2-cell-edited ver. .pdf

THE CELL CHEMICAL BASIS OF LIFE  Chemicals makes up the body’s structure, and the interaction of chemicals with one another are responsible for the body’s functions ELEMENTS AND ATOMS:  ELEMENTS: is the simplest type of matter having unique chemical properties  ATOM: is the smallest parti...

THE CELL CHEMICAL BASIS OF LIFE  Chemicals makes up the body’s structure, and the interaction of chemicals with one another are responsible for the body’s functions ELEMENTS AND ATOMS:  ELEMENTS: is the simplest type of matter having unique chemical properties  ATOM: is the smallest particle of an element that has the chemical properties of that element ATOMIC STRUCTURE:  Atoms are composed of sub atomic particles. The three major types of sub atomic particles are:  1. Neutrons: have no electrical charge  2. Protons: have positive charges  3. Electrons: have negative charge The Cell  Smallest living sub-units of a multicellular organism such as human being.  Human cells vary in size, shape and function.  Human cells must work together and function interdependently to maintain homeostasis Functions of the Cell 1. Basic unit of life 2. Protection and support 3. Movement 4. Communication 5. Cell metabolism and energy release 6. Inheritance The Cell  Major Parts are: ________  ____________ ____________ ____________. Cell Membrane  The Cell membrane is a semi-permeable membrane that serves as the boundary separating the cellular structures from the external environment  Made up of phospholipids, cholesterol, & proteins Phospholipids Allows a lipid soluble substances to easily enters or leave the cell It makes up most of the cell membrane Forms the myelin sheath to provide electrical stimulation for neurons Cholesterol: decreases the fluidity of the membrane thus making it more stable Converted to vit. D in the skin upon exposure to uv rays of the sun Nucleus  All human cells have nucleus: except RBC  It contains one or more nucleotides and chromosomes of the cell  Because of chromosomal content: it is consider as the “control centre of the cell  Nucleotides is a small sphere made of RNA, DNA, & protein Nucleic Acids 1. DNA (deoxy-ribonucleic acid) 2. RNA (ribonucleic acid) Nucleic acids are large molecules made up of smaller sub units of nucleotides. A nucleotide consist of: pentose sugar, phosphate group, and several nitrogenous base. In DNA nucleotides the sugar is: deoxyribose, the bases are: adenine, guanine, cytosine and thymine. In RNA nucleotides, the sugar is Ribose and the bases are adenine, guanine cytosine and uracil. Both DNA and RNA consist of basic building blocks called nucleotides NUCLEUS  Chromosomes are made of DNA and proteins  Some chromosomal proteins provides a structural framework so that cell division can takes place. Others regulates the activity of DNA.  But only a small number of genes are actually active or switched on in a particular cell.  These active genes are the codes for the proteins necessary for specific ___________________________  DNA is a double helix of nucleotides  DNA makes up the chromosome of the cell and is therefore the genetic code for hereditary characteristics.  The sequence of bases in the DNA strand is actually a code for many kinds of proteins living things produce.  The sequence of bases for one protein is called genes. RNA  RNA is a single helix of nucleotides  Synthesized from DNA in the nucleus of the cell but carries out a major function in the cytoplasm.  Actively involve in protein synthesis Proteins: - made up of smaller sub-units or building blocks called amino acids. - Contains elements such as: carbon, hydrogen, & nitrogen. ATP  Energy currency of cells  Capable of both string and providing energy. CYTOPLASM Watery solution of minerals, gases, organic molecules, and cell organelles that is found between the cell membrane and the nucleus Cytosol – a water portion of the cytoplasm wherein many chemical reactions takes place.  Cell connections Tight junction= binds adjacent cell together and form permeability barrier, which regulates what material crosses Desmosome= mechanical link that functions to bind cell to one another Hemidesmosomes- anchor the cell to the basement membrane Gap junction= small channel that allows small channel that allows molecules and ions to pass from one another The cellular organelles  These are the cellular metabolic units with specific functions to maintain the life of the cell. It includes:  Mitochondrion  endoplasmic reticulum  Ribosome  Golgi apparatus  Lysosomes  Peroxisomes  Cytoskeleton  centrosomes  The mitochondrion  The powerhouse of the cell  Contains enzymes and the complexes responsible for the production of the ATP  Also contains mitochondrial DNA  Metabolic processes occurring in this organelle include – beta-oxidation of fats, urea cycle, heme synthesis  This organelle is maternally inherited The endoplasmic reticulum  An extensive network of membrane-enclosed tubules  There are two types- Rough and Smooth endoplasmic reticulum  Rough endoplasmic reticulum is covered with ribosomes site of protein synthesis  Smooth endoplasmic reticulum has no ribosome site of lipid synthesis  Ribosome  Together with the endoplasmic reticulum is the site of protein synthesis  Maybe found in the cytoplasm and in the mitochondria  They may be free or attached to the endoplasmic reticulum Golgi Apparatus  This organelle modifies, concentrates and packages proteins  This also packages enzymes into lysozomes  Proteins and enzymes usually are transported from the rough endoplasmic reticulum to the golgi apparatus  The lysosomes  These are membrane-limited digestive bodies that contain enzymes that break down foreign or damaged materials  The enzymes digest all materials brought in by phagocytosis  The peroxisomes  Similar to lysosomes, these are membrane- bound sacs containing oxidases (not found in the lysosomes)  Oxidases are enzymes capable of reducing oxygen to hydrogen peroxide  Cytoskeleton  A series of tubules and rods that runs through the cytoplasm supporting the cellular structures  This is also responsible for cellular movements  Centrosomes  This contains the centrioles short cylinders adjacent to the nucleus responsible for cellular division The cellular inclusions  These are non-functional units made up of chemical substances  These may or may not be present in all cells  Examples are pigments, granules, & fat globules  Cilia and Flagella  Cilia are short, hair-like extensions that