Cells Pages 29 – 49 Chapter 3

Page 30 Cells Cell = the basic unit of structure & function of all living things Our bodies are made up of trillions of cells that live mostly for a few weeks or moths, die, & are replaced by new cells.

Protoplasm Page 30 Cells are composed: Protoplasm = an aqueous solution of carbohydrates, proteins, lipids, nucleic acids, & inorganic salts surrounded by a cell membrane. Organelles = structures that have a specific function in the cell Nucleus Mitochondria Ribosomes Lysosomes Centrosomes Peroxisomes Centrioles The Golgi apparatus Endoplasmic reticulum cytoskeleton Protoplasm inside the nucleus of a cell is called nucleoplasm & outside the nucleus is called cytoplasm

Cell/Plasma Membrane Page 30 Cell membrane (plasma membrane/semipermeable membrane) = surrounds the cell & separates it from the external environment & from neighboring cells. It also regulates the passage or transport of certain molecules into & out of the cell, while preventing the passage of others. Its composed of a double phospholipid layer, with proteins embedded in the layer. Phospholipid layer looks like balloon with tails the round balloon like part is hydrophilic (attacks water) & the double tails are hydrophobic (repels water). This arrangement allows for easy passage of water molecules through the cell membrane by osmosis. The proteins embedded in the double phospholipid layer allows for the passage of molecules & ions across the cell membrane.

Page 30 Nucleus Nucleus = Most important organelle within the cell, usually located in the center of the cell, spherical in shape with a nucleus membrane surrounding it. Contains DNA & chromatin Function: Control the activities of the cell Facilitate cell division Chromosomes = chromatin condensed to form short rod-like structures. (only happens during mitosis & these are visible on a microscope) Chromatin = DNA & protein arranged in a loose diffuse state

Functions of Organelles Page 31 – 32 Functions of Organelles Nuclear membrane (nuclear envelope) = Regulates transport of substances into & out of the cell Nucleoplasm = A clear, semi-liquid medium that fills the spaces around the chromatin & the nucleoli Nucleolus = Reservoir for RNA Ribosomes = Serve as site for protein synthesis Cytoplasm = Provides an organized watery environment where life functions take place via the activities of the organelles, which reside there

Functions of Organelles Page 32 – 33 Functions of Organelles Centrosome = Contains two centrioles that are functional during animal cell division Endoplasmic reticulum = Provides passage for the transport of substances in the cytoplasm Mitochondria = Serve as sites of cellular respiration & energy production; Store ATP Golgi apparatus = Manufactures carbohydrates & packages secretions for discharge from the cell

Functions of Organelles Page 33 – 34 Functions of Organelles Lysosomes = Serve as center for cellular digestion Perioxisomes = Enzymes that oxidize cell substances Cytoskeleton = Forms internal framework Pinocytic vesicles = Provide mechanism by which large molecules can enter the cell Cilia & flagella = Create movement

Cellular Metabolism Page 34 Chemical reactions occur within the cells Energy supplied by ATP ATP created from carbohydrates, proteins, & fats that we eat

Cell Division Page 34 Meiosis Involves reproduction Each daughter cell carries only half of the chromosomes (23) Mitosis Involves growth & maintenance of cells Each daughter cell carries the complete set of chromosomes (46)

Meiosis Page 34 Process of cell division of the sex cell or gamete Ovum & spermatozoa reduce chromosomes from 46 to 23 Fertilization = union of ovum & spermatozoa Zygote is formed from two sex cells to obtain full set of 46 chromosomes

Mitosis Page 34 Two distinct processes of cell division: Division of the nucleus Division of the cytoplasm Mitosis essentially is an orderly series of steps by which the DNA in the nucleus or the cell is equally distributed to two daughter, or identical, nuclei. During the process, the nuclear material is distributed to each of the two nuclei. This followed by the division of the cytoplasm into two approximately equal parts through the formation of a new membrane between the two nuclei. Mitosis is a smooth, continuous process. For ease & convenience of study, however, five stages, or phases, have been identified by the cell biologist.

Page 35 Mitosis Stages Phase I – Interphase = (resting stage) refers only to the fact that the cell is not actively undergoing cell division At the start of mitosis, each chromosome has already replicated. Each strand of the replicated chromosome is called a chromatid. The two chromatid strands are joined by a small structure called the centromere. During interphase, two centrioles located near the periphery of the nucleus are quite visible. The two centrioles are found in an area called the centrosome. Replication = the duplication of the molecules of DNA within a chromosome (occurs in interphase)

Mitosis Stages (Cont’d) Pages 35 – 36 Mitosis Stages (Cont’d) Phase II – Prophase = During this phase, the two pairs of centrioles start to separate toward the opposite ends the cell. As the two pairs of centrioles migrate, an array of cytoplasmic microtubules form between them. There are changes in the nucleus as well. The nuclear membrane starts to dissolve & the nucleus disappears. The DNA in the chromosomes becomes more coiled or condensed & forms very deeply staining, rod-like structures. cytoplasmic microtubules

Mitosis Stages (Cont’d) Pages 35 – 36 Mitosis Stages (Cont’d) Phase III – Metaphase = the nuclear membrane has dissolved completely. The chromatid pairs arrange themselves in a single file, one chromatid pair per spindle fiber between the two centrioles The area where the chromatid pairs align is called the equatorial plate. Phase IV – Anaphase = During this phase the chromatid pairs separate & are pulled by the shortening spindle fibers toward the centrioles. The two chromatids of each replicated chromosome are now fully separated.

