Chapter 3 Cells and Tissues In the late 1600s, Robert Hooke was looking through a microscope at some plant tissue - cork. He saw some cube-like structures that reminded him of the long rows of monk's rooms (or cells) at the monastery, so he named these structures cells. The living cells that had formed the cork were long since dead. However, the name stuck and is still used to describe the unit, or building block, of all living things, plants and animals alike. The human body has trillions of these microscopic building blocks. Cells Name the four elements that make up the bulk of living matter and list several trace elements. o Carbon, oxygen, hydrogen, nitrogen = bulk o Iron, sodium, potassium – smaller amounts o Calcium, iron, iodine = trace Define cell, organelle, and inclusion. o Cell – The basic structural and functional units of all organisms – enclosed by a limiting membrane – could be prokaryotic or eukaryotic o Organelle – metabolic machinery of the cell – each carries out a specific function for the cell such as nucleus, mitochondria, Golgi apparatus, ER, cytoplasm… o Inclusion – not functioning units, but are chemical substances that may or may not be present depending on the type of cell such as fat droplets, glycogen granules, pigments (melanin), crystals Identify on a cell model or diagram the three major cell regions (nucleus, cytoplasm, and plasma membrane). o See page 57 List the structures of the nucleus and explain the function of chromatin and nucleoli. o Nuclear envelope – double membrane, selectively permeable with nuclear pores o Nucleoplasm – jelly-like substance inside the nucleus that holds the nucleoli and chromatin o Nucleoli – sites of ribosome construction and partial assembly – may be more than one o Chromatin – uncoiled DNA being used for transcription o Chromosomes – shortened, coiled DNA ready for cell division Identify the organelles on a cell model or describe them, and discuss the major function of each. o Plasma membrane – selectively permeable barrier, communication Tight junctions – impermeable junctions to bind cells together into leakproof sheets Desmosomes – anchoring junctions that prevent cells subject to mechanical stress from being pulled apart Gap junctions – function mainly to allow communication between cells o Cytoplasm – hold organelles and dissolved nutrients – site of most cellular activities o Nucleus – control center containing the DNA o Mitochondria – makes ATP o Ribosomes – sites of protein synthesis o Endoplasmic reticulum Rough ER – has ribosomes attached – network of channels for processing and shipping proteins out of the cell Smooth ER – no ribosomes – cholesterol synthesis and breakdown, fat metabolism, detoxification o Golgi apparatus – modify and package proteins for shipment o Lysosomes – contain enzymes for digestion of old cell components and foreign substances such as bacteria and viruses Peroxisomes – contain powerful oxidase enzymes that use molecular oxygen to detoxify harmful or poisonous substances such as alcohol and formaldehyde, also functions to disarm free radicals (highly reactive chemicals that can damage cell components) o Cytoskeleton – the cell’s bones and muscles – internal framework that determines cell shape, supports other organelles, and provides the machinery needed for intracellular transport and cell movement Intermediate filaments – form desmosomes and provide internal guy wires to resist pulling forces on the cell Microfilaments – cell motility and in producing changes in cell shape – made of actin and myosin Microtubules – determine overall shape and distribution of organelles also important in cell division o Centrioles – direct formation of the mitotic spindle used to separate the chromosomes o Cilia and flagella – move substances across the cell surface or for cell movement Define selective permeability, diffusion (including simple and facilitated diffusion and osmosis), active transport, passive transport, solute pumping, exocytosis, endocytosis, phagocytosis, bulkphase endocytosis, hypertonic, hypotonic, and isotonic. o Selective permeability – allows some substances to pass while excluding others o Passive transport – does not require ATP energy Diffusion – molecules and ions scatter themselves throughout the available space via kinetic energy (random movement) down their concentration gradient Simple – unassisted movement of solutes through the membrane Facilitated – uses a protein carrier to assist molecules across the membrane Osmosis – movement of water across the membrane o Active transport – does require ATP to move substances that are either too large or need to be moves against their concentration gradients Solute pumping – uses protein carriers that combine reversibly with the substances to be transported – usually carries substances against the concentration gradient Bulk transport – moves substances that cannot get through the membrane Exocytosis – moves substances out of the cell using sacs that fuse with the membrane and release their contents outside of the cell Endocytosis – moves substances into the cell – cell engulfs substances and wraps membrane around it and the sac pinches off inside the cell Phagocytosis – cell eating – white blood cells can bring in bacteria and other harmful substances and destroy them Bulk-phase endocytosis – A.K.A. Pinocytosis – cell drinking – brings in fluids containing dissolved proteins and fat o Hypertonic – solution that contains more solutes, dissolved substances, than there are inside the cell – cells will crenate or shrivel up o Hypotonic – solution that contains fewer solutes than there are inside the cell – cells will expand and possibly lyse open o Isotonic – solution with the same concentration of solutes as inside the cell - cell is normal Describe the structure of the plasma membrane, and explain how the various transport processes account for the directional movements of specific substances across the plasma membrane. o Flexible double membrane made up of phospholipids arranged tail to tail (hydrophobic tails (nonpolar) point inward while hydrophilic (polar) heads point outward) in which protein and cholesterol molecules float o Proteins scattered in the lipid bilayer are responsible for the specialized functions of the membrane o Glycoproteins can act as enzymes or carriers, form channels or pores, provide receptor sites for hormones and other chemicals or play a role in cellular recognition and interactions during development and immune responses Describe briefly the process of DNA replication and of mitosis. Explain the importance of mitotic cell division. o DNA replication – DNA double