Cell Structure

Two Cell Types 1. Prokaryotic Cells- Simple cells made up of a cell wall, cell membrane, cytoplasm, and DNA. They do not have membrane bound organelles. Ex. Bacteria 2. Eukaryotic Cells- are cells with specialized organelles that are held together by a membrane. They have a central organelle called a nucleus that controls all the cell’s activities and contains the DNA.

Plasma Membrane Is the flexible boundary of a cell that separates a cell from its surroundings. Is the flexible boundary of a cell that separates a cell from its surroundings. It allows nutrients to enter the cell and waste to be removed. It allows nutrients to enter the cell and waste to be removed. –This healthy balance is called Homeostasis. To maintain this homeostasis the plasma membrane allows some molecules into the cell and keeps others out. This is called Selective Permeability. Pg 176 To maintain this homeostasis the plasma membrane allows some molecules into the cell and keeps others out. This is called Selective Permeability. Pg 176 Some molecules are allowed in at any time and others are only admitted at certain times and in limited quantities. Others are not allowed in at all. Some molecules are allowed in at any time and others are only admitted at certain times and in limited quantities. Others are not allowed in at all.

Structure of the Plasma Membrane The plasma membrane is made up of two layers of phospholipids that are arranged back to back. This is called the phospholipid bilayer. Pg 177 The plasma membrane is made up of two layers of phospholipids that are arranged back to back. This is called the phospholipid bilayer. Pg 177 The phosphate group or the head is polar (which water is also polar so they interact well together) which allows the plasma membrane to interact with its watery environment. The phosphate group or the head is polar (which water is also polar so they interact well together) which allows the plasma membrane to interact with its watery environment. The fatty acid tail is nonpolar which avoids water and is water insoluble. The fatty acid tail is nonpolar which avoids water and is water insoluble. So the outside of the plasma membrane is water soluble and the inside of the membrane is water insoluble. This means that water soluble molecules will not easily move through the membrane b/c they are stopped by this water insoluble layer. So the outside of the plasma membrane is water soluble and the inside of the membrane is water insoluble. This means that water soluble molecules will not easily move through the membrane b/c they are stopped by this water insoluble layer.

Transport Proteins They regulate which molecules are allowed to enter and which are allowed to leave the cell. Called Selective Permeability. They regulate which molecules are allowed to enter and which are allowed to leave the cell. Called Selective Permeability.

Eukaryotic Cell Structure Cellular Boundaries pg 180 Cellular Boundaries pg 180 –Cell wall is a rigid wall outside the plasma membrane that dives extra support and protection to the cell. –Plasma Membrane is inside the cell wall and acts as a flexible boundary of the cell.

Eukaryotic Cell Structure The Nucleus and Cell Control pg 181 The Nucleus and Cell Control pg 181 –The nucleus directs the activity of a cell’s organelles and contains directions to make proteins.  The nucleus is surrounded by the nuclear envelope which is the boundary in between the nucleus and the cytoplasm. –It also contains the DNA that is in strands called Chromatin. The chromatin tells the cell what kinds of proteins to make. When the cell divides the chromatin condenses and becomes chromosomes.

Eukaryotic Cell Structure The Nucleolus, which is inside the nucleus, makes ribosomes. The Nucleolus, which is inside the nucleus, makes ribosomes. –Ribosomes are where the cell makes protein, which is made up of RNA.  Ribosomes make the proteins in the cytoplasm. –The Cytoplasm is a thick fluid in the cell.

Eukaryotic Cell Structure Assembly, Transport, and Storage pg 182 Assembly, Transport, and Storage pg 182 –Endoplasmic Reticulum (ER) is a series of tightly folded membranes floating in the cytoplasm. It is the site of cellular chemical reactions.  Two types –Rough ER is where ribosomes attach and make proteins. Other ribosomes float freely in the cytoplasm. Each protein has a specific job. Ex. Part of the plasma membrane. –Smooth ER does not have ribosomes attached and also performs chemical activities such as making and storing lipids.

Eukaryotic Cell Structure Other Organelles pg 183 Other Organelles pg 183 –Golgi Apparatus) (or golgi body) sorts proteins and then packs them into structures called vesicles. The vesicles are then sent to where they are needed.  When the golgi body packages digestive enzymes they form a lysosome. A lysosome breaks down old cell parts and removes waste. –Vacuole is a sac inside a membrane where materials needed by the cell are temporarily stored. Some store food and enzymes and others store waste until they can be removed or excreted.

Eukaryotic Cell Structure Energy Transformers pg 184 & 185 Energy Transformers pg 184 & 185 –Mitochondria is the cell’s powerhouse. It transforms energy for the cells of plants and animals. –Mitochondria stores the energy in bonds that the cells can access easily when energy is needed.  In green plants and some protists energy is received from light energy by the chloroplasts.  Chloroplasts are a type of plastid that re plant organelles that store things.  Chloroplasts contain chlorophyll (a green pigment) which makes leaves and stems green.

Eukaryotic Cell Structure Support and Locomotion Support and Locomotion –Cytoskeleton is inside the cell and supports the organelles in the cytoplasm. It can be take apart in on place and put back together in another, when this happens the cell changes shape.  It is made up of microtubules and microfilaments. –Microtubules are tiny cylinders of protein. –Microfilaments are even smaller solid protein fibers. –They support the organelles and help materials move around the cell.  Centrioles are made of microtubules and are very important in cell division.

Eukaryotic Cell Structure Two other organelles made from Microtubules are Two other organelles made from Microtubules are –Cilia which are short projections that look like hairs. They move in a wave like motion and cells have many of them. –Flagella are longer projections that move in a whip like motion. A cell usually has one or two flagella. –In a one celled organism the cilia and flagella are the most important way of moving.