Cell Structure and Function

Cell Structure and Function
? Cell
- The simplest, functioning part of an organism is a cell.
- Although cells are small in size, they contain all the necessary information to keep an organism alive.
- There are trillions of cells in the human body.
- Many cells are necessary to carry out the specialized functions of the body.
- There are also organisms that are made up of just one cell.
- There are many types of cells.
- Every organism contains cells that are unique to that organism. Animals, plants, and bacteria all have specialized cells.
? Characteristics of All Cells
• A surrounding membrane
• Protoplasm – cell contents in thick fluid
• Organelles – structures for cell function
• Control center with DNA
? Cell Types
All cells fall into one of the two major classifications of either prokaryotic or eukaryotic
• Prokaryotic
• Eukaryotic
? Prokaryotic cell
Prokaryotes, which include all bacteria, are the simplest cellular organisms. They have genetic material but no nucleus.
• All prokaryotic organisms are unicellular, that are found in all environments.
• Prokaryotes are the simplest type of cell.
• Prokaryotes are the largest group of organisms
• Prokaryotes do not have a nuclear membrane. Their circular shaped genetic material dispersed throughout cytoplasm.
• Prokaryotes do not have membrane-bound organelles.
• Prokaryotes have a simple internal structure.
• Prokaryotes are smaller in size when compared to Eukaryotes.
? Eukaryotic cells
Eukaryotic cells contain a membrane-bound nucleus and numerous membranes-enclosed organelles (e.g., mitochondria, lysosomes, Golgi apparatus) not found in prokaryotes.
• Eukaryotic organisms unlike prokaryotic can be unicellular or multicellular
• Eukaryotes are generally more advanced than prokaryotes
• Nuclear membrane surrounds linear genetic material (DNA)
• Eukaryotes have a complex internal structure.
• Eukaryotes are larger than prokaryotes in size.
? How do the similarities line up?
• Both types of cells have cell membranes , ribosomes, DNA, cytoplasm
? Cytoplasm AND Organelles
• The jelly-like fluid that fills a cell is called cytoplasm. It is made up of mostly water and salt.
• Cytoplasm is present within the cell membrane of all cell types and contains all organelles and cell parts.
• Cytoplasm has various functions in the cell. Most of the important activities of the cell occur in the cytoplasm.
• Cytoplasm contains molecules such as enzymes which are responsible for breaking down waste and also aid in metabolic activity.
• Cytoplasm is responsible for giving a cell its shape. It helps to fill out the cell and keeps organelles in their place.
• Without cytoplasm, the cell would be deflated and materials would not be able to pass easily from one organelle to another.
? Cytoskeleton
• Chief functions include:
– movement of material through the cell for stuff not diffusion or osmosis
– maintaining the shape of the cell
– keeping the cell from getting smashed
? Organelles
? Cell Walls
• Found in plants, fungi, & many protists
• Surrounds plasma membrane.
? Plasma Membrane /Cell Membrane
• Contains cell contents
• Double layer of phospholipids & proteins.
• holds the cell together
• keeps all of the pieces (like the organelles and the cytoplasm) inside the cell
• allows nutrients to enter the cell and waste to be removed
? Golgi Apparatus:
• sorts proteins made by the ribosomes and sends them to needed places in the cell
• Receives, processes, and packages large molecules for export from cell
• Packages molecules in secretory vesicles that fuse with cytoplasmic membrane
• Composed of flattened hollow sacs surrounded by phospholipid bilayer
• Not in all eukaryotic cells
• Golgi apparatus is associated with the ER.
• It modifies and packages the lipids and proteins manufactured by the ER and place them in vesicles for cellular use.
? Centrioles
• they look like two cylinders at right angles to one another
• When viewed with an electron microscope, the cylinders show up as nine bundles of tiny microtubules arranged in a circle (Pairs of microtubular structures).
• they help to form the fibers that move chromosomes around when the cell is dividing
• As animal cells prepare for cell division these two centrioles separate and go to opposite ends of the cell.
? Nucleus
• Control center of cell
• Contains Nucleolus and Chromosomes ( genetic material – DNA)
• Directs cell activities
• Separated from cytoplasm by nuclear membrane
? Nuclear Envelope
• Separates nucleus from rest of cell
• Double membrane
• Has pores (Openings allow material to enter and leave nucleus)
? Nucleolus
• The dark area in the nucleus
• Like a tiny nucleus inside the nucleus.
• Most cells have 2 or more
• Directs synthesis of RNA to build proteins
? Chromosomes
• are found inside the nucleus and carry the information that determines what traits a living thing will have , Made of DNA
? Endoplasmic Reticulum
• Helps move substances within cells
• Network of interconnected membranes
• Two types
– Smooth endoplasmic reticulum: lacks ribosomes
– Rough endoplasmic reticulum: ribosomes embedded in surface

? Smooth Endoplasmic Reticulum
• No attached ribosomes
• Main function is to collect, maintain & transport things
• Shaped slightly tubular
• Creates steroids
• Stores Ions for the cell to keep nutrients balanced
• Has enzymes that help build molecules :Carbohydrates ,Lipids
? Rough Endoplasmic Reticulum
• It has bumps all over it giving it a “rough” appearance
• Bumps are called ribosomes
• ER collects the proteins (built by the ribosomes) and creates a bubble around them
? Ribosomes
• Each cell contains thousands ribosomes
• ribosomes small dot-like structures in cells
• they are often associated with forming rough ER
• Ribosomes are the site of protein synthesis in cells
• they are made in the nucleus of the cell
• A ribosome can make the average protein in about one minute
? Lysosomes
• When an organelle no longer works, the lysosome will attach itself to it and break it down like food (kind of like a cannibal)
– Chemicals can then be reabsorbed or excreted
• Lysosomes can also destroy the cell if it breaks open accidentally
– UV light damages lysosome membrane
• The enzymes inside the lysosome spread throughout the cell and digest it
? Mitochondria (release energy)
• Have their own DNA
• Bound by double membrane
• Produces energy (ATP) through chemical reactions – breaking down fats & carbohydrates
• Controls level of water and other materials in cell
• Recycles and decomposes proteins, fats, and carbohydrates
• If a cell needs a lot of energy…it will have more mitochondria