Cell Theory 1.All living things are composed of cells. 2.Cells are the simplest form of life 3.All cells come from preexisting cells.

Compound Light Microscope

Different methods for seeing cell structures. TECHNIQUE RESULT Brightfield (unstained specimen). Passes light directly through specimen. Unless cell is naturally pigmented or artificially stained, image has little contrast. (a) Brightfield (stained specimen). Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved). (b) Phase-contrast. Enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells. (c) 50 µm

Scanning Electron Microscope …provides for detailed study of the surface of a specimen TECHNIQUE RESULTS Scanning electron microscopy. Micrographs taken with a scanning electron microscope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps move inhaled debris upward toward the throat. (a) Cilia 1 µm

Transmission Electron Microscope provides for detailed study of the internal structure of cells Longitudinal section of cilium Cross section of cilium 1 µm

All cells have several basic features in common. 1.bounded by a plasma membrane 2.contain a semi-fluid substance called the cytoplasm. 3.contain chromosomes 4.all have ribosomes

Prokaryote vs. Eukaryote Cells prokaryotic Do not contain a nucleus Have their DNA located in a region called the nucleoid eukaryotic Contain a true nucleus, bounded by a membranous nuclear envelope Have extensive and elaborately arranged internal membranes, which form organelles Are generally quite a bit bigger than prokaryotic cells

Animal Cell

Plant Cell

Plant Cell Structure Onion Cells Elodea with chloroplasts

M2X1c4K1x0

Cell Membrane

Phospholipid Bilayer w/ Proteins

Plasma (cell) Membrane Functions as a selective barrier Allows sufficient passage of nutrients and waste Outside of cell Inside of cell Hydrophilic region Hydrophobic region Hydrophilic region (b) Structure of the plasma membrane Phospholipid Proteins TEM of a plasma membrane. The plasma membrane, here in a red blood cell, appears as a pair of dark bands separated by a light band. (a) 0.1 µm

Mitochondria

Chloroplasts

Ribosomes in the Endoplasmic Reticulum

Ribosomes

other miscellaneous structures/functions golgi apparatus- distributes molecules within the cell. lysosomes- digest/recycle obsolete cell organelles. Not found in plant cells. vacuoles- store materials in the cell. cytoskeleton- “cyte” = cell – support, protein fiber construction.

Cytoskeleton

7.3 Cell Transport daAH0

Passive Transport Movement of molecules across the membrane using diffusion/osmosis No energy is required Concentration gradient is required Substances move from high concentration to low concentration

Section 8.1 Summary – pages Passive Transport

Section 8.1 Summary – pages Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Osmosis: Diffusion of Water In a cell, water always moves to reach an equal concentration on both sides of the membrane.

Section 8.1 Summary – pages The diffusion of water across a selectively permeable membrane is called osmosis. Osmosis: Diffusion of Water Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.

Solvent – substance doing the dissolving (most of the time it is water) Solute – the dissolved substance

Section 8.1 Summary – pages Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. What controls osmosis? Before Osmosis After Osmosis Water molecule Sugar molecule Selectively permeable membrane

Section 8.1 Summary – pages Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions. Cells in an isotonic solution H2OH2O H2OH2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages Cells in an isotonic solution In an isotonic solution, the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages Cells in an isotonic solution In an isotonic solution, water molecules move into and out of the cell at the same rate, and cells retain their normal shape. H2OH2O H2OH2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution. Animal cells prefer this situation

Section 8.1 Summary – pages Cells in a hypotonic solution In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. There are fewer solute molecules & more water molecules outside the cell than inside. H2OH2O H2OH2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages Cells in a hypotonic solution Plant cells prefer this situation. Animal cells do not

Section 8.1 Summary – pages Cells in a hypertonic solution In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. H2OH2O H2OH2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall.

Section 8.1 Summary – pages Osmosis in action

Section 8.1 Summary – pages Active Transport Movement of materials through a membrane against a concentration gradient is called active transport and requires energy from the cell. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

Section 8.1 Summary – pages How active transport occurs

Section 8.1 Summary – pages Transport of Large Particles Endocytosis is a process by which a cell surrounds and takes in material from its environment. Endocytosis Exocytosis Digestion Nucleus Wastes

Section 8.1 Summary – pages Transport of Large Particles The material is engulfed and enclosed by a portion of the cell’s plasma membrane. Exocytosis Digestion Nucleus Wastes Endocytosis

Section 8.1 Summary – pages Transport of Large Particles The resulting vacuole with its contents moves to the inside of the cell. Exocytosis Digestion Nucleus Wastes Endocytosis

Section 8.1 Summary – pages Transport of Large Particles Exocytosis is the expulsion or secretion of materials from a cell. EndocytosisExocytosis Digestion Nucleus Wastes

Section 8.1 Summary – pages Transport of Large Particles Endocytosis and exocytosis both move masses of material and both require energy. EndocytosisExocytosis Digestion Nucleus Wastes