cells

basic functional unit of all living things

• bounds the cell together
• encloses the nucleus and cytoplasm
• separates internal metabolic events from the external environment
• controls the movement of materials into and out of the cell
• is a double lipid bilayer

consists of specialized bodies (organelles) suspended in cytosol

consists of water and dissolved substances such as proteins and nutrients

proteins may attach loosely to the inner or outer surface of the membrane

proteins that may extend into the membrane

integral proteins may span across the membrane appearing at both surfaces

• selectively permeable
• small, uncharged, polar molecules, & hydrophobic molecules freely pass across the membrane
• large polar molecules and all ions are permeable

in the plasma membrane provide a wide range of functions

provide open passageway through the membrane for certain hydrophilic (water-soluble) substances such as polar and charged molecules

allow the passage of ions across the membrane

• ion channels in nerve and muscle cells
• open and close in response to specific chemical or electrical stimuli to allow the passage of specific ions (like Na⁺ and K⁺)

proteins that allow the passage of certain ions and small polar molecules through membranes

found in the plasma membranes of certain cells (kidneys and plant roots) dramatically increase the passage of H₂O molecules

• USE energy (ATP) to transport materials across the membrane
• when energy is used it's called active transport

• carrier protein that uses energy
• materials are actively transported

uses ATP to maintain higher concentrations of Na⁺ and K⁺ on opposite sides of the plasma membrane

• give each cell a type of unique identification
• these proteins are glycoproteins because they have short polysaccharide chains attached
• oligosaccharide part of the glycoprotein extends away from the surface of the membrane

attach cells to neighboring cells or provide anchors for the internal filaments and tubules that give stability to the cell

• provide binding sites for hormones or other trigger molecules
• in response or trigger molecules, a specific cell response is activated

• molecules distributed throughout the phospholipid bilayer provide some rigidity to the plasma membranes of animal cells.
• in plant cells they are called sterols

• carbohydrate coat that covers the outer face of the cell wall of some bacteria and the outer face of the plasma membrane of certain animals cells
• consists of various oligosaccharides that are attached to the membrane phospholipids and proteins
• may provide adhesive capabilities, barrier to infection, or markers for cell-cell recognition

bodies within the cytoplasm that serve to physically separate the various metabolic reactions that occur within cells

• bounded by the nuclear envelope that consists of two phospholipid bilayers
• contains DNA
• serves as the site for the separation of chromosomes during cell division
• you can also see one or more nucleoli, concentrations of DNA in the process of manufacturing the components of ribosomes
• where ribosomes are made

• DNA which is spread out within the nucleus as a threadlike matrix
• found inside nucleus
• major components are DNA and histone
• functions: package DNA into a smaller volume to fit in the cell, strengthen the DNA to allow mitosis and meiosis, and to serve as a mechanism to control expression and DNA replication
• contains genetic material-instructions to direct cell functions

• shape:rod-shaped bodies
• when cells begin to divide, the chromatin condenses into rod-shaped bodies

serve to organize the lengthy DNA

coiled bundles from chromosomes

• subunits manufactured in nucleus
• consist of RNA molecules and proteins
• in the cytoplasm: assist in the assembly of amino acids into proteins
• two subunits: 60S & 40S move across the nuclear envelope and into the cytoplasm where they are assembled into a single 80S

• S (ex. 40S, 60S, 80S)
• expresses how readily a product a product forms a sediment in a centrifuge, a larger values represents larger and heavier products

• consists of stacks of flattened sacs involved in the production of various materials
• often closely related to nucleus

• has ribosomes attached
• creates glycoproteins by attaching polysaccharide groups to polypeptides as they are assembled by the ribosomes

• without ribosomes
• responsible for various activities including the synthesis of lipids and hormones, especially in cells that produce these substances for export from the cell
• liver cells:breaks down toxins, drugs, and toxic by products from cellular reactions

• group of flattened sacs arranged like a stack of bowls
• modify and package proteins and lipids into vesicles
• these vesicles release their contents to the outside of the cell

• vesicles from a golgi apparatus that contain digestive enzymes
• break down food, cellular debris, and foreign invaders
• low pH (acidic) are favorable to the activity of the enzymes (inside lysosome)
• enzymes that escape from the lysosome remains inactive in the neutral pH of the cytosol
• do no occur in plant cells

• breaks down various substances (H₂O₂, fatty acids, and amino acids)
• common in liver and kidney because they break down toxic substances
• plants cells: modify by-products of photorespiration
• germinating seeds: break down store fatty acids to help generate energy for growth

carry out aerobic respiration, which is energy (form of ATP) is obtained from carbohydrates

• carry out photosynthesis
• plant process of incorporating energy from sunlight into carbohydrates

• internal structure of the cytoplasm
• microtubules, intermediate filaments, and microfilaments establish the shape or coordinate movements (all are proteins fibers)

• made of tubulin (protein)
• provide support and motility for cellular activities
• found in spindle apparatus and in the flagella and cilia

guides the movement of chromosomes during cell division

provide support for maintaining the shape of a cell

• made of the protein actin and are involved in cell motility
• found in the muscle cells and in cells that move by changing shape such as phagocytes

white blood cells that wander throughout the body attacking bacteria and other foreign invaders

move materials between organelles or between organelles and the plasma membrane

• temporary receptacles of nutrients
• often merge with lysosomes whose digestive enzymes break down food