Mitosis Stages (Cont’d) Page 36 Mitosis Stages (Cont’d) Phase V – Telophase = During this phase the chromosomes migrate to the opposite poles of the cell. There they start to uncoil to become loosely arranged chromatin granules. The nucleolus granules. The nuclear membrane & the nucleolus reappear to help reestablish the nucleus as a definite organelle again. When the cytoplasmic division is finished, two new daughter cells are formed. Cycle back to interphase

Page 36 Mitosis Stages Mitosis is a smooth, continuous process. For ease & convenience of study, however, five stages, or phases, have been identified by the cell biologist.

Page 37 Cell Death Necrosis = the name given to the unprogrammed death of cells & living tissue. Apoptosis = death that is the predestined fate of individual cells or organisms. There are many causes of necrosis, including injury, infection, cancer, infarction (blood clot), toxins, & inflammation. Cells that die from necrosis may release harmful chemicals that damage other cells. Apoptosis is an orderly process by which cells intentionally die. The cell itself initiates, regulates, & executes its death with an elaborate arsenal of cellular & molecular activity. The term apoptosis is used interchangeably with the term programmed cell death (PCD). Apoptosis confers advantages during an organism’s life cycle, for example, the differentiation of fingers & toes. In a developing human embryo, the cells in the tissues between the fingers & toes initiate apoptosis so that fingers & toes can separate.

Protein Synthesis Page 37 Cells produce proteins that are essential to life DNA RNA Within each cell, the DNA determines the kinds of proteins that are produced. The blueprint for each individual kind of protein is contained within a specific gene that resides in the DNA chain. As stated in Chapter 2, massager RNA carries the instruction for protein synthesis from the DNA to the ribosome in the cytoplasm. The transport RNA molecule picks up the amino acid molecule in the cytoplasm & takes it to the ribosome, where they combine to form a specific protein. Proteomics is the large-scale study of the proteins that are made as a result of genetic instructions from RNA & ribosomes. Because proteins play a central role in the life of an organism, the study of proteomics will be instrumental in the discovery of biomarkers (substances found in the blood or tissue in small amounts) that may indicate a specific disease.

Stem Cells Page 38 Embryonic stem cells Adult stem cells Umbilical cord blood stem cells Induced pluripotent stem cells These cells retain the ability to renew themselves through cell division & to differentiate themselves into a wide range of specialized cell types

Movement of Materials Across Cell Membranes Pages 37 – 40 Movement of Materials Across Cell Membranes Passive transport = Does not require an energy source Diffusion = a physical process whereby molecules of gases, liquids, or solid particles spread or scatter themselves evenly through a medium. Osmosis = the diffusion of water or any other solvent molecule through a selective permeable membrane. Filtration = the movement of solutes & water across a semipermeable membrane. Generally molecules move from an area where they are greatly concentrated to an area where they are less concentrated. Solvent = the liquid in which a solute is dissolved to form a solution. Solute = the minor component in a solution, dissolved in the solvent

Movement of Materials Across Cell Membranes Pages 40 – 41 Movement of Materials Across Cell Membranes Active transport = Requires an energy source Phagocytosis = the substances engulfed are within particles Pinocytosis = the substances engulfed by the cell membrane are in solution molecules move from an area where they are of low concentration to an area where they are more concentrated. Human white blood cells undergo phagoctosis. The particulate substance is engulfed by an enfolding of the cell membrane to form a vacuole enclosing the material. When the material is completely enclosed within the vacuole, digestive enzymes pour into the vacule from the cytoplasm to destroy the entrapped substance.

Figure 3 – 9 The Active Transport Model Page 42 Figure 3 – 9 The Active Transport Model

Specialization Page 41 May lose some functions, such as reproduction Interdependence among cells Nerve cells – Specialize in response Red blood cells – Specialize in oxygen transport

Disorders of Cell Structure Page 42 Disorders of Cell Structure Atrophy = cells decrease in size usually due to ageing or disease Hypertrophy = cells increase in size usually due to workload Hyperplasia = cells increase in number which is related to hormonal stimulation Metaplasia = cells change into another type of cell this may be a protective response to a stimulus Dysplasia = change in size, shape, & organization of cells as result to stimulus. Can progress to neoplasia Neoplasia = changes in cell structure that occur in an uncontrolled growth patterns. Hypoxia = a decrease in the amount of oxygen in the blood flow to cellular structure Anoxia = a lack of oxygen flow to cellular structures, most commonly cause death in cells.

Pages 43 – 44 Tumor When cell division does not occur in the usual pattern – also called neoplasms Benign tumors = composed of cells confined to the local area Malignant tumors = can spread to other parts of the body through a process called metastasis Roman Numeral Staging Stage 0: Cancer is in situ (limited to surface cells) Stage I: Cancer is limited to the tissue of origin Stage II: There is limited local spread of cancerous cells; it may involve an adjacent lymph node Stage III: There is extensive local & regional spread to lymph nodes Stage IV: Cancers have often metastasized, or spread to other organs or throughout the body.

Aging Page 43 Aging is a phase of normal development Older person may have 30% fewer cells Cells may change in ability to perform specialized tasks Physiologic changes are universal and progressive Aging is not a disease