Chapter 3: Cellular Level of Organization Flashcards
name and describe the three main parts of a cell.
Cell: living structural and functional units enclosed by a membrane. Cells carry out a multitude of functions that help each system contribute to the homeostasis of the entire body. At the same time, all cells share key structures and functions that support their intense activity. Cell division: a process through which one cell divides into two identical cells. Cell biology: also called cytology; the study of cellular structure and function.
Major components of a cell:
- Plasma Membrane: forms the cell’s flexible outer surface, separating the cell’s internal environment from the external environment. - A selective barrier that regulates the flow of materials into and out of a cell- This selectivity helps establish and maintain the appropriate environment for normal cellular acitivities and plays role in communication among cells and between their external environment
- Cytoplasm: consists of all the cellular contents between plasma membrane and nucleus. Has two components: - Cytosol: the fluid portion of cytoplasm (intracellular fluid) contains water, dissolved solutes, and suspended particles.- organelles (little organs) within the cytosol that have characteristic shapes and specific function
- Nucleus: a large organelle that houses most of a cell’s DNA. Within the nucleus, each chromosome, a single molecule of DNA associated with several proteins, contains thousands of hereditary units called genes that control most aspects of cellular structure and function
distinguish between cytoplasm and cytosol.
Cytoplasm: consists of all the cellular contents between plasma membrane and nucleus.
Has two components: - Cytosol: the fluid portion of cytoplasm (intracellular fluid) contains water, dissolved solutes, and suspended particles.- organelles (little organs) within the cytosol that have characteristic shapes and specific function
explain the concept of selective permeability.
Selective Permeability: permeable means that a structure permits the passage of substances through it. The perme- ability of the plasma membrane to different substances varies. Plasma membranes permit some substances to pass more readily than others. This property of membranes is termed selective permeability
define the electrochemical gradient and describe its components.
Electrochemical gradient: The combined influence of the concentration gradient and the electrical gradient on movement of a particular ion produced by the cell for export or as cellular waste products must move out of the cell. Substances generally move across cellular membranes via transport processes that can be classified as passive or active, depending on whether they require cellular energy
Substances move down their concentration/electrical gradient.
describe the processes that transport substances across the plasma membrane.
1) Passive Transport- No ATP [High] to [Low]. Naturally equilibrium
Simple Diffusion (without a protein): is a passive process in which the random mixing of particles in a solution occurs because of the particles’ kinetic energy. Both the solutes, the dissolved sub- stances, and the solvent, the liquid that does the dissolving, undergo diffusion. Substances move down their concentration/electrical gradient.
Carrier Mediated (w protein) - Larger molecules, sugar amino acid, activated by [ ] gradient
Channel Meditated (w protein) - small lipid insoluble solutes (IONS), selected by size and charge Most numerous ion channels: K+ and CL-, fewer for Na+ and Ca2+
osmosis – type of passive diffusion in which there is a net movement of a solvent through a selectively permeable membrane. In living systems, the solvent is water, which moves across membranes from an area of higher water concentration to lower water concentration. Water molecules pass through the plasma membrane in 2 ways: by moving via simple diffusion and 2) by moving through aquaporins. Occurs only when a membrane is permeable to water but not permeable to certain solutes. aquaporins – integral membrane proteins that fcn as water channelshydrostatic pressure – pressure exerted by a liquid on its side of the membrane, which forces water molecules to move back through the membrane. Equilibrium is reached when water molecules move across the membrane in both directions at the same rate.osmotic pressure – the amount of pressure needed to restore the starting condition; proportional to the concentration of the solute particles that cannot cross the membrane, the higher the solute concentration, the higher the solution’s osmotic pressure. Tonicity – a measure of the solutions ability to change the volume of cells by altering their watercontent. isotonic solution – any solution in which a cell maintains its normal shape and volumehypotonic solution – a solution that has a lower concentration of solutes than the cytosol inside the cell. Causes water molecules to enter the cells faster than they leave, cell swells and eventually bursts. Hemolysis – the rupture of a RBC because of placement in a hypotonic solutionLysis – the rupture of any other type of cell due to placement in a hypotonic sol’nhypertonic solution – has a higher concentration of solutes than the cytosol inside RBCs. Causes water molecules to leave the cell faster than they enter, causes the cell the shrink.Crenation – shrinkage of cells caused by placement in a hypertonic solution
2) Active Transport: cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient. The cellular energy used is usually in the form of adenosine triphosphate (ATP).
