Anatomy & Physiology Notes (Week 2) PDF

Anatomy & Physiology August 13, 2024 (Week 2) (Lecture) THE CELLULAR LEVEL OF ORGANIZATION A Generalized Cell 1. Plasma Membrane Forms the cel...

Anatomy & Physiology August 13, 2024 (Week 2) (Lecture) THE CELLULAR LEVEL OF ORGANIZATION A Generalized Cell 1. Plasma Membrane Forms the cell’s outer boundary Separates the cell’s internal environment from the outside environment Is a selective barrier Plays a role in cellular Plasma Membrane communication Flexible yet sturdy barrier 2. Cytoplasm The fluid mosaic model – the All the cellular contents arrangement of molecules between the plasma membrane within the membrane resembles and the nucleus a sea of lipids containing many Cytosol - the fluid portion, types of proteins mostly water The lipids act as a barrier to Organelles – subcellular certain substances structures having The protein act as characteristic shapes and “gatekeepers” to certain specific functions molecules and ions 3. Nucleus Structure of a Large organelle that contains Membrane DNA Contains chromosomes, each of Consists of a lipid bilayer – made up which consists of a single of phospholipids, cholesterol and molecule of DNA and associated glycolipids proteins Integral proteins – extend into or A chromosome contains through the lipid bilayer thousands of hereditary units Transmembrane proteins – most called genes integral proteins, span the entire lipid bilayer Peripheral proteins – attached to the inner or outer surface of the  membrane, do not extend through steroids, but impermeable to it. glucose Glycoproteins – membrane Transmembrane proteins act as proteins with a carbohydrate channels and transporters to group attached that protrudes assist the entrance of certain into the extracellular fluid. substances, for example, glucose Glycocalyx – the “sugary coating” and ions. surrounding the membrane made up of the carbohydrate portions Passive vs. Active Processes of the glycolipids and glycoproteins. Passive processes – substances move across cell membranes without the input of any energy; use the kinetic energy of individual molecules or ions. Active processes – a cell uses energy, primarily from the breakdown of ATP, to move a substance across the membrane. i.e., against a concentration gradient Diffusion Functions of Membrane Steepness of concentration Proteins gradient Some integral proteins are ion Temperature channels Mass of diffusing substance Transporters – selectively move Surface area substances through the Diffusion distance membrane Receptors – for cellular recognition; a ligand is a molecule that binds with a receptor Enzymes – catalyze chemical reactions Others act as cell-identity markers Membrane Permeability The cell is either permeable or impermeable to certain substances The lipid bilayer is permeable to oxygen, carbon dioxide, water and  Simple Diffusion, Channel-mediated 2. Through aquaporins, integral Facilitated Diffusion, and Carrier- membrane proteins mediated Facilitated Diffusion Tonicity and its effect on RBCS Channel-mediated Facilitated Diffusion of Potassium ions through a Gated K+ Channel Active Transport Osmosis Solutes are transported across plasma membranes with the use of energy, Net movement of water through a from an area of lower concentration to selectively permeable membrane an area of higher concentration Sodium- from an area of high potassium pump concentration of water (lower concentration of solutes) to one of lower concentration of water Water can pass through plasma membrane in 2 ways: 1. Through lipid bilayer by simple diffusion  Transport in Vesicles - provides structural support for the cell Vesicle – a small spherical sac - three types according to formed by budding off from a increasing size; microfilaments, membrane intermediate filaments, and Endocytosis – materials move into microtubules a cell in a vesicle formed from the plasma membrane Organelles Three types: 1) Receptor-mediated Centrosome – located near the endocytosis nucleus, consists of two centrioles 2) Phagocytosis and pericentriolar material 3) Bulk-phase endocytosis Cilia – short, hair-like projections (pinocytosis) from the cell surface, move fluids along a cell surface Exocytosis – vesicles fuse with the Flagella – longer than cilia, move an plasma membrane, releasing their entire cell; only example is the contents into the extracellular sperm cell’s tail fluid Ribosomes – sites of protein Transcytosis – a combination of synthesis endocytosis and exocytosis Endoplasmic reticulum - network of membranes in the shape of flattened sacs or tubules Cytoplasm – o Rough ER – connected to the 2 Components nuclear envelope, a series of flattened sacs, surface is 1. Cytosol studded with ribosomes, - Intracellular fluid, surrounds the produces various proteins organelles o Smooth ER – a network of - Site of many chemical reactions membrane tubules, does not - Energy is usually released by these have ribosomes, synthesizes reactions fatty acids and steroids, - Reactions provide the building detoxifies certain drugs blocks for cell maintenance, Golgi