Functions of Lipids• Energy storage – In the form of fat in humans and oil in plants• Heat insulation – A layer of fat under the skin reduces heat loss• Buoyancy – Lipids are less dense than water to help animals to float• To provide a layer of protection – Fat on your body – Membranes in cells 2
Steroids include cholesterol and certain hormones• Steroids are lipids with a carbon skeleton consisting of four fused carbon rings. – Different steroids are created by varying functional groups attached to the rings• Cholesterol, an important steroid, is a component in animal cell membranes.• Cholesterol is also the precursor from which all other steroids are synthesized. www.pearsonsuccessnet.com activity 5.3 page 3 8
Using Carbohydrates and Lipids in Energy Storage• Both lipids and Advantages of Advantages of carbs can be used for energy Lipids Carbs storage in living Lipids contain more Carbohydrates are organisms. energy per gram than more easily digested Both types of carbs so stores of than lipids so the storage lipids are lighter than energy stored by them compound have stores of carbs that can be released more advantages. contain the same rapidly Carbohydrates amount of energy 4 kcal/g are usually for 9 kcal/g energy storage Lipids are insoluble in Carbohydrates are over short water, so they do not soluble in water so are periods and cause problems with easier to transport to lipids for long- osmosis in cells and from the storage term storage area 9
The primary structure of a protein: CHAIN• primary protein structure: – polypeptide chain• The folding of a protein from a chain of amino acids occurs spontaneously• The precise primary structure of a protein is determined by inherited genetic 15 information.
• The secondary Secondary Structure: structure of aα Helix and β Pleated Sheets protein results from hydrogen bonds at regular intervals along the polypeptide backbone. • Typical shapes that develop from secondary structure are coils (an alpha helix) or folds (beta pleated sheets). 16
Tertiary Structure: Twists in on itself• Tertiary structure is determined by a variety of interactions among R groups and between R groups and the polypeptide backbone. 17
The quaternary structure of proteins: multiple chains together 18
Spider silk: a structural protein• The structural properties of silk are due to beta pleated sheets. – The presence of so many hydrogen bonds makes each silk fiber stronger than steel. 19 http://www.sciencedaily.com/releases/2008/02/080214114448.htm
A protein’s function depends on its specific conformation • A functional proteins consists of one or more polypeptides that have been precisely twisted, folded, and coiled into a unique shape. • It is the order of amino acids that determines what the three-dimensional conformation will be. 20
At present, scientists use X-ray crystallography to determine protein conformation. 21
The Nucleotide Subunits of DNA• Although DNA is the genetic material of living organisms and is therefore of immense importance, it is made of relatively simple subunits• These are called nucleotides P• Each nucleotide consists of three parts: B S – A sugar, deoxyribose – A phosphate group – And a nitrogen base• DNA nucleotides do not all have the same base• Four different bases are found 33 – Adenine, guanine, cytosine, thymine
nucleotide monomerphosphate group PO4 nitrogen base CH2 5’ 4’ 1’ 3’ 2’ OH deoxyribose sugar Numbering the carbons on deoxyribose: 1’ = nitrogen base 3’ = hydroxyl group 34 5’ = phosphate group
Building DNA Molecules• Two DNA nucleotides can be linked together by a covalent bond between the sugar of one nucleotide and the phosphate group of the other• More nucleotides can be added in a similar way to form a strand of nucleotides• DNA molecules consist of two strands of nucleotides wound together into a double helix• Hydrogen bonds link the two strands together• These form between the bases of the two strands• However, adenine only forms hydrogen bonds with thymine and cytosine only forms hydrogen bonds with guanine• This is called complementary base pairing 36
•The bonds between 5’ the phosphate group and the deoxyribose sugar on an individual nucleotide is a covalent bond – phosphodiester bond. •Phosphodiester bonds are arranged phosphate – oxygen – carbon. •Bonding nucleotides together: occurs between 3’ OH group on one nucleotide and 5’ phosphate group on the other through a •Strands run antiparallel to each condensation other = one strand has the 5’ C on reaction (release of the top, 3’ C on the bottom, and water) the other is reversed3’ •There will always be a free 5’ end 3’ on 37 each strand of DNA
NUCLEOSOME STRUCTURE:- 8 histones, (+) charged, (protein) in the core - 2 molecules of 4 different histones- DNA, (-) charged, wraps around the core 2x- 1 histone holds the 2 ends of the DNA, histone H1- with 2 ends of linker DNA- nucleosomes help to supercoil chromosomes and help to 38regulate transcription
In nuclear DNA there are three types:1. Unique/Single-copy genes: - genes with coding functions - essential to producing proteins - Human Genome Project: to sequence all the coding genes, less than 2% of chromosomes are coding genes - Coding parts of DNA are not strung together neatly; there are noncoding regions interspersed within between coding regions - coding parts = EXONS; noncoding parts = INTRONS - EXONS are allowed to EXIT the nucleus to be translated into a protein - INTRONS must stay IN the nucleus because they don’t code for a protein2. Highly repetitive sequences: - found in eukaryotes - from 5%-45% of the total genome - 5-300 base pairs per sequence - Clustered together? = satellite DNA - usually dispersed throughout the genome = transposable - Barbara McClintock; 1950 39
RNA• Usually single strands• Unlike DNA, contains the pyrimidine base uracil in place of thymine• Contains ribose sugar rather than deoxyribose sugar• Three types are key players in protein 40 synthesis
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