Memmler's Structure and Function of the Human Body 10e: Chapter 3 Cells and Their Function

explain the importance of cellular reproduction.

Cellular reproduction is important because for growth, repair, and reproduction, cells must multiply to increase their numbers.

Linking proteins (linkers)

give shape to membrane and help cells attach to each other.

flagellum

moves the cell; single, long whiplike projection extending from cell, such as the tail of the male sperm cell.

Hypotonic solution

less concentrated than the intracellular fluid: hemolysis blood cell bursts because it draws in water

Centrioles

paired organelles. Separate chromosomes during cell division. They are rod-shaped and lie at right angles to each other.

Enzymes

participate in reactions at the surface of the membrane

three major components of a cell

plasma membrane cytoplasm nucleus

Receptors

points of attachment for materials coming to the cell in the blood or tissue fluid. Hormones, e.g., must attach to receptors on cell surface before they can act upon cell

Channels

pores that allow specific substances to enter or leave. Certain ions travel through channels

Endoplasmic reticulum (ER)

rough ER sorts proteins and forms them into more complex compounds; smooth ER involved with lipid synthesis. Network of membranes within cytoplasm.

Nuclear membrane

surrounds nucleus

Bulk transport

(vesicular transport) Moving large quantities of materials in and out of cell

RNA FUNCTION IN PROTEIN SYNTHESIS

+RNA interprets and acts upon DNA blueprint. *RNA like DNA except that it is a single strand of nucleotides and has uracil (U) instead of thymine (T). So when RNA pairs up with molecule of amino acid to manufacture proteins A bond with U.

Membrane potential (trans-membrane potential)

- plasma membrane carries a difference in electric charge (voltage) on either side. Difference created by positive and negative ions (Na+, Cl-, Ca2+), concentrated on either side of membrane and by negatively charged proteins held inside plasma membrane. Inside membrane negative 70 mV compared to outside. In mitochondria generates ATP. Key in cellular communication. Reversals of potential creates reversal of charge along membrane (outside negative, inside positive). Reversals from forces: chemicals, electric energy (voltage), light and pressure.

Cell

-basic unit of all life -shows all characteristics of life including: organization, metabolism, responsiveness, homeostasis, growth and reproduction.

Ribosomes

ASSEMBLE AMINO ACIDS INTO PROTEINS. attached to and are part of the rough ER but may also be free in the cytoplasm. made up of a special kind of RNA called ribosomal RNA. named "protein factories" because of their very complex function.

PROTEIN SYNTHESIS:

Begins with transfer of info from DNA to RNA in nucleus, process known as transcription. Before transcription begins, DNA breaks its weak H bonds and uncoils into single strands. Then matching strand of RNA forms along one of the DNA strands by process of nucleotide pairing. Example, if DNA strand CGAT, corresponding mRNA will be GCUA. When complete messenger RNA leaves nucleus and travels to a ribosome in cytoplasm. Ribosomes are site of protein synthesis. Ribosomes are composed of ribosomal RNA (rRNA) and also a protein. At ribosomes, genetic message in mRNA decoded to build amino acids into long chains that form proteins, process called translation. This final step requires transfer RNA (tRNA), small molecules present in cytoplasm. Both rRNA and tRNA formed by transcription. Each tRNA carries specific amino acid that can be added to protein chain. Nucleotide code on each tRNA determines whether amino acid will be added. After amino acid chain formed, must be coiled and folded to proper shape for that protein.

Endocytosis

Bulk movement of large materials into cell

Exocytosis

Cell moves materials out in vesicles. Eg. Export of neurotransmitters from neurons.

Mitochondria

Convert energy from nutrients into ATP. supply most of the power for cellular work. They have been nicknamed the cell's "power plants." The survival of the cells and the body depends on the mitochondrial chemical reactions.

PASSIVE TRANSPORT SYSTEMS

DEPEND ON INTERNAL ENERGY OF MOVING PARTICLES OR APPLICATION OF OUTSIDE SOURCE OF ENERGY. i. Diffusion ii. Facilitated diffusion iii. Osmosis iv. Filtration

Phagocytosis

Large particles engulfed by plasma membrane and moved into cell (phag/o "to eat") -the intake of food by the cell membrane at the expenditure of energy from ATP.

