Biology 211 Anatomy & Physiology I Cells

Recall: SYSTEMS are composed of one or more organs, all serving a common function ORGANS are composed of one or more types of tissues, all serving a common function TISSUES are composed of one or more types of cells and their products, all serving a common function CELLS are composed of different types of organelles, all serving a common function ORGANELLES are composed of different types of molecules, all serving a common function

Cells: Highly organized; composed of organelles and cytoplasm In human, all eukaryotic: nuclei and other organelles surrounded by membranes With one exception, all living cells have at least one nucleus Some cells have more than one nucleus Except for sperm and egg cells (which have 23) each nucleus will contain the same 46 chromosomes Some cells: highly specialized & have only one function Others = relatively unspecialized with many functions

Cells: Shape: Highly variable:

Cells: Size: Highly variable Spheroid/polygonal/cuboidal: Average = 10-15 micrometers diameter Range = 2 micrometers (sperm) 100 micrometers (oocyte) Skeletal muscle cells may be 300 millimeters long Nerve cells may be more than a meter long

Cells: Limited lifespan: Most cells die & must be replaced. This lifespan is highly variable. On average: Leukocytes in your blood: ½ -3 days Cells lining your stomach & intestines: 2 - 4 days Cells in epidermis of your skin: 1 - 2 months Erythrocytes in your blood: 1 - 4 months Macrophages (in most tissues): months – years Gland cells in your pancreas: 1 - 4 years Skeletal muscle cells: 10 - 20 years Bone cells: 20 - 50 years Cardiac muscle cells: > 40 years Nerve cells: > 80 years

Cells: Some mature cells can divide to replace the ones which die. Others are replaced from Unspecialized cells called stem cells Except for the production of sperm and egg cells, this involves a type of cell division called mitosis which is described in Chapter 4 of your Saladin text. Be sure you understand how mitosis results in two cells which are the same as the original cell.

Independent Study: Chapter 3 of your Saladin text discusses the organelles of most cells. You should understand the basic structure and function of each of the following: Nucleus Ribosomes Endoplasmic reticulum Golgi complex Mitochondria Lysosomes Peroxisomes Vesicles Cytoskeleton You should also understand the basic structure and function of cilia and flagella You will be responsible for these on exams

Plasma Membrane: Also called "plasmalemma" May have special names in specific types of cells e.g. "sarcolemma" in muscle cells, "neurolemma" in nerve cells - Keeps inside in and outside out while - Controlling movement of ions/molecules into and out of cell - Interacts with other cells and with extracellular materials around cell - Allows cell to recognize and respond to chemical signals

Plasma Membrane: Basic structure = double layer of phospholipids with proteins and cholesterol embedded within it

Plasma Membrane: Proteins and glycoproteins: a) Channels and carriers to allow ions and molecules to pass in or out b) Identity markers to allow cells to identify each other c) Cell adhesion molecules to hold cells together d) Receptors to allow the cell to respond to hormones and other chemical signals e) Enzymes to form cellular messengers or to remove unwanted molecules

Plasma Membrane: Has many types of specialized junctions for cell-to-cell attachment and/or communication. We will focus on three: 1. Tight junctions: Protein molecules in plasma membranes of two adjacent cells form bonds; hold cells strongly together and prevent materials from passing between them

Plasma Membrane: Has many types of specialized junctions for cell-to-cell attachment and/or communication. We will focus on three: 2. Desmosomes: Protein molecules in plasma membranes of two adjacent cells form bonds in isolated spots; hold cells strongly together

Plasma Membrane: Has many types of specialized junctions for cell-to-cell attachment and/or communication. We will focus on three: 3. Gap Junctions: Protein molecules in plasma membranes of two adjacent cells form channels between them; allow molecules to flow from cell to cell

Movement of Materials Across Plasma Membrane: Thousands of different materials are actively crossing the plasma membranes of your cells every second of every day of your life, both into and out of the cell: e.g. Water Nutrients like amino acids, monosaccharides, fatty acids, nucleotides, vitamins Gases like oxygen, carbon dioxide Waste products like lactic acid, urea, bilirubin Ions (electrolytes) like sodium, potassium, magnesium, iron, calcium, chloride, phosphate, sulfate Hormones like insulin, estrogens, growth hormone Neurotransmitters Proteins the cell secretes Debris which phagocytic cells ingest (many others)

Movement of Materials Across Plasma Membrane: Thousands of different materials are actively crossing the plasma membranes of your cells every second of every day of your life, both into and out of each cell: This is not a random process! Each cell has a variety of different processes to regulate this exchange so that The right materials cross the membrane In the right concentrations At the right time In the right direction etc.

Plasma Membrane: This regulated movement of ions and molecules is due to: a) Solubility of phospholipids for nonpolar molecules b) Channels for passive movement of materials across the membrane. Channels can open and close. c) Pumps to actively transport molecules across the membrane. Pumps turn on and off. d) Vesicles which form from (or fuse to) the plasma membrane

More Independent Study: Saladin text discusses various types of membrane transport. Be sure you understand, in moderate detail, how each of the following occurs and what it accomplishes: - Filtration - Simple diffusion, including osmosis - Carrier-mediated transport Facilitated diffusion Active transport (including cotransport & countertransport) - Vesicular transport Pinocytosis Receptor-mediated endocytosis Phagocytosis Exocytosis You will be responsible for these on exams

Let's move on to tissues