Ap biology-chapter 6/7

Important cell membrane functions

Serves as the boundary of the cell, maintains its integrity; protein molecules embedded in plasma membrane perform various functions; for example, they serve as markers that identify cells of each individual, as receptor molecules for certain hormones and other molecules, and as transport mechanisms

Major function(s) of: Plasma membrane

Serves as the boundary of the cell, maintains its integrity; protein molecules embedded in plasma membrane perform various functions; for example, they serve as markers that identify cells of each individual, as receptor molecules for certain hormones and other molecules, and as transport mechanisms

Diffusion

refers to a natural phenomenon caused by the tendency of small particles to spread out evenly within any given space; molecules move from an area of high concentration to an area of low concentration; occurs down a concentration gradient

Carrier-mediated transport

ACTIVE PASSIVE TRANSPORT: Endocytosis--phagocytosis and pinocytosis, Exocytosis

Characteristics that differentiate mature human cells from immature ones

All human cells (except mature sex cells) have 46 chromosomes. Immature cells have the potential to reproduce many different kinds of daughter cells, including more stem cells-thus populating the body with all the different cells and tissues needed for body function. Mature cells are undifferntiated cells found scattered within a differentiated, mature tissue. Many different tissues contain adult stem cells and can usually produce any of the specialized cell types within its particular tissue.

Major function(s) of: Rough endoplasmic reticulum

Attached ribosomes synthesize proteins that leave cells via the Golgi apparatus (intracellular transportation)

Compare/Contrast: Catabolism vs. anabolism and examples of each

CATABOLISM: cellular respiration - glycolysis, citric acid cycle, electron transport system; breaks down molecules, usually nutrient molecules, and thereby releases energy from the broken molecules. ANABOLISM: protein synthesis; build larger molecules from smaller ones, usually require a net input of energy.

Nuceleus & its main components

Two membranes (nuclear envelope) perforated by pores enclose the nucleoplasm. Nuclear pores are intricate structures often called nuclear pore complexes (NPC), act as gatekeepers and transport mechanisms that selectively permit molecules and other structures to enter or leave the nucleus. Organelles called vaults may also assist with such transport. The most important factor to remember about the nucleus is that it contains DNA molecules which appear as tiny bunches of tangled threads sprinkled with granules, chromatin. The functions of the nucleus are primarily functions of DNA molecules, contain the master code for making all the RNA plus the many enzymes and other proteins of a cell --> ultimately dictate both the structure and function of cells. The nucleolus (nonmembranous) is the most prominent structure visible in the nucleus. Nucleolus functions to synthesize ribosomal RNA (rRNA) and combine it with protein to form the subunits that will later combine to form ribosomes.

Major function(s) of: Lysosomes

Vesicles that have pinched off from the Golgi apparatus. Help cell break down proteins that are not needed to get them out of the way; cell's own digestive system; enzymes in lysosomes digest the protein structures of defective cell parts, including integral membrane proteins, and particles that have become trapped in the cell

Cytosol

Watery fluid in which the various organelles and molecules are suspended, sometimes called intracellular fluid

Major function(s) of: Mitochondrion

"Power plant"; Extracts energy from food molecules and use it to build ATP molecules; site of ATP production; the more work a cell does the more mitochondria a cell contains; contains its own DNA molecule so it can make its own enzymes, can also divide and produce genetically identical daughter mitochondria

Desmosomes

Category of cell junction that holds adjacent cells together; consists of dense plate or band of connecting structures at point of adhesion. Spot desmosomes, which resemble Velcro, have fibers on the outer surface that interlock with each other; achored internally by intermediate filaments. Belt desmosomes are belt-like versions that completely encircles the cell.

Gap junction

Cell connection formed when membrane channels of adjacent plasma membranes adhere to each other; they form gaps or "tunnels" that join the cytoplasm of two cells, and they fuse the two plasma membranes into a single structure; electrical impulses traveling along a membrane can travel over many cell membranes in a row without stopping in between; heart muscle cells are joined by gap junctions

Tight junction

Connection between cells in which they are joined by "collars" of tightly fused membrane; occur in cells that are joined near the apical surfaces; molecules cannot easily permeate the cracks between the cells; occur in the lining of intestines, where it is important to control what gets past a sheet of cells

