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Notes: 1- We ask you kindly to go through the below listed topics of biology and to concentrate on the main concepts and outlines i.e. you don’t need to learn by heart all texts, figures and tables, it is just to give you a sufficient explanation for the different topics and to deepen your understanding to the material. 2- Please notify, for the interview you need to study all the below listed topics and concentrate on at least ten topics. TOPICS ON BIOLOGY FOR ADMISSION TEST
- Basic structure and characteristics of the eukaryotic cell (cellular organelles, structure, function).
- Basic metabolic pathways: glycolysis, biological oxidation, photosynthesis (the biological role and basic characteristics of enzymes).
- The DNA and its role in heredity: the structure of DNA, the genetic code, the replication of the genetic material.
- Cell division I.: Chromatin, chromosomes. The behaviour of chromosomes during mitosis.
- Cell division II.: Meiosis. The role of meiosis in sexually reproducing organisms.
- Genetics I.: Genotype, phenotype, genes, alleles. Monohybrid cross, dominant-recessive type of inheritance, co-dominance. The first Mendelian law of inheritance.
- Genetics II.: X-linked inheritance. Dihybrid cross: the second Mendelian law of inheritance. Genetic linkage, crossing-over.
- From DNA to protein: Translation, mRNA, rRNA, tRNA, ribosomes.
- Basic anatomy and physiology of the human respiratory system.
- Basic anatomy and physiology of the human circulatory system.
- Basic anatomy and physiology of the human digestive system.
- Basic anatomy and physiology of the human excretory(Urinary) system., importamt
- Homeostasis: the basic structure and function of the human nervous system.
- Homeostasis: hormones, the human endocrine system.
- Basic structure and function of skeletal muscle cells, locomotion in humans.
- The basic defense systems against infections: the humoral and cellular immune response in humans.
Answers
Macromolecules: Giant Polymers
Macromolecules are polymers constructed by the formation of covalent bonds between smaller molecules called monomers. Macromolecules in living organisms include polysaccharides, proteins, nucleic acids and lipids. Proteins: Polymers of Amino Acids The functions of proteins include support, protection, catalysis, transport, defense, regulation, and movement. Protein function sometimes requires an attached prosthetic group. There are 20 amino acids found in proteins. Each amino acid consists of an amino group, a carboxyl group, a hydrogen, and a side chain bonded to the α carbon atom. The side chains, or R groups, of amino acids may be charged, polar, or hydrophobic; there are also special cases, such as the —SH groups of cysteine, which can form disulfide bridges. The side chains give different properties to each of the amino acids. Basic structure of amino acid: COOH | H 2 N-C-H | R Amino acids are covalently bonded together into polypeptide chains by peptide linkages, which form by condensation reactions between the carboxyl and amino groups.
The pentoses are five-carbon monosaccharides. Two pentoses, ribose and deoxyribose, are components of the nucleic acids RNA and DNA, respectively. Glycosidic linkages may have either α or β orientation in space. They covalently link monosaccharides into larger units such as disaccharides, oligosaccharides, and polysaccharides. Cellulose, a very stable glucose polymer, is the principal component of the cell walls of plants. It is formed by glucose units linked together by β-glycosidic linkages Lipids: Water-Insoluble Molecules Fats and oils are triglycerides, composed of three fatty acids covalently bonded to a glycerol molecule by ester linkages. Saturated fatty acids have a hydrocarbon chain with no double bonds. Phospholipids have a hydrophobic hydrocarbon "tail" and a hydrophilic phosphate "head." In water, the interactions of the hydrophobic tails and hydrophilic heads of phospholipids generate a phospholipid bilayer that is two molecules thick. The head groups are directed outward, where they interact with the surrounding water. The tails are packed together in the interior of the bilayer. Nucleic Acids: Informational Macromolecules DNA is the hereditary material. Both DNA and RNA play roles in the formation of proteins. Information flows from DNA to RNA to protein. Nucleic acids are polymers made up of nucleotides. A nucleotide consists of a phosphate group, a sugar (ribose in RNA and deoxyribose in DNA), and a nitrogen-containing base. In DNA the bases are adenine, guanine, cytosine, and thymine, but in RNA uracil substitutes for thymine.
Not to be memorized In the nucleic acids, the bases extend from a sugar-phosphate backbone. The information content of DNA and RNA resides in their base sequences. RNA is single-stranded. DNA is a double-stranded helix in which there is complementary, hydrogen-bonded base pairing between adenine and thymine (A-T) and guanine and cytosine (G-C). The two strands of the DNA double helix run in opposite directions The Cell: The Basic Unit of Life
- All cells come from preexisting cells and have certain processes, types of molecules, and structures in common.
- To maintain adequate exchanges with its environment, a cell's surface area must be large compared with its volume.
- Cells can be visualized by various methods using microscopes.
