Chapter 3. Cells. Cells. Cells

Transcription

1 Chapter 3 Cells Cells Cytology The basic unit of life Humans have about 75 trillion cells Largest human cell is the egg While there are many varieties to cells there are many common characteristics. Cells measured in micrometers 1/1000 of a millimeter Cells Cells - building blocks of all living things Cells differ in size and shape Carry out all chemical activities needed to sustain life 1

2 Cell Diversity Cells have a variety of shapes & sizes Cell differentiation cells differ based on its function Shape related to function Cube Spherical Columnar Branching Disc Cell Diversity Cells have a variety of functions Cover & protect structures Store nutrients Motility Fight diseases Connect body parts Gather info Digest materials Respond to environment Reproduction Cell Diversity 2

3 Anatomy of the Cell Cells are organized into 4 regions Plasma membrane or cell membrane Nucleus Cytoplasm Organelles Cell Membrane Barrier for cell contents Selectively permeable Flexible membrane Double phospholipid layer Hydrophilic heads polar; outside Hydrophobic tails nonpolar; inside Cell Membrane Other materials in plasma membrane Proteins hormone or enzyme receptors & transports materials in or out of cell Integral proteins go completely thru membrane Peripheral proteins on membrane surface Cholesterol stabilizes membrane Glycoproteins & glycolipids ID s cell, determines blood type, & cell to cell communications CAMs cellular adhesion molecules allows cells to touch and bind (WBC to injured cells) 3

4 Functions of Proteins Proteins: Receptors Forms pores, channels and carriers Enzymes trigger reactions CAMS allow cells to stick together Self-markers cell ID Cell Membrane Specializations Microvilli Finger-like projections that increase surface area for absorption Pinocytic vesicles Indentations or pockets in the membrane that take in materials through pinocytosis 4

5 The Nucleus Anucleated cells w/out a nucleus Only Multinucleated cells with more than I nucleus The Nucleus Control center Contains genetic material (DNA) 4 regions Nuclear envelope Nucleolus Chromatin Nucleoplasm Nuclear pores Nuclear Membrane Protective barrier of nucleus Consists of double phospholipid layer & proteins Selectively permeable Contains nuclear pores that allow for exchange of dissolved materials w/rest of cell 5

6 Nucleoplasma Fluid material within the nucleus Nucleolus Composed of RNA & protein Site of ribosome production Ribosomes then migrate to the cytoplasm through nuclear pores Nucleus may contain 1 or more nucleoli Chromatin Thin strands composed of DNA & protein Chromatin coils to form Normal chromosome # is 46 6

7 Cytoplasm Area between nucleus & plasma membrane Cytosol Fluid material Inclusions Non-functioning units; chemicals Organelles Cytoplasmic Organelles Pinocytic vesicle Organelles Ribosomes Site of protein synthesis Found free in cytoplasm or attached to rough ER 7

8 Organelles Endoplasmic reticulum (ER) Fluid-filled tubes that transport substances 2 types of ER Rough ER Has ribosomes Site where building materials are formed Smooth ER Functions in lipid & cholesterol synthesis & fat metabolism ER Smooth ER Nuclear envelope Rough ER Ribosomes View of smooth and rough ER Vesicles Membranous sacs that store substances Seen in Golgi and ER Formed when materials enter the cell 8

9 Organelles Golgi apparatus Flat sacs that modify & package proteins as secretory vesicles Produces different types of packages Organelles Organelles Mitochondria Powerhouses of the cell Endosymbiosis of bacteria; double membrane and DNA Site of cellular respiration; Inner membrane called cristae; 9

10 Organelles Lysosomes Contain enzymes that digest materials within the cell Reason for fingers & toes Peroxisomes Sac containing peroxidase enzymes Detoxify harmful substances; H 2 O 2 to H 2 O Break down free radicals Organelles Centrosome Centrioles the 2 rod-shaped bodies made of microtubules Only in Lie just outside nucleus cells Helps form spindles during cell Organelles Cytoskeleton Protein fibers that provides cell w/an internal framework 2 different types Microfilaments Microtubules - 10

11 Cellular Projections Not found in all cells Used for movement Cilia short hair like projections; microtubules; moves materials across the cell surface EX. Esophagus, oviducts Flagellum long hair like projections that propel the cell; microtubules EX. Sperm cells Membrane Transport Membrane Transport movement of substances in & out of the cell Selectively permeable membrane 2 types of transport Passive transport No energy required Goes from high con. to low conc. Active transport Energy required Goes from low to high conc. Types of Transport Passive Diffusion Osmosis Facilitated diffusion Filtration Active Active transport Endocytosis Exocytosis 11

