Cell Theory SNC 2DI
Robert Hooke was the first person to use the term cell to describe the small structures he saw through his microscope.
Cell Theory says... The cell is the fundamental unit of structure and function in living things. All cells come from pre-existing cells by division. Energy flow (metabolism and biochemistry) occurs within cells. Cells contain genetic information (DNA) which is passed from cell to cell during cell division All cells are basically the same in chemical composition. All known living things are made up of cells. Some organisms are unicellular, i.e., made up of only one cell. Others are multicellular, composed of a number of cells. The activity of an organism depends on the total activity of independent cells.
Exceptions Viruses are considered alive by some, yet they are not made up of cells. Viruses have many features of life, but by definition of the cell theory, they are not alive. The first cell did not originate from a pre-existing cell. There was no exact first cell since the definition of cell is imprecise. Mitochondria and chloropolasts have their own genetic material, and reproduce independently from the rest of the cell.
Cell Organelles
Cell Membrane Found in both plant & animal cells Animal cell membrane is more fluid than a plant cell’s membrane Controls the movement of materials into and out of the cell (selectively permeable ) Maintains homeostasis (constant internal environment) Protects & Supports
Diffusion Diffusion is the process of moving particles from an area of high concentration (the amount of substance dissolved in solution) to an area of lower concentration Can occur either through a fluid-like cytoplasm or a semi-permeable membrane like the cell membrane and cell wall
The Cell Wall Found in plant cells only Stiff, rigid, nonliving, made of cellulose Protects and supports the cell Permeable
Cytoplasm Thick, jellylike substance in both Provide shape/support to the cell membrane Contains and supports cell organelles Site for many cellular reactions like protein synthesis, lysosomal digestion
The Nucleus Found in both plant & animal cells Control center Inside is chromatin and a dark region called a nucleolus which makes ribosomes (necessary for protein synthesis.) Surrounded by a double membrane which has numerous pores to allow for the movement of materials
DNA Chromatin Deoxyribonucleic acid Contains the cell’s “blueprints” or genetic (hereditary) information for making new proteins and molecules Thick string-like strands of DNA and proteins found in the nucleus Condenses to form chromosomes
Ribosomes Cells normally have millions of these Free-living or attached to Endoplasmic Reticulum Composed of proteins & RNA Responsible for building proteins in the cell
Endoplasmic Reticulum Two forms – smooth & rough Forms a tubular network throughout the cell Transports chemicals within cells Forms sacs to store proteins & other substances produced by the cell Provides site for chemical reactions & synthesis
Golgi Bodies looks like a stack of pancakes Acts as a packaging department ready to deliver the protein products made in the cell Exports proteins out of the cell
Mitochondria Composed of a modified double unit membrane Inner membrane infolded for form cristae Converts energy from sugar & oxygen Two compartments allow for a H+ ion difference
Chloroplast Site of photosynthesis, which is the basic food source for the organism When a fruit ripens, the chloroplasts in the green tissue are changed to non photosynthetic organelles and turn color
Vacuole Fluid-filled membrane bound sacs with little or no internal structure used to store cell products In plants, the central vacuole is large and helps maintain the necessary internal pressure (called turgor pressure. ) Lysosome Membrane bound sac (vacuoles) filled with digestive enzymes They help break down and remove old worn out cell parts They digest food particles brought into the cell Only needed by animal cells
Cilia & Flagella used primarily by animal cells for movement Flagella are larger single versions of cilia Cilia are short but numerous compared to flagella.
Organelles and microscope Quiz on Wednesday