Human Anatomy and Physiology Lab Lecture 2

Queens College

Performed by Most Cells

• Maintain integrity and shape of cell

• Obtain nutrients and form chemical building blocks

• Dispose of waste

Performed by some cells

Cell division

Plasa Membrane

Cilia, flagellum, microvilli

Cytoplasm

Cellular contents between plasma membrane and the nucleus

Cytosol

Viscous fluid of the cytoplasm

Membrane-bound Organelles

• Surrounded by membrane

• Differ in shape, membrane composition, enzymes

• Include the nucleus, endoplasmic reticulum, Golgi apparatus, lysosome, peroxisomes, mitochondria

Nucleus

• Cells control center

• Number and shape per cell

Nuclear envelope

• Double phospholipids membrane enclosing nucleus

• Separates cytoplasm from nucleoplasm

• Externally continuous with rough ER

• Contains channel-like open passageways

Nucleolus

• Dark-staining, spherical body

• Not membrane bound

• Composed of protein and RNA

• Not present in all cells

Endoplasmic Reticulum

• Synthesizes

• Transports

• Packaging and storage

• Detoxification

• Structure formation

Golgi Complex

• Modification, packing and sorting

• Structure formation: secretary vesicles and lysosomes

Endomembrane System

• Synthesis, modification, and shipping of proteins

Lysosomes

• Small, membranous sacs

• Contain digestive enzymes formed by Golgi

• Participate in digestion of unneeded substances

Peroxisomes

• Membrane-enclosed sacs smaller than lysosomes

• Pinched off vesicles from rough ER

• Contain oxidative enzymes

• Serve in detoxification

• Most abundant in liver

Mitochondria

• Contains genes for producing mitochondrial proteins

• Complete digestion of fuel molecules to synthesize ATP

• Termed powerhouse of the cell

• Increase through fission

Ribosomes

• Protein synthesis

Non-membranous organelle

• Arranges microtubules and supports their growth in nondividing cells

• Cell division: directs formation of mitotic spindle in dividing cells

Cytoskeleton

• Maintains cell shape

• Protein support of microvilli, cilia, and flagella

• Stabilizes cell junctions

• Organizes organells

• Separates chromosomes during cell division

• Splits cell into two daughter cells

Cytoskeleton

• Intracellular support

• Organization of organelles

• Cell division

• Movement of materials

• Includes microfilaments, intermediate filaments, microtubules

Microfilaments

• Smallest components of the cytoskeleton

• Actin protein monomers in two twisted filaments

Intermediate filaments

• Intermediate-sized components on the cytoskeleton

• More rigid than microfilaments

• Support cells structurally and stabilize cell junctions

• Varied protein composition between cells (keratin)

Microtubules

• Largest components of the cytoskeleton

• Hollow cylinders

• Long chains of tubular protein

Cilia and Flagella

• Projections extending from the cell

• Contain both cytoplasm and microtubule proteins

• Enclosed in plasma membrane

Cilia

• Usually found on exposed surfaces of specific cells

Flagella

• Similar to cilia in structure

• Longer and usually appear alone

• Helps propel an entire cell

• Only example is a sperm cell

Microvilli

• Microscopic extensions from surface of plasma membrane

• Much smaller than cilia

• More densely packed, lack powered movement

• Supported by microfilaments

Interphase

• Includes mitosis

• Later overlapped by cytokinesis

Prophase

• First stage of mitosis

• Chromatic supercooled into chromosomes with sister chromatids

• Nucleolus dissolves/break down

• Microtubules (spindle fibers) growing from centrioles

Metaphase

• Second stage of mitosis

• Chromosomes aligned on equatorial plate of cell

• Spindle fibers extending from centriole attach at centromere of chromosome

Anaphase

• Starts as spindle fibers move sister chromatids apart toward poles

• Each chromatid now a chromosome of one DNA helix

Telophase

• Arrival of new chromosomes at each pole

• Begin to uncoil and return to chromatic

• New nucleolus formed in each cell

• Mitotic spindle broken up

• New envelope forms around chromosomes

Cytokinesis

• Division of cytoplasm between two newly formed cells

• May overlap with anaphase and telophase

• Contractile ring of microfilament proteins at cell periphery resulting in a cleavage furrow

• Interphase follows

Plasma Membrane

• Regulating movement of materials into and out of a cell

• Occurs through process of membrane transport

• Can be categorized as passive or active transport

Passive Process of membrane transport

• Does not require energy

• Depend on substances moving down concentration gradient

Diffusion

• When something goes from an area of high concentration to low

• Does not have a semi permeable membrane

• Molecules and ions in constant motion due to kinetic energy

• Continues until substance reaches equilibrium

• Environmental conditions affecting rate of diffusion: temperature, molecular weight of solute, steepness and viscosity

Osmosis

• The movement of water from high concentration to low concentration

• Semipermeable membrane

• Moves through integral proteins of water channels called aquaporins

• Cell gains or loses water with osmosis

Simple Cellular Diffusion

• Molecules passing between phospholipid molecules: water, O2, CO2, N2, Alcohol, Ammonia

• Solutes small and nonpolar

• Movement dependent on concentration gradient alone

• Unregulated

Osmotic Pressure

• Exerted by movement of water across semipermeable membrane

• Steeper gradient, more water moved by osmosis, and greater osmotic pressure

• Can be measured indirectly

• Would create hydrostatic pressure within the tube

Tonicity

Ability of a solution to change the volume or pressure of the cell by osmosis

Isotonic solution

• Both cytosol and solution with same relative concentration of solutes

• No net movement of water

Hypotonic solution

• Solution with a lower concentration of solutes than cytosol

• Water moving down concentration gradient

• Moves from inside the cell to outside

• Decreased volume and pressure of cell

• May cause cell to shrink: crenation