Cells

1. Cells Uyanga Ganbold-Battulga Mr. Miller Period 4 18 October 2010

2. Cell Structure and function • Cells=Basic unit of life • They are the smallest living organism • They are highly organized • There are over 200 different types of cells, but they are all similar. • They are surrounded by cell membrane. • The nucleus contains most of the genetic information. -This genetic information(DNA) create new cell parts.

3. Unicellular/Multi-cellular • Unicellular cells produce unicellular organisms that are identical to the cells that produce them. • Multi-cellular organisms begin their lives as one cell. • Mature multi-cellular(adults) organisms have changing cells(multiple) as they mature. • Differenation: Cells of multi-cellular organisms become different from each other as they multiply. -Cells start playing different roles supplied by the genetic information.

4. Cell Diversity • Humans carry about 200 different cell types. • Few cells can be seen without the unaided eye. Example: A giraffe’s nerve cell can grow up to 2 meters long. • Most plant cells are .002 inches in diameter. -Therefore, most cells can be seen with a microscope. • If a cell keeps the same shape as it grows, the volume will increase more than the surface area(This is important to remember because nutrients, oxygen, and other compounds a cell needs enters through the surface.

5. Shapes(animal cell) • Remember: A diversity of form=diversity of function. • Nerve cell: The long extensions that reach out from the center of the cell enables the cell to receive, transmit nerve pulses. • Skin Cells: The flat shape covers the body of an organism. • White blood cell: They can shape, leave the blood, and enter areas surrounding the blood vessels. This allows them to move through narrow passages, isolate, engulf and destroy bacteria.

6. Cell theory • When cells were discovered, theories were soon followed right after the discovery. • 1) All living things are made up of cells. • 2) Cells are basic unit of structure. • 3) Cells come from reproduction of existing cells.

7. Internal organization • Cells contain internal structures called “organelles” (a cell component that performs certain functions of the cell) • A cell is surrounded “cell membrane”. Organelles also are surrounded by their own type of membrane. • Nucleus(a type of organelle): Contains the majority of the genetic information and conducts activities of the cell. • Organisms that have membrane surrounding the nucleus is known as “eukaryotes.” • Bacteria also has a cell membrane(but the organelles are not) • Organisms that lack membrane around the nucleus and other organelles are known as “prokaryotes.”

8. Cell membrane • Eukaryotic cells usually have three main components: A membrane, nucleus, and other organelles. • Nutrients and wastes usually pass through the membrane. • Cell membranes allow certain substances to pass, but not all. • Structures of cells depend on the functions. • In a multi cellular organism, some cells release materials into their environments for other uses. • Other cells recognize harmful invaders and destroy them. • A cell’s membrane is made up of liquids and protein.

9. Membrane lipids • A major type of lipid is phospholipids. • Lipids are large non-polar organic molecules that do not dissolve in water and stores energy. • Because of its hydrophilic nature (attracted to water) phospholipids will orient its head around so that it faces towards water molecules. • Hydrophobic tails will tend to turn away from water molecules. • Cells bathe in a watery environment. • Since both sides of a cell has water, a cell membrane is surrounded by water on both sides. • These water molecules cause phospholipids to form two layers: a lipid bi layer • Phospholipids are arranged so that the heads point out while the tails are confined to the interior of the membrane.

10. More lipids. • Lipids are divided into categories according to their structures. • Three types of lipids living things need that contain fatty acid: triglycerides, phospholipids, and waxes.

11. Plant cells and animal cells • A plant’s membrane isn’t on the outside like animal cells. • A plant’s cell has three extra features: a cell wall, a vacuole, and plastids. • The cell wall is the base of holding the cell together. • It’s not solid. It has tiny openings that let things in and out. • This is called “semi- permeable” which means the cell membrane can be entered through various places

12. Proteins • There are many proteins in a cell. • Some of these proteins are found in the bilayer. • These proteins stick out on both sides of the membrane, guarding it. • The proteins decide who can come in and out of the membrane. • Proteins: Carry force inside muscles, carry oxygen, help digest food, and make up sex hormones.

13. Membrane Proteins: • Some proteins are attached to surfaces of cell membrane. The peripheral proteins are located on both the interior surface and the exterior surface of the membrane. • Weak bonds link peripheral proteins to membrane lipids or other proteins that are in the lipid bilayer. • The proteins that are embedded in the bilayerare called "integral proteins“ • Because the membrane is selectively permeable, cells must have mechanisms for transporting molecules through the lipid bilayer

14. Mosaic model of cell membrane • Scientists have discovered that cell membranes are actually very dynamic. Today, they use the "fluid mosaic model" to describe the cell membrane. • The bilayer behaves more like a fliud than a solid. Because of this, the membrane's lipids and proteins can move within the lipid bilayer

15. Organelles • Between the cell membrane and the nucleus, there's a "cytoplasm“ • The organelles are in a gelatin-like water fluid called the "cytosol“ • In the cytosol, there are dissolved salts, minerals, and organic molecules.