Primary - energy from hydrolysis of ATP cause shape change of protein and Ions are pumped against gradient (EX NA+/K+ pump makes NA higher in ECF and K higher in ICF (not natural))
Secondary - INDIRECT ATP uptake of glucose due to NA+ gradient. co transporter takes glucose/amino acid/small molecules and Na+ back to ICF
3) Vesicular transport (large molecules across plasma membrane and around cell) Pinocytosis ingesting small Phagocytosis ingesting and eliminating large
describe the structure and function of cytoplasm, cytosol, and organelles.
Cytoplasm—all the cellular contents within the plasma membrane except for the nucleus—consists of cytosol and organelles.
Cytosol is the fluid portion of cytoplasm, containing water, ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste products. It is the site of many chemical reactions required for a cell’s existence. Organelles are specialized structures with characteristic shapes that have specific functions
Components of the cytoskeleton, a network of several kinds of protein filaments that extend throughout the cytoplasm, include microfilaments, intermediate filaments, and microtubules. The cytoskeleton provides a structural framework for the cell and is responsible for cell movementsThe centrosome consists of pericentriolar material and a pair of centrioles. The pericentriolar material organizes microtubules in nondividing cells and the mitotic spindle in dividing cells
Cilia and flagella, motile projections of the cell surface, are formed by basal bodies. Cilia move fluid along the cell surface; flagella move an entire cellRibosomes consist of two subunits made in the nucleus that are composed of ribosomal RNA and ribosomal proteins. They serve as sites of protein synthesis
Endoplasmic reticulum (ER) is a network of membranes that form flattened sacs or tubules; it extends from the nuclear envelope throughout the cytoplasm. Rough ER is studded with ribosomes that synthesize proteins; the proteins then enter the space within the ER for processing and sorting. Rough ER produces secretory proteins, membrane proteins, and organelle proteins; forms glycoproteins; synthesizes phospholipids; and attaches proteins to phospholipids. Smooth ER lacks ribosomes. It synthesizes fatty acids and steroids; inactivates or detoxifies drugs and other potentially harmful substances; removes phosphate from glucose-6-phosphate; and releases calcium ions that trigger contraction in muscle cellsThe Golgi complex consists of flattened sacs called cisternae. The entry, medial, and exit regions of the Golgi complex contain different enzymes that permit each to modify, sort, and package proteins for transport in secretory vesicles, membrane vesicles, or transport vesicles to different cellular destinations.
Lysosomes are membrane-enclosed vesicles that contain digestive enzymes. Endosomes, phagosomes, and pinocytic vesicles deliver materials to lysosomes for degradation. Lysosomes function in digestion of worn-out organelles (autophagy), digestion of a host cell (autolysis), and extracellular digestion.
Peroxisomes contain oxidases that oxidize amino acids, fatty acids, and toxic substances; the hydrogen peroxide produced in the process is destroyed by catalase. The proteases contained in proteasomes, another kind of organelle, continually degrade unneeded, damaged, or faulty proteins by cutting them into small peptides
Mitochondria consist of a smooth outer membrane, an inner membrane containing mitochondrial cristae, and a fluid-filled cavity called the mitochondrial matrix. These so-called powerhouses of the cell produce most of a cell’s ATP and can play an important early role in apoptosis.
describe the structure and function of the nucleus.