complex structure, function, and growth - consists of 3-20 flattened, membranous sacs called 2. Organelles cisternae - Specialized structures within the - modify, sort, and package cell proteins for transport to different destinations The cytoskeleton - proteins are transported by - network of protein filaments various vesicles throughout the cytosol  Lysosomes – vesicles that form substances between nucleus from the Golgi complex, contain and cytoplasm powerful digestive enzymes Peroxisomes – smaller than Nucleolus – spherical body that lysosomes, detoxify several toxic produces ribosomes substances such as alcohol, Genes – are the cell’s hereditary abundant in the liver units, control activities and Proteasomes – continuously structure of the cell destroy unneeded, damaged, or faulty proteins, found in the Chromosomes – long molecules cytosol and the nucleus of DNA combined with protein molecules Mitochondria Somatic Cell Division – - the “powerhouses” of the Mitosis cell - generate ATP - The cell cycle is a sequence - more prevalent in of events in which a body cell physiologically active cells: duplicates its contents and muscles, liver and kidneys divides in two - inner and outer - Human somatic cells contain mitochondrial membranes 23 pairs of chromosomes - Cristae – the series of folds (total = 46) of the inner membrane - The two chromosomes that - Matrix – the large central make up each pair are called fluid-filled cavity homologous chromosomes - Self-replicate during times (homologs) of increased cellular demand - Somatic cells contain two or before cell division sets of chromosomes and are called diploid cells Nucleus Cell Division - Spherical or oval shaped Interphase structure - The cell is not dividing - Usually most prominent - The cell replicates its DNA feature of a cell - Consists of three phases, G1, Nuclear envelope – a double S, and G2, replication of DNA membrane that separates the occurs in the S phase nucleus from the cytoplasm Mitotic phase – consists of a Nuclear pores – numerous nuclear division (mitosis) and openings in the nuclear envelope, a cytoplasmic division control movement of  (cytokinesis) to form two - The cell eventually splits into two identical cells daughter cells - Interphase begins when cytokinesis is complete Nuclear Division: Mitosis Prophase – the chromatin fibers change into chromosomes Metaphase – microtubules align the centromeres of the chromatid pairs at the metaphase plate Reproductive Cell Division Anaphase – the chromatid pairs - During sexual reproduction each split at the centromere and move new organism is the result of the to opposite poles of the cell; the union of two gametes chromatids are now called (fertilization), one from each chromosomes. parent Telophase – two identical nuclei are formed around the identical sets Meiosis – reproductive cell division of chromosomes now in their that occurs in the gonads (ovaries chromatin form and testes) that produces gametes with half the number of Cytoplasmic Division: chromosomes Cytokinesis Haploid cells – gametes contain a - Division of a cell’s cytoplasm to single set of 23 chromosomes form two identical cells - Usually begins in late anaphase - Fertilization restores the diploid - The plasma membrane constricts number of chromosomes (46) at its middle forming a cleavage - Meiosis occurs in two successive furrow stages: meiosis 1 and meiosis 11  Summary: Meiosis 1 begins with a Passive Diffusion Active Diffusion diploid cell and ends with two cells having the haploid number of - no energy - use of ATP chromosomes; in Meiosis 11, each of - downhill - uphill the two haploid cells divides, the net result is four haploid gametes that are genetically different from the original diploid starting cell. Found in the inner leaflet or outer leaflet Hydrophilic head – outside Hydrophobic tail – inside TYPE MOVEMENT Isotonic Solution – normal (equal solute I. NON-CARRIER MEDIATED TRANSPORT concentration) Simple Diffusion High concentration - Has equal concentrations of Low concentration solutes inside and outside the cell (Passive; Downhill) Effects on Cells: Water moves in and out of the cell at an equal rate, so Endocytosis the cell maintains its normal shape and size. Exocytosis Hypotonic Solution – not equal tonicity II. CARRIER MEDIATED TRANSPORT (kulang), lower external solute Osmosis concentration, can cause cellular swelling - has a lower concentration of Primary Active Low concentration solutes outside the cell compared Transport High concentration to inside the cell. (Active; Uphill)  Effects on Cells: Water moves into the cell, which can cause the cell to swell and possibly burst (lyse) if the influx is excessive. Hypertonic Solution – shrink, mas madami sa labas, higher external solute concentration - has a higher concentration of solutes outside the cell compared to inside the cell Effects on Cells: Water moves out of the cell, which can cause the cell to shrink (crenate) due to loss of water. Active Transport - uses energy - Na+ , K+ PISO – potassium in, sodium out TRINA TOKEN – 3 sodium, 2 potassium