Transcript notes
Cells • First discovered and named by Robert Hooke in 1665 • Saw them in cork samples • Looked like rooms where monks stayed • 1673 Anton van Leewenhoek saw first live cells Cells • 1838 Max Schleiden…all plants made of cells • 1839 Theodor Schwann…all animals made of cells • Rudolf Virchow…all cells come from other cells Cell Theory • All living things are made of cells • Cells come from other cells • Cells are the basic unit of life (i.e. life functions happen at cell level; cells can do all life functions) Cells • Have different shapes, according to their functions • Limited in size by the ratio of surface area to volume • As a cell gets bigger, it’s volume increases faster than surface area • Bigger cells need more substances (water, oxygen, etc.) but don’t have enough surface area to let everything in/out Cell shapes 2 kinds of cells • Prokaryotic – Have no membranes around nucleus or organelles – Still have DNA, just not in a nucleus – Still perform life functions (use energy, make proteins), but they’re done in cytoplasm – e.g. bacteria, Archaea 2 kinds of cells • Eukaryotic – Have nucleus with membrane and organelles (with membrane) – A few life functions go in cytoplasm, most in specialized organelles – e.g. plants, animals, fungi, protists Cell membrane • Also called plasma membrane • Allows only certain things to enter and leave the cell (selectively permeable). • Membrane around organelles has similar structure. • Phospholipid bilayer: – 2 layers of phospholipids (phosphate group (PO4) and two fats (lipids)) Cell membrane • Fluid Mosaic: – Bilayer also contains proteins (mark the cell as one of yours and help things move in and out of cell) – Things in the cell membrane move around, they don’t stay still…it’s dynamic, not static – https://www.youtube.com/watch?v=LKN5sq5dtW4 – https://www.youtube.com/watch?v=Pfu1DE9PK2w Cell membrane Cytoplasm • Jelly-like substance inside of cells, does have a structure (cytoskeleton) • Contains all the organelles • A few cell processes take place here • Also has things dissolved in it – Protein – Water – Salts Microtubules/ Microfilaments • Part of the cytoskeleton • Microtubules hold the cell’s shape and act as tracks as organelles move around • Microfilaments contribute to the whole cell moving Microtubules / Microfilaments Nucleus • Controls the functions of the cell (by helping to make proteins that control chemical processes) • Holds DNA (genetic info) • Surrounded by a double membrane called the nuclear envelope or nuclear membrane • Dark area called the nucleolus – Makes ribosomes Nucleus Mitochondria • Change energy from food into ATP (energy for your cell) • More mitochondria a cell has, the more energy it uses • Has a 2-layer membrane • Has folds inside of it called cristae • Has its own DNA Mitochondria Ribosome • Build proteins • No membrane, actually is made of RNA (similar to DNA) and protein • Made of two parts, a large and small subunit that come together • Some float freely around the cytoplasm, others are attached to endoplasmic reticulum Ribosome Endoplasmic reticulum • System of tubes and sacs • Make proteins and transports things from one part of the cell to another • Rough ER – Has ribosomes on surface, makes proteins • Smooth ER – No ribosomes Endoplasmic reticulum Golgi Apparatus • Flattened sacs near the nucleus • Modifies proteins and moves things from the ER either to the rest of the cell or outside the cell Golgi Apparatus Lysosome • Contains digestive enzymes – Break down food brought into the cells – Break down the cell when it dies Lysosome Cilia/Flagella • Both help cells move (which, btw, most cells don’t) • Found on cell surface, but usually one or the other, not both. • Cilia – Short hair-like structures – Usually many of them • Flagella – Long, whip-like structure on cell surface – Usually only 1 Cilia/Flagella (This is a bacteria, not an animal cell) Centrioles • Two cylinders of microtubules at right angles to each other • Only in animal cells • Help in cell division by lining up so things can move when cell divides Centrioles Cell wall • Rigid layer outside cell membrane • Only in plants • Made of lots of sugar molecules put together (cellulose) • Not digested by us = fiber! • Gives strength and support to the plant Cell wall Central Vacuole • Large central area • For storage – Mostly water • Can take up 90% of plant cell volume! • Animal cells have them, too, but they are much smaller. Central Vacuole Chloroplasts • Only in plant cells • Surrounded by membrane • Contains chemical chlorophyll • Where photosynthesis takes place (make food (sugars) for plant) • Those sugars are used to build the plant or go to mitochondria to make energy Chloroplasts Like your body • Cell membrane? Skin • Nucleus? Brain • ER? Circulatory system • Lysosome? Digestive system • Microtubules/Microfilaments (cell wall for plants? Bones and muscles • Cilia/Flagella? Arms/legs