The prime regulator of nucleus functions

DNA

Osmosis

Diffusion of water through a selectively permeable membrane; does not allow diffusion of one or more other substances; potential osmotic pressure is a prediction of what the actual osmotic pressure would be, therefore it cannot be measured directly, one can predict the direction of osmosis and the amount of pressure it will produce by knowing the concentrations of impermeant solutions in two solutions; isotonic - same pressure, hypertonic - higher pressure; cells shrivel, hypotonic - lower pressure; cells swell

Compare/Contrast: Hypotonic vs. hypertonic solutions and their effect

HYPOTONIC: Lower pressure; cells swell in hypotonic solutions. HYPERTONIC: Higher pressure; cells always shrivel in hypertonic solution

Compare/Contrast: Cilia and flagella

Human cilia are shorter and more numerous than flagella; cilia look like tiny hairs, often move in a rhythmic, coordinated way to push substances such as mucus along the cell surface; in respiratory tract, movement of cilia keeps contaminated mucus on cell surfaces moving toward the throat where it can be swallowed; in lining of female reproductive tract, cilia keep the ovum moving toward the uterus; cilia also have a sensory function, detecting changes in the mucus being moved. Primary cilia often act as sensory organelles that permit sensations such as vision, hearing, blanace. In the kidney, primary cilia monitor urine flow - and if damaged - can cause kidney failiure. Primary cilia also play a critical role in centriole replication and regulation of cell reproduction. Flagella are single, long structures in the only type of human cell that has this feature: human sperm cell. A sperm cell's flagellum moves like the tail of an eel to allow the cell to "swim" toward the female sex cell (ovum).

Compare/Contrast: Hydrophobic vs. hydrophilic arrangement of cell membrane

Hydrophobic tails of phospholipid bilayer face away from the water; lipid soluble.. Hydrophilic heads of phospholipid bilayer face toward water; water soluble.

General structure of functioning ribosome & where it is found

Innumerable small granules that dot the rough endoplasmic reticulum, and many of them lie free, scattered through the cytoplasm. Nonmembranous structure made of two tiny, interlocking pieces: one piece is a large subunit and the other a small subunit. Temporary structure; subunits only link together when there is an mRNA present and ready to direct the formation of a new polypeptide strand.

Phagocytosis

Large particles are engulfed by the plasma membrane and enter the cell in vesicles. They fuse with the membranous walls of lysosomes, which then digest the particles. "Condition of the cell eating"

Elements that control movement of materials through the cell membrane

Membrane: phospholipid bilayer in simple diffusion, channels: aquaporin for osmosis; sodium ion channels or chloride ion channels, pumps: sodium, potassium, calcium ion pumps, membrane carriers: vesicle-mediated transport in endocytosis or exocytosis; Passive/Active transport processes

Compare/Contrast: Membranous vs. nonmembranous organelles

Membranous - sacs or canals made of cell membrane: plasma membrane, ER, golgi apparatus, vesicles, lysosomes, peroxisomes, mitochondria, nucleus; Nonmembranous - not made of membrane, made of microscopic filaments or other particles: Ribosomes, proteasomes, cytoskeleton, centrosome, microvilli, cilia and flagella, nucleolus

Cell structures that contain DNA

Mitochondria and nucleus

Site for ATP production

Mitochondrion

Nucleolus

Most prominent structure visible in the nucleus, small nonmembranous body that stains densely when studied in lab; consists chiefly of nucleic acid but NOT DNA, it is RNA; functions to synthesize ribosomal RNA (rRNA) and combine it with protein to form the subunits that will later combine to form ribosomes, the protein factories of cells

Cytoskeleton

Network of interconnecting flexible filaments, stiff tubules, and molecular motors within the cell. Supporting framework of the cell and its organelles; functions in cell movement (using molecular motors); forms cell extensions (microvilli, cilia, flagella); cell fibers (microfilaments, intermediate filaments, microtubules)

Ribosomes

Nonmembranous structure made of two tiny, interlocking pieces: one piece is a large subunit and the other a small subunit. Organelle in the cytoplasm of cells that synthesizes proteins; sometimes called "protein factory"

