Cells Part 2

Parts of the Eukaryotic Cell(organelles)

Nucleus Cell membrane Ribosome Endoplasmic reticulum Mitochondria Cytoskeleton Vesicle

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

Structure of DNA

Nucleic acid bases are attached to a special sugar and a phosphate to hold them in place

The four bases of DNA may be in any order and thus function as “letters” A matches T, C matches G

DNA to RNA to Protein Permanent information

is stored in DNA DNA information is

copied using RNA The information is for

protein sequences Alterations to the DNA

are faithfully copied and result in different protein sequences

This is mutation!

DNA to RNA The DNA sequence is copied onto a strand of

RNA in a process called transcription Referred to as messenger RNA or mRNA

Technically must be processed first to be mRNA

Ribosome: The Machine Shop

Site of protein synthesis Proteins perform major cell

functions, including making up the cytoskeleton

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,

called translation Molecules called tRNA attach the amino acids together

using the ribosome as the workbench Cytoplasmic ribosomes make the cytoskeleton and cell

enzymes (proteins that stay in the cell) The endoplasmic reticulum is a membrane-bound

organelle that uses ribosomes to make cell structures and secretions

Protein synthesis is essential for all cells to stay alive This is why ribosomal inhibitors like ricin are lethal poisons

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)

• 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!

Cytoskeleton: The City Streets Every cell has long

strands 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 Enzymes are proteins designed

to speed up chemical reactions Vesicles are storage organelles

that are kept in the cytoplasm