Body Fluids & Membrane Transport Intracellular Extracellular: Interstitial (intercellular): derived from blood Plasma: blood component found within vessels Cerebrospinal fluid: bathing brain & spinal cord Body cells are bathed in the interstitial fluid Interstitial fluid contains substances needed by cells Substances have to be moved selectively across the cell membrane

Two main ways of transport: Types of Transport Two main ways of transport: Passive processes: No energy input needed form the cell Active processes: The cell provide metabolic energy (ATP)

Passive Transport Two main types of passive transport: Diffusion: Particles move along concentration gradient Driven by kinetic energy of moving molecules In a closed system, equilibrium (equal movement) is reached Filtration: Occurs only across capillary walls Filtrate (containing solute) moves along pressure gradient Driven by hydrostatic (fluid) pressure

Passive Transport: Diffusion Two types : Simple diffusion Facilitated diffusion Simple diffusion: Direct substance diffusion through the lipid bilayer: Nonpolar and lipid soluble substances They include O2, CO2, and fat soluble vitamins Simple diffusion of water is called osmosis

Complete and explain why? O2 always diffuses from ____ to ______. (blood, tissue) CO2 always diffuses from ____ to _____. (blood, tissue)

Simple Diffusion Through the Plasma Membrane Extracellular fluid Lipid- soluble solutes Cytoplasm (a) Simple diffusion directly through the phospholipid bilayer Figure 3.7

Passive Transport: Facilitated Diffusion For molecules unable to pass thru the lipid bilayer Facilitated passage is thru one of the following: Specific binding to a protein carrier (shape change) Ex: amino acids and glucose Water-filled protein channels (size & charge) Ex: water and ions

Facilitated Diffusion: Carrier Mediated “specific binding” Lipid-insoluble solutes (b) Carrier-mediated facilitated diffusion via protein carrier specific for one chemical; binding of substrate causes shape change in transport protein Figure 3.7

Facilitated Diffusion: Channel Mediated Small lipid- insoluble solutes (c) Channel-mediated facilitated diffusion through a channel protein; mostly ions selected on basis of size and charge Figure 3.7

Passive Membrane Transport: Osmosis Occurs when water concentration is different on opposite sides of a semipermeable membrane Water molecules pass: Thru transmembrane protein (aquaporins) channels Directly thru bilayer lipid (???) Osmolarity: The total concentration of all solute particles in a solution Tonicity Ability of a solution to change the shape or tone of cells by changing their internal water volume

Simple Diffusion: Osmosis Water molecules Lipid bilayer (d) Osmosis, diffusion of water through a specific channel protein (aquaporin) or through the lipid bilayer Figure 3.7

Effect of Membrane Permeability on Diffusion and Osmosis Figure 3.8a

Effect of Membrane Permeability on Diffusion and Osmosis Figure 3.8b

Passive Membrane Transport: Filtration Passage of water and solutes through a membrane Driving force is hydrostatic (fluid) pressure Pressure gradient pushes solute & fluid from: High pressure area to low pressure area Occurs only across capillary walls Ex. Transport in kidneys

Effects of Solutions of Varying Tonicity Isotonic solution: A solution with the same concentrations of nonpenetrating solutes as those of the cytosol (0.9% saline or 5% glucose) Hypertonic solution: A solution with a greater concentration of nonpenetrating solutes than that in the cytosol Hypotonic solution: A solution having lesser nonpenetrating solute concentration than that in the cytosol

Uses ATP to move solutes across a membrane Two types: Active Transport Uses ATP to move solutes across a membrane Two types: Active transport: Requires carrier proteins Vesicular transport: Vesicle formation Used for macromolecules and fluid transport Uses ATP (sometimes GTP) Ex: Exocytosis, endocytosis, transcytosis, vesicular trafficking

