Anatomy & Physiology: Cell Structure and Organelles

Cell Theory: 1. All living things are composed of cells. 2. Cells are the basic unit of living things. 3. New cells are produced from existing cells.

Human cells come in various shapes and sizes –a typical cell is 5-50 micrometers in diameter –smallest cells (sperm) are 1 micrometer across –biggest cells (egg cells) can be 120 micrometers across – visible with the naked eye SpermEgg Cell

Cell Structure How is a cell like a factory? –Organelles perform specific, repetitive tasks “Organelles” means little organs Cell can be broken into two major parts –Nucleus –Cytoplasm Organelles inside a cell

Cell Structure & Organelles Nucleus –Contains DNA (instructions for making proteins) –Control center for cellular activities –Nuclear anatomy Nuclear envelope (porous) Chromatin (DNA attached to proteins) –Chromatin becomes chromosomes during cell division Muscle cells: Nuclei are stained purple.

Ribosomes –Made of RNA and proteins –Ribosomes make proteins (important!) Use amino acids to make chains that form proteins Cell Structure & Organelles

7-2: Eukaryotic Cell Structure Endoplasmic Reticulum –Lipid components of cell membrane and proteins that get exported from the cell are made on the endoplasmic reticulum –Two types of ER Smooth ER – synthesis of membrane lipids and detoxification of drugs Rough ER –Called “rough” because of ribosomes on surface –proteins bound for export are chemically modified

Golgi Apparatus (AKA Golgi Body) –It’s a stack of membranes (like pancakes) –Final touches on proteins after they leave the endoplasmic reticulum, before they leave the cell –Lysosomes are made by the Golgi apparatus Cell Structure & Organelles

Protein Synthesis Ribosomes, ER and Golgi work together to make proteins Cell Structure & Organelles

Lysosomes –Made by the Golgi apparatus –Contain digestive enzymes – garbage men of the cell Cell Structure & Organelles

Mitochondria –Power House –Power House of the cell –Energy from glucose is converted into energy that organelles can use –Inherited from your mother Cell Structure & Organelles

Cytoskeleton –A network of protein filaments that help to support eukaryotic cells (also help some cells to move) –Composed primarily of microfilaments and microtubules Microfilaments in red Microtubules in green Cell Structure & Organelles

Cell membrane –Regulates what enters and leaves the cell –Provides protection and support –Composed of lipid bilayer –Many surface and integral membrane proteins dot the surface of cells. (Fluid Mosaic) Cell Structure & Organelles

Diffusion Through Cell BoundariesDiffusion Through Cell Boundaries –The cell membrane regulates what goes into and out of a cell –Diffusion is the movement of molecules from an area of greater concentration to an area of lesser concentration. –Concentration is measured in terms of grams/Liter or grams/mL (ex: 6 grams of salt in 3 mL of water = a concentration of 2 g/mL) –Diffusion is a passive process –Substances will diffuse across a cell membrane until equilibrium is reached. Cell Structure & Organelles

Cell size is limited by the rate of diffusion –As the surface area of a cell increases, so does its volume. –If a cell gets too big, necessary solutes cannot diffuse fast enough throughout the cell. Surface area = 600 cm 2 Volume = 1000 cm 3 Surface area = 6 cm 2 Volume = 1 cm 3 Cell Structure & Organelles

Osmosis –The diffusion of water across a selectively permeable membrane –If a cell is in a hypertonic solution, water will diffuse out of the cell. –If a cell is in a hypotonic solution, water will diffuse into the cell. –If a cell is in an isotonic solution, there will be no net movement of water. HypertonicHypotonic Cell Structure & Organelles

Isotonic sol’nHypertonic sol’nHypotonic sol’n Osmotic Pressure

–Cells in a hypotonic solution will eventually swell until they burst. –Cells in hypertonic solution will shrivel. –Most cells are in an isotonic solution (i.e. interstitial fluid, blood). Cell Structure & Organelles

Some molecules are too big, or a too charged to pass directly through the cell membrane. Instead they pass the channel proteins in a process called facilitated diffusion. Cell Structure & Organelles

Active Transport –Requires energy –Integral membrane proteins do the work. –Often moves solutes against their concentration gradient. (ex: H + ion pump) Cell Structure & Organelles

Two types of active transport include endocytosis and exocytosis. –Endocytosis: taking material into the cell Phagocytosis: taking in solid material Pinocytosis: taking in liquid material –Exocytosis: sending material out of a cell, usually by fusing a vacuole (containing material) with the cell membrane Phagocytosis Cell Structure & Organelles

Cells of multicellular organisms are specialized. They perform different tasks. From smallest to biggest, multicellular organisms are composed of cells, tissues, organs, and organ systems. Cell Structure & Organelles

Stem Cells –Undifferentiated cells –Embryonic stem cells give rise to all tissues in the body. –Adult stem cells give rise to the cell types of the tissues that they are in. The adult tissues reported to contain stem cells include brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin and liver Cell Structure & Organelles