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41 Cards in this Set
- Front
- Back
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Cell Theory
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- Cells are the structural “building blocks” of all plants and animals
- Cells are produced by the division of preexisting cells - Cells form all the structures and perform all vital functions of the body |
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Light Microscopy
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- Magnification up to 1000 times (sometimes 2000)
- Show details as fine as .25 µm - Can identify cell types and see large intracellular structures; general distribution of proteins, lipids, carbs and nucleic acids - Beam of light passed through tissue that has been poisoned, dehydrated, impregnated with wax/ plastic/epoxy, sliced into thin sections, rehydrated, dehydrated, and stained |
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Transmission Electron Microscopy
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- Magnifies more than light microscopy
- Uses focused beam of electrons to produce TEM - Shows fine structure of cell membrane and details of intracellular structures |
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Scanning Electron Microscopy
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- Shows three-dimensional images
- Uses electrons bouncing off exposed surfaces that have been coated with gold-carbon film to create SEM - Less magnification than transmission |
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Cells
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- Trillions of cells in the body
- Sex or somatic cells - Fundamental units of all living things - Enormous individual variations in type and number of organelles based on particular function of cell |
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Components of Cells
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- Plasmalemma/cell membrane- separates extracellular fluid from the:
- Cytoplasm- all material inside cell - Cytosol- intracellular fluid; contains dissolved nutrients, ions, soluble/insoluble proteins, and waste products - Organelles- intracellular structures that perform specific functions - nonmembranous or membranous |
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Plasmalemma
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- outer boundary of cell 6-10 µm
- composed of: - Phospholipids - Glycolipids - Proteins - Cholesterol |
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Integral Proteins
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- proteins embedded in membrane, usually spanning width one or more times (transmembrane proteins)
- can form channels that let water molecules, ions and small water soluble compounds into/ out of cell - some can open and close to regulate= gated - responsible for most of the communication between interior and exterior of cell - also can function as catalysts or receptor sites in cell-cell recognition - can move within membrane |
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Glycolipids and glycoproteins
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- carb component extending away from cell forms glycocalyx= viscous, superficial coating
- some function as receptors: bind to specific molecule in extracellular fluid→ triggers change in cellular activity |
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Functions of Plasmalemma
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1. Physical isolation- separates inside of cell from extracellular fluid
2. Regulation of exchange with the environment (permeability)- controls entry of ions and nutrients, elimination of wastes, and release of secretory products 3. Sensitivity- first to be affected by changes in extracellular fluid; receptors to recognize and respond to specific molecules and communicate with other cells 4. Structural support- connections between adjacent membranes or membranes and extracellular materials give tissue stable structure |
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Passive processes of crossing membrane
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1. Diffusion- net movement of material from an are of high concentration to low concentration
- occurs through membrane channel or across lipid portion of membrane (must be lipid soluble) 2. Osmosis- very permeable to water molecules 3. Facilitated diffusion- essential nutrients that are not lipid soluble and too large for channels bind to receptor site on integral membrane protein and transported by carrier protein - glucose and amino acids |
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Active Processes of Crossing Membrane
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- require energy (usually from ATP) and can transport substances against concentration gradient
1. Active Transport 2. Endocytosis |
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Active Transport
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ATP provides energy needed to move ions/molecules across membrane
- all cells actively transport Na+, Ca2+, Mg2+, and K+ -Ion pumps move specific ion in one direction - Exchange pump is one that moves two ions simultaneously in opposite directions |
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Endocytosis
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Packaging of extracellular materials into vesicle at cell surface for importation into cell
- also called bulk transport - produce small membrane bound compartments called endosomes that eventually fuses with plasmalemma - contents of vesicle will only enter cell if can pass through vesicle wall→ active transport, simple or facilitated diffusion, or destruction of vesicle membrane |
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Types of Endocytosis
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1. Phagocytosis: “cell eating”
- pseudopodia (extensions of cytoplasm) surround object and membranes fuse, forming phagosome which may then fuse with lysosome - performed only by specialized cells of immune system 2. Pinocytosis: “cell drinking” - deep groove forms in plasmalemma and pinches off forming pinosomes; nutrients (lipids, sugars, amino acids) then diffuse/ active transport into cell - in cells of capillaries, pinosomes may be transported to other side of cell and contents discharged through exocytosis - displayed by most cells 3. Receptor-mediated endocytosis: - Ligands will only bind specific molecules to the receptors thereby allowing only specific molecules to enter the cell - cholesterol and iron atoms |
