LATG Chapters 6 - 7 Cells & Tissues Organic Chemistry, Biochemistry and Infectious Diseases
Cells Prokaryotic = bacteria, blue-green algae Eukaryotic = plants, animals, fungi, many unicellular organisms Both cell types: have DNA, are membrane bound, have ribosomes, have similar basic metabolism Eukaryotic cells: larger (~1000X), more complex DNA, have a nuclear and organelle membranes, have cytoskeleton
Cells Plasma membrane: proteins and lipids that allows fat soluble molecules to penetrate easily but prohibits water soluble molecules from going across without facilitated diffusion or active transport
Cells Within the lipid bilayer are many types of proteins: cell receptors, transport proteins, enzymes
Cells Lipid soluble substances can enter and leave the cell by passive diffusion following concentration gradients
Cells Substances can also cross the membranes without energy expenditure via osmosis = solvent molecules (usually H20) move across a semi-permeable membrane due to osmotic pressure Isotonic Hypotonic Hypertonic
Cells Facilitated or carrier-mediated diffusion occurs with molecules that are not normally fat soluble, but become so when combined with a carrier substance allowing entry or exit from the cell
Cells Active transport is the movement of substances against a concentration or electrochemical gradient and usually requires energy expenditure by the cell
Cells Large molecules or entire cells can enter the host cell by endocytosis either via pinocytosis or phagocytosis and exit the cell via exocytosis
Cells The nucleus is made up of DNA = deoxyribonucleic acid, and RNA = ribonucleic acid, and is involved in cell reproduction and metabolic activities Nucleoli may be present in resting cells and are sites of ribosomal RNA production The nucleus is surrounded by a nuclear membrane containing pores and continuous with the endoplasmic reticulum in some areas
Cells DNA is made up of chains of nucleotides and form the basic element of genes which determine all of our inherited characteristics Nucleotides consist of a sugar molecule = deoxyribose bonded with a phosphate group and a nitrogenous base Nitrogenous bases can be either adenine, guanine, cytosine or thymine
Cells DNA is usually found in double, complementary strands that are held together by hydrogen bonds between the nitrogenous bases Adenine binds with thymine, cytosine binds with guanine When the DNA is not replicating, these strands form a spiral or double helix
Cells During DNA replication, the complementary strands separate and enzymes known as polymerases add new bases that are identical to the original opposite strand
Cells After the DNA replicates itself, the cell is ready to divide. At this point there is condensing down of the DNA in the nucleus from the loosely arranged chromatin into distinct chromosomes.
Cells Mitosis, or cell division, produces two genetically identical cells
Cells DNA replicates itself, but also can produce RNA in a process called transcription. The RNA leaves the nucleus as a single strand DNA areas in the nucleolus produce ribosomal RNA or rRNA Other RNA types are messenger (mRNA) and transfer (tRNA)
Cells rRNA combines with proteins to form ribosomes Ribosomes then ‘read’ the mRNA to synthesize proteins from amino acids in a process called ‘translation’
Cells ‘Translation’ uses rRNA, mRNA, and tRNA to create protein molecules from amino acids
Cells Translation occurs on the surface of the endoplasmic reticulum, a membrane bound organelle in the cell’s cytoplasm
Cells Electron microscope pictures showing the rough ER and ribosomes producing proteins
Cells There are other organelles found within the cytoplasm: The Golgi apparatus is found close to the nucleus and endoplasmic reticulum. It’s job is to receive, sort and process the biomolecules it receives from the ER and resecrete them.
Cells Mitochondria are used for aerobic respiration and production of energy (ATP) for the for proper functioning of the cells metabolic processes.
Cells Lysosomes are full of enzymes that break down fats, protein and carbohydrates into their smallest elements to be used by the mitochondria for energy. Vacuoles are often found in the cytoplasm and assist in getting rid of water and waste products from the cell
Cells Microtubules provide support for the cell known as the cytoskeleton to help the cell keep its shape and control flow of elements through the cell. Centrioles are bundles of microtubules that assist in separation of the chromosomes during mitosis when they form into mitotic spindles. Microtubules also make up cilia and flagella that are hair-like surface projections used to move the cells themselves or material around the outside the cells.