Types of Active Transport Primary active transport: Hydrolysis of ATP Phosphorylation of the transport protein Conformational change of protein Bound solute pumped across membrane Secondary active transport Indirect use of an active pump (Na+-K+ pump) to drive the transport of other solutes Energy is stored in ionic gradient created by the pump

Active Transport (Primary) Cytoplasm Extracellular fluid K+ is released and Na+ sites are ready to bind Na+ again; the cycle repeats. Cell ADP Phosphorylation causes the protein to change its shape. Concentration gradients of K+ and Na+ The shape change expels Na+ to the outside, and extracellular K+ binds. Loss of phosphate restores the original conformation of the pump protein. K+ binding triggers release of the phosphate group. Binding of cytoplasmic Na+ to the pump protein stimulates phosphorylation by ATP. Na+ K+ ATP P Pi Note that: [Na+] is higher extracellularly than intracellularly [K+] is higher intracellularly than extracellularly Na+ has three binding sites K+ has two binding sites Figure 3.10

Active Transport (Secondary) Figure 3.11

Vesicular Transport Transport of large particles and macromolecules across plasma membranes Exocytosis Moves substance from the cell interior to the extracellular space Endocytosis Enables large particles and macromolecules to enter the cell

Exocytosis Figure 3.12a

Vesicular trafficking Vesicular Transport Transcytosis Moving substances: Into the cell, Across the cell, and Then out of a cell Vesicular trafficking Moving substances from one area in the cell to another

Vesicular Transport: Types of Endocytosis There are three types of endocytosis; all use protein (clathrin)-coated vesicles Phagocytosis (cell eating): Pseudopods engulf and internalize solid substances into the cell Fluid-phase endocytosis (pinocytosis “cell drinking”): Plasma membrane infolds, bringing extracellular fluid containing dissolved solutes into the cell Receptor-mediated endocytosis: Specific endocytosis using special membrane proteins

Phagocytosis Figure 3.13b

The Cell Cycle

Cell Cycle Interphase Mitotic phase Growth (G1), synthesis (S), growth (G2) Mitotic phase Mitosis and cytokinesis Figure 3.30

Interphase G0: G1 (gap 1): S (synthetic): G2 (gap 2): Cells that permanently cease dividing G1 (gap 1): Metabolic activity and vigorous growth S (synthetic): DNA replication G2 (gap 2): Preparation for division

DNA Replication Means synthesis of new DNA (duplication) Occurs during the interphase of the cell cycle DNA helices begin unwinding Helicase exposes complementary strands Each nucleotide strand serves as a template DNA polymerase III is the enzyme for synthesis It adds complementary nucleotides to the template

DNA Replication Figure 3.31

Cell Division Essential for: Mitosis: Cytokinesis: Body growth Tissue repair Mitosis: Nuclear division Cytokinesis: Division of the cytoplasm

Types of Cell Division Mitotic: Meitic: Body growth Tissue repair Daughter cells have parental chromosome number (dipoid ) Meitic: Gamete formation Daughter cells have half the parental chromosome number (haploid)

The phases of mitosis are: Prophase Metaphase Anaphase Telophase

Cytoplasm is pinched into two parts after mitosis ends Cytokinesis Cleavage furrow: formed in late anaphase by contractile ring Cytoplasm is pinched into two parts after mitosis ends

Early and Late Prophase Asters: Seen as chromatin condenses into chromosomes Anchors spindle to cell membrane Nucleoli: Disappear Centriole Pairs: Separate and migrate to the poles Organize the mitotic spindle

Early &Late Prophase Figure 3.32.3

Metaphase Centromeres aligned at the exacte quator of the cell Chromosomes arrange along a plane midway between the poles This arrangement is called the metaphase plate

Anaphase Centromeres of the chromosomes split Proteins pull chromosomes toward poles

Telophase and Cytokinesis New sets of chromosomes extend into chromatin New nuclear membrane forms Nucleoli reappear Generally cytokinesis completes cell division

Break Slide 2401.5039 Fri, Sep. 14,’12