helix uncoils and the two strands separate and act as templates for new complementary strands to be added – end with two DNA strands that are identical – A=T and C=G o Mitosis – cell replication for growth and repair of damaged tissues – results in two identical cells with identical copies of the DNA and organelles In relation to protein synthesis, describe the roles of DNA and of the three varieties of RNA. o DNA template strand is used to produce the mRNA strand during the process of transcription o Translation involves the three types of RNA mRNA made in the nucleus is a single, uncoiled strand of RNA travels to the cytoplasm and finds a ribosome tRNA carries corresponding amino acids on their tops that match the anticodon on their bases to the mRNA strand attached to the ribosome and matches up with the codons on the mRNA strand – amino acids are bonded together with peptide bonds rRNA along with proteins make up the ribosomes where protein synthesis takes place Name some cell types and relate their overall shape and internal structure to their special functions. o Cells that connect body parts Fibroblasts - elongated shape that produces cable-like fibers Erythrocytes – streamlined concave disk shape for extra surface area to transport oxygen o Cells that cover and line body organs Epithelial – hexagonal shape allows for them to be packed together in sheets o Cells that move organs and body parts Skeletal and smooth muscle – elongated and filled with contractile filaments to shorten to move bones or change the shape of internal organs o Cells that store nutrients Fat cells – spherical shape produced by lipid droplets in the cytoplasm o Cells that fight disease Macrophages – white blood cells – no determined shape – very flexible to squeeze into tight spots and in-between cells to fight disease o Cells that gather information and controls body functions Nerves – long processes for receiving messages and transmitting them to other structures o Cells of reproduction Oocyte – largest cell in the body – egg cell Sperm – long and streamlined, built for swimming with a flagella Body Tissues Name the four major tissue types and their chief subcategories. Explain how the four major tissue types differ structurally and functionally. o Epithelial – fit closely together to form continuous sheets, membranes have one free surface, lower surface rests on a basement membrane, no blood supply of their own (diffusion brings in nutrients), if well nourished can regenerate themselves easily Simple – one layer of cells Stratified – more than one layer of cells Squamous - flat Cuboidal – cube-like Columnar – column-like Glandular – consists of one or more cells that make and secrete a particular product Endocrine – lose their connections to the surface (duct) and release their secretions into the blood – secrete hormones Exocrine – retain their ducts and secretions empty through the ducts to the epithelial surface – sweat and oil glands o Connective – variations in blood supply depending on the type, extracellular matrix associated Bone – bone cells sitting in cavities called lacunae and surrounded by layers of very hard matrix containing calcium salts in addition to large numbers of collagen fibers Cartilage – less hard and more flexible than bone with abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance Dense connective tissue – crowded between collagen fibers are rows of fibroblasts Tendons – muscle to bone Ligaments – bones to bones – more stretchy with more elastic fibers Loose connective tissue – softer and have more cells and fewer fibers Areolar – soft, pliable, cobweb to cushion and protect body organs – glue that helps hold internal organs together and in place Adipose – fat – areolar tissue in which fat cells predominate – forms the subcutaneous tissue beneath the skin for insulation and protection of internal organs as well as serving as an energy reserve Reticular – delicate network of interwoven reticular fibers associated with reticular cells – supports many free blood cells (lymphocytes) in lymphoid organs Blood – vascular tissue – blood cells surrounded by nonliving, fluid matrix called blood plasma to function in gas exchange o Muscle – specialized to contract, or shorten, to produce movement Skeletal – voluntary, long, cylindrical, multinucleated, striations – move bones Cardiac – only in heart – involuntary, branching cells, uninucleate, striations Smooth – involuntary, spindle-shaped, uninucleate, no striations o Nervous – cytoplasm is drawn out into long extensions to conduct an impulse over long distances – nerves are supported by supporting cells that insulate, support, and protect Give the chief locations of the various tissue types in the body. o See above section Describe the process of tissue repair (wound healing). o Occurs in two major ways – regeneration and fibrosis depending on the type of tissue damaged and the severity of the injury The capillaries become very permeable allowing clotting proteins other substances to seep into the area Granulation tissue forms – made of new capillaries that grow into the damaged area that freely bleed – tissue also contains phagocytes to remove blood clot and bacteria – also contains connective tissue cells that synthesis collagen fibers to stitch the gap together The surface epithelium regenerates – as surface epithelium begins to regenerate, it makes its way across the granulation tissue just beneath the scab, which then detaches Developmental Aspects of Cells and Tissues Define neoplasm, and distinguish between benign and malignant neoplasms. o Neoplasm – mass of cell that forms when cells fail to honor normal controls on cell division and multiply wildly forming an abnormal mass of proliferating cells o Benign – local, tend to be surrounded by a capsule, grow slowly, seldom kill the host if removed before they compress vital organs o Malignant – nonencapsulated masses that grow more relentlessly and may become killers, cells resemble immature cells and they invade their surroundings rather than pushing them aside, tend to spread via blood to other parts of the body (metastasis) to form new masses Explain the significance of the fact that some tissue types (muscle and nerve) are largely amitotic after the growth stages are over. o Amitotic tissues are severely handicapped by injury because the lost cells cannot be replaced by the same type of cells o Damaged heart tissue is not replaced by heart cells but by scar tissue that cannot contract making the heart weaker o Once nerves are damaged or lost, a person becomes paralyzed and looses all feeling in that area serviced by that nerve