Tissues Cells bound together and serving a specific function are called tissues and include epithelium, connective tissue, muscle tissue, and nerve tissue. Epithelium consists of sheets of cells that have a basal lamina and an unattached or free edge. It is typically found lining cavities, blood vessels, gland ducts and hollow organs.
Tissues Epithelium serves different functions depending on its type and location but may be for protection, absorption, secretion or facilitate movement of substances over its free surface.
Tissues Connective tissue is found throughout the body and contains a variety of different cell types, depending on its location. Dense and loose connective tissue contains fibroblasts and collagen fibers which provide elasticity to the tissue.
Tissues Adipose tissue contains adipocytes which store fat for metabolism and is primarily white. Brown fat is in many species but the greatest amount is found in species that hibernate and it is thought to have a role in maintaining body temperature by producing heat.
Tissues Cartilage contains chondrocytes that are embedded in a semi-rigid matrix. The number of fibers and density of the matrix determines whether it is hyaline cartilage, elastic cartilage, or fibrocartilage.
Tissues Bone is made up of osteocytes and ground substance that consists of calcium phosphate. The ends of long bones contain spongy or cancellous bone while the shaft is compact bone that surrounds the medullary cavity containing the bone marrow.
Tissues The cells found within connective tissue can be fixed as seen with fibroblasts, chondrocytes, osteocytes, and adipose cells. They can also be wandering, usually coming from the blood, as seen with eosinophils, neutrophils, lymphocytes, monocytes, and mast cells.
Tissues Muscle cells can either be smooth or striated, depending on their function and appearance under a microscope. Smooth muscle is found in most of the our internal organs and exhibits involuntary rhythmic and tonic contractions.
Tissues Striated muscle can be either skeletal muscle, that contracts voluntarily, or cardiac muscle that contracts involuntarily.
Tissues Nerve tissue is made up of neurons that are cells characterized by a nucleated cell body, dendrites, and an axon. Nerves respond to stimuli by polarizing and depolarizing by varying the concentration of sodium and potassium ions inside the cell.
Tissues Many nerves are covered with a myelin sheath that speeds the conduction of the impulses down the axon. The myelin is made from part of an oligodendrocyte cell that wraps around the axon and has gaps in it called nodes of Ranvier.
Tissues The axons end either in synapses with other nerve cells, or in motor end plates, innervating muscle cells. The end releases neurotransmitters which are chemicals that stimulate the next nerve or muscle to respond.
Biochemistry • The study of chemistry within living organisms • Inorganic molecules-water, sodium, potassium, calcium--molecules without carbon • Organic molecules-carbohydrates, lipids, proteins--molecules with carbon
Carbohydrates • The sugar family of molecules • Found as mono-, di- and polysaccharides • Used as energy source, supportive structures and nucleic acids
Monosaccharides • Glucose--the most common simple sugar found in biological systems • Provides energy for all body systems • Only source of energy for central nervous system • Galactose and fructose are other simple sugars commonly found
Disaccharides • Molecules made up of two simple sugars • Sucrose, maltose and lactose are two commonly found disaccarhides • Both mono- and disaccharides are known as simple sugars
Polysaccarhides • Complex molecules made up of many (sometimes thousands) simple sugars • Starch, cellulose and glycogen are the majors forms in animal and plant life • Glycogen is the major storage form for sugars in the mammalian body, primarily in muscle and liver
Lipids • Fatty molecules with multiple functions within the mammalian body • Energy storage • Protection • Insulation • Cell membranes
Lipids • Major forms are • Fatty acids • Triglycerides • Steroids
Fatty Acids • The building blocks of most lipids • Classified as saturated and unsaturated fatty acids • Some of the unsaturated fatty acids are classified as essential--can not be made by the body