Lecture 3 Flashcards
Define the following terms: monosaccharide, oligosaccharide, polysaccharide.
Monosaccharide: “one sugar” molecule
Oligosaccharide: 3-10 monosaccharides
Polysaccharide: >10 monosaccharides
The digestion of starch in the mouth by the salivary amylase produces a sugary taste after a fair degree of digestion. Explain why this is so.
Salivary amylase breaks down complex carbohydrates into simple sugars, which our taste receptors detect as sweet.
Amylose and amylopectin are both polysaccharides formed by linking glucose monomers. Amylose is linked into straight chains by repeating (1-4C) bonds. Amylopectin is much more branched and linked by two different kinds of bonds (1-4C and 1-6C). Amylopectin has a higher glycemic index, meaning when digested it breaks down more quickly into simple sugars. Explain why you think the higher branching and two different types of glycosidic bonds would increase the rate of digestion for amylopectin.
The branching allows more access points for digestive enzymes to cleave the molecule, allowing for faster breakdown into smaller glucose units.
What is the general function of proteins in our body?
Cellular “machinery” and structure. Crucial for regulation of cell processes and maintenance.
What are the monomers of proteins? What is the basic structure of the monomer?
Monomer: amino acid.
Basic structure: carbon center, amino group, carboxylic acid, hydrogen, and R group.
How many different protein monomers are there and how do they differ?
20 - they differ based on the unique structure of their R group.
How are protein monomers linked? What bond links individual monomers?
They are linked via dehydration synthesis and form peptide bonds to link individual monomers.
What is the difference between a dipeptide, oligopeptide, polypeptide and a protein?
Dipeptide: 2 amino acids linked
Oligopeptide: 3-10 amino acids linked
Polypeptide: greater than 10 amino acids link
Protein: greater than 100 amino acids that possess a specific 3D shape where normal function depends on protein structure.
What are the four levels of protein structure? What molecular bonding results in each?
Primary, secondary, tertiary, quaternary.
Primary: covalent peptide bonds
Secondary: hydrogen bonds
Tertiary: R-group interactions
How stable do you think each level of structure is relative to each other.
More stable: primary > secondary > tertiary > quaternary :Less stable
Do all proteins need to have quaternary structure? What is the difference between a polypeptide and a protein?
No, not all proteins need to have a quaternary structure. A protein is a polypeptide with a specific 3D shape that carries out a specific function. All proteins are polypeptides but not all polypeptides are yet proteins.
Explain why pH, hydrophobic or hydrophilic and temperature changes in the environment of a protein can result in denaturization.
PH: too many H+ ions can cause bonds to break and find stability with the H+ ions, therefore breaking the 3D structure of the protein and denaturing it.
Temperature: increased temperature can cause too much molecular movement leading to the breaking of bonds, causing the 3D structure to change and denaturing it.
What level of protein structure is most susceptible to denaturization and why?
Tertiary because it is held together by relatively weak R-group interactions like hydrogen bonds, Vanderwall’s forces, hydrophobic interactions, and some ionic bonds.
What are the four main families of lipids? What property unifies the broad category of lipids together?
Triglycerides, phospholipids, steroids, and prostaglandins. They are all insoluble in polar solvents.
Why are lipids hydrophobic? Is water really afraid of lipid?? Why does is tend to isolate the lipids when they are mixed with water?
Lipids are hydrophobic because they uncharged (non-polar). Water is not really afraid of lipid. Water molecules create hydrogen bonds with each other and prefer to hydrogen bond. Lipids are unable to form hydrogen bonds, so then water naturally bonds with other water molecules to form H+ bonds. It is energetically favorable.
What is the cellular significance of the triglycerides? Describe their structure.
Body energy storage. Triglyceride is formed by a glycerol molecule and three fatty acid chains.
What are the structural difference between saturated and unsaturated lipids? Which have a higher concentration of hydrogens, which have more double bonds? What is the affect of double bonds on the fatty acids overall structure and fluidity? ? Why are most Polyunsaturated fats liquid at room temperature?
Saturated lipids contain no double bonds. Unsaturated lipids have at least one double bond. Saturated fats have a higher concentration of hydrogen. Unsaturated fats have more double bonds. The double bond creates a bend in the fatty acid and increase fluidity. Most poly unsaturated fats are liquid at room temperature because they are difficult to stack due to their bent nature.
Explain how hydrogenation increases a unsaturated fats rigidity? Why does the food industry hydrogenate? Why is hydrogenation unhealthy?
Hydrogenation adds hydrogen to the double bonds in the unsaturated fatty acids. This allows for them to stack more tightly with each other due to decreased amount of bends, leading to increased rigidity. The food industry hydrogenates because it increases stability, increases convenience, foods have better taste and texture, and it melts better for cooking. Hydrogenation is unhealthy because it increases risk for heart disease by raising bad cholesterol levels and lowering good cholesterol level.
What is the cellular significance of the phospholipids? Describe their structure.
Phospholipids are the lipids present in a cell membrane. They have a glycerol three carbon “anchor” , two uncharged hydrocarbon chains, and a charged phosphate group
What unique property in water does the phosphate head group provide to the phospholipid?
The phosphate group is charged and therefore hydrophilic and attracting water. This creates an orientation of phospholipid heads towards water.
What happens to phospholipids when they are placed in water?
Phospholipids orient in a way that the polar head orient toward water and the hydrophobic hydrocarbon chains orient away from water.
What is the cellular significance of steroids? Chemically how can they be identified?
Steroids are chemical messengers. Its structure is made of four fused carbon rings.
What is the cellular significance of prostaglandins?
Prostaglandins are cell activity moderators. It is insoluble in water, produced by essentially all tissues. Mediates inflammatory responses and normal tissue function.
What is the difference between trans and cis fats?
Trans fats do not commonly occur naturally and has hydrogen on the opposite side of the double bond. This restricts movement and creates less bending. Cis fats occur naturally and have hydrogen on the same side of the double bond, allowing for movement and bending.