16. Major Organelles for both plant cells and animal cells. • Mitochondrion: transfers energy from organic compounds to ATP (which is a chemical used throughout the body to transfer/hold energy. It is made up of adenine) • Ribosome: Organizes the synthesis of proteins(the formation of proteins using information coded on DNA and carried by RNA) • Endoplasmic reticulum (ER): Prepares proteins for export(rough ER); synthesizes steroid, regulates calcium level, breaks down toxic substances(smooth ER). • Golgi apparatus: processes and packages substances produced by the cell. • Lysosome: digests molecules, old organelles, and foreign substances • Microfilaments and microtubules: contribute to the support, movement, and division of cells. • Cilia and flagella: propel cells through the environment; move materials over the cell surface • Nucleus: stores most of the genetic information(DNA) • Cell wall: supports and protects the cells (only found in plant cells) • Vacuole: stores enzymes and waste products (only found in plant cells) • Plastid: stores food; one type(chloroplast) transfers energy from light to organic compounds.(Only found in plant cells)

17. Mitochondria • Scattered around the cytosol, are large organelles called "mitochondria(the sites of chemical reactions that transfer energy from organic compounds to ATP) • ATP is a molecule that most cells use as their main energy currency. The energy of ATP drives most of the chemical reactions that occur in a cell. Therefore, mitochondria are usually more numerous in cells that have a high energy requirement. Example: liver cells, carry out a host of biochemical activities, andeach cell may contain about 2,500 mitochondria. • Mitochondrion is surrounded by two membranes. The smoother outer membrane serves as a boundary between the mitochondrion and cytosol. • The inner membrane has long folds, known as "cristae" (which enlarge the surface area of the inner membrane, making more space for chemical reactions that happen in the mitochondrion. • Mitochondria have their own DNA and new mitochondria arise when only existing ones grow and divide.

18. Ribosomes • Most numerous organelle in any cell. • They are made up of RNA and proteins. • They are not surrounded by membrane. • Inside cell's nucleus, proteins and RNA are packaged into ribosome, which are then transported to the cytosol. Some ribosome remain free within the cytosol, while others become attached to an organelle called the "endoplasmic reticulum“ • Ribosomes play important roles in the synthesis of proteins. • Proteins that are used within the cytosol are produced on the ribosome that are free in the cytosol. Proteins to be inserted into membranes or exported from the cell are produced on the ribosome that are attached to endoplasmic reticulum.

19. Endoplasmic Reticulum • The abbreviation is ER. • The ER functions as an intracellular highway, a path along which molecules move from one part of the cell to another. • The amount of ER inside a cell fluctuates, depending on the cell's activity. • A cell contains two types of ER. • Rough endoplasmic reticulum, is prominent in cells that make large amounts of proteins to be exported from the cell or inserted into the cell membrane. • The second type of ER is not covered in ribosome. Becuase it's looks lighter, the ER looks smoother, so it's called "smooth endoplasmic reticulum" • Smoother ER is involved in the synthesis of steroid, the regulation of calcium levles in muscle cells, and the breakdown of toxic substances by liver cells.

20. Golgi Apparatus: • It is a processing,packaging,and secreting organelle of the cell. • Like the endoplasmic reticulum, the Golgi apparatus is a system of membranes. It works close association with the endoplasmic reticulum, the Golgi apparatus modifies preotins for export in the cell.

21. Lysosomes • They're small spherical organelles that enclose hydrolytic enzymes(a protein in a living system) within single membranes. • These enzymes can digest proteins, carbohydrates, lipids, DNA,and RNA. They also digest old organelles as well as viruses and bacteria. • Lysosome are common in the cells of animals, fungi, and protests, but they are rare in plant cells • In some multi cellular organisms, lysosomeplay a role during early development. • As embryo develops, lysosomal enzymes destroy tissue to form the spaces between the fingers.

22. Cytoskeleton: • A cell needs a structure to maintain its shape and size. • In many cells, the structure is called "cytoskeleton, a network of long protein strands located in the cytosol. • Like ribosome, these strands are not surrounded by membranes. • The cytoskeleton participates in movement of organelles within the cytosol. • Two major components of the cytoskeleton are "microfilaments and microtubules" • Microfilaments are threads made up of a protein called acting. Each microfilament contain many acting molecules that are linked together to form a polymer chain. Microfilaments constitute the smallest strands that make up the cytoskeleton. They contribute to cell movement and play a role in the contraction of muscle cells. • The largest strands of the cytoskeleton are hollow tubes known as microtubules. In ashy cells, microtubules extend outward from a central point near the nucleus to various sites of the membranes. When a cell is about to divide, bundles of microtubules come together and extend across the cell. These bundles are known as "spindle fibers" They are thick enough to be visible with a light microscope. Spindle fibers assist in the movement of chromosomes during a cell division. When cell division is complete, the spindle fibers are disassembled, and the microtubules resume their task of providing support to the cell.

