Movement into and out of the Cell And Cell Division Anatomy & Physiology I Movement into and out of the Cell And Cell Division Instructor: Mary Holman

A membrane is permeable to things that can pass through it and A membrane is permeable to things that can pass through it and impermeable to things that can’t. The cell membrane is not completely permeable to anything but does allow some substances to pass through it more easily than others - this property is called selective permeability.

4 ways for molecules to pass through the cell membrane Passive Transport A. Directly through the phospholipid membrane B. Through membrane channels Active Transport A. Via carrier molecules B. Via vesicles

Simple Diffusion Fig. 3.20 Time

Diffusion Across a Permeable Membrane Fig. 3.21 Diffusion Across a Permeable Membrane Permeable membrane Solute molecule Water molecule A B A B A B (1) (2) (3) Time Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Oxygen and carbon dioxide move down the concentration gradient by diffusion Fig. 3.22 High O2 Low O2 High CO2 Low CO2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fig. 3.23 Facilitated Diffusion Fig. 3.23 Region of higher concentration Transported substance Region of lower concentration Protein carrier molecule Cell membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fig. 3.24 Osmosis Fig 3.24 Selectively permeable membrane Protein molecule Water molecule A A B B (1) (2) Time Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

A solution with the same osmotic pressure as physiological conditions Isotonic solution A solution with the same osmotic pressure as physiological conditions Hypertonic A solution with higher than physiological osmotic pressure Hypotonic A solution with lower than physiological osmotic pressure

Rbc in isotonic solution (a) Rbc in hypertonic solution Fig. 3.25 (b) Rbc in hypotonic solution 5,000x (c) © David M. Phillips/Visuals Unlimited Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fig. 3.26 Filtration Filter paper Water and solids Solids Water Gravitational force Water Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Filtration in the Body Capillary wall Tissue fluid Blood pressure Fig. 3.27 Filtration in the Body Capillary wall Tissue fluid Blood pressure Blood flow Larger molecules Smaller molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Active Transport Transport against (up) a concentration gradient Facilitated by a carrier molecule Requires energy Fueled by the breakdown of ATP

Fig. 3.28 Active Transport Carrier protein Binding site Region of higher concentration Cell membrane Region of lower concentration Active Transport Phospholipid molecules Transported particle Carrier protein with altered shape Cellular energy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Endocytosis Exocytosis Both require energy supplied by ATP Vesicular Transport Endocytosis Exocytosis Both require energy supplied by ATP

Endocytosis The internalization of substances into the cell by the formation of a vesicle Pinocytosis - “cell drinking” Phagocytosis - “cell eating” Receptor-mediated endocytosis - Receptor sites select specific substances to be internalized

Pinocytosis Fig. 3.29 Cell membrane Fluid-filled vesicle Fluid Cytoplasm Nucleolus Nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Phagocytosis Fig. 3.30 Cell membrane Particle Phagocytized particle Vesicle Nucleus Nucleolus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Receptor-mediated Endocytosis Molecules outside cell Receptor-ligand combination Vesicle Receptor protein Cell membrane Cell membrane indenting Cytoplasm (a) (b) (c) (d) Fig. 3.32 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Exocytosis The externalization of substances from the cell by the formation of a vesicle Requires energy

Fig. 3.33 Secretion via Exocytosis Endoplasmic reticulum Golgi apparatus Nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Exocytosis after Phagocytosis Digestive products Vesicle Residue Lysosome Phagocytized particle Nucleus Nucleolus Fig. 3.31 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Transcytosis Combines receptor-mediated endocytosis and exocytosis to transport particles through a cell

Transcytosis Fig. 3.34 HIV-infected white blood cells Anal or vaginal canal V iruses bud HIV Receptor-mediated endocytosis Lining of anus or vagina (epithelial cells) Exocytosis Cell membrane Receptor-mediated endocytosis Fig. 3.34 Virus infects white blood cells on other side of lining Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

THE CELL LIFE CYCLE The changes within a cell from the time it is formed until it divides to produce two new identical cells The cell cycle has two major stages Interphase Cell division stage - Mitosis

Fig. 3.35 The Cell Cycle Mitotic Phase DNA Replication Fig. 3.35 G2 phase Mitotic Phase Prophase Interphase Mitosis S phase: genetic material replicates Metaphase Anaphase Telophase Proceed to division Cytokinesis G1 phase cell growth Remain specialized Restriction checkpoint Apoptosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Interphase The phase between cell divisions ~ 90% of typical cell’s time is spent in interphase Cells carry out metabolic activities and specialized functions while in Interphase In addition, while in Interphase, cells prepare to divide Three stages: G1, S, and G2

Late Interphase Fig. 3.36a ~360x Late Interphase Cell has passed the restriction checkpoint and completed DNA replication, as well as replication of centrioles and mitochondria, and synthesis of extra membrane. Nuclear envelope ~360x Chromatin fibers Centrioles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Mitotic Phase of the Cell Cycle Consists of karyokinesis and cytokinesis Described in four stages - PMAT Prophase Metaphase Anaphase Telophase These events plainly visible under the light microscope

Prophase Mitosis Fig. 3.36b ~360x Aster Prophase Chromosomes condense and become visible. Nuclear envelope and nucleolus disperse. Spindle apparatus forms. Microtubules (b) Centromere Spindle fiber Late prophase Sister chromatids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Ed Reschke

© Biophoto Associates, SPL/Photo Researchers, Inc. Chromosomes © Biophoto Associates, SPL/Photo Researchers, Inc. 36,000x Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

© SPL/Photo Researchers, Inc. This normal karyotype shows 23 pairs of chromosomes: Pairs 1-22 are autosomes (they do not determine sex) Pair 23 are the sex chromosomes Pg. 909 1 2 3 4 5 6 7 10 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 Sex chromosomes (female) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © SPL/Photo Researchers, Inc. 32

Metaphase Mitosis Fig 3.36 c ~360x Metaphase Chromosomes align along equator, or metaphase plate of cell. © Ed Reschke Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Anaphase Mitosis Fig. 3.36d ~360x Anaphase Sister chromatids separate to opposite poles of cell. Events begin which lead to cytokinesis. © Ed Reschke Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Mitosis - Telophase and Cytokinesis ~360x Chromosomes Nuclear envelopes Telophase and Cytokinesis Nuclear envelopes begin to reassemble around two daughter nuclei. Chromosomes decondense. Spindle disappears. Division of the cytoplasm into two cells. © Ed Reschke Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Early Interphase Fig. 3.36e Early Interphase of daughter cells— a time of normal cell growth and function. Cleavage furrow (e) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

5,100x Pg. 83

Control of Cell Division Number of divisions dependent on cell type Telomeres Contact density Genetic control tumor suppressor gene oncogenes Apoptosis Loss of control of cell division leads to tumors/cancer

Cell Differentiation Fig. 3.40 Self- renewal Stem cell (hematopoietic stem cell) Stem cell Progenitor cell (e.g., myeloid progenitor cell) Specialized cells (white blood cells) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cell Death Fig. 3.42 Death receptor on doomed cell binds signal molecule. Caspases are activated within. Caspases destroy various proteins and other cell components. Cell becomes deformed. Blebs Cell fragments Phagocyte attacks and engulfs cell remnants. Cell components are degraded. © Peter Skinner/Photo Researchers, Inc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.