1. n Chapter 6 A Tour of the Cell

2. Cell Theory n 1. Cells are the smallest structures that perform the processes essential to life, including food consumption, waste production, and the creation of new cells through reproduction. n 2. All cells arise from the division of existing cells. n 3. Every organism is made up of one or more cells.

3. Cell size n Cell size is limited by metabolic requirements n Organisms must exchange matter with the environment to grow, reproduce and maintain organization. n Surface area-to-volume ratios affect a biological system’s ability to obtain necessary resources or eliminate waste products. – As cells ↑ in volume, the relative surface area ↓ and demand for material resources ↑; more cellular structures are necessary to adequately exchange materials and energy with the environment. These limitations restrict cell size. – The surface area of the plasma membrane must be large enough to adequately exchange materials; smaller cells have a more favorable surface area- to-volume ratio for exchange of materials with the environment. n Ex. root hairs, cells of the alveoli, cells of the villi, microvilli Volume of a Sphere V = 4/3 π r3 Volume of a Cube (or Square Column) V = l w h Volume of a Column V = π r2 h Surface Area of a Sphere A = 4 π r2 Surface Area of a Cube A = 6 a Surface Area of a Rectangular Solid A = Σ (surface area of each side)

4. Prokaryotic Cells n Bacteria; Archaea n Always unicellular n Small - < 5 µm n Nucleoid (region): DNA (circular) concentration – Have plasmids – small circles of DNA separate from the main strand n No organelles with membranes n No cytoskeleton n Ribosomes: protein synthesis (all cells) n Plasma membrane (all cells); semi-permeable n Cytoplasm/cytosol (all cells)

5. Eukaryotic Cells Nucleus n Genetic material... – Chromatin – threadlike DNA – Chromosomes – condensed DNA – Nucleolus: ribosome (rRNA) synthesis n Nuclear envelope - double membrane with nuclear pores n Protein synthesis (mRNA) – instructions copied here and sent out

6. Ribosomes n Smallest, most numerous organelles n Have no membranes n Protein manufacture n Free – found in cytosol; produce proteins that function in cell n Bound – attached to endoplasmic reticulum; produce proteins that are exported

7. Endomembrane system, I n Endoplasmic reticulum (ER) n Network of membranes/sacs - cisternae n Continuous with nuclear envelope n Smooth ER – No ribosomes – Synthesis of lipids – Detoxifies drugs and poisons in liver n Rough ER – With ribosomes – Synthesis of secretory proteins (glycoproteins), membrane production – sent out by transport vesicles to golgi apparatus

8. Endomembrane system, II n Golgi apparatus – ER products are modified, stored, and then shipped – Cisternae: flattened membranous sacs – trans face (shipping) & cis face (receiving) – Receives transport vesicles from ER; sends transport vesicles to function site

9. Endomembrane system, III n Lysosomes – Animal cells – Sac of hydrolytic enzymes; digestion of macromolecules – Phagocytosis – Autophagy: recycle cell’s own organic material – Tay-Sachs disease~ lipid-digestion disorder – Aka “the suicide bag” – older lysosomes’ membranes break and digest its own cell

10. Endomembrane system, IV n Vacuoles – Plant cells – Membrane-bound sacs (larger than vesicles) – Food (phagocytosis) – Contractile (pump excess water) – Central (storage in plants) n Tonoplast membrane – around vacuole n May be 80% of cell