CELLS The Fundamental Units of Life

Cell Theory 1.All organisms are composed of 1 or more cells. 2.The cell is the basic living unit, providing organization for all organisms. 3.All cells arise from preexisting cells.

Cells Are Small Most are too small to be seen with the unaided eye…so Microscopes are used. A Light Microscope uses visible light shone through glass lenses. A “thin section” of specimen is required. van Leeuwenhoek

Principles of Microscopy LIGHT REFRACTION MAGNIFICATION RESOLUTION

MAGNIFICATION Image size exceeds real size. Achieved with convex lenses. There are limits… …involving the nature of light. First, you need enough light to penetrate the thin specimen.

RESOLUTION Next, you need light of appropriate wavelength…or RESOLUTION is compromised. A measure of clarity – of focus. Minimum distance between two points that allow the points to be distinguishable. Light microscopy not very useful below 0.2um.

RESOLUTION

Electron Microscopy Uses e - rather than light. Electrons have a much shorter wavelength. SEM = Scanning Electron Microscopy TEM = Transmission Electron Microscopy

Electron Microscopy

Cells!

ALL CELLS Plasma Membrane (Cell Membrane) –Separate the contents of the cell from the environment. Cytoplasm (Cytosol) –Semi-fluid contents of the cell –Lots of “floaties” Nucleus “area” –Location of DNA

CELLS Eukaryotic Cells (animals, plants, fungi, protists) –Complex & relatively large. –Membrane-bound nucleus & organelles. –80-S Ribosomes. Prokaryotic Cells (archaea, bacteria) –Simple & relatively small. –NO Membrane-bound nucleus & organelles. –70-S Ribosomes.

Prokaryote vs Eukaryote

CELLS PROKARYOTIC EUKARYOTIC

EUKARYOTIC CELLS Organelles = “little organs” (not really) Membrane-bound

ORGANELLES Nucleus –Isolates the DNA & provides access to its hereditary information. –The “control center” of the cell (Transcription).

Nucleus 1.Nuclear Envelope (a double membrane) with Pores. 2.Nucleolus rRNA Proteins Ribosomes 3.Nucleoplasm with Chromatin/Chromosomes.

Ribosomes Not true organelles, more “structures”. Protein factories. 2 sub-units. Free (in cytoplasm), more for intracellular activities. Bound (on E.R.), often for extracellular activities (secretion) & packaging within certain organelles.

Endomembrane System Synthesis of Proteins & their transport into membranes and/or organelles. Packaging of Proteins for transport out of the cell (secretion) or to other areas of the cell. Modification of Proteins. Transport of lipids, lipoproteins, glycoproteins, etc.

Endomembrane System 1.Endoplasmic Reticulum (E.R.) –Rough E.R. –Smooth E.R. 2.Golgi Apparatus 3.Vesicles –Lysosomes (also, nuclear envelope, vacuoles, and plasma membrane)

Endoplasmic Reticulum Network of interconnected membranes (continuous with the nuclear envelope). Flattened or tubular Cisternae.

Rough E.R. The site of protein synthesis, particularly secretory proteins. Initial modification of proteins. –Especially, formation of Glycoproteins. Formation (budding) of Transport Vesicles. Formation of NEW Membrane = Phospholipid Synthesis

Smooth E.R. Modification of Proteins. Formation of Lipids, detoxification. –Lipid-derived hormones (steroids) are synthesized, including sex hormones (testosterone, etc.) in certain glands. –Solubilization of toxins (drugs, alcohol, caffeine, etc. ) in liver cells.

Golgi Apparatus Modification, storage, sorting, & shipping of ER- produced molecules (esp. for secretion). Addition of non-protein portions to protein molecules.

Golgi Apparatus Stacks of cisternae, with cis & trans faces. –Cis – receiving (takes in vesicles). –Trans – sending (gives rise to vesicles).

Lysosomes Specific vesicles carrying digestive enzymes – hydrolytic (proteolytic) enzymes. Animal Cells. Digestion of food brought in by phagocytosis.

Lysosomes Digestion and recycling of old & damaged organelles within the cell: Autophagy.

Endomembrane System

Vacuoles Large vesicles with particular functions. –Food Vacuoles. –Contractile Vacuoles. –Central Vacuole w/ tonoplast in Plant Cells. Storage. Dissolved Solutes. Dumping Ground. Protection. Shape.

Mitochondrion Surrounded by a double membrane – an envelope. Outer Membrane Inner membrane (Cristae) Matrix

Mitochondrion Site of cellular respiration = energy production. Carbohydrates ATP Not part of endomembrane system. Have their own DNA, RNA, Proteins, and Ribosomes (70-S). Grow and reproduce independently. Animals, Plants, Fungi, Protists.

Chloroplast Surrounded by a double membrane – an envelope. Inner Membrane (Grana composed of stacked Thylakoids) Stroma Outer Membrane

Chloroplast Site of Photosynthesis = acquisition of chemical energy from sunlight. Sunlight + CO 2 Carbohydrates A plastid (not part of endomembrane system). Have their own DNA, RNA, Proteins, and Ribosomes (70-S). Grow and reproduce independently. Plants, Protists.

Cytoskeleton Fiber-like structures that lend organization. Support (providing a scaffolding onto which organelles & vesicles can be organized). Shape (maintain particular shape depending on the cell’s location and/or function). Transport of materials around or out of the cell. Motility of the whole cell from one location to another.

Cytoskeleton Microtubules Microfilaments Intermediate Filaments Keratin Subunits Tubulin Actin Keratin

Cytoskeleton Permanent –Flagella –Cilia –Muscle Contraction –Scaffolding & Shape Maintenance

Cytoskeleton Transient –Spindle Fibers –Transport filaments

Cell Wall OUTSIDE the Cell Membrane (technically, outside the cell!) Various proteins & glycoproteins in Prokaryotes. Cellulose in Plants. Chitin in Fungi.

Eukaryotic Cell

Endosymbiont Theory

Onion Cells

Membranes Phospholipid Bilayer + Proteins