1. PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 3 Cells: The Living Units: Part A

2. Copyright © 2010 Pearson Education, Inc. Cell Theory The cell is the smallest structural and functional living unit Organismal functions depend on individual and collective cell functions Biochemical activities of cells are dictated by their specific subcellular structures Continuity of life has a cellular basis

3. Copyright © 2010 Pearson Education, Inc. Cell Diversity Over 200 different types of human cells Types differ in size, shape, subcellular components, and functions

4. Copyright © 2010 Pearson Education, Inc. Fibroblasts Erythrocytes Epithelial cells (d) Cell that fights disease Nerve cell Fat cell Sperm (a) Cells that connect body parts, form linings, or transport gases (c) Cell that stores nutrients (b) Cells that move organs and body parts (e) Cell that gathers information and control body functions (f) Cell of reproduction Skeletal Muscle cell Smooth muscle cells Macrophage Figure 3.1

5. Copyright © 2010 Pearson Education, Inc. Generalized Cell All cells have some common structures and functions Human cells have three basic parts: Plasma membrane—flexible outer boundary Cytoplasm—intracellular fluid containing organelles Nucleus—control center

6. Copyright © 2010 Pearson Education, Inc. Figure 3.2 Secretion being released from cell by exocytosis Peroxisome Ribosomes Rough endoplasmic reticulum Nucleus Nuclear envelope Chromatin Golgi apparatus Nucleolus Smooth endoplasmic reticulum Cytosol Lysosome Mitochondrion Centrioles Centrosome matrix Cytoskeletal elements Microtubule Intermediate filaments Plasma membrane

7. Copyright © 2010 Pearson Education, Inc. Plasma Membrane Bimolecular layer of lipids and proteins in a constantly changing fluid mosaic Plays a dynamic role in cellular activity Separates intracellular fluid (ICF) from extracellular fluid (ECF) Interstitial fluid (IF) = ECF that surrounds cells

8. Copyright © 2010 Pearson Education, Inc. Figure 3.3 Integral proteins Extracellular fluid (watery environment) Cytoplasm (watery environment) Polar head of phospholipid molecule Glycolipid Cholesterol Peripheral proteins Bimolecular lipid layer containing proteins Inward-facing layer of phospholipids Outward- facing layer of phospholipids Carbohydrate of glycocalyx Glycoprotein Filament of cytoskeleton Nonpolar tail of phospholipid molecule

9. Copyright © 2010 Pearson Education, Inc. Membrane Lipids 75% phospholipids (lipid bilayer) Phosphate heads: polar and hydrophilic Fatty acid tails: nonpolar and hydrophobic (Review Fig. 2.16b) 5% glycolipids Lipids with polar sugar groups on outer membrane surface 20% cholesterol Increases membrane stability and fluidity

10. Copyright © 2010 Pearson Education, Inc. Lipid Rafts ~ 20% of the outer membrane surface Contain phospholipids, sphingolipids, and cholesterol May function as stable platforms for cell- signaling molecules

11. Copyright © 2010 Pearson Education, Inc. Membrane Proteins Integral proteins Firmly inserted into the membrane (most are transmembrane) Functions: Transport proteins (channels and carriers), enzymes, or receptors Animation: Transport Proteins PLAY

12. Copyright © 2010 Pearson Education, Inc. Membrane Proteins Peripheral proteins Loosely attached to integral proteins Include filaments on intracellular surface and glycoproteins on extracellular surface Functions: Enzymes, motor proteins, cell-to-cell links, provide support on intracellular surface, and form part of glycocalyx Animation: Structural Proteins PLAY Animation: Receptor Proteins PLAY

13. Copyright © 2010 Pearson Education, Inc. Figure 3.3 Integral proteins Extracellular fluid (watery environment) Cytoplasm (watery environment) Polar head of phospholipid molecule Glycolipid Cholesterol Peripheral proteins Bimolecular lipid layer containing proteins Inward-facing layer of phospholipids Outward- facing layer of phospholipids Carbohydrate of glycocalyx Glycoprotein Filament of cytoskeleton Nonpolar tail of phospholipid molecule

14. Copyright © 2010 Pearson Education, Inc. Functions of Membrane Proteins 1.Transport 2.Receptors for signal transduction 3.Attachment to cytoskeleton and extracellular matrix

15. Copyright © 2010 Pearson Education, Inc. Figure 3.4a A protein (left) that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute. Some transport proteins (right) hydrolyze ATP as an energy source to actively pump substances across the membrane. (a) Transport

16. Copyright © 2010 Pearson Education, Inc. Figure 3.4b A membrane protein exposed to the outside of the cell may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The external signal may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell. (b) Receptors for signal transduction Signal Receptor

17. Copyright © 2010 Pearson Education, Inc. Figure 3.4c Elements of the cytoskeleton (cell’s internal supports) and the extracellular matrix (fibers and other substances outside the cell) may be anchored to membrane proteins, which help maintain cell shape and fix the location of certain membrane proteins. Others play a role in cell movement or bind adjacent cells together. (c) Attachment to the cytoskeleton and extracellular matrix (ECM)

18. Copyright © 2010 Pearson Education, Inc. Functions of Membrane Proteins 4.Enzymatic activity 5.Intercellular joining 6.Cell-cell recognition

19. Copyright © 2010 Pearson Education, Inc. Figure 3.4d A protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution. In some cases, several enzymes in a membrane act as a team that catalyzes sequential steps of a metabolic pathway as indicated (left to right) here. (d) Enzymatic activity Enzymes

20. Copyright © 2010 Pearson Education, Inc. Figure 3.4e Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions. Some membrane proteins (CAMs) of this group provide temporary binding sites that guide cell migration and other cell-to-cell interactions. CAMs (e) Intercellular joining

21. Copyright © 2010 Pearson Education, Inc. Figure 3.4f Some glycoproteins (proteins bonded to short chains of sugars) serve as identification tags that are specifically recognized by other cells. (f) Cell-cell recognition Glycoprotein