins running through it

When organelles are moved they move along the cytoskeleton

If the cell moves under its own power it uses the cytoskeleton as well

Key Cytoskeleton Facts:

There are several different types of fibers and they have different functions

All cells must produce each of these fibers These fibers are made of different kinds of

proteins (keratin, collagen, actin, myosin, etc) If the genes for any of these fibers are no

good, no cells can form and the organism will never develop, grow or be born

This makes these genes essential for life

Cytoplasm: The Marketplace The liquid of the cell is called

cytosol Cytosol plus the organelles are

called cytoplasm All the cell's chemical reactions

and growth take place here Many exchanges are made Many chemicals are stored

in vesicles in the cytoplasm

Key Cytoplasm Facts:

Cytosol is a clear liquid but it is filled with salts and sugars

Cytoplasm is held within the cell membrane If the cell membrane develops a hole,

cytoplasm can leak out and the cell can die If the cell membrane bursts all at once, this is

called lysis and is instant cell death

Ribosome: The Machine Shop

Site of protein synthesis Some are free floating in

cytoplasm Some are attached to

membranes called the endoplasmic reticulum

Made with a combination of protein and RNA

Probably the first structure in the original cells

Key Ribosome Facts Ribosome is the site for proteins to be synthesized

That process will be discussed next week Cytoplasmic ribosomes make the cytoskeleton and

cell enzymes Rough endoplasmic reticulum produces proteins

that will enter the membrane or leave the cell Smooth endoplasmic reticulum is for synthesis of

other macromolecules such as lipids

Golgi Apparatus: The Shipping Center

• Vesicles from the endoplasmic reticulum are organized here

• Different vesicles have different destinations– The chemical reactions

that determine where these vesicles go occur here

Key Golgi Facts

• The Golgi manipulates cell membrane material into many types of vesicles– Peroxisomes contain peroxides– Lysosomes contain destructive enzymes (that can

lyse chemicals or even other cells)– Secretory vesicles are designed for exocytosis

(they will secrete their contents)

Mitochondria: The Power Plant

• Mitochondria (singular: mitochondrion) produce the cell's supply of energy molecules– Cells use a molecule called

ATP– Made using the energy from

blood sugar

• Must have oxygen to work– Process that requires oxygen

is called aerobic

Key Mitochondria Facts: Mitochondria were once bacteria

Captured/adopted by animal cells billions of years ago and now we work together

Mitochondria must have oxygen to burn sugar Produce CO2 as a waste product This is why we breathe in oxygen and breathe

out carbon dioxide Mitochondria sustain our high metabolic rate

Cyanide blocks mitochondrial activity, which is why it is a lethal poison to us

Mitochondria Activity

• Mitochondria perform aerobic respiration (requiring O2)– This is the key part of cellular respiration that will

be covered next week

• Prokaryotes have no membrane-bound organelles, therefore they do not have mitochondria– Some bacteria are aerobic, which means they

perform the same processes as a mitochondrion!

See you in lab!