1.2.2. Describe the transcription: synthesis of rna.The basic stages of transcription

Synthesis of RNA is usually catalyzed by an enzyme—RNA polymerase—using DNA as a template, a process known as transcription. Initiation of transcription begins with the binding of the enzyme to a promoter sequence in the DNA (usually found "upstream" of a gene). The DNA double helix is unwound by the helicase activity of the enzyme. The enzyme then progresses along the template strand in the 3’ to 5’ direction, synthesizing a complementary RNA molecule with elongation occurring in the 5’ to 3’ direction. The DNA sequence also dictates where termination of RNA synthesis will occur. Primary transcript RNAs are often modified by enzymes after transcription. For example, a poly(A) tail and a 5' cap are added to eukaryotic pre-mRNA and introns are removed by the spliceosome.There are also a number of RNA-dependent RNA polymerases that use RNA as their template for synthesis of a new strand of RNA. For instance, a number of RNA viruses (such as poliovirus) use this type of enzyme to replicate their genetic material. Also, RNA-dependent RNA polymerase is part of the RNA interference pathway in many organisms.

Transcription is the DNA-directed synthesis of RNA

RNA synthesis

• Is catalyzed by RNA polymerase, which pries the DNA strands apart and hooks together the RNA nucleotides

• Follows the same base-pairing rules as DNA, except that in RNA, uracil substitutes for thymine

Transcription

• Is the synthesis of RNA under the direction of DNA

• Produces messenger RNA (mRNA)

RNA is single stranded, not double stranded like DNA

1.2.3 Describe the vitamins b6,a biological role and mineral substances of food

Vitamin B6 is needed for more than 100 enzymes involved in protein metabolism.It is also essential for red blood cell metabolism and hemoglobin formation. The nervous and immune systems need vitamin B6 to function efficiently. Vitamin B₆ deficiency also can cause anemia.

Other Names: Pyridoxine, pyridoxal, pyridoxamine, B6 RDA: Adults: 1.3 mg/day (19-50 yr) Upper Level: Adults: 100 mg/day

Functions: ÷Part of coenzymes PLP (pyridoxal phosphate) and PMP (pyridoxamine phosphate) used in amino acid and fatty acid metabolism ÷Helps convert tryptophan to niacin and to serotonin ÷Helps to make red blood cells

Food Sources: ÷Meats, fish, poultry, liver ÷Potatoes, legumes, soy products ÷Non-citrus fruits ÷Fortified cereals

Destruction: Easily destroyed by heat

Deficiency Symptoms: ÷Scaly dermatitis ÷Anemia (small-cell type) ÷Depression, confusion, convulsions

Toxicity Symptoms: ÷Depression, fatigue, irritability, headaches, nerve damage causing numbness and muscle weakness leading to an inability to walk and convulsions ÷Skin lesions

1.2.4. What is the difference between monosaccharides and disaccharides. What are some examples of them.

Monosaccharides are simple carbohydrates molecules that cannot be broken down into other carbohydrates. Glucose and fructose are examples of monosaccharides. Disaccharides are carbohydrates made up of two monosaccharides and which are missing one molecule of water (dehydration). The chemical bond between two monosaccharides is known as a glycosidic bond.Sucrose (table sugar) is a disaccharide that consists of a bond between one molecule of glucose and one molecule of fructose. Maltose is a disaccharide that consists of two glucose molecules. Lactose (milk sugar) is another disaccharide and it is created by a bond between one molecule of galactose and one molecule of glucose.

Simple Carbohydrates: ÷monosaccharides ÷disaccharides

Monosaccharrides are single sugars (most are hexoses).

• Glucose serves as the essential energy source, and is commonly known as blood sugar or dextrose.

• Fructose is the sweetest, occurs naturally in honey and fruits, and is added to many foods in the form of high-fructose corn syrup.

• Galactose rarely occurs naturally as a single sugar.

Disaccharides are pairs of monosaccharides, one of which is always glucose

• Condensation reactions link monosaccharides together.

• Hydrolysis reactions split molecules and commonly occur during digestion.

• Maltose consists of two glucose units. It is produced during the germination of seeds and fermentation.

• Sucrose is fructose and glucose combined. It is refined from sugarcane and sugar beets, tastes sweet, and is readily available.

• Lactose is galactose and glucose combined. It is found in milk and milk products.