Chapter 6 - Chapter 6 The Cell I The cell A All organisms...

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Chapter 6 – The Cell I. The cell A. All organisms are made of cells B. Cells are the simplest form of matter that are living C. Cell structure is correlated to cellular function D. All cells are related by their descent from earlier cells II. Prokaryotic cells A. Nucleoid – Area where hereditary material (DNA) is found B. No nuclear membrane C. DNA is usually circular. Only one double stranded molecule D. No cytosolic compartmentalization by cytoplasmic membranes E. All metabolic activity occurs in the cytoplasm F. Plasmalemma and cell walls are characteristic of prokaryotes II. Eukaryotic cell A. Plasma membrane – has cytosol and phospholipid bilayer that surrounds and defines the cell B. Nucleus 1. Nuclear envelope – double membrane separated by 20-40 nm-encloses nucleus, separating it from the cytoplasm 2. Nuclear pores – 100 nm diameter pores that allow macromolecules out of nucleus 3. Pore complexes – proteins that form the pores 4. Nuclear lamina – on the inner nuclear membrane. Protein filaments that give the nucleus stability and structure 5. Chromosomes - discrete units of hereditary material and associated proteins 6. Chromatin – the complex of DNA and proteins that form chromosomes during cell division 7. Each organism has a set number of chromosomes. Human has 46; 23 in the reproductive cells 8. Nucleolus – a dense mass of rRNA and proteins found in the nucleus 9. DNA – mRNA – ribosomes (rRNA + proteins) and tRNA 10. Plasma membrane-selective barrier 11. Phospholipids-have polar head and nonpolar tails 12.The logistics of carrying out cellular metabolism sets limits on the size of cells 13.The surface area to volume ratio of a cell is critical
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volume increases by a factor of n3 15.Small cells have a greater surface area relative to volume 16.Has internal membranes that partition the cell into organelles C. Ribosomes 1. rRNA and proteins – where mRNA is translated into protein 2. Ribosomes are composed of 2 subunits 3. Two forms a. Free ribosomes – found free in the cytoplasm * Polyribosomes or polysomes – free ribosomes associated with mRNA in the cytoplasm of a cells and appear as a circular string of ribosomes (making proteins for import) b. Bound ribosomes – attached to the endoplasmic reticulum or to the outer nuclear envelope. They usually make proteins for extracellular transport (making proteins for export) Components of the endomembrane system: -Nuclear envelope -Endoplasmic reticulum -Golgi a -Lysosomes -Vacuoles -Plasma membrane Components are either continuous or connected via transfer by vesicles D. Endoplasmic reticulum 1. Extensive network of cytoplasmic membranes 2. Cisternae – term applied to ER tubules and sacs 3. ER has a lumen that is separated from the cytosol 4. ER is continuous with the nuclear membrane 5. Rough ER – RER – has ribosomes
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This note was uploaded on 10/01/2009 for the course BIOL 101 taught by Professor Hall during the Spring '07 term at Texas A&M.

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Chapter 6 - Chapter 6 The Cell I The cell A All organisms...

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