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
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
Copyright © 2010 Pearson Education, Inc. Cell Diversity Over 200 different types of human cells Types differ in size, shape, subcellular components, and functions
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
Copyright © 2010 Pearson Education, Inc. Generalized Cell All cells have some common structures and functions. Refer to table 3.1 Structures in Human Cells (textbook p 40)
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
Copyright © 2010 Pearson Education, Inc. Plasma Membrane Separates the inside of the cell (cytoplasm) from the outside. Phospholipid bilayer Polar heads-hydrophilic (face outward) Non polar tails-hydrophobic (face inward)
Copyright © 2010 Pearson Education, Inc. Plasma Membrane Contains the following: Cholesterol molecules-stabilize the membrane Glycoproteins- short chains of sugars attached to a protein molecule. Glycolipids- short chains of sugars attached to a lipid molecule. Markers, characteristics (blood type), hormone
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
Copyright © 2010 Pearson Education, Inc. Functions of Membrane Proteins 1.Transport 2.Receptors for signal transduction 3.Attachment to cytoskeleton and extracellular matrix
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
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
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)
Copyright © 2010 Pearson Education, Inc. Functions of Membrane Proteins 4.Enzymatic activity 5.Intercellular joining 6.Cell-cell recognition
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
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 provide temporary binding sites that guide cell migration and other cell-to-cell interactions. Proteins (e) Intercellular joining
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
Copyright © 2010 Pearson Education, Inc. Membrane Transport Plasma membranes are selectively permeable Some molecules easily pass through the membrane; others do not
Copyright © 2010 Pearson Education, Inc. Types of Membrane Transport Passive processes No cellular energy (ATP) required Substance moves down its concentration gradient. (moves from high concentration to low concentration) Example- simple diffusion, osmosis
Copyright © 2010 Pearson Education, Inc. Types of membrane transport Active processes Energy (ATP) required Occurs only in living cell membranes Substance moves against its concentration gradient. (moves from low concentration to high concentration) PLAY Animation: Membrane Permeability
Copyright © 2010 Pearson Education, Inc. Active Processes Example- Active transport- requires a protein plus ATP; ions, sugars Endocytosis- Into the cell Phagocytosis- “cell eating”- bacterial cells, viruses, cell debris Pinocytosis- “ cell drinking- breast milk absorption in infants.
Copyright © 2010 Pearson Education, Inc. Passive Processes: Simple Diffusion Exocytosis- Out of the cell- hormones, chemicals PLAY Animation: Diffusion
Copyright © 2010 Pearson Education, Inc. Figure 3.7a Extracellular fluid Lipid- soluble solutes Cytoplasm (a) Simple diffusion of fat-soluble molecules directly through the phospholipid bilayer
Copyright © 2010 Pearson Education, Inc. Figure 3.7b Lipid-insoluble solutes (such as sugars or amino acids) (b) Carrier-mediated facilitated diffusion via a protein carrier specific for one chemical; binding of substrate causes shape change in transport protein
Copyright © 2010 Pearson Education, Inc. Facilitated Diffusion Using Channel Proteins Aqueous channels formed by transmembrane proteins selectively transport ions or water Two types: Leakage channels Always open Gated channels Controlled by chemical or electrical signals
Copyright © 2010 Pearson Education, Inc. Figure 3.7c Small lipid- insoluble solutes (c) Channel-mediated facilitated diffusion through a channel protein; mostly ions selected on basis of size and charge
Copyright © 2010 Pearson Education, Inc. Passive Processes: Osmosis Movement of solvent (water) across a selectively permeable membrane Water diffuses through plasma membranes:
Copyright © 2010 Pearson Education, Inc. Figure 3.7d Water molecules Lipid billayer Aquaporin (d) Osmosis, diffusion of a solvent such as water through a specific channel protein (aquaporin) or through the lipid bilayer
Copyright © 2010 Pearson Education, Inc. Figure 3.8a (a) Membrane permeable to both solutes and water Solute and water molecules move down their concentration gradients in opposite directions. Fluid volume remains the same in both compartments. Left compartment: Solution with lower osmolarity Right compartment: Solution with greater osmolarity Membrane H2OH2O Solute molecules (sugar) Both solutions have the same osmolarity: volume unchanged
Copyright © 2010 Pearson Education, Inc. Figure 3.8b (b) Membrane permeable to water, impermeable to solutes Both solutions have identical osmolarity, but volume of the solution on the right is greater because only water is free to move Solute molecules are prevented from moving but water moves by osmosis. Volume increases in the compartment with the higher osmolarity. Left compartment Right compartment Membrane Solute molecules (sugar) H2OH2O
Copyright © 2010 Pearson Education, Inc. Importance of Osmosis When osmosis occurs, water enters or leaves a cell Change in cell volume disrupts cell function PLAY Animation: Osmosis
Copyright © 2010 Pearson Education, Inc. Tonicity Tonicity: The ability of a solution to cause a cell to shrink or swell Isotonic: A solution with the same solute concentration as that of the cytosol Hypertonic: A solution having greater solute concentration than that of the cytosol Hypotonic: A solution having lesser solute concentration than that of the cytosol
Copyright © 2010 Pearson Education, Inc. Figure 3.9 Cells retain their normal size and shape in isotonic solutions (same solute/water concentration as inside cells; water moves in and out). Cells lose water by osmosis and shrink in a hypertonic solution (contains a higher concentration of solutes than are present inside the cells). (a) Isotonic solutions (b) Hypertonic solutions (c) Hypotonic solutions Cells take on water by osmosis until they become bloated and burst (lyse) in a hypotonic solution (contains a lower concentration of solutes than are present in cells).
Copyright © 2010 Pearson Education, Inc. Summary of Passive Processes Also see Table 3.1 ProcessEnergy Source Example Simple diffusion Kinetic energy Movement of O 2 through phospholipid bilayer Facilitated diffusion Kinetic energy Movement of glucose into cells OsmosisKinetic energy Movement of H 2 O through phospholipid bilayer or
Copyright © 2010 Pearson Education, Inc. Cell Cycle The cell cycle has two major portions: 1.Interphase 2.Mitotic stage
Copyright © 2010 Pearson Education, Inc. Interphase Period from cell formation to cell division Nuclear material= chromatin 3 subphases: G 1 (gap 1)—vigorous growth and metabolism S (synthetic)—DNA replication G 2 (gap 2)—preparation for division
Copyright © 2010 Pearson Education, Inc. Figure 3.31 G 1 Growth S Growth and DNA synthesis G 2 Growth and final preparations for division M G 2 checkpoint G 1 checkpoint (restriction point)
Copyright © 2010 Pearson Education, Inc. Mitosis 1.Mitosis—four stages of nuclear division: Prophase Metaphase Anaphase Telophase 2.Cytokinesis—division of cytoplasm by cleavage furrow