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

1. all organisms are made of cells
2. all cells are produced by other living cells
3. 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

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