23. Cilia and Flagella: • They are hair like organelles that extend from surface of the cell. • Cilia and flagella can be found in many eukaryotic cells. • When these organelles are short and present in large numbers on a cell, they are called "cilia" The external surfaces of unicellular organisms are covered with the cilia. The movements of cilia propel these tiny organisms through the water as they search for food or escape the predators. Cilia are also found on surfaces of cells in multi cellular organisms. The cells in our respiratory tract, for example, have a bunch of cilia that trap particles and debris from the air you inhale. As cilia move, they sweep the trapped materials back up to your throat, where they are removed from your respiratory tract when you swallow. • When hair like organelles are long and not so much on a cell, they are called "flagella" • On many cells, including the sperm cells, only one flagellum is present. By whipping back and forth, flagella can swiftly propel unicellular organisms or specialized cells in multi cellular organisms, such as sperm cells. • Cilia and flagella have a similar internal structure. Both organelles are composed of nine pairs of microtubules arranged around a central pair.

24. Nucleus: • Nucleus is the most prominent structure in a eukaryotic cell. The "nuclear matrix" develops of shape. • The nucleus is surrounded by double membrane called "nuclear envelope" • Inside the nuclear envelope, there are strands of "chromatin"(a combination of DNA and protein) • When a cell is about to divide, chromatin strains coil up and become closely packed, forming "chromosomes" • Nucleus stores hereditary information in its DNA. The nucleus is also the site where RNA is copied from DNA. This means that RNA must travel from nucleus to the cytosol before it can direct protein synthesis. • RNA makes the journey by passing through "nuclear pores, small holes in the nuclear envelope" • Most nuclei contain at least on spherical area called the "nucleolus". • The nucleolus is where ribosome are synthesized and partially assembled before they pass through the nuclear pores to the cytosol.

25. Main types of protein in the membrane: • Integral protein: Protein that are apart of membrane and make contact with the inside, and outside of the cell. • Transmembrane channel proteins: Kind of like integral protein,but connect the cytoplasm to the extracellular fluid(They channel things in and out. • Surface membrane proteins: On the outer layer of the membrane. • Inner membrane proteins: Inner layer of the membrane, and makes contact with cytoplasm.

26. Plant cells • Plant cells have three extra structures(three more than animal cells): cell walls, vacuoles, and plastids. • -They are extremely important to the plant function.Cell Wall: Plant cells are covered by "cell wall" that lies outside the cell membrane. • It's rigid, which helps support and protect the plant. Cell walls contain long chains of cellulose(a complex carbohydrates. It contains proteins and other carbohydrates that harden the whole structure. • Pores in the cell wall allow ions and molecules to enter and exit the cell. • There are two types of cell walls: primary and secondary. • While a plant cell is being formed, a primary cell wall develops outside of the cell membrane. As the cell expands in length, cellulose and other molecules are added, enlarging the cell wall. When the cell reaches its full size, a secondary cell wall may develop. The secondary cell wall develops between the primary cell all and the membrane. • the secondary cell wall is tough and woody. Therefore, once it is completed, a plant cell can grow no further.

27. Vacuoles: • Vacuoles are second common characteristic of plant cells. • They are fluid-filled. • They store enzymes and metabolic wastes. • They are large. • Some vacuoles may take up 90 percent of a plant cell's volume, pushing the other organelles up against the cell membrane. • Some wastes stored by vacuoles are toxic and must be kept away from the rest of the cell. • The storage of these materials may be beneficial to a plant in other ways. For instance, the poisons that certain acacia trees have in their vacuoles provide a defense against plant-eating animals.

28. plastids • Plastids are organelles that are surrounded by two membranes and contain DNA. • Some plastids store starch or fats, while others contain compounds called pigments, which absorb visible light. • Familiar type of plastid= chloroplast. • Chloroplast is made up of flattened, membranous sacs called "thylakoid" • Chloroplasts are organelles in a plant cell in which the energy of sunlight is converted into chemical energy in organic compounds. • The conversion occurs in the thylakoids during the process of photosynthesis. • Chloroplasts have green pigment that gives leaves their green color. • Photosynthesis= the conversion of light energy into chemical energy stored in organic compounds. • Organisms obtain sunlight energy and store it within organic compounds(transfer is called "photosynthesis"