BIOL164Ch3,19,21NotesWin12

BIOL164Ch3,19,21NotesWin12 - Ch. 3 The Cell The cell theory...

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1 Ch. 3 – The Cell • The cell theory states that: – 1. Living organisms are composed of one or more cells – 2. Cells arise from the division of pre-existing cells – 3. Cells are the smallest units of life (that perform all vital physiological functions) There are over 200 types of cells in the body, and each type has a specific structure and function(s)! Why are cells so small? • They need a large surface area (supply) to volume (demand) ratio Figure 3.3
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2 A “general- ized” animal cell Note : not all cells will look exactly like this or contain all of the organelles shown here Figure 3.2b •= a phospholipid bilayer with embedded proteins, and some other lipids and carbohydrates • Is referred to as a “fluid mosaic” The cell membrane (plasma membrane) Figure 3.6
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3 The structure of the cell membrane • It’s a mixture of lipids and proteins… • Lipids : Phospholipids • Their tails are hydrophobic (“water-fearing”) • Their heads are hydrophilic (“water-loving”) Cholesterol (a steroid) helps maintain the consistency of membrane fluidity • Proteins of many types (see the next slide) Figure 3.6 Membrane proteins • Membrane proteins may function as : – Cell-to-cell anchors – Recognition proteins – Enzymes – Receptors – Carriers (transporters) – Channels (pores) Figure 3.6
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4 • The cell membrane : – Maintains the structural integrity of the cell – Regulates the movement of substances into and out of the cell • I.e., the membrane is selectively permeable – Allows recognition between cells and recognition of the body’s own “self” cells vs. foreign/“non-self” cells – Allows communication between cells (via receptors) – Catalyzes chemical reactions (via enzymes) – Binds cells together (via anchoring proteins) Functions of the cell membrane Permeability and membranes Permeability refers to the ease with which substances (particles) can cross the cell membrane – Nothing can pass through an impermeable membrane – Anything can pass through a freely permeable membrane – Our cell membranes are selectively permeable (sometimes called “semipermeable”) • Permeability is affected by the : – Particle solubility in lipid – Particle size vs. the protein channel (pore) size – Particle electric charge vs. the local membrane charge and/or channel charge – Presence of specific protein carriers (transporters) for the particle – Temperature
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5 Membrane transport processes Passive processes : do not use ATP energy – The energy for transport is provided by constant random molecular motion (due to the heat energy present) – Particles move from a higher to lower concentration (i.e.
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BIOL164Ch3,19,21NotesWin12 - Ch. 3 The Cell The cell theory...

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