Chapter 7 A View of the Cell

7.1 Microscopes  Compound light microscopes Use a series of lenses to magnify objectsUse a series of lenses to magnify objects Can magnify up to 1500 timesCan magnify up to 1500 times Uses a beam of lightUses a beam of light  Electron Microscopes Uses a beam of electrons to magnify objectsUses a beam of electrons to magnify objects Can magnify up to 500,000 timesCan magnify up to 500,000 times Specimens must be examined in a vacuumSpecimens must be examined in a vacuum Two types:Two types:  Scanning electron microscope scans the surface of cells to view the 3 dimensional shape  Transmission electron microscopes allow scientists to study structures in a cell

7.1 Cell Theory  With the invention of microscopes, scientists were able to conduct more in-depth investigations and created the cell theory, which has 3 basic ideas: All organisms are composed of one or more cellsAll organisms are composed of one or more cells The cell is the basic unit of structure and organization of organismsThe cell is the basic unit of structure and organization of organisms All cells come from cells that already existedAll cells come from cells that already existed

7.1 Types of cells  There are 2 basic types of cells ProkaryotesProkaryotes  Do not have membrane bound organelles  Include most single celled organisms EukaryotesEukaryotes  Have membrane bound organelles  Includes most multi celled organisms  Have a nucleus, which manages and controls cellular functions  Organelles each have a specific function within the cell

7.1 Prokaryotic cells  Prokaryotic cells have the following structures: Cell wallCell wall Plasma membranePlasma membrane RibosomesRibosomes DNADNA CytoplasmCytoplasm

7.1 Eukaryotic Cells  Eukaryotic Cells contain the following structures: Plasma membranePlasma membrane CytoplasmCytoplasm ChromosomesChromosomes NucleusNucleus NucleolusNucleolus OrganellesOrganelles

7.2 Plasma Membrane  The plasma membrane is the flexible boundary between the cell and its environment It allows nutrients to enter and exit the cellsIt allows nutrients to enter and exit the cells It allows waste to exit the cellIt allows waste to exit the cell It is described as being selectively permeable, because it lets some things through but not othersIt is described as being selectively permeable, because it lets some things through but not others  It can also change what it allows to pass through at different times

7.2 Plasma Membrane Structure  The plasma membrane is made of a phospholipid bilayer, which is composed of 2 layers of phospholipids back to back Phospholipids are composed of a glycerol backbone, 2 fatty acids chains and a phosphate groupPhospholipids are composed of a glycerol backbone, 2 fatty acids chains and a phosphate group  The fatty acid tails are non-polar These are on the inside of the bilayerThese are on the inside of the bilayer  The phosphate head is polar This is on the outside of the bilayerThis is on the outside of the bilayer

7.2 Fluid Mosaic Model  The model of the plasma membrane is called the fluid mosaic model Fluid because the phospholipids move within the membrane (similar to water waves moving in a lake)Fluid because the phospholipids move within the membrane (similar to water waves moving in a lake) Mosaic because proteins create a pattern on the surface of the bilayerMosaic because proteins create a pattern on the surface of the bilayer

7.2 Other components  Cholesterol Stabilizes the phospholipids by preventing their fatty acid tails from sticking togetherStabilizes the phospholipids by preventing their fatty acid tails from sticking together Cholesterol can be harmful in large quantities, but some is necessary for this purposeCholesterol can be harmful in large quantities, but some is necessary for this purpose  Transport proteins Regulate which substances enter and leave the cellsRegulate which substances enter and leave the cells

7.3 Cell Structures  Eukaryotic Cells are divided into 2 categories: plant cells and animal cells Animal cell structures include a plasma membrane, ribosomes, a cytoskeleton, an endoplasmic reticulum, a golgi apparatus, lysosomes (some cells), mitochondrion, a nucleus, a nucleolus, and vacuoles (some animal cells)Animal cell structures include a plasma membrane, ribosomes, a cytoskeleton, an endoplasmic reticulum, a golgi apparatus, lysosomes (some cells), mitochondrion, a nucleus, a nucleolus, and vacuoles (some animal cells) Plant cells include these items plus a cell wall and chloroplastsPlant cells include these items plus a cell wall and chloroplasts

7.3 Cell Parts & Functions I  Plasma membrane- flexible cell boundary that is selectively permeable  Cell wall- rigid cell boundary outside the plasma membrane that provides additional structural support  Nucleus- controls organelle activity and includes directions to make proteins in the DNA, which is in a stringy form called chromatin  Nucleolus- inside the nucleus-makes ribosomes

7.3 Cell Parts & Functions II  Ribosomes- where cells produce proteins according to the directions in DNA  Cytoplasm-clear gelatinous fluid inside a cell-suspends organelles  Endoplasmic reticulum (ER)- site of cellular chemical reactions Rough ER has ribosomesRough ER has ribosomes Smooth ER does not have ribosomesSmooth ER does not have ribosomes

7.3 Cell Parts & Functions III  Golgi Apparatus- modifies proteins by sorting and packaging them and sending them to the correct location  Vacuoles- temporary storage of materials (food, enzymes, waste)  Lysosomes- contain digestive enzymes that digest extra or worn out organelles, food, and viruses/bacteria They can fuse with vacuoles to empty their contentsThey can fuse with vacuoles to empty their contents

7.3 Cell Parts & Functions IV  Chloroplasts- trap light energy and convert it to chemical energy; contain chlorophyll a green pigment that traps light energy  Mitochondria- transform energy for the cell  Cytoskeleton- a network of rods (microtubules) and filaments (microflaments) inside the plasma membrane that provide structure and maintain the shape of the cell

7.3 Cell Parts & Function V  Centrioles- play a role in cell division  Cilia- short numerous projections that look like hairs that allow the cell to move  Flagella-long projections (1 or 2 per cell) that allow the cell to move  Nuclear membrane- separates the cytoplasm from the nucleus

7.3 Animal Cell Golgi Apparatus Plasma membrane mitochondria ribosomes Endoplasmic reticulum lysosome cytoplasm nucleus nucleolus centriole vacuole Nuclear membrane

7.3 Plant Cell Cell wall Plasma membrane Vacuole mitochondria cytoskeleton Endoplasmic reticulum Golgi apparatus cytoplasm ribosomes nucleus nucleolus chloroplast Nuclear membrane