RAD 114 RADIATION PROTECTION OVERVIEW OF CELL BIOLOGY
PROTOPLASM z PROTEINS z CARBOHYDRATES z LIPIDS z NUCLEIC
ACIDS z INORGANIC SALTS z WATER
PROTEINS Formed by combining amino acids (from among 22 known) and serve STRUCTURAL or ENZYMATIC functions. Proteins can also exist as hormones (regulatory functions) and antibodies (immune response).
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CARBOHYDRATES Are simple sugars (saccharides). Serve the short-term energy needs of cells. They also comprise parts of cell walls and intercellular (inter=between) materials.
LIPIDS Loosely called “fats,” are substances made up of fatty acids, the constituents of amino acids. They do not dissolve in water, and form long chains of molecules (macromolecules). Lipids provide long-term storage of energy and comprise portions of cell membranes.
NUCLEIC ACIDS Complex macromolecules consisting of linked molecules called nucleotides. Nucleotides consist of a nitrogen-containing organic base, a five-carbon sugar molecule and a phosphate molecule.
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NUCLEIC ACIDS z DEOXYRIBONUCLEIC
ACID (DNA) z RIBONUCLEIC ACID (RNA)
DNA Responsible for control of cell functions. Also contains genetic information representing the cell. Reproductive cells contain DNA for the whole organism.
DNA DNA is contained in the nucleus of each cell. Cellular activities cannot be carried out directly by DNA, but is mediated by the creation of messenger RNA.
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RNA Ribonucleic acid is a partial copy of DNA. Each copy is representative of the type of protein to be made from amino acids. The instruction code contained in mRNA is transferred to another kind of RNA called transfer RNA.
RNA The tRNA obtains the correct amino acid in the correct order and links them together with the help of the RIBOSOMES. The linked amino acids become proteins.
PROTEIN SYNTHESIS
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ANATOMY OF DNA DNA is structured like a spiral staircase, with the rails consisting of alternating bands of sugar and phosphate molecules (sugar-phosphatesugar-phosphate). The rungs consist of nitrogenous bases arranged in specific order...
DNA
DNA MACROMOLECULE P
S
P
C
S
PURINE ADENINE (A) GUANINE (G)
P
P
S WITH
S
P
G
T
G P
S A
C P
S
P
PYRIMIDINE THYMINE (T) CYTOSINE (C)
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OTHER CELL COMPONENTS ENDOPLASMIC RETICULUM LYSOSOMES z GOLGI APPARATUS z MITOCHONDRIA z CENTROSOME (CENTRIOLES) z NUCLEUS z NUCLEOLUS z RIBOSOMES z z
ENDOPLASMIC RETICULUM The transportation network of the cell. Certain reticula are speckled with ribosomes and are called ROUGH ENDOPLASMIC RETICULA. These are essential to protein synthesis.
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LYSOSOMES Serve the digestive or debris removal function of the cell. Lysosomes are sac-like structures which contain enzymes to digest cellular fragments.
GOLGI APPARATUS Serves the packaging and export needs of the cell. A network of tubes and tiny sacs extend from the nucleus to the cell membrane. Hormones and enzymes are transported to the extracellular environment via the golgi apparatus.
MITOCHONDRIA Large bean-shaped structures responsible for energy production. Nutrients are broken down to produce adenosine triphosphate (ATP). Mitochondria are responsible for active transport within the cell.
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ACTIVE TRANSPORT A biochemical process that causes the movement of solutes across a membrane from lower concentration to higher concentration. This is not the same as osmosis, which causes the solvent (water) to move across a membrane from lower concentration to higher concentration.
CENTROSOMES Located in the center of the cell near the nucleus. They contain the CENTRIOLES which are believed to form spindle fibers during cellular division.
NUCLEUS The “heart” of the cell, contains genetic material in its molecular structure. Controls all aspects of cell function including replication. Within the nucleus is the NUCLEOLUS which contains large amounts of RNA.
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RIBOSOMES Small spherical structures which are attached to certain endoplasmic reticula. These are responsible for protein synthesis. Ribosomes consist of RNA (2/3) and protein (1/3).
CELL MEMBRANE Semi-permeable barrier between the cell and its environment. Serves to protect the cell and acts to control the passage of water and other materials into and out of the cell.
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TYPES OF CELL DIVISION z MITOSIS z MEIOSIS
MITOSIS Cell reproduction involving “somatic” cells. This process results in the formation of two daughter cells containing roughly equal amounts of cellular material. Each human somatic cell contains 46 chromosomes.
MEIOSIS Cell division involving reproductive cells (sperm or egg cells). Each MATURE daughter cell contains half the number of chromosomes contained in somatic cells (23).
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CELL DIVISION CYCLE z INTERPHASE z PROPHASE z METAPHASE z ANAPHASE z TELOPHASE
INTERPHASE A preparatory period for the cell prior to cell division. The period is divided into three phases: G1, S and G2. G1 involves the production of RNA helpful to DNA replication. S is the actual DNA replication phase. G2 involves the production of RNA and proteins needed for mitosis (M).
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PROPHASE Is characterized by the loss of the nuclear membrane and the genetic material coiling up to take shape as chromosomes. Centrioles manufacture spindle fibers.
METAPHASE Spindle fibers attach to organelles called centromeres (connect 2 pairs of chromatids). Chromosomes align at the cell’s middle. During this phase, cell division can be stopped and the chromosomes examined under a microscope.
ANAPHASE The centromeres split and the chromatids migrate to opposite sides of the cell, drawn by the spindle fibers.
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TELOPHASE Genetic material uncoils, becoming indistinct. Two nuclear membranes appear. The cytoplasm divides, surrounding each nucleus. Finally, they separate to become two daughter cells.
2ND (MEIOTIC) DIVISION Sperm and egg cells must divide one additional time in order to halve the number of chromosomes. Therefore 2 daughter cell become 4 “granddaughter” cells, each containing 23 chromosomes.