Structure – Spherical or oval shaped structure that usually is the most prominent feature of the cell, consists of a double nuclear envelope, nuclear pores control movement of substances between the nucleus and cytoplasm, nucleoli, which produces ribosomes and genes arranged on chromosomes Function – Controls cellular activities, produces ribosomes in nucleoli
describe the sequence of events in protein synthesis
- Cell makes protein by transcribing and translating information in DNA
- Transcription – Transfer of genetic instruction in DNA to mRNA in the nucleus. Includes initiation, elongation and termination after complete carries the instruction to a ribosome in the cytoplasm
- Translation – Occurs at the ribosome, consists of rRNA and proteins, Instructions in mRNA are read, and tRNA bring the correct sequence of amino acids to the ribosome. rRNA helps bonds form between the amino acids producing a polypeptide chain
- After synthesized the polypeptide chain may undergo additional processing to form the finished protein
discuss the stages, events, and significance of somatic and reproductive cell division
SOMATIC CELL DIVISION (MITOSIS and cytokinesis) 2n - diploid cells
1) Interphase (period b/w cell divisions)
- G1 phase (replicate organelles and chromosomes)
- S phase Reification of DNA and centrosomes
- G3 phase Cell growth protein synthesis continues, centrosome replication complete
2) Mitotic Phase - produce identical daughters cell
-Prophase - Chromatin pairs into chromatids, nucleaur envelope dissapears, centrosomes move to opposite sides,
-Metaphase Centromeres line up at metaphase plate
-Anaphase - centromeres split and move chromosomes move to opposite sides
Telophase - nucleaur enveloves come back, and mitotic spindle dissapears
-Cytokinesis - cytoplasmic division, cleavage furrow splits in two.
REPRODUCTIVE CELL DIVISION (MEISOS) n haploid cells (2 haploid - 1 diploid - 2 diploid with new info)
Meiosis 1 - prophase 1, metapase 1, anaphase 1, telophase 1 - exchange of chromatid and genetic recomination (
Meisos 2 - same stages with 2
describe the signals that induce somatic cell division.
Cell division, the process by which cells reproduce themselves, consists of nuclear division (mitosis or meiosis) and cytoplasmic division (cytokinesis). Cell division that replaces cells or adds new ones is called somatic cell division and involves mitosis and cytokinesis. Cell division that results in the production of gametes (sperm and ova) is called reproductive cell division and consists of meiosis and cytokinesis
The cell cycle, an orderly sequence of events in which a somatic cell duplicates its contents and divides in two, consists of interphase and a mitotic phase. Human somatic cells contain 23 pairs of homologous chromosomes and are thus diploid (2n). Before the mitotic phase, the DNA molecules, or chromosomes, replicate themselves so that identical sets of chromosomes can be passed on to the next generation of cells
describe how cells differ in size and shape.
The body of an average human adult is composed of nearly 100 trillion cells. All of these cells can be classified into about 200 different cell types. Cells vary considerably in size. The sizes of cells are measured in units called micrometers- They may be round, oval, flat, cube-shaped, column-shaped, elongated, star-shaped, cylindrical, or disc-shaped. A cell’s shape is related to its function in the body- cellular di- versity also permits organization of cells into more complex tissues and organs- Although many millions of new cells normally are produced each minute, several kinds ofcells in the body—including skeletal muscle cells and nerve cells—do not divide becausethey are ar- rested permanently in the G0 phase- Cancer is a group of diseases characterized by uncontrolled or abnor- mal cell division. When cells in a part of the body divide without con- trol, the excess tissue that develops is called a tumor or neoplasm- Cells of malignant tumors duplicate rapidly and continuously. As malignant cells invade surrounding tissues, they often trigger angio- genesis (an’-je -o -JEN-e-sis), the growth - -of new networks of blood vessels.- Several factors may trigger a normal cell to lose control and become cancerous. One cause is environmental agents, others are genes (oncogenes)
