DNA and ATP - Writers Writing - http://maxpages.com/fanficsnstuff/DNA_and

DNA is made of four types of molecules called nucleotides: Adenine (A), Guanine (G), Cytosin (C), and Thymine (T). During DNA synthesis, nucleotides are converted into nucleic acids that are linked to form DNA (a double helix figure.)

Nucleotides A-T and G-C are joined together by a hydrogen bond to form a base pair. Base pairs are joined by sugar (phosphate) bonds to form a helix.

RNA also consists of strands of nucleic acids joined together by sugar-phosphate bonds. The only difference is that thymine is replaced with uracil and it exists as single strands. After DNA is converted into mRNA (messenger RNA) it is sent to ribosomes for protein synthesis.

Amino acids are the subunits of proteins. Proteins are made of a chain of amino acids linked by peptide bonds. There are 20 common amino acids used in protein synthesis, in four families: acidic, basic, uncharged polar, and nonpolar. The combination of different nucleotides make different amino acids.

Lipids are made of fatty acid moleculres (palmitic acid) that consist of hydrophobic hydrocarbon and hydrophilic carboxylic acid groups.

Active Transport

ATP is a nucleotide that is a carrier of chemical energy. ATP is adenine with 3 phosphate groups attached. The bond connecting these three phosphates to the adenine is highly charged. Two of the phosphate groups are added by a covalent bond during processes such as respiration (these can be easily broken down into energy.)

ATP is used for active trasnport, photosynthesis (in plant cells) and cellular respiration.

ATP is broken down by hydrolysis (reaction with water) to make Adenosin Diphosphate (ADP), inorganic phosphates, and energy. This can be broken down into Adenosine Monophosphate, or (AMP), along with inorganic phosphates and energy. Extra phosphorous is later used to make more ATP from AMP.

Oxygen, ethanol and carbon dioxide cross the cell membrane by diffusion. Proteins, polynucleotides, and polysacharrides must rely on active transport becuase they are too big to be diffused through the cell membrane.

Exocytosis

Macromolecules are fused into vesicle membrane and released to the cell membrane. Proteins to be excreted are made on the rough ER. They are taken to the Golgi Complex by the ER to induced vesicles that seperate off the Golgi and fuse with the cell membrane.

Endocytosis

Pinocytosis- ingestion of small molecules/fluids surrounding the cell. Phagocytosis is the ingestion of large molecules using vacoules.

Pinocytosis occurs almost continually in eukaryotic cells. This means that they are ingesting their own cell membrane at a rapid rate; the membrane must be added by exocytosis at the same rate it is being removed by endocytosis.

Most ingested molecules (surrounded by vesicles) fuse with lysosomes. The molecules that have been ingested are deposited in cytosol to be used by the cell.

White blood cells use phagocytosis to remove foriegn particles from the bloodstream. These cells engulf foriegn particles of the same size. Macrophages and polymorphic leukocytes are phagocytes . Particles have to bind to receptors on the phagocyte to be engulfed and absorbed.

Sugar provides energy for cells. Glucose is the simplest form of sugar. It is the principal food source for cells.

Water molecules are polarized. Becuase of this, two water molecules can be linked by a hydrogen bond. This means other molecules are either hydrophilic (like water) or hydrophobic (afraid of water). This lets certain molecules dissolve into the cells while preventing others from entering.

Water can trasnport molecules through osmosis. Water will always move from areas of high concentration to areas of low concentration. This allows the movement of certain small particels through water into the cell while keeping the larger molecules from entering.

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