Largest human cell

Ovum

Enzyme reactions

Oxidation-reduction enzymes - oxidases, hydrogenases, dehydrogenases: energy release for muscular contraction and all physiological work depends on these enzymes. Hydrolizing enzymes, or hydrolases - lipase, sucrase, maltase: digestive enzymes belong to this group. Phosphorylating enzymes - phosphorylases or phosphatases: these add or remove phosphate groups. Enzymes that add or remove carbon dioxide - carboxylases, decarboxylases. Enzymes that rearrange atoms within a molecule - mutases, isomerases. Enzymes that add water to a molecule without splitting it - hydrases

Compare/Contrast: Active vs. passive transport and examples of each

PASSIVE TRANSPORT: Simple diffusion, osmosis, facilitated diffusion--channel-mediated passive transport and carrier-mediated passive transport; Simple diffusion: movement of particles through the phospholipid bilayers; movement of carbon dioxide out of all cells. Osmosis: diffusion of water through a selectively permeable membrane in the presence of at least one impermeant solute; diffusion of water molcules into and out of cells to correct imbalances in water concentration. Channel-mediated passive transport: diffusion of particles through a membrane by means of channel structures in the membrane; diffusion of sodium ions into nerve cells during a nerve impules. Carrier-mediated passive transport: diffusion of particles through a membrane by means of carrier structures in the membrane; diffusion of glucose molecules into most cells; ADP-ATP carrier found in membranes of mitochondrion. ACTIVE TRANSPORT: Pumping, endocytosis--phagocytosis and pinocytosis, exocytosis; Pumping: movement of solute particles from an area of low concentration to an area of high concentration by means of an energy-consuming pump structure in the membrane; in muscle cells, pumping of nearly all calcium ions to special compartments-or out ofthe cell. Phagocytosis: movement of cels or other large particles into cell by trapping it in a section of plasma membrane that pinches off to form an intracellular vesicle; a type of vesicle-mediated transport; trapping of bacterial cells by phagocytic white blood cells. Pinocytosis: movement of fluid and dissolved molecules into a cell by trapping them in a section of plasma membrane that pinches off to form an intracellular vesicle; a type of vesicle-mediated transport; trapping of large protein molecules by some body cells. Exocytosis: movement of proteins or other cell products out of the cell by fusing a secretory vesicle with the plasma membrane; a type of vesicle-mediated transport; secretion of hormone prolactin by pituitary cells

Composition of cell membrane

Phospholipid bilayer reinforced with cholesterol and embedded with proteins and other organic molecules

Main cell structures

Plasma membrane; cytoplasm including organelles; nucleus

Major function(s) of: Golgi apparatus

Prepares molecules for export from the cell. Synthesizes carbohydrate, combines it with protein, and packages the product as globules of glycoprotein.

Major function(s) of: Ribosomes

Protein synthesis; cell's "protein factories". Make both its structural and its functional proteins (enzymes). Make proteins for "export" or to be embedded in the plasma membrane; free ribosomes make proteins for the cell's domestic use.

Compare/Contrast: The major 3 cell fibers

Smallest to largest: microfilaments, intermediate filaments, microtubles. Microfilaments: "cellular muscles"; are made of thin, twisted strands of protein molecules; proteins can be pulled by little "motors" and slide past one another to cause shortening of the cell. Intermediate filaments: twisted protein strands that are slightly thicker than microfilaments; form much of the supporting framework in many types of cells; act as tendons and ligaments of the celll, holding the cell together as it is pushed and pulled. Microtubules: thickest of the cell fibers, tiny, hollow tubes; made of protein subunits arranged in a spiral fashion; "engines" of the cell because they often move things around the cell -- or even cause movement of the entire cell.

Major substances that can pass vs. those that cannot pass through the cell membrane

Some small, uncharged molecules can easily pass through the phospholipid membrane, but water an urea rarely get through the membrane. Larger uncharged molecules and ions (charge molecules) may not pass through the phospholipid membrane at all.

Major function(s) of: Smooth endoplasmic reticulum

Synthesizes lipids incorporated in cell membranes, steroid hormones, and certain carbohydrates used to form glycoproteins - also removes and stores Calcium ions from the cell's interior; *makes membrane for use throughout the cell

Compare/Contrast: Translation vs. transcription

TRANSCRIPTION: Beginning steps of protein synthesis; synthesis of any RNA molecule copies or "transcribes" a portion of the DNA code which is then edited and prepared for translation. TRANSLATION: After the edited mRNA molecule attracts the subunits of a ribosome to form an mRNA sandwich, it is now ready to interpret or "translate" the genetic code and form a specific sequence of amino acids.