The Cell Cell Types Cell Parts Diffusion & Osmosis
Prokaryotic Cells (Prokaryotes) Bacteria
Capsule • a protective covering • made up of polysaccharides (complex carbohydrates). • keep the bacterium from drying out and to protect it from phagocytosis (engulfing) by larger microorganisms. • The capsule is a major virulence factor in the major disease-causing bacteria, such as Escherichia coli and Streptococcus pneumoniae. Nonencapsulated mutants of these organisms are avirulent, i.e. they don't cause disease.
Cell Wall • composed of peptidoglycan, a protein-sugar. • gives the cell its shape • surrounds the cytoplasmic membrane, protecting it from the environment. • helps to anchor appendages like the pili and flagella, which originate in the cytoplasm membrane and protrude through the wall to the outside. • responsible for keeping the cell from bursting when there are large differences in osmotic pressure between the cytoplasm and the environment.
Nucleoid • A region of cytoplasm where the chromosomal DNA is located. • It is not a membrane bound nucleus • Most bacteria have a single, circular chromosome that is responsible for replication, although a few species do have two or more. • Smaller circular auxiliary DNA strands, called plasmids, are also found in the cytoplasm.
Pili • Small hairlike projections emerging from the outside cell surface. • Assist the bacteria in attaching to other cells and surfaces, such as teeth, intestines, and rocks. • Without pili, many disease-causing bacteria lose their ability to infect because they're unable to attach to host tissue.
Prokaryotic Ribosomes • Site of protein synthesis • Prokaryotic are smaller and have a slightly different composition and molecular structure. • Bacterial ribosomes are never bound to other organelles as they sometimes are (bound to the endoplasmic reticulum) in eukaryotes • free-standing structures distributed throughout the cytoplasm.
Eukaryotic Cells (Eukaryotes) Nucleus & Membrane Bound Organelles
Animal Cell Vacuole Cytoplasm Centriole Cell Membrane Smooth Endoplasmic Reticulum Nucleolus Nucleus Ribosome Rough Endoplasmic Reticulum Mitochondria Nuclear Membrane Golgi Apparatus Lysosome
Plant Cell Nucleolus Smooth Endoplasmic Reticulum Nucleus Chloroplast Nuclear Membrane Golgi Apparatus Cell Wall Cell Membrane Rough Endoplasmic Reticulum Vacuole Mitochondria Ribosome Cytoplasm
Cell Membrane • Control what comes in and out • Protects and supports the cell • Phospholipid Bi-layer • Proteins – act as channels to pass molecules into or out of the cell and others act as pumps to “push” molecules from one side to the other. • Cholesterol molecules prevent phospholipids from sticking to each other • Fluid Mosaic
Cell Membrane • Carbohydrate chains • Act like chemical ID cards – allows cells to recognize each other.
Cell Wall • Plants, algae, some bacteria • Helps support and protect cell • 2 or more layers thick • Outer layer is where cells meet – gluey substance – pectin • Primary cell wall is next – made of cellulose
Nucleus • large dark structure • Not all cells have a nucleus • Eukaryotes • Prokaryotes • Information center and holds DNA (genetic code) • Chromosomes – DNA and Proteins – Genetic code
Nucleolus • Inside Nucleus • Made of RNA • Makes Ribosomes • Ribosomes are the site of protein synthesis
Cytoplasm • Jelly like substance • Holds organelles • Most reactions happen here
Mitochondria • Powerhouse of the cell • Break down sugars for energy • Convert ADP to ATP • 2 Membranes • Outer surrounds mitochondria • Inner increases surface area – more efficient
Chloroplast • Only in plant cells • Have Chlorophyll • Convert Sun energy into chemical energy
Ribosome • Composed of RNA and protein • some attached to membranes, some free • smallest organelles ·25 nanometers (1 billionth of a meter)
Endoplasmic Reticulum • Network of channels – ER • Transports materials through the inside of the cell • Smooth and rough ER – Rough has Ribosomes all around it • Synthesised proteins are moved to Golgi Apparatus for modification
Golgi Apparatus ·Golgi for Italian scientist Camillo Golgi • Looks like flattened stack of pancakes • Modifies, collects, packages, and distributes proteins
Lysosomes – The Cleanup Crew • Lysosomes help digest particles – contain enzymes and chemicals necessary for digestion • Break down organelles that have outlived their usefulness • Formed by Golgi Apparatus • Only in Animal Cells
CELL • The basic unit of structure & function in living organisms
Anton Van Leeuwenhoek 1632-1723 Was a merchant that ground up glass to make lenses • Invented microscope • Made over 500 in his lifetime • 1st person to examine bacteria
Robert Hooke • 1635-1702 • Used Van Leeuwenhoek’s microscopes • Named cells after looking at cork
Robert Brown • 1773-1858 • Discovered the nucleus in plant cells (1833)
Matthias Schleiden • 1804-1881 • Discovered all plants are made up of cells (1838)
Theodor Schwann • 1810-1882 • Discovered that all animals are made up of cells(1839)
Rudolph Virchow • 1821-1902 • Proposed that all cells come from pre-existing cells (1855)
The Cell Theory The cell theory states: • All living things are composed of cells B. Cells are the basic units of structure & function in living things C. All cells come from preexisting cells
Lynn Margoulis • Proposed that certain organelles were once free-living organisms themselves (1970)
Movement of Materials Through the Cell Membrane • Cells are in a liquid environment • Why is this important? • Easier for materials to get into and out of the cells
Passive Transport • Requires no energy • Occurs due to natural concentration gradient • Molecules move from high concentration to low concentration (DOWN the gradient) 3 Types • Diffusion • Osmosis • Faciliated Diffusion
Diffusion: • Can’t have cell membrane too effective • How would materials get into or out of the cell? • What materials would we want to get into or out of the cell? • Oxygen, Carbon Dioxide, Food, Wastes • Molecules are constantly moving. They spread out as volume permits
Diffusion: • Diffusion – the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration
Selectively Permeable: • Molecules can pass through a solid if it contains spaces large enough • Window screen can keep out flies, but lets air in and out it acts as a barrier • If only certain substances can pass through, but not others, it is said to be selectively permeable
Selectively Permeable: • Substances present in unequal amounts on either side • Each substance moves toward area of lower concentration • Equilibrium – when concentration is equal throughout, or on both sides of the membrane
Equilibrium: • Does equilibrium mean the molecules stoped moving? • NO!
Osmosis: • Molecules that can dissolve in the lipid bilayer of the cell membrane can pass through easily. Most other molecules do not. • Water does • The diffusion of water molecules through a selectively permeable membrane is called osmosis
Osmosis: • What happens to raisins if you soak them in water overnight? • Moves water from more dilute to more concentrated side • Osmotic pressure – can be serious for cell – can rupture cell