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Transcript
Cell Structure and Function Robert Hook • 1665 - Hook used a primitive microscope to view cork. What he saw (cell walls) he described as “cells” because they looked like rooms in a monastery. The Cell Theory (1835-1855) Schleiden, Schwann, and Virchow 1. All living things are composed of cells. 2. Cells are the basic units of structure and function in living things. 3. New cells are produced from existing cells. Two categories of cells • Eukaryotes (eu “true”; karyon “nucleus”) are cells that have a nucleus. • Prokaryotes (pro “before”) do not contain nuclei. • Nucleus – large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA. Comparison Prokaryotes • Smaller and simpler than eukaryotes • Genetic material not contained in nucleus • Carry out activities associated with living things: grow, reproduce, respond to environment and some move • Example: bacteria Eukaryotes • Contain a nucleus in which their genetic material is separated from the rest of the cell. • Can be unicellular: amoeba, protozoa • Can be multicellular: animals, plants, fungi • Contain organelles – “little organs” 2 Parts of Eukaryotic Cell • Nucleus and the cytoplasm • Cytoplasm is the portion of the cell outside the nucleus. Nucleus • Contains almost all DNA and with it the coded instructions for making proteins and other important molecules. • Surrounded by nuclear envelope (double membrane) dotted with nuclear pores; allows movement of info into & out of nucleus • Contains chromatin (granular material) – consists of DNA bound to protein; cell divisions, forms chromosomes: genetic info passed on Ribosomes • Formed in the nucleolus (small region of nucleus) • Very small dotlike structures • Make proteins Vacuoles • Round membrane storage sac for holding food, water, or waste Mitochondria • Double membrane structures, where cellular respiration (the break down of sugar) occurs to release energy Chloroplast • Double membrane structure, where photosynthesis takes place (making of carbohydrates or sugars), contains green pigment called chlorophyll Cell Membrane • • • • aka Plasma Membrane Thin, flexible barrier that surrounds the cell Regulates which molecules enter and leave Provides protection and support Cell Wall • Rigid structure around cell, outside of cell membrane • Provides support and protection • Plant cells: mostly cellulose