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Cells, Tissues, and Organs Chapter 4 Modern Cell Biology Makes 6 Assumptions: 1. All living material is made up of cells or products of cells 2. All cells are formed from previously existing cells -cell division -fusion of sperm and egg 3. Most elementary unit of life 4.Every cell is bound by a plasma membrane 5. All cells have strong biochemical similarities 6. Most cells are small -.001cm (.00004 inches) in length 3 functions of most cells: 1. Maintenance 2. Synthesis of cell products 3. Cell division Cell Membrane: • Encloses the cell Cytoplasm: • Material in the cell membrane that contains organelles and granules in suspension Examples of organelles: • • • • • • • • Golgi apparatus Nucleaus Ribosomes Centrioles Microfilaments Microtubles Lysosomes Storage particles Plasma Membrane: • Cells are surrounded by this thin membrane of lipid (fat) and protein • Controls the transport of molecules in and out of the cell • Serves as the boundary between the cell and surrounding tissue Nucleus: • Enclosed by a nuclear envelope, or membrane, with pores Nucleoli: • Discrete structures in the nucleus • Site of RNA synthesis Chromosomes in the nucleus: • Contain DNA • Carries hereditary information The nucleus directs the activity of the cell: • Example: information is transcribed into the RNA, which serves as a messenger. Messenger moves out of the nucleus to the ribosome where it guides the synthesis of protein. Ribosomes: • Made of RNA and protein • Site of protein synthesis Endoplasmic Reticulum: • A complex set of membranous structures • Rough or smooth • Rough = large amounts of protein Golgi Body: • Membrane mixture found near nucleus • Accumulates secreted lipids and proteins Mitochondria: • Almost all of the energy passes through this molecule before being used in cell function Microfilaments: • Long, thin rods that contract • Responsible for movement of cells Lysosomes: • Large number of enzymes are stored Morphogensesis: • Process of cell development • Each cell contains the same total genetic information that was present in the fertilized egg • Cells aren’t identical because genes are controlled (switched on and off) by various biochemical processes Cell Division Depends On: • 1. copying of DNA • 2. orderly separation of the products of this copy Chromatids: • Each chromosome contains two sister chromosomes called this 6 Stages of Mitosis: 1. 2. 3. 4. 5. 6. Prophase Prometaphase Metaphase Anaphase Telophase Interphase Prophase Metaphase Anaphase Telephase Interphase Meiosis: • Produce gametes (sex cells) • 2 cell divisions • Reduce number of chromosomes Meiosis Stages: • • • • • Prophase with 5 sub-stages Prometaphase Metaphase Anaphase Interphase • Only one in four of the female gametes is functional because the division of cytoplasm is unequal • The functional ovum requires more cytoplasm to serve as food for the developing ovum • Fertilization: restores the cell to the original number of chromosomes which was reduced during meiosis • Humans: 46 chromosomes • Horse: 64 chromosomes DNA consists of 3 components: • Deoxyribose sugar • Phosphate • 4 nitrogen bases: A – Adenine T – Thymine G - Guanine C - Cytosine Tissue: • Structured groups of cells specialized to perform a common function necessary for the survival of the horse Classification of Tissues: • Nerve • Epithelial (cover external and cushion internal) • Muscle (cardiac) • Connective (tendons and ligaments) • Fluid (blood and lymph)