By Calypso Harmon Fall 2002
This is an extremely thin slice through a plant cell. Are there any structures you recognize?
Chloroplasts collect the energy from the sun and change it into chemical energy in the form of sugar. Only plants have chloroplasts. They are disk shaped, and are about 4-6 micrometers in diameter. One cell may contain 40-50 chloroplasts. Chloroplasts are surrounded by two membranes and have their own DNA.
Chloroplasts Location of photosynthesis Found only in plants One cell can have many (40-50) Double Membrane Bacterial DNA (not Eukaryotic DNA)
Mitochondria burn sugar molecules to release that energy stored in the sugar so that it can be used by the cell. All plant and animal cells have mitochondria. They are about ½ a micrometer in diameter. One cell may have 100-2,000 mitochondria. Mitochondria are surrounded by two membranes. The inner membranes is extensively folded, giving it more surface area for the enzymes to attach to. They have their own DNA
Mitochondia Burn glucose to make to give the cell energy In both plant and animal cells more mitochondria in muscle cells (more energy is needed in muscles) Double Membrane Bacterial DNA (not Eukaryotic DNA)
Double Membranes and their own DNA Scientists noticed that chloroplasts, the nucleus, and mitochondria have double membranes and their own DNA. A current theory to explain this is that a long, long time ago, bacteria specializing in photosynthesis, data storage, and energy production were swallowed by another cell. Symbiosis between the swallower and the swallowed helped both to survive. Eventually the swallowed (chloroplasts, the nucleus, and mitochondria) lost their ability to survive outside on their own.
The nucleus determines which proteins will be made and when they will be made. It also carries and transmits genetic information. Plant and animal cells have A nucleus. Usually cells only have one nucleus. The nucleus is surrounded by two membranes called the nuclear envelope. This envelope has pores that allow molecules to move through the envelope.
The cell wall provides structure and support for a cell, and it prevents a cell from taking in so much water it bursts. Plant and bacterial cells have cell walls. The cell walls are made of cellulose and other strong macromolecules.
The cell membrane is made of a phospholipid bilayer with proteins embedded in it. Different proteins have different functions. For example, some transport materials, some are enzymes, some are self-markers, and some help the cell stay attached to the cell next to it. The cell membrane separates the cell from its surroundings. It also transports things into and out of the cell, and receives messages from other cells. All cells have a cell membrane.
The vacuole stores water, wastes, or food. In plants, the vacuole is very large and the pressure it exerts allows the plant to be stiff and upright, instead of wilting. Plant cells usually contain one large vacuole. Animal cells usually contain several small vacuoles. It s surrounded by a plasma membrane.
The endoplasmic reticulum transports materials through the cell. When the endoplasmic reticulum is studded with ribosomes, it is called rough ER. This ER transports proteins, the product of ribosomes. When it doesn t have ribosomes it is called smooth ER. This ER transports lipids. The endoplasmic reticulum is located next to the nucleus, and extends to many parts of the cell.
Rough endoplasmic reticulum Smooth endoplasmic reticulum
Peroxisomes (P) Mitochondria (M). Smooth and Rough ER
The golgi apparatus modifies proteins. Both plant and animal cells have golgi apparatuses. Cells can have one to several hundred golgi apparatuses. The golgi apparatus is a stack of flatten sacks. It is made of a phospholipid bilayer, just like the cell membrane, and endoplasmic reticulum. One side receives proteins from the ER, the other side buds off small vesicles of protein it modified.
If the vesicle contains a product that is leaving the cell, it travels to the cell membrane and fuses with it, emptying its protein outside of the cell.
An example of this is in nerve cells. When one nerve cell communicates with the cell next to it, many vesicles of neurotransmitters fuse with the cell membrane and dump their contents into the space between the two cells.
If the vesicle from the golgi apparatus contains an enzyme used for digestion, it called a lysosome. It joins with something that needs to be broken down, such as a mitochondria that no longer functions. It is also used to break down macromolecules. This is a diagram of a white blood cell eating a bacteria then joining that to a lysosome to digest the bacteria.
Animal Cell Color code: Mitochondria = orange Cell membrane = yellow Golgi = yellow Nucleus = pink
Cytoskeleton made of microtubules and microfilaments
The cytoskeleton helps to maintain the different shapes of cells, and helps organelles move within the cell.
Differences Plant Cell wall Chloroplasts Large Vacuole Animal no cell wall no chloroplasts generally no large vacuole
Similarities nucleus endoplasmic reticulum mitochondria Golgi apparatus
Flagella and Cilia Flagella - long, thin, and whip-like move in wave-like S motion. Cilia - more numerous and shorter move back and forth (row boat like)