occur in large numbers on the outer surface of the cell  Flagella are long projections formed by centrioles that propel the cell CELL GROWTH AND CELL DIVISION Cells in the body that do not undergo cell division: 1. Gametes 2. Red blood cells 3. Neurons 4. some muscle cells Somatic cell is a general term for a body cell, and all human cells, except for the cells that produce eggs and sperm (which are referred to as germ cells), are somatic cells. Somatic cells contain two copies of each of their chromosomes(one copy received from each parent). A homologous pair of chromosomes is the two copies of a single chromosome found in each somatic cell. The human is a diploid organism, having 23 homologous pairs of chromosomes in each of the somatic cells. The condition of having pairs of chromosomes is known as diploid Cells in the body replace themselves over the lifetime of a person. For example, the cells lining the gastrointestinal tract must be frequently replaced when constantly “worn off” by the movement of food through the gut. But what triggers a cell to divide, and how does it prepare for and complete cell division? The cell cycle is the sequence of events in the life of the cell from the moment it is created at the end of a previous cycle of cell division until it then divides itself, generating two new cells. THE CELL CYCLE One cell Cycle = One Turn CONSIST OF: Two General Phases 1. Interphase 2. Mitosis and Cytokinesis Interphase is the period of the cell cycle during which the cell is not dividing.  majority of cells are in interphase most of the time.  Mitosis is the division of genetic material, during which the cell nucleus breaks down and two new, fully functional, nuclei are formed.  Cytokinesis divides the cytoplasm into two distinctive cells. Interphase 1. G1 Phase ( gap 1 phase)  a cell grows and carries out all metabolic functions and processes  Growth phase in the cell cycle 2. S Phase ( synthesis phase)  The period where the cell replicates its DNA  DNA replication stage 3. G2 Phase ( 2nd Gap Phase)  Cell continues to grow and makes necessary preparations for mitosis. 4. G 0 (G.o Phase) – resting phase of the cell cycle  Cells that have temporary stopped and are resting  Cells that are permanently ceased dividing  Not all cells undergo Go phase: Cell Division  Formation of two daughter cell from a single parent cell. a. Mitosis – formation of new cell necessary for growth and tissue repair. b. Meosis – formation of sex cell necessary for the reproduction Cellular division  Two types- Mitosis and Meiosis  Mitosis- equal division of materials which yields two exact duplicates of the original cell  The diploid number (46) of chromosomes is maintained  All of the body cells undergo mitosis except the gametes or sex cells Mitosis  All body cell undergo mitosis except sex cell. There are two step in mitosis: a. Genetic material within the cell is replicated. b. Cell divided to form two daughter with same amount and type of DNA. The phases of mitosis)  Prophase-Chromatin coils to form chromosomes, centrioles begin to assemble  Metaphase  chromosomes line the equator, and they split lengthwise  Anaphase-Chromatids separate and move to the opposite poles  Telophase-chromosomes uncoil and nucleoli reappear CYTOKINESIS  Cytokinesis follows after the phases of mitosis  Dividing the cytoplasm and the cell body in two new cells. INTERPHASE TWO NEW DAUGHTER CELLS The cellular division  Meiosis is a reduction division occurring in the sex cells  Sex cells have only one pair of chromosomes (23)haploid number  The cells produce are either egg or sperm cells  Fertilization will restore the diploid number in the fertilized ovum CELL CYCLE CONTROL A very elaborate and precise system of REGULATION controls direct the way cells proceed from one phase to the next in the cell cycle and begin mitosis. The control system involves molecules within the cell as well as external triggers. These internal and external control triggers provide“stop”and“advance”signals for the cell. Precise regulation of the cell cycle is critical for maintaining the health of an organism, and loss of cell cycle control can lead to cancer Mechanism of cell cycle control  As the cell proceeds through its cycle, each phase involves certain processes that must be completed before the cell should advance to the next phase.  A checkpoint is a point in the cell cycle at which the cycle can be signaled to move forward or stopped.  At each of these checkpoints, different varieties of molecules provide the stop or go signals, depending on certain conditions within the cell.  A cyclin is one of the primary classes of cell cycle control molecules.  A cyclin dependent kinase (CDK) is one of a group of molecules that work together with cyclins to determine progression past cell checkpoints.  By interacting with many additional molecules, these triggers push the cell cycle forward unless prevented from doing so by “stop” signals, if for some reason the cell is not ready.  At the G1 checkpoint the cell must be ready for DNA synthesis to occur.  At the G2 checkpoint the cell must be fully prepared for mitosis. Even during mitosis, a crucial stop and go checkpoint in metaphase ensures that the cell is fully prepared to complete cell division.  The metaphase checkpoint ensures that all sister chromatids are properly attached to their respective microtubules and lined up at the metaphase plate before the signal is given to separate them during anaphase. Cellular Differentiation Differentiation – process by which unspecialized cell develop with specialized function.  Egg and sperm cell formed single cell during fertilization divided by mitosis to form two cell then become four cell and so forth which differentiate, give rise to different cell. E.g. bone cell, muscle cell Stem Cells  Differentiate unspecialized cells into a distinct specialized cells.  There are different stem cells present in the stages of human life: 1. Embryonic stem cells – embryo 2. Fetal stem cells – fetus 3. Adult stem cells – adult Adult Stem Cells 1. Epithelial stem cell: give rise to skin layers 2. Hematopoietic stem cells: give rise to blood cells 3. Endothelial stem cells: give rise to blood and lymphatic vessels 4. Mesenchymal stem cells: give rise to all types of muscle cells  The capacity of stem cells to differentiate into a specialized cell makes them potentially valuable in therapeutic applications designed to replace damage cells of different body tissues.