Presentation on theme: "Cells The smallest unit of life. Which of these is the smallest object? 1.Human cell 2.Protein molecule 3.Virus 4.Bacteria 5.Amino acid."— Presentation transcript:
Cells The smallest unit of life
Which of these is the smallest object? 1.Human cell 2.Protein molecule 3.Virus 4.Bacteria 5.Amino acid
Prokaryotic organisms lack a nucleus in their cells. Which of these organisms is prokaryotic? 1.Plants 2.Fungi 3.Protists (such as Amoeba and Paramecium) 4.Bacteria
Which of these objects can be seen with the aid of an ordinary student microscope? 1.Human cell 2.Virus 3.Protein molecule 4.Oxygen atom
Which of these is made up of cells? 1.Animals 2.Plants 3.Fungi 4.Bacteria 5.Only animals and plants 6.All of these
Discovering the Cell Robert Hooke
Anton van Leeuwenhoek - late 17th, early 18th centuries
1839 – Cell Theory is proposed independently by Theodore Schwann and Matthias Jakob Schleiden.
Cell Theory: The cell is the fundamental structure of all living things. All living things are made of cells. Cells arise from pre-existing cells through cell division.
Light micrograph Scanning electron micrograph Paramecium
Cell Membrane Transmission electron micrograph Scanning electron micrograph
Which of these can be seen with an electron microscope but not a light microscope? 1.Human cells 2.Bacteria 3.Protein molecules 4.Amino acids
Discuss and write down your ideas: How did the invention of the microscope change the human view of the world? How did the invention of the electron microscope change our understanding of cells? WORKTOGETHERWORKTOGETHER
Prokaryotic Features No membrane-bound organelles, such as a nucleus. DNA in one large ring-shaped chromosome An enormous variety of metabolic pathways. Highly successful and adaptable.
True or False: A virus is a kind of bacteria. 1.True 2.False
Viruses A virus is usually not considered living. A virus consists only of a protein coat (sometimes with a lipid outer layer) and a piece of genetic material (DNA or RNA).
Bacteria vs. Virus FeaturesBacteriaVirus Reproduces independently? Has genetic material? Has cell membrane? Has metabolism? Living? YesNo Yes No Yes
Which of these does a bacteria NOT have? 1.DNA 2.Cell membrane 3.Nucleus 4.Bacteria have none of these.
Eukaryotic Features Cells contain membrane-bound organelles. Nucleus holds multiple strands of DNA, which condense into chromosomes during cell division. May be single-celled or multi-cellular organisms.
Leucoplasts and other plastids starch globules 0.5 micrometer plastid
What do chloroplasts do? 1.Make energy 2.Use energy to make molecules. 3.Break sugar down to release energy.
Chloroplasts carry out photosynthesis to make sugars and other monomers. What does the plant use these monomers for? WORKTOGETHERWORKTOGETHER
One-celled Eukaryotic organisms have unique challenges. A Paramecium must: ingest food excrete waste sense and respond to the environment
(a) Cilium (b) Flagellum propulsion of fluid return strokepower stroke plasma membrane direction of locomotionpropulsion of fluid continuous propulsion
cilium Paramecium 0.1 micrometer protein "arms" central pair of microtubules section of cilium (transmission EM) basal body plasma membrane
contractile vacuole full reservoir contracted reservoir
pore collecting ducts central reservoir Reservoir contracts, expelling water through pore. Water enters collecting ducts, fills central reservoir.
In a one-celled organism, which organelle is most like: A stomach (assists with digestion)? A kidney (removes excess water)? WORKTOGETHERWORKTOGETHER
Recap Prokaryotic cells have no membrane- bound organelles. Eukaryotic cells have membrane-bound organelles, which compartmentalize processes for better efficiency. ALL cells have a cell membrane and DNA.