Cell Structures And Function PDF

Chapter IV CELL STRUCTURES AND FUNCTION CELL STRUCTURE - The cell is the basic living unit of all organisms. - The simplest organisms consist of single cells, whereas humans are composed of multiple cells. - Cell was discovered i...

Chapter IV CELL STRUCTURES AND FUNCTION CELL STRUCTURE - The cell is the basic living unit of all organisms. - The simplest organisms consist of single cells, whereas humans are composed of multiple cells. - Cell was discovered in late 1600’ s by Robert Hooke through dead plant. THREE MAIN PARTS OF THE CELL - Plasma Membrane - Cytoplasm - Nucleus FUNCTIONS OF THE CELL - Cell metabolism and energy use. The chemical reactions that occur within cells are collectively called cell metabolism. Energy released during metabolism is used for cell activities, such as the synthesis of new molecules, muscle contraction, and heat production, which helps maintain body temperature. - Synthesis of molecules. Cells synthesize various types of molecules, including proteins, nucleic acids, and lipids. The different cells of the body do not all produce the same molecules. Therefore, the structural and functional characteristics of cells are determined by the types of molecules they produce. - Communication. Cells produce and receive chemical and electrical signals that allow them to communicate with one another. For example, nerve cells communicate with one another and with muscle cells, causing muscle cells to contract. - Reproduction and inheritance. Each cell contains a copy of the genetic information of the individual. Specialized cells (sperm cells and oocytes) transmit that genetic information to the next generation. PLASMA MEMBRANE - Also known as CELL MEMBRANE. The outermost component of a cell. A fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment. CELL MEMBRANE - Cell membrane is a double layer of phospholipid molecules. Extracellular Substances - Substances outside the cell - Na + and Cl- are found in greater concentrations and extracellularly. Intracellular Substances - Substances inside the cell. - Substances such as glycogen, and potassium ions (K+) are found at higher concentrations intracellularly. NUCLEUS - The "HEADQUARTERS" or the CONTROL CENTER of the cell. - A large organelle that houses most of a cell's deoxyribonucleic acid (DNA). - The site of ribosome formation. NUCLEAR ENVELOPE - A double semipermeable membrane barrier. - Allows some but not all substances to pass through it NUCLEAR PORE - Opening that is made up of fused nuclear membrane. NUCLEOLUS - One or more small, dark staining, essentially round bodies called NUCLEOLI. - Site where cell structures called ribosomes are assembled. - The nuclei of human cell contain 23 PAIR OF CHROMOSOMES. CHROMATIN - Tangled spread out form of DNA inside nuclear membrane. - Threads coil and condense to form dense, rod-like bodies called CHROMOSOMES during CELL DIVISION. CYTOPLASM - The cellular material outside the nucleus and inside the plasma membrane. - Gel-like fluid inside the cell. TWO MAJOR COMPONENTS - CYTOSOL - also known as INTRACELLULAR FLUID - The fluid portion of cytoplasm surrounding the organelles Constitutes about 55% of total cell volume. - 75-90% water plus various dissolved and suspended components ORGANELLES - also known as LITTLE ORGANS - specialized structures within the cell that have characteristic and shape and perform specific functions. - Mitochondria - Rod-like, double membrane structures - The POWERHOUSE of the cell. - Inner membrane fold into projections called CRISTAE. - Site of aerobic respiration (the "burning" of glucose) Site for ATP synthesis. MITOCHONDRIA RIBOSOMES -Dense particles consisting of two subunits, each composed of ribosomal RNA and protein -The sites for protein synthesis. - Found at two locations: Free in the cytoplasm. Attached to rough endoplasmic reticulum. ROUGH ENDOPLASMIC RETICULUM - Membranous network of flattened sacs or tubules. - Externally studded with ribosomes - Site where building materials of cellular membrane are formed - Site of protein synthesis SMOOTH ENDOPALSMIC RETICULUM - Membranous system of tunnels and sacs - Free of ribosomes - Functions: Lipid synthesis Fat metabolism Detoxification of chemicals within cells GOLGI APPARATUS - A stack of flattened membranes and associated vesicles close to the ER. - Packages, modifies, and segregates proteins for secretion from the cell. - Forms new cell membrane components - Packages Lysosomes LYSOSOMES - Membranous sacs containing acid hydrolases (powerful digestive enzymes). - Vesicle formed from Golgi complex. - Sites of intracellular digestion - The stomach of the cell Responsible for autolysis of injured cells CENTRIOLES - Paired cylindrical bodies, each composed of NINE TRIPLETS OF MICROTUBULES - Also known as CENTROSOME - A specialized zone of cytoplasm close to the nucleus, where microtubule formation occurs. - Also known for directing the formation of the chromosomes during cell division. CYTOSKELETON - Acts as a cell's "bones and muscles" - Determines cell shapes, supports organelles, and provides the machinery for intracellular transport and various types of cellular movements. MICROFILAMENTS - Small fibrils formed from protein subunits that structurally support the cytoplasm. - Most involved in cell motility and in producing changes in cell shape. INTERMEDIATE FILAMENTS - Smaller in diameter than microtubules but larger in diameter than microfilaments. - Strong, stable, rope-like made up of fibrous subunits. - Provides mechanical support to the cell MICROTUBULES - Made up of repeating subunits of protein tubulin. - Determines the overall shape of a cell and the distribution of organelles. PEROXISOMES - Enzymes that digest fatty acids and amino acids. - Enzymes that catalyze the breakdown of hydrogen peroxide CARBOHYDRATES AND LIPID STORAGE Pompe Disease Lipid Storage Disorder Tay-Sachs Disorder