Proteins. Big Idea 4: Biological Systems Interact

Transcription

1 Proteins Big Idea 4: Biological Systems Interact

2 Essential Knowledge Essential knowledge 4.B.1: Interactions between molecules affect their structure and function. a. Change in the structure of a molecular system may result in a change of the function of the system. b. The shape of enzymes, active sites, and interaction with specific molecules are essential for basic functioning of the enzyme.

3 Protein Functions! Structural support, storage, transport, cellular communications, movement, and defense against foreigners Make up more than 50% of dry mass of cells

4 Example: Hemoglobin Iron-containing protein found in red blood cells. Transports oxygen to body

5 Example: Antibodies Antibodies Defensive protein fights bacteria and viruses

6 Example: Lactase, an Enzyme Enzyme that helps break down sugar lactose into galactose and glucose. Speeds up reactions rates: Lactose intolerant: Mutation of Chrom. 2. Cramps, bloating, flatulence

7 Example: Insulin Hormonal protein: regulates sugar in blood (tells cells to take it in), pancreas

8 Polymers built from same set of 20 amino acids A protein consists of one or more polypeptides Polypeptides

9 Amino Acid Monomers

10 Amino Acid Polymers Amino acids are linked by peptide bonds

11 Protein Structure and Function Consists of 1/more polypeptides twisted, folded, and coiled into a unique shape (determined by amino acid sequence)

12 Four Levels of Protein Structure Primary, Secondary, Tertiary, Quartenary! Watch Videos!

13 Chaperonins are protein molecules that assist the proper folding of other proteins Cap Polypeptide Correctly folded protein Hollow cylinder Chaperonin (fully assembled) Steps of Chaperonin Action: 1 An unfolded polypeptide enters the cylinder from one end. 2 The cap attaches, causing the 3 cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide. The cap comes off, and the properly folded protein is released.

14 Sickle-Cell Disease: A Change in Primary Structure A change in primary structure can affect a protein s structure and ability to function Ex: Sickle-cell disease: results from a single amino acid substitution in protein hemoglobin

15 Fig. 5-22a Primary structure Normal hemoglobin Val His Leu Thr Pro Glu Glu Secondary and tertiary structures subunit Quaternary structure Normal hemoglobin (top view) Function Molecules do not associate with one another; each carries oxygen.

16 Fig. 5-22b Primary structure Sickle-cell hemoglobin Val His Leu Thr Pro Val Glu Secondary and tertiary structures Exposed hydrophobic region subunit Quaternary structure Sickle-cell hemoglobin Function Molecules interact with one another and crystallize into a fiber; capacity to carry oxygen is greatly reduced.

17 Fig. 5-22c 10 µm 10 µm Normal red blood cells are full of individual hemoglobin molecules, each carrying oxygen. Fibers of abnormal hemoglobin deform red blood cell into sickle shape.

18 Messing Up Proteins? Alterations in ph, salt concentration, temp., or other environmental factors can cause a protein to unravel denaturation inactive protein

19 Enzyme Proteins! Acts as a catalyst to speed up chemical reactions Can perform functions repeatedly workhorses!

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23 Cofactors A non-protein chemical compound required for enzyme activity Ex: Fe Helper Molecules" that assist in biochemical transformations.

24 Coenzymes A protein chemical compound required for enzyme activity Helper Molecules" that assist in biochemical transformations.

25 Cofactors and Coenzymes Work together to regulate enzyme function. Usually the interaction relates to a structural change that alters the activity rate of the enzyme

26 Competitive Inhibitors Binding of inhibitor molecule to active site of enzyme prevents binding of the substrate and vice versa.

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28 Allosteric Competition Binding of inhibitor to another (allosteric) site of enzyme (rather than active site) prevents binding of substrate

29 Model Interpretations The change in function of an enzyme can be interpreted from data regarding the concentrations of product or substrate as a function of time. These representations demonstrate the relationship between an enzyme s activity, the disappearance of substrate, and/ or presence of a competitive inhibitor.