12 Solutions & Transport Solution homogeneous mixture of 2 or more components Solvent Solutes components being dissolved Intracellular fluid fluids inside the cell Interstitial fluid fluid on the exterior of cell Contains nutrients, cellular products, & waste Passive Transport Processes Diffusion gradual movement of molecules from high conc. to low conc. Affected by temp High temp diffusion; Cold temp diffusion Affected by particle size Small particle size rate of diffusion; large Equilibrium point where molecules are evenly distributed Passive Transport Processes Types of diffusion Osmosis - Facilitated diffusion substances require a protein carrier or channel for passive transport Channels or protein carriers are specific for certain molecules 12

13 Diffusion thru Plasma Membrane Osmosis Movement of water across a selectively permeable membrane Moves from high conc. to low conc. Remember water follows salt Osmotic Pressure - ability of osmosis to generate enough pressure to move a volume of water Osmotic pressure increases as the conc. of non-permeable solutes increases. Cellular Solutions 3 cellular environmnets Isotonic- = conc of solutes and solvent; cells remain normal; same osmotic pressure as body Hypertonic a solution that has a higher conc. of solutes and a lower conc. of water. Cells placed in this solution will shrink. Known as plasmolysis (movement of water out) or crenate (shrinking) Hypotonic a solution that has a lower conc. of solutes and a higher conc of water. Cells expand as water moves in. Known as cytolysis 13

14 Filtration Smaller molecules are forced through porous membranes Separates solids from water Hydrostatic pressure important in the body Examples: Molecules leaving blood capillaries Kidney filters waste Active Transport Processes Bulk transport movement of extremely large particles Exocytosis - Materials exit cell Material is carried in a vesicle Vesicle joins w/plasma membrane & is pushed out Endocytosis substances move into cell Materials are engulfed & enclosed in a vescicle Types of endocytosis Pinocytosis Phagocytosis Receptor-mediated - requires the substance to bind to a membrane-bound receptor Exocytosis 14

15 Endocytosis Cell Cycle The series of changes a cell undergoes from the time it is formed until it divides. The 2 resulting cells are called daughter cells Cells should be exact copies of mother cell Cell Cycle Cell cycle have 2 major stages Interphase no cell, G1 - Cell grows & carries out metabolic processes S (synthesis) DNA replicates G2- organelles replicate; cell prepares for M phase Mitosis - Cell replicates itself for growth & repair Cytokinesis 15

16 Cell Cycle Events of Cell Division Mitosis of the Results in the formation of 2 daughter nuclei Cytokinesis of the cytoplasm Begins when mitosis is near completion Results in the formation of 2 daughter cells Stages of Mitosis Prophase 1st stage of cell Chromosomes form from chromatin Centrioles separate & migrate to opposite poles Nucleus & nucleolus disappear Spindle fibers form between poles Centromeres attach to spindle fibers 16

17 Stages of Mitosis Metaphase Chromosomes are aligned at equator Anaphase Daughter chromosomes are pulled apart & move towards opposite poles Now called chromatids May see beginning of cytokinesis Telophase Daughter nuclei begin forming A cleavage furrow well developed (cytokinesis) Stages of Mitosis 17

18 Control of Cell Division Skin cells about every Blood cells about every Neurons a specific number of times then cease Growth factors & hormones stimulate cell division Telomeres (chromosome tips) shorten with cell ; provides a mitotic clock Cancer tumors are the result of uncontrolled cell 52 Tumors 2 types of tumors Benign usually remains localized Malignant invasive & can metastasize; cancerous 2 major types of genes cause cancer Oncogenes activate other genes that increase cell division Tumor suppressor genes normally regulate mitosis; if inactivated they are unable to regulate mitosis Stem and Progenitor Cells Stem cells retain the ability to repeatedly to form 2 new cells Stem cells can differentiate into different cell types (260 types) Totipotent cells from early embryo can give rise to every cell type Pluripotent cells from later fetal development can give rise to a restricted number of cell types Progenitor cells can to become any of a restricted number of cells 54 18

19 Cell Death Apoptosis Cell death Acts as a protective mechanism Is a continuous process 19