Cell Structure

Microscopes Light Uses a beam of light Can magnify up to 2000x Can observe living specimens Electron Uses a beam of electrons Can magnify up to 500,000x Can only observe dead specimens TEM – looks through a thin layer of tissue SEM – Used to observe external features

Cell Theory All living things are made of one or more cells Cells are the basic unit of structure and function in living organisms All cells arise from existing cells * Memorize this *

Formation of the Cell Theory Van Leeuenhoek – created the microscope and used it to see “animalcules” in pond water Hooke – looked at bark and saw empty boxes he named “cells” Schleiden – looked at plants and determined they were all made of cells Schwann – looked at animals and determined they were all made of cells Remak, Virchow, Redi – biogenesis – “life comes from life”

Pasture – finally “proved” the theory of biogenesis

Features of all cells Cell Membrane – made of phospholipids –Polar head and non polar tail –Selectively permeable – only some things pass through –Fluid –Mosaic model

Cytoplasm – fluid inside the cell –Organelles “float” in it Ribosomes – make proteins DNA – provides the instructions for the cell

Prokaryotic Cells Do not have membrane bound structures inside of them Cell wall – a rigid outer structure that helps give shape and provide protection. The DNA is a single loop – NOT in a nucleus! Flagella – a hair-like projection used for movement Smaller than eukaryotic cells

Many Bacteria Live in Extreme Environments Halophiles Thermophiles Aerobic Anaerobic –Facultative anaerobes –Obligate Anaerobes

Eukaryotic Cells (Plant and Animal Cells) Cells have a nucleus –Nucleus is where the DNA is located –Surrounded by a nuclear envelope Membrane-bound organelles –Organelles are structures that carry out specific jobs in the cell May use cilia or flagella for movement or to move substances across the cell surface –Cilia are little hairs

Cytoskeleton – supports the shape of the cell, helps transport organelles and substances –Microtubules Thin, hollow Made of proteins –Microfilaments Smaller than microtubules Solid Centrioles – help move chromosomes during cell division –Made of microtubules –Found in animals

Endoplasmic reticulum – (ER) Rough (RER) – has ribosomes on it – makes proteins Smooth (SER) – makes lipids and breaks down toxins

Vesicle – a small sac that is used to transport substances Golgi apparatus – modifies, packages and distributes proteins

Lysosomes – small sacs that contain digestive enzymes Mitochondria – the cell’s power plant –Endosymbiotic theory – A prokaryote began to live in a larger cell as the result of a symbiotic relationship. Has a double membrane Has DNA – circular like prokaryotes Reproduces independently of the cell

Plant Cells Cell wall – made of cellulose Chloroplasts – site of photosynthesis –Also thought to be endosymbionts –DNA is very similar a photosynthetic bacteria Central Vacuole – takes up most of the plant cell – contains water, food, and wastes –When the vacuole is full, the plant stands upright –When it is not full the plant wilts and droops