- All cells are surrounded by a plasma membrane Prokaryotic Cells
Cell organelles (cell ultra structures) 1- The Nucleus 2- Endoplasmic reticulum 3- Golgi apparatus 4- Mitochondria and Chloproplast 5- Lysosomes
Organelles that Process Information (The nucleus) The nucleus is usually the largest organelle in a cell. It is surrounded by a double membrane (the nuclear envelope), which disassembles during cell division. Within the nucleus, the nucleolus is the source of the ribosomes which is produce their and export to the cytoplasm. The cell nucleus is a remarkable organelle because it forms the package for our genes and their controlling factors. It functions to: Store genes on chromosomes Organize genes into chromosomes to allow cell division. Transport regulatory factors & gene products via nuclear pores Produce messages ( messenger Ribonucleic acid or mRNA) that code for protein synthesis. Produce ribosomes in the nucleolus
The Golgi Apparatus
- The Golgi apparatus consists of a stack of membrane- bounded cisternae located between the endoplasmic reticulum and the cell surface. A myriad of enzymes (proteins) are present in the Golgi to perform its various synthetic activities.
- The Golgi apparatus receives materials (proteins) from the rough ER by means of vesicles that fuse its cis region:
- Some of these ( proteins ) will eventually end up as integral membrane proteins embedded in the plasma membrane.
- Other proteins moving through the Golgi will end up in lysosomes
- or be secreted by exocytosis (e.g., digestive enzymes).
- The major processing activity is glycosylation : the adding of sugar molecules to form glycoproteins.
Organelles that Process Energy ( Mitochondria and chloroplasts)
- Mitochondria are enclosed by an outer membrane and an inner membrane that folds inward to form cristae. Mitochondria contain the proteins needed for cellular respiration (electrons transport chain, proton pumping and ATP synthesis ), lipid synthesis and the Kreb’s cycle (Citric acid cycle) Kreb’s cycle takes place in the matrix. Mitochondria contain their own DNA and ribosomes and are capable of making some of their own proteins Mitochondrial Substructure
Mitochondria contain two membranes, separated by a space. Both are the typical "unit membrane" (railroad track) in structure. The space which is enclosed by the inner membrane is the matrix. This appears moderately dense and one may find strands of DNA, ribosomes, or small granules in the matrix. The mitochondria are able to code for part of their proteins with these molecular tools. The above cartoon shows the diagram of the mitochondrial membranes and the enclosed compartments.
How are mitochondria organized to be powerhouses?
The food we eat is oxidized to produce high-energy electrons that are converted to stored energy. This energy is stored in high energy phosphate bonds in a molecule called adenosine triphosphate, or ATP. ATP is converted from adenosine diphosphate by adding the phosphate group with the high-energy bond. Various reactions in the cell can either use energy (whereby the ATP is converted back to ADP, releasing the high energy bond) or produce it (whereby the ATP is produced from ADP).
Steps from glycolysis to the electron transport chain. Why are mitochondria
important?
Lets break down each of the steps so you can see how food turns into ATP energy packets and water. The food we eat must first be converted to basic chemicals that the cell can use. Some of the best energy supplying foods contain sugars or carbohydrates ...bread, for example. Using this as an example, the sugars are broken down by enzymes that split them into the simplest form of sugar which is called glucose. Then, glucose enters the cell by special molecules in the membrane called “glucose transporters”. Once inside the cell, glucose is broken down to make ATP in two pathways. The first pathway requires no oxygen and is called anaerobic metabolism. This pathway is called glycolysis and it occurs in the cytoplasm outside the mitochondria. During glycolysis, glucose is broken down into pyruvate. Other foods like fats can also be broken down for use as fuel (see following cartoon). Each reaction is designed to produce some
Plasma Membrane Composition and Structure Biological membranes consist of lipids, proteins, and carbohydrates. The fluid mosaic model of membrane structure describes a phospholipid bilayer in which proteins can move about laterally within the membrane. Integral membrane proteins are at least partially inserted into the phospholipid bilayer. Peripheral membrane proteins are attached to the surface of the bilayer by ionic bonds. The two surfaces of a membrane may have different properties because of their different phospholipid composition, exposed domains of integral membrane proteins, and peripheral membrane proteins. Carbohydrates attached to proteins or phospholipids project from the external surface of the plasma membrane and function as recognition signals for interactions between cells. Membrane components may: be protective regulate transport in and out of cell or subcellular domain allow selective receptivity and signal transduction by providing transmembrane receptors that bind signaling molecules allow cell recognition provide anchoring sites for cytoskeletal filaments or components of the extracellular matrix. This allows the
cell to maintain its shape and perhaps move to distant sites. provide a stable site for the binding and catalysis of enzymes.
Membrane transport
Passive Membrane Transport Substances can diffuse passively across a membrane by three processes : simple diffusion through the phospholipids bilayer, facilitated diffusion through protein channels, or facilitated diffusion by means of a carrier protein. A solute diffuses across a membrane from a region with a greater concentration of that solute to a region with a lesser concentration of that solute. Equilibrium is reached when the concentrations of the solute are identical on both sides of the membrane. The rate of simple diffusion of a solute across a membrane is directly proportional to its concentration gradient across the membrane. An important factor in simple diffusion across a membrane is the lipid solubility of the solute. In osmosis, water diffuses from regions of higher water concentration to regions of lower water concentration. Channel proteins and carrier proteins function in facilitated diffusion. The rate of carrier-mediated facilitated diffusion reaches a maximum when a solute concentration is reached that saturates the carrier proteins so that no increase in rate is observed with further increases in solute concentration.
