Presentation on theme: "Tour of the Cell Cell theory says: -All living things are made up of cells… And… -Cells come from preexisting cells. “Like begets like” The cell is the."— Presentation transcript:
Tour of the Cell Cell theory says: -All living things are made up of cells… And… -Cells come from preexisting cells. “Like begets like” The cell is the smallest unit of living matter…if you take apart the cell, it is no longer living. Cell size is determined by the cell’s function. Surface to Volume ratio also keeps cells same relative size: Cell must be large enough to perform the duties important to the organism such as metabolism and protein making. Cells that are too large cannot export waste quickly enough and will eventually poison themselves. Eosinophils are important in combatting parasitic diseases
Microscopes are important “tool” for scientists to view cells. Microscopes provide both: MAGNIFICATION- an increase in the apparent size of the object. RESOLVING POWER- the ability of the microscope to show two objects as being separate. This is the clarity of the objects. Magnification and resolving power must be balanced to observe the image. When magnification is increased, resolving power is decreased. When resolving power is increased, magnification is decreased. Many kinds of microscopes available. Most common type used in Life Sciences is the LIGHT MICROSCOPE (LM)-visible light passes through the image and then glass lenses enlarge the image and project it into the human eye or a camera.
Light microscope is what you will use in lab and also what the first “scientists” used…with a candle and mirror!! Electron microscopes are not used as much in life science. -use electron beams that reflect off the specimen. -much higher resolving power than light scopes -image must be projected onto screen or photographed -specimens must be placed in a Vacuum for viewing…a space void of all particles including air and water. -not used to view living or functioning organisms Light microscopes very important for viewing living specimens and moving parts.
Two Categories of Cells: Prokaryotic -Domains Bacteria and Archaea -small cells -first ones appeared over 3.5 billion years ago -lack internal organelles -DNA is coiled in a nucleoid region but is not separated from rest of cell insides. Eukaryotic -Kingdoms Protista, Fungi, Plantae and Anamalia -typical cell is about 10x larger than prokaryote -first ones appeared about 1.7 billion years ago -internal organelles compartmentalize everything -DNA is found in cell nucleus
Comparison of a Prokaryotic Cell and a Eukaryotic Cell
Prokaryotic and Eukaryotic cells share TWO universal parts. Plasma membrane (cell membrane)- -outer layer of cell -keeps cell contents separate from outside contents -is fluid…allows for movement -selectively permeable…only allows certain particles to pass across…water has free passage. -made up of phospholipids found in a bi-layer -bi-layer composition is important for cell shape -insures cell membrane will always “close off” to protect hydrophobic tails of phospholipids
Cytoplasm is second part. -liquid inside of the cell -colorless so it is not visible -allows for movement of things inside the cell Cell membrane is like a bowl and cytoplasm is like soup broth!! Other cell parts might appear in both prokaryotic and eukaryotic cells at different times, but they are not universal. Cell Organelles: Nucleus- -cell “brain” controls all cell activities -DNA is found here -protected from cytoplasm by nuclear membrane which controls entrance into and out of nucleus
Ribosomes- -in both prokaryotic and eukaryotic cells -assemble all proteins for the cell -found “free floating” in cytoplasm or attached to Endoplasmic Reticulum and the “rough ER” Endoplasmic Reticulum- -produce many types of molecules -rough ER has ribosomes on it and produces proteins -smooth ER does not have ribosomes, thus it has a “smooth” appearance many different functions depending on the cell type it is in. In liver cells it detoxifies the blood In muscle cells it stores calcium Golgi Apparatus- -works with other organelles to refine and distribute chemicals made in the cell
Lysosomes -digestive enzyme sacs in cytoplasm -digest worn out and non-functioning cell organelles and sometimes whole cells -important for cleaning up cell “trash” and helping to digest large molecules for the cell to use -digest webbing between toes and fingers of developing fetus -digest tadpole tail -malfunction of lysosomes causes Tay-Sachs disease
Vacuoles- -found in both prokaryotic and eukaryotic cells -storage sacs for things such as water, food, waste, scents, proteins, pigments and poisons Chloroplasts and Mitochondria are important energy organelles for some cells.
Mitochondria- “Power House” -found in both plant and animal cells -important in the respiration process -have a network of cristae inside (Fig. 4.18, p. 65) -cells ATP is manufactured in mitochondria -cells contain different amounts of mitos depending upon their function and energy needs Chloroplast- -found only in photosynthetic organisms (make their own food) -contain green pigment, chlorophyll, which captures light -chlorophyll contained in small sacs called thylakoids, stacked up to form grana (solar power packs) -light eventually becomes sugar and provides energy to plant and other organisms as well “How do we know we are not photosynthetic?” “Why do plants need mitochondria?”
Cell Wall- -found only in photosynthetic organisms and bacteria -provides protection and structure -is “skeletal system” for organisms that lack a skeleton -think about how high a tree grows without a backbone! -don’t forget…most organisms cannot digest the cell wall because it is made up of cellulose!! Cytoskeleton- -made up of fibers in cytoplasm -provide shape to cells that lack a cell wall -help anchor organelles inside the cell
Cilia and Flagella- -outside of cell usually attached to cell membrane or wall -help cells move or move parts -cilia are small and more numerous, like in a paramecium -flagella is usually a single, long tail, like that on a euglena Some cilia can be found lining the nasal and throat passages. Why??
Communication between cells: plant cells use PLASMODESMATA -tiny holes in cell wall between adjoining cells -cell wall is impermeable so need plasmodesmata to transport nutrients, relay messages, allow water to pass in and out, export waste, etc. -cell membrane is semi-permeable so plasmo- desmata only goes through cell wall animal cells use JUNCTIONS -different types perform different functions -communicating junctions similar to plasmodesmata because they allow passage between adjoining cells -tight and anchoring junctions hold cells together to form sheets such as muscle or nerve -Fig. 4.22, pg. 68