Introduction to Cells and Organelles
discovery of cells
- robert hooke: 1665 - looked at cork (tree bark), noticed hollow compartments that looked like rooms in a monastery called "cells"
- cell theory: developed by scientists Schleiden, Schwan, and Virchow; states that
- all organisms are made of cells
- all cells are produced by other living cells
- cells are the basic units of life
two types of cells
- prokaryotic, eukaryotic
prokaryotes: do not have a nucleus or membrane-bound organelles
- eg bacteria
eukaryotes: cells that have a nucleus and membrane-bound organelles
can be single or multicellular
any living thing that is not a prokaryote
plant cells: have chloroplasts, central vacuole and cell wall
animal cells: have centrioles and lysosomes
- bio bob does not like centrioles; canceled
cell parts (organelles)
cytoskeleton: a network of protein fibers with many functions
microtubules: long, hollow tubes used for cell shape, movement of organelles, manipulating chromosomes during division
nucleus: contains the cell's genetic information. DNA has the instructions for making protein and can't leave the nucleus (RNA used as a messenger bc of this)
chromatin: spread out form of DNA condenses into tightly coiled chromosomes before cell division
nucleolus: inside the nucleus, responsible for making ribosomes
endoplasmic reticulum: an extensive network of folded membranes. produces the membranes of the cell and other organelles
- can be rough or smooth \n \n rough er: studded with ribosomes, appears bumpy under a microscope \n \n smooth er: detoxifies drugs and poisons, synthesizes lipids \n
organelles in the cytoplasm
ribosomes: factories that make protein. made by the nucleolus in two subunits
ribosomes on rough er - make proteins destined to be exported from the cell or embedded into the cell membrane
ribosomes free in the cytoplasm - make protein to be used within the cell (to be embedded in cell membrane)
golgi apparatus: layered stacks of membrane-enclosed spaces that process, sort, and ship out proteins. they alter proteins and send them on their way.
vesicles: small baggies from the endoplasmic reticulum used to transport proteins and substances to and from the golgi bodies
mitochondria: the powerhouse of the cell. responsible for making ATP through cellular respiration
vacuole: a fluid-filled sac used for storage of water, food molecules, ions and enzymes
plant cell-specific organelles
chloroplasts: use CO2 and water to make sugar in photosynthesis
central vacuole: responsible for storing water, poisons and some pigments of fruits and flowers. when it fills with water, it increases the cell's turgor pressure
- should have high turgor pressure (should be full of water) → keeps standing upright, prevents wilting
contractile vacuole: found in protists. used to pump out excess water to prevent the cell from bursting
animal cell-specific organelles
lysosomes: contains digestive enzymes to break down food, and defend against bacteria and viruses; can recycle cell parts. dubbed "suicide sac" - programmed cell destruction
centrioles: organize microtubules to form cilia and flagella
cilia: microscopic hairs on the exterior surface of a cell. they beat back and forth like oars for a boat. help more the cell or materials around the cell (respiratory tract)
flagella: whiplike tail for movements of the cell
cell membrane
cell membrane: selectively permeable. controls the passage of materials into and out of the cell
selectively permeable: allows some but not all materials to pass through
- eg clothing (waterproof but breathable) - vapor can leave but water can't enter
cholesterol: keeps the membrane more fluid - carbohydrates attached serve as identification tags so cells can distinguish one cell from another
important for organ transplants (intruder cells, matching, immune response)
- slight immune shut down so as not to attack new organ → leaves body more susceptible to pneumonia, flu, etc. so it's important to find as close a match as possible