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Microvilli
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small finger-like projections of plasmalemma
- found in cells actively engaged in absorbing materials from extracellular fluid (small intestine and kidneys) - increase surface area exposed to extracellular environment for increased absorption - supported and anchored to terminal web (dense supporting network within underlying cytoskeleton) by network of microfilaments - interactions between microfilaments and cytoskeleton produce waving motion that helps circulate fluid around microvilli bringing dissolved nutrients into contact with receptors |
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Cytosol
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- high concentration of K+ as opposed to the high concentration of Na+ in extracellular fluid
- transmembrane potential exists that is positive on the outside and negative in cell - contains relatively high concentration of dissolved and suspended proteins - contains relatively small quantities of carbs (broken down to provide energy) and large reserves of amino acids (manufacture of proteins) and lipids (maintain cell membranes and energy source) - contains inclusions= masses of insoluble nutrients such as stored nutrients |
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Nonmembranous organelles
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- Cytoskeleton
- Microvilli - Centrioles - Cilia - Flagella - Ribosomes |
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Cytoskeleton
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internal protein framework that gives cytoskeleton strength and flexibility
1.Microfilaments 2. Intermediate filaments 3. Thick filaments 4. Microtubules |
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Microfilaments
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slender strands composed primarily of actin that form dense network under plasmalemma
- Anchor cytoskeleton to integral proteins - Stabilize the position of membrane proteins - Anchor plasmalemma to the cytoplasm - provides additional mechanical strength to cell - interact with structures composed of myosin to produce movement portion of the cell or change shape of entire cell |
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Intermediate filaments
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- Provide strength
- Stabilize organelle position - Transport material within the cytosol - eg. neurofilaments found in axons |
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Thick filaments
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relatively massive filaments composed of myosin protein subunits
- Found in muscle cells: involved in muscle contraction |
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Microtubules
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hollow tubes built from protein tubulin that aggregate for a while and then disassembles
- array is centered near nucleus of cell in region know as centrosome/ microtubule-organizing center (MTOC) and microtubules radiate outward - primary components of cytoskeleton, giving cell strength and rigidity and anchoring major organelles - assembly/disassembly changes cell shape (cell movement?) - during cell division form spindle apparatus that distributes chromosomes - attach to organelles and other intracellular materials and move around cell - Involved in the formation of centrioles, which are involved in cell reproduction - form structural components of organelles that function individually |
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Microtubule Organelles
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1. Centrioles
- cylindrical structure composed of short microtubules - 9 + 0 array= nine groups of microtubules each a triplet of microtubules - found only in cells capable of division at right angles to each other in the MTOC (clear region of cytoplasm) - direct movement of chromosomes during cell division |
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Cilia
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- 9 +2 array= nine groups of microtubule doublets surrounding central pair
- anchored to basal body (structure similar to centriole) situated just beneath cell surface - beat rhythmically causing movement of fluids or secretions across cell surface |
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Flagella
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- resemble cilia but much longer
- moves cell through surrounding fluid - in humans found only in sperm cell |
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Ribosomes
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- small, dense structures consisting of 60% RNA and 40% protein
- intracellular factories that manufacture proteins using info from DNA - consists of large and small subunit that interlock when synthesis begins and then separate when complete - free ribosomes scattered throughout cytoplasm (proteins enter cytosol) - fixed ribosomes attached to rough ER (proteins enter lumen where they are modified and packaged for export) |
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Membranous organelles
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surrounded by phospholipid bilayer that allows organelle to store secretions, enzymes, or toxins that could harm cell
- Mitochondria - Nucleus - Endoplasmic reticulum - Golgi apparatus - Lysosomes - Peroxisomes |
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Mitochondria
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- have outer membrane that surrounds entire organelle and second inner membrane containing numerous folds called cristae which increase surface area exposed to fluid contents/matrix
- matrix contains metabolic enzymes that perform reactions that provide energy for cell functions - Produce ATP (95% needed to keep cell alive) through breakdown of oxygen and generate CO2 - control own maintenance, growth, and reproduction - number in cell depends on cells energy demands |