Golgi apparatus

MAKES COMPOUNDS CONTAINING PROTEINS. Sorts and prepares these compounds for transport to other parts of cell or out of cell.

nucleolus ("little nucleus")

MAKES RIBOSOMES thus vital in protein formation because it "programs" the formation of ribosomes in the nucleus. composed of RNA, DNA, and protein

ACTIVE TRANSPORT SYSTEMS

MOVEMENT ACROSS MEMBRANE REQUIRES ENERGY I. Active transport II. Bulk transport A. Endocytosis i. Phagocytosis ii. Pinocytosis iii. Receptor mediated endocytosis B. Exocytosis

DNA FUNCTION IN PROTEIN SYNTHESIS

Most DNA organized into chromosomes within nucleus (small amount in mitochondria in cyto.) DNA is double strand. E.g. Ladder - sugar and phosphate units of nucleotide make up side rails, nitrogen bases are ladders steps. DNA paired according to nitrogen bases in nucleotides. Adenine (A) always pairs with thymine (T); guanine (G) always pairs with cytosine (C). Two strands of DNA held together by weak H bonds. Doubled strands then coil into spiral double helix. Message of DNA in gene is pattern of four nucleotides along strand. DNA can make variety of words with nucleotides. Words represent amino acids used to make proteins, and long string of words make up gene. Each gene codes for building of amino acids into specific cellular protein. Enzymes are proteins and are needed for all cellular reactions. DNA cells master blueprint. Different cells vary because only portions of DNA in given cell are active at any one time. Some cells, regions of DNA can be switched on and off, under hormone influence. However, as cells differentiate during development and become specialized, regions of DNA permanently shut down, leading to variations in cells. DNA action involves NOT only DNA but proteins

Flagellum

Moves the cell; single, long whiplike projection extending from cell, such as the tail of the male sperm cell.

Compare and discuss DNA and RNA and their function in protein synthesis.

a. DNA with its coded genetic information is contained in the nucleus of the cell. Protein synthesis, however, occurs in ribosomes and on ER. The process of transferring genetic information from the nucleus into the cytoplasm, where proteins are actually produced, requires completion of two specialized steps called transcription and translation. b. During transcription the double-stranded DNA molecule separates or unwinds and a special type of RNA called messenger RNA is formed. The messenger RNA is said to have been "transcribed" from its DNA mold or template. c. Translation is the synthesis of a protein by ribosomes, which use the information contained in an mRNA molecule to direct the choice and sequencing of the appropriate chemical building blocks.

MITOSIS

all other body cells, somatic cells, formed by mitosis. In process, each original parent cell becomes two identical daughter cells.

mRNA (messenger)

built on strand of DNA in nucleus and transcribes the nucleotide code; moves to cytoplasm and attaches to ribosome

Anaphase

centromere splits and duplicated chromosomes separate and begin to move toward opposite ends of cell.

Metaphase

chromosomes line across center (equator) of cell attached to spindle fibers.

Nucleus (Identify and discuss the basic structure and function of the three major components of a cell.)

circular structure usually located toward the center of the cell. Its function is to control heredity and reproduction. Control center of the cell because it contains chromosomes (govern all cellular activity) Largest organelle, dark staining, near center of cell, made of DNA and proteins. • nucleolus (globule) "little nucleus"composed of RNA, DNA, and protein: assembles ribosomes. • Nuclear membrane

Lysosomes

contain chemicals that can digest food compounds, thus the name "digestive bags." They can also digest and destroy microbes that invade the cell. Lysosomes can protect cells but also can damage or destroy "good" cells. If enzymes escape from the lysosome sacs into the cytoplasm, they kill the cell by digesting it. Nicknamed the "suicide bags."

Prophase

double strands of DNA return to tight spiral organization and become visible under microscope as dark threadlike chromosomes. Nucleolus and nuclear membrane begin to disappear. In cytoplasm two centrioles move toward opposite ends of cell, and spindle shaped structure made of thin fibers begins to form between them.

Cytosol

fluid portion of the cytoplasm

Osmotic pressure

force driving osmosis measured by applying enough pressure to liquid to stop inward flow of water. Tendency to draw water in. This force related to concentration: higher concentration, greater draw water in (more force).

Nucleus

function is to control heredity. Control center of the cell because it contains chromosomes (govern all cellular activity) Largest organelle, dark staining, near center of cell, made of DNA and proteins.

Receptor mediated endocytosis

intake of substances using specific binding sites, or receptors, in the plasma membrane. a. ligand - the bound material drawn into cell (eg. Lipoproteins involved in cholesterol metabolim, hormones, vitamins

Cytoplasm (Identify and discuss the basic structure and function of the three major components of a cell.)

material fills cell from plasma membrane to nuclear membrane. It contains all the organelles (little organs)

Telophase

membrane appears around each group of separated chromosomes, forming two new nuclei. o Plasma membrane pinches off to divide cell. Midsection between two areas becomes progressively smaller until, finally, cell splits into two. o Now two new cells, or daughter cells, each with exact same kind and amount of DNA as present in parent cell

peroxisomes

membrane enclosed containing enzymes; breakdown harmful substances produced in metabolism and toxins such as alcohol and drugs.

