A View of the Cell Chapter 7 Notes

Microscopes  The microscope was invented by Leeuwenhoek.  A compound light microscope has a series of lenses and light.  Electron microscope uses a beam of electrons instead of light. Can magnify objects up to 500,000 times their size.

The Cell Theory  All organisms are made of one or more cells.  The cell is the basic unit of structure of organization of organisms.  All cells come from existing cells.

The 2 types of Cells Prokaryotes and Eukaryotes  There are 2 types of cells.  Prokaryotic cells – these cells do not have a nucleus, they do not have organelles attached to the cell membrane. These are small cells.  Bacteria cells are prokaryotic cells.

Eukaryotic cells  Eukaryotic cells – these cells do have a nucleus, they do have organelles attached to the membrane. These cells can be much larger than prokaryotic cells.  An organelle is a specialized structure in a cell that carries out a specific function. A “little organ.”

The Plasma Membrane  All cells are surrounded by a plasma membrane.  This is a flexible boundary between the cell and its environment, to allow a steady supply of nutrients to come into the cell no matter the external conditions.  The plasma membrane helps to maintain homeostasis.  It has selective permeability. A process in which only certain molecules can pass through the membrane and others are kept out.

Structure of the Plasma Membrane  The plasma membrane is made up of a phospholipid bilayer.  This is two layers of phospholipid molecules.

Plasma Membrane (cont.)  The membrane is referred to as a “fluid mosaic.” This means it is not a rigid membrane, it’s shape and form can change and move.  Cholesterol molecules throughout the membrane help stabilize the phoshopholipids and keep the fatty acid tails from sticking together.  Transport proteins are also found in the membrane to move needed substances or waste materials through the membrane.

Cell Structures and Their Functions  Some organisms have an additional boundary between the cell and the environment. This is the cell wall. Plants, fungi, bacteria, and some protists have cell walls.  Cell wall – a fairly rigid structure located outside the plasma membrane that provides additional support and protection. Plant cells are separated by transparent cell walls.

Nucleus  The nucleus is the control center of the cell. It contains directions to make proteins. The nucleus controls the activities of the organelles.  The nucleus is surrounded by a nuclear membrane.  Nucleolus – an organelle in the nucleus that makes ribosomes. Micrograph of a cell nucleus showing the darkly stained nucleolus.

Cytoplasm  The cytoplasm is everything inside the cell membrane and outside the nucleus.  It contains most of the organelles for the cell. It is the clear, gelatinous fluid inside a cell.

Organelles and their Functions  Endoplasmic reticulum – the site of cellular reactions.  Rough endoplasmic reticulum – it is ER with ribosomes attached to its surface.  Ribosomes – carry out protein synthesis. (they make proteins).  Golgi apparatus – sorts and packages proteins to be sent out to where they are needed.

Nucleus, ER, and Golgi Apparatus 1.Nucleus 2.Nuclear Pore 3.Rough Endoplasmic Reticulum 4.Smooth Endoplasmic Reticulum 5.Ribosome on rough ER 6.Proteins that are transported 7.Transport vesicle 8.Golgi Apparatus

Vacuoles and Lysosomes  Vacuole – a membrane bound compartment used for temporary storage of materials. (10) They are used to store food, enzymes, wastes, and other materials.  Lysosome – contain digestive enzymes (12)

Energy transformers  Chloroplasts – cell organelles that capture light energy and convert it to chemical energy. Found in plant cells and some protists. This is the site of photosynthesis.  Mitochondria – membrane bound organelles in plant and animal cells that transform energy for the cell. Break down chemicals and into usable forms.

Organelles for Cellular Support  Cytoskeleton – forms a framework for the cell. It is a constantly changing structure.  Microtubules – thin, hollow cylinders made of protein that make up the rods for the cytoskeleton.  Microfilaments – small, solid fibers that help make up the cytoskeleton  Centrioles – occur in pairs, made of microtubules, help in cell division. Microtubules are green, Microfilaments are red, Nuclei are blue.

Organelles for Locomotion  Cilia – short, numerous hair-like projections that aid in locomotion. Motion is similar to that of oars on a boat.  Flagella – a long, whip- like projection used in locomotion. A cell can have one or two flagella.  Unicellular organisms use these a major means of locomotion. Flagella on e. coli bacterium.