• seen in plants
• sotre starch, pigments, and toxic substances

• large bodies occupying most of the interioir of certain plant cells
• when fully filled-they exert turgor (pressure) on the cell walls and maintains rigidity in the cell
• store nutrients and carry out functions otherwise assumed by lysosomes in animal cells

specialized organelles in single-celled organisms that collect and pump excess water out of the cell

• region outside the plasma membrane
• ex: cell wall, extracellular matrix

• found in plants, fungi, protists, and bacteria
• develop outside the plasma membrane and provide support for the cell
• plants: made of cellulose (made from B-glucose)
• fungi: made of cellulose and chitin

• cell walls of fungi
• modified polysaccharide differing from cellulose in that one of the hydroxyl group is replaced by a group containing nitrogen

• found in animals in the area between adjacent cells
• area is occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by cells
• matrix provides mechanical supports and helps bind adjacent cells together
• most common substance in this region is the protein collagen

serve to anchor cells to one another or to provide a passageway for cellular exchange

protein attachments between adjacent animal cells

• an anchoring junction
• consists of proteins that bind adjacent cells together, providing mechanical stability to tissues
• associated with protein filaments that extend into the interior of the cell and serve to hold cellular structures together

• tightly stitched seams between animal cells
• completely encircles each cell, producing a seal that prevents the passage of materials between the cells
• characteristics of cells lining the digestive tract where materials are required to pass through cells to penetrate the blood stream

• passageways between cells that allow the transfer of chemical or electrical signals
• 2 types: gap junctions & plasmodesmata

• narrow tunnels between animal cells that consist of proteins called connexins
• proteins prevent the cytoplasm from each cell from mixing, but allows the passage of ions and small molecules
• allow communication between cells through the exchange of materials or through the transmission of electrical impulse
• channel proteins of 2 adjacent cells that are closely aligned

proteins prevent the cytoplasm from each cell from mixing, but allows the passage of ions and small molecules

• narrow channels between plant cells
• narrow tube of endoplasmic reticulum ,(desmotubule) surrounded by cytoplasm and plasma membrane, passes through the channel
• material exchange occurs through the cytoplasm surrounding the demotubule

• presence of cells wall, chloroplasts, central vacuoles in plants cells (absent in animals)
• presence of lysosomes, centrioles, and cholesterol in animal cells (absent in plants)

all organism except for bacteria, cyanobacteria, archaebacteria

• bacteria, cyanobacteria, archaebacteria
• lack all the organelles
• have plasma membrane, DNA molecule, ribosome, cytoplasm, and cell wall
• do not have a nucleus
• single "naked" DNA molecule without the protein that is associated with the DNA in eukaryotic chromosomes
• ribosomes are smaller (70S,50S,30S)
• cells walls of bacteria and cyanobacteria (when present) are constructed from peptidoglycan
• cell wall of cyanobacteria contains various polysaccharides, NOT peptidoglycan, cellulose, or chitin
• flagella are not constructed microtubules

polysaccharide protein molecule

collective movement of substances in the same direction in response to a force or pressure

• process describes the movement of substances from a region of higher to lower concentration
• do not require energy
• "down" a concentration gradient

• net movement of substances from an area of higher concentration to an area of lower concentration
• random, constant, independent motion

• diffusion of water molecules across a selectively permeable membrane
• turgor pressure: osmotic pressure that develops when water enters the cells of plants and microorganisms

diffusion of solutes across a selectively permeable membrane

movement of water out of a cell that results in the collapse of a cell

• diffusion of solutes or water through channel proteins in the plasma membrane
• water can pass through plasma membrane without the aid of special proteins, aquaporins increase the rate of transfer by facilitated diffusion

describes the diffusion of substances between two regions in which substances are moving by bulk flow in opposite directions

• movement of solutes against a gradient and requires the expenditure of energy (ATP)
• transport proteins in the plasma membrane transfer solutes such as small ions, amino acids, and monosaccharides across the membrane

uses vesicles or other bodies in the cytoplasm to move macromolecules or large particles across the plasma membrane

describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell

• describes the capture of a substance outside the cell when the plasma membrane merges to engulf it.
• 3 types: phagocytosis, pinocytosis, receptor-mediated

• "cellular eating"
• occurs when undissolved material enters the cell
• plasma membrane wraps around the solid material and engulfs it forming a phagocytic vesicle
• phagocytic vesicles then attack and engulf the material

• "cellular drinking"
• occurs when dissolved substances enter the cell
• plasma membrane folds inward to form a channel allowing the liquid to enter
• plasma membrane closes off the channel encircling the liquid to make a vesicle

• endocytosis occurs when specific molecules in fluid surround the cell bind to specialized receptors that concentrate in coated pits in the plasma membrane
• membrane pits, receptors, and specific molecules fold inward and the formation of a vesicle follows
• proteins that transport cholesterol in blood and certain hormones target specific cells by receptor-mediated endocytosis