Hypertonic solution

more concentrated than the cellular fluid and leads to crenation in which blood cell shrinks because it loses water to the surrounding fluids

Cilia

move cell or fluids around cell; hairlike extensions on the surface of some cells. They are capable of moving a substance such as mucus upward over the cells that line the respiratory tract.

Filtration

movement of both water and solutes through a membrane because of a greater pushing force on one side of the membrane than on the other side. This force is called mechanical (pushing) force. Eg. Movement of materials out of capillaries and into tissues under force of blood pressure created by heart contractions. Kidneys materials filtered out of blood in urine formation. Car pump. Espresso coffee.

Cell identity markers

proteins unique to a person's cells; important in the immune system and in transplantation of tissue from one person to another.

Meiosis

sex cells divide by meiosis which cuts chromosome number in half to prepare for union of egg and sperm in fertilization. If not for this reduction number of chromosomes would constantly double.

vesicles

small membrane sacs in the cytoplasm that store materials and move materials into or out of the cell in bulk.

Isotonic solution

solution with concentration of solute equal to the concentrations of cytoplasm

Osmosis

special diffusion. Applies to water through a semipermeable membrane with the help of aquaporins. The solvent moves from lower solute (sodium,glucose) concentration to an area of higher solute concentration. Water molecules move, as expected, from area of high water concentration (more solvent) to an area of lower water concentration (less solvent).

Pinocytosis (cell drinking)

the intake of fluid droplets by the cell membrane at the expenditure of energy from ATP. How large protein molecules in suspension travel into cell.

Plasma membrane (Identify and discuss the basic structure and function of the three major components of a cell.)

this membrane encloses the cytoplasm and forms the outer boundary of the cell. It is made up of layers of fat molecules called phospholipids. Protein molecules can also be found in the plasma membrane. The primary function of the cell membrane is to control what moves into and out of the cell. Participates in many cellular activities: growth, reproduction, communication between cells. Microvilli - Absorption materials into cell Bilayer made of phospholipids: cholesterol between the phospholipids. Glycoproteins, glycolypids.- carbs combined with proteins or lipids present in small amounts in plasma membrane, help cells to recognize each other and to stick together. Proteins all the way through membrane, some near inner or outer surface.

Facilitated diffusion

water soluble materials move across the plasma membrane in the direction of the concentration gradient, but transporters (proteins) are used to move the material at a faster rate. Eg. Glucose uses this form of diffusion.

rRNA (ribosomal)

with protein makes up ribosomes (sites of protein synthesis in cytoplasm); involved in process of translating genetic message into a protein.

tRNA (transfer)

works with other forms of RNA to translate the genetic code into protein, each molecule of tRNA carries an amino acid that can be used to build a protein at the ribosome

PREP FOR MITOSIS

• Before mitosis can occur, the genetic information (DNA) in the parent cell must be replicated (doubled) so two daughter cells receive a complete set of chromosomes. A human cell that divides by mitosis must produce two cells with 46 chromosomes each, same number in original parent cell. • Interphase- • DNA replicates during INTERPHASE, stage between one mitosis and next. • DNA uncoils from double strand, each strand takes on a matching strand of nucleotides according to pattern A-T, G-C pairing. Now 2 strands, each identical to original double helix. • Two strands held together at centromere until separate during mitosis. Cell lives in interphase most of life

Proteins all the way through plasma membrane, some near inner or outer surface.

• Channels - pores that allow specific substances to enter or leave. Certain ions travel through channels • Transporters - shuttle substances from one side of the membrane to the other. Glucose carried into cells using transporters. • Receptors - points of attachment for materials coming to the cell in the blood or tissue fluid. Hormones, e.g., must attach to receptors on cell surface before they can act upon cell • Enzymes - participate in reactions at the surface of the membrane • Linking proteins (linkers) - give shape to membrane and help cells attach to each other. • Cell identity markers - proteins unique to a person's cells; important in the immune system and in transplantation of tissue from one person to another.

STAGES OF MITOSIS (continuous process)

• Prophase • Metaphase - • Anaphase - • Telophase -

Diffusion

• a process in which substances scatter themselves evenly throughout an available space until equilibrium. • Constant movement of particles from a region of higher concentration to lower concentration. • Particles follow concentration gradient from higher to lower concentration. • Gases and lipids only

Active transport

• process that moves substances from an area of low concentration to an area of high concentration against the concentration gradient using transporters. Energy is required for this process and is obtained by breaking down adenosine triphosphate (ATP) molecules. Examples of active transport systems include: • nervous and muscular system depend on the active transport of sodium, potassium, calcium. • Cell can take what it needs from the surrounding fluids and remove materials from cell.

Transporters

• shuttle substances from one side of the membrane to the other. Glucose carried into cells using transporters.