Cell Structure
Review
Prokaryotic Cells
• Do not have a nucleus
• Found in bacteria
Eukaryotic Cells• Have a nucleus
• Found in multi-cellular organisms & some unicellular organisms
Cell Membrane
• Thin, flexible layer
• Separates the cell from its surrounding environment
• Controls movement of materials into and out of the cell
• Helps maintain the cell’s internal environment
Nucleus
• Control center of the cell
• Manages all of the cell’s activities
• Largest organelle
• Contains the genetic material (chromatin) the cell needs to reproduce and function.
• Is surrounded by the nuclear envelope and also contains the nucleolus and chromatin.
Nucleolus
� The nucleolus is
located in the nucleus.
� It manufactures the subunits that combine
to form ribosomes, the cell's protein-producing factories.
Chromatin
• Coils of DNA and protein that form chromosomes.
• Can be thought of as chromosomes without shape.
• Granular-like material found in the nucleus containing genetic information
Chromosome
� Worm-like / rod-like structures formed from chromatin during cell reproduction.
• They become distinct during the reproductive part of the cell cycle as the cell divides.
• Composed of DNA
DNA
• The genetic material found in all living cells.
• Contains the information needed for an organism to grow, maintain itself, and reproduce
• Stands for deoxyribonucleic acid
Nuclear Envelope
• Has a double-layered membrane that separates the nucleus from the cytoplasm.
• Contains pores to help facilitate the exchange of materials between the nucleus and the cytoplasm
Cytoplasm
• Thick, jelly-like substance contained within the cell membrane
• Most of the work of the cell is carried out here.
• The majority of the organelles are suspended in the cytoplasm.
Endoplasmic Reticulum
• Network of channels/tubes leading from the nuclear membrane into the cytoplasm
• Helps transport materials between the nucleus and the cytoplasm
• Also involved in transporting proteins
• Two types:
- Smooth E.R. = no ribosomes
-Rough E.R. = contains ribosomes
Ribosomes
• Sites of protein manufacturing in the cell
• Assemble proteins that:• Create chemical messages
to run a cell.
• Build cell organelles
• Line the membrane of the rough endoplasmic reticulum & are found in the cytoplasm
Protein
� Your muscles, your organs, and your immune system are made up mostly of protein
� whether you're running or just hanging out, protein is doing important work like moving your legs, moving your lungs, and protecting you from disease.
� Proteins are sometimes described as long necklaces with differently shaped beads.
� Each bead is a small amino acid. These amino acids can join together to make thousands of different proteins.
� Scientists have found many different amino acids in protein, but 22 of them are very important to human health.
Golgi Bodies
� Serve as storage and packaging centers.
• Look like stacks of flattened sacs
• Proteins made by the ribosomes are packaged into vesicles (small pockets)
• These packages are used by the cell and sometimes are released from it.
Lysosomes
� Sac-like structures that contain enzymes
• Where digestion of cell nutrients & food molecules take place
• Breaks down cellular waste or things that are harmful to the cell
• Similar to the job of white blood cells
Mitochondria
� Organelles that cause the release of energy by using oxygen to break down sugars.
• Usually round or tube shaped
• Releases food molecules that supply energy to the cell; it is known as the powerhouse of the cell.
• Usually more than one in a cell