Ch. 3 CELLS AND TISSUES. Copyright 2010 Pearson Education, Inc.

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1 Ch. 3 CELLS AND TISSUES

2 Generalized Cell All cells: Human cells have three basic parts: Plasma membrane flexible outer boundary Cytoplasm intracellular fluid containing organelles Nucleus control center

3 Chromatin Nucleolus Smooth endoplasmic reticulum Mitochondrion Cytosol Lysosome Centrioles Centrosome matrix Cytoskeletal elements Microtubule Intermediate filaments Peroxisome Nuclear envelope Nucleus Plasma membrane Rough endoplasmic reticulum Ribosomes Golgi apparatus Secretion being released from cell by exocytosis Figure 3.2

4 Plasma Membrane The plasma membrane separates the intracellular fluid (ICF) from extracellular fluid (ECF) The plasma membrane is semi-permeable which means that some things can cross the membrane and some things cannot

5 Extracellular fluid Intracellular fluid Figure 3.3

6 Types of Membrane Transport A concentration gradient is: Passive Transport No cellular energy (ATP) required Substance moves down its concentration gradient Active Transport Energy (ATP) required Substances are moved or pumped against their gradient

7 Passive Transport What determines whether or not a substance can passively cross the plasma membrane? 1. Is the substance a lipid (Lipid solubility of substance) 2. Size of substance passing

8 Three Types of Passive Transport Across Cellular membranes Simple diffusion Facilitated diffusion Osmosis

9 Passive Transport: Simple Diffusion What types of substances use simple diffusion to cross the plasma membrane? Small, nonpolar, hydrophobic substances diffuse directly through phospholipid bilayer (O 2, CO 2 )

10 Extracellular fluid Lipidsoluble solutes Cytoplasm Figure 3.7a

11 Passive Transport: Facilitated Diffusion What types of substances use facilitated diffusion to cross the plasma membrane? Larger, hydrophilic molecules (glucose, amino acids) Can pass through carriers or channels

12 A Carrier Protein Hydrophilic molecules Figure 3.7b

13 Passive Transport: Osmosis Movement of solvent (water) across a selectively permeable membrane from where it is most concentrated to where it is less concentrated Water diffuses through plasma membranes: mainly through channels

14 A Channel Protein Water molecules Lipid billayer Aquaporin Figure 3.7d

15 (a) Membrane permeable to both solutes and water Solute and water molecules move down their concentration gradients in opposite directions. Both solutions have the same osmolarity: volume unchanged H 2 O Solute Membrane Solute (sugar) Figure 3.8a

16 (b) Membrane permeable to water, impermeable to solutes Solute molecules are prevented from moving but water moves by osmosis. Volume increases in the compartment with the higher osmolarity. Left compartment Right compartment Both solutions have identical osmolarity, increases on the right because only water is free to move H 2 O Membrane Solute (sugar) Figure 3.8b

17 Importance of Osmosis When osmosis occurs, water enters or leaves a cell A change in cell volume disrupts cell function

18 Tonicity Defined as: The ability of a solution to cause a cell to shrink or swell Isotonic: A solution that does not cause a change in cell volume Hypertonic: A solution that causes a cell to shrink Hypotonic: A solution that causes a cell to swell.

19 (a) Isotonic solutions (b) Hypertonic solutions (c) Hypotonic solutions Figure 3.9

20 Active Transport Defined as: The Sodium-potassium pump (Na + -K + ATPase) is a specific example of active transport Located in all plasma membranes Maintains electrochemical gradients essential for muscle and nerve functions

21 Other Cellular Organelles Membranous structures Nucleus with chromatin- Mitochondria Endoplasmic Reticulum (ER) (rough and smooth) Golgi Apparatus- Lysosomes-

22 Smooth ER Nucleus Nuclear envelope Vesicle Plasma membrane Lysosome Rough ER Golgi apparatus Transport vesicle

23 Smooth ER Nuclear envelope Rough ER Ribosomes

24 Rough ER ER Phagosome membrane Plasma membrane Vesicle becomes lysosome Golgi apparatus Secretory vesicle Secretion by exocytosis Extracellular fluid

25 Mitochondria Organelle with shelflike folds called cristae Provide most of cell s ATP (enzymes for this process are located on cristae)

26 Other Organelles Non-Membranous structures Centrioles- involved in cell division Cytoskeleton- protein filaments that help maintain cell shape, cell movement and in cell division (microtubules)

27 Centrosome matrix Centrioles (a) Microtubules

28 Extensions of the plasma membrane Cilia are: short, hairlike structures; move substances across cell surfaces Flagella are: Whiplike, tails that move the entire cell Microvilli are: fingerlike extensions found on absorptive cells

29 Microvillus Actin filaments Terminal web

30 The Cell Cycle Includes: Interphase Period from cell formation to cell division Three sub phases of Interphase: G 1 (gap 1) growth and metabolism S (synthetic) DNA replication G 2 (gap 2) preparation for division Cell division (mitotic phase or mitosis) Consists of four sub phases of mitosis (PMAT) and cytokinesis

31 Mitosis (Cell Division) Purpose: Does not occur in:

32 G 1 Growth S Growth and DNA synthesis G 2 Growth and final preparations for division M

33 During the S-phase of Interphase DNA is Replicated Helicase untwists the double helix and exposes complementary chains Each nucleotide strand serves as a template for building a new complementary strand DNA polymerase forms new DNA strand

34 DNA Replication End result: two DNA molecules formed from the original This process is called semiconservative replication After DNA has been replicated the cell progresses into mitosis and cytokinesis

35 Chromosome Free nucleotides DNA polymerase Template for synthesis of new strand Leading strand Old DNA Helicase unwinds the double helix and Exposes bases Adenine Thymine Cytosine Guanine Replication fork Lleading and lagging strands are synthesized in opposite directions Lagging strand DNA polymerase Old (template) strand

36 Mitosis and Cytokinesis Mitosis four stages of nuclear division: Prophase- Metaphase- Anaphase- Telophase- Cytokinesis division of cytoplasm by cleavage furrow

37 G 1 Growth S Growth and DNA synthesis G 2 Growth M

38 Early Prophase Early mitotic spindle Aster Early Prophase Chromosome consisting of two sister chromatids Centromere

39 Late Prophase Microtubule Fragments of nuclear envelope Late Prophase Microtubule

40 Metaphase Spindle Metaphase Metaphase plate

41 Anaphase Anaphase Daughter chromosomes

42 Cytokinesis Begins during late anaphase Ring of actin microfilaments contracts to form a cleavage furrow Two daughter cells are pinched apart, each containing a nucleus identical to the original

43 Telophase and Cytokinesis Nuclear envelope forming Nucleolus forming Contractile ring at cleavage furrow Telophase