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Nucleus
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control center of the cell; determines structural and functional characteristics by controlling what proteins are synthesized and in what amounts
- consists of: 1. Nucleoplasm- fluid contents of nuclear; ions, enzymes, RNA and DNA nucleotides, proteins, small amounts of RNA, and DNA 2. Nuclear envelope- double membrane enclosing perinuclear space - connected to rough ER at several points - has nuclear pores- complex of proteins that regulates movement= allows water, ions, and small molecules to pass, but restricts passage of proteins, DNA, and RNA 3. Nuclear matrix- network of filaments that provides structural support and may be involved in regulation of genetic activity 4. Nucleoli- 1-4 nuclear organelles found in most nuclei that synthesize components of ribosomes - contains chromosomes, histones, and RNA and forms around chromosomal region containing genetic instructions for producing ribosomal proteins and RNA |
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DNA
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- found as chromosomes: DNA strands wound around histones forming a nucleosome which may coil around other histones
- dividing chromosomes are very tightly coiled while non dividing chromosomes are loosely coiled forming tangle of filaments called chromatin |
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Endoplasmic reticulum
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- network of intracellular membranes that form hollow tubes, flattened sheets, and rounded chamber (cisternea) that functions to:
1. synthesis- contains enzymes that manufacture carbs, steroids, and lipids 2. storage- can hold synthesized molecules or substances absorbed from cytosol 3. Transport- substances can travel from one place to another in cell 4. Detoxification- cellular toxins can be absorbed by ER and neutralized by its enzymes |
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Smooth endoplasmic reticulum (RER)
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- no ribosomes
- Synthesizes lipids, steroids, and carbohydrates - Storage of calcium ions - Detoxification of toxins |
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Rough endoplasmic reticulum (RER)
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- Consists of fixed ribosomes whose proteins enter the ER cisternae where they may be modified and are then packaged into transport vesicles and delivered to Golgi apparatus
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Golgi Apparatus
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- flattened membrane discs called cisternae (5-6) that form stacks near nucleus
- Synthesis and packaging of secretions - Packaging of enzymes (modifies protein) - Renewal and modification of the plasmalemma - communicate with ER and cell surface through formation, movement, and fusion of vesicles |
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Lysosomes
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vesicles filled with digestive enzymes formed by RER and then packaged by Golgi
- primary lysosomes contain inactive compounds that become active secondary lysosomes upon fusion - Fuse with phagosomes to digest solid materials - Recycle damaged organelles - remove bacteria, fluids, and debris from surroundings and isolate them, break them down, and release as usable substances - Sometimes rupture, thus killing the entire cell (called autolysis) |
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Peroxisomes
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- enzymes formed by free ribosomes in cytoplasm and inserted into already existing peroxisomes
- Consist of catalase - absorb and break down fatty acids - Abundant in liver cells - oxidases- enzymes that convert hydrogen peroxide to water and oxygen |
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Membrane flow
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Continuous movement and recycling of the cell membrane
- Transport vesicles connect the endoplasmic reticulum with the Golgi apparatus - Secretory vesicles connect the Golgi apparatus with the plasmalemma |
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Intracellular Attachment
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1. Communicating junctions- two cells held together by interlocked membrane proteins which as channel proteins, form a narrow passage for ions, small metabolites, and regulatory molecules
2. Adhering junctions include: - Tight junctions/ occluding junction- lipid portions of two plasmalemmae are bound together to seal off intercellular space between cells= prevent passage of material from apical region to basolateral region and prevent passage of water-soluble material between cells - Anchoring junctions- provide mechanical linkage between two adjacent cells at lateral or basal surfaces; very strong a) adhesion belt- zonulae herons- non epithelial b) desmosome- epithelial c)focal adhesions- intramolecular filaments to protein fibers of basal lamina; epithelial undergoing dynamic change d) hemidesmosomes- attaches cell to extracellular filaments and fibers; found in epithelial tissues subjected to large amount of abrasion |
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Interphase
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Everything inside the cell is duplicating
Consists of G1, S, and G2 phases G0: cell is performing all normal functions G1: duplication of organelles and protein synthesis S: DNA replication G2: protein synthesis |
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Mitosis
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1. Prophase- two pairs of centrioles move apart with spindle fiber extending between that attach to kinetochore of each chromatid; nuclear envelope disappears
2. Metaphase- Paired chromatids line up in the middle of the nuclear region 3. Anaphase- Paired chromatids separate to opposite poles of the cell 4. Telophase- Two new nuclear membranes begin to form cytokinesis- cytoplasm is divided; overlaps with anaphase and telophase - the longer the life expectancy of cell, the slower the mitotic rate - stem cells undergo frequent mitosis to replace other more specialized cells |
