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- are a second group of macromolecules important to all living organisms. Lipids, just like carbohydrates, are made primarily from atoms of carbon, hydrogen, and oxygen, but the atoms are in different proportions. The lipids in your diet, for example, tend to have significantly more energy-rich carbon-hydrogen bonds than carbohydrates, and so contain significantly more stored energy.
- lipids do not dissolve in water and are greasy to the touch—think of salad dressings
TYPICAL FEATURES OF LIPIDS
- Nonpolar molecules that do not dissolve in water
- Greasy to the touch
- Can be significant source of energy storage
Structure of Fats
- All fats have two distinct components: they have a “head”region and two or three long “tails” (FIGURE 2-29). The head region is a small molecule called glycerol. It is linked to “tail”molecules known as fatty acids. A fatty acid is simply a long hydrocarbon—that is, a chain of carbon molecules, often a dozen or more, linked together with one or two hydrogen atoms attached to each carbon.
are fatshaving three fatty acids linked to the glycerol molecule. For this reason, the terms “fats” and “triglycerides” are often used interchangeably. Triglycerides that are solid at room temperature are generally called “fats,” while those that are liquid at room temperature are called “oils.”
- In saturated fats,each carbon in the hydrocarbon chain is bound to two hydrogen atoms.
- Straight fatty acids can be packed together tightly. As a result, saturated fats are solid at room temperature.
- In unsaturated fats,at least one carbon in the hydrocarbon chain is bound to just one hydrogen,causing the fatty acid to have a crooked shape.
- Crooked fatty acids cannot be packed together tightly. As a result, unsaturated fats on their own(such as olive oil) are liquid at room temperature.
- Most plant fats are unsaturated.
Unsaturated fats part 2
Unsaturated fats may be mono-unsaturated (if a fatty acid hydrocarbon chain has only one pair of neighboring carbon atoms in an unsaturated state—that is, has only one double bond) or polyunsaturated (if more than one pair of carbons is unsaturated—there’s more than one double bond). Unsaturated fats are still high in calories, but because they can lower cholesterol, they are generally preferable to saturated fats. Foods high in unsaturated fats include avocados, peanuts,and olive oil. Relative to other animals, fish tend to have less saturated fat.
- is the artificial addition of hydrogen atoms to an unsaturated fat. This can improve a food’s taste, texture, and shelf-life.
- Hydrogenation converts some double bonds to single bonds, but it adds hydrogens in the less healthful "trans"position, which changes the orientation of the double bond.
- Hydrogenation of unsaturated fats is doubly problematic from a health perspective because it also creates trans fats
- A second group of lipids, called the sterols,plays an important role in regulating growth and development. This group includes some very familiar lipids: cholesterol and the steroid hormones such as testosterone and estrogen. These molecules are all variations on one basic structure formed from four interlinked rings of carbon atoms.
is an important component of most cell membranes. For this reason, it is an essential molecule for living organisms.
Dietary cholesterol can attach to and thicken vessel walls and may cause serious health problems.
- • Regulate sexual development, maturation,and sex cell production.
- • Estrogen influences memory and mood.
- • Testosterone stimulates muscle growth.
are the major component of the membrane that surrounds the contents of a cell and controls the flow of chemicals into and out of the cell.
resemble fats but have only one long-chain fatty acid linked to the glycerol head of the molecule. Because the fatty acid chain is highly non-polar, waxes are strongly hydrophobic;that is, these molecules do not mix with water but repel it.
are the chief building blocks of all life. They make up skin and feathers and horns. They make up bones and muscles. In your bloodstream, proteins fight invading microorganisms and stop you from bleeding to death from a shaving cut.Proteins control the levels of sugar and other chemicals in your bloodstream and carry oxygen from one place in your body to another.
initiate and assist every chemical reaction that occurs.
- the monomer of a protein
- Building blocks of proteins.
- 20 amino acids total
- are bonded together by peptide bonds
- Twenty amino acids make up all the proteins necessary for growth, repair, and replacement of tissue in living organisms.Of these amino acids, about half are essential for humans: they cannot be synthesized by the body so must be consumed in the diet. Complete proteins contain all essential amino acids, while incomplete proteins do not
Proteins are formed by linking individual amino acids together with a peptide bond, in which the amino group of one amino acid is bonded to the carboxyl group of another.Two amino acids joined together form a dipeptide, and several amino acids joined together form a polypeptide.
Primary Structure of Proteins
Secondary Structure of Proteins
TERTIARY STRUCTURE of Proteins
QUATERNARY STRUCTURE of Proteins
- The overall shape of a protein molecule determines its function—how it behaves and the other molecules it interacts with. For proteins to function properly, they must retain their three-dimensional shape. When their shapes are deformed, they usually lose their ability to function. We can see proteins deforming when we fry an egg. The heat breaks the hydrogen bonds that give the proteins their shape. The proteins in the clear egg white unfold, losing their secondary and tertiary structure. This disruption of protein folding is called denaturation
molecules that help initiate and accelerate the chemical reactions in our bodies. Enzymes emerge unchanged—in their original form—when the reaction is complete and thus can be used again and again
provides a place for the participants in a chemical reaction, the reactants or substrate molecules, to nestle briefly
The chemical reactions that occur in organisms can either release energy or consume energy. But in either case, there is a certain minimum energy—a little “push”—needed to initiate the reaction
ENZYME ACTIVITY (ENZYME AND SUBSTRATE CONCENTRATION)
- Reaction rates increase with increased amounts of enzyme (or substrate), but only up to the point at which all of the enzyme molecules are bound to substrate. At that point, additional enzyme (or substrate) no longer increases the reaction rate.
ENZYME ACTIVITY (Temperature)
- Reaction rates generally increase at higher temperatures, but only up to the optimum temperature for an enzyme. At temperatures above the optimum, reaction rates decrease as enzymes lose their shape or even denature.
ENZYME ACTIVITY (pH)
- Reaction rates generally increase as pH nears the optimum level for an enzyme. Above or below this pH, enzyme function can be disrupted and reaction rates decrease.
ENZYME ACTIVITY (PRESENCE OF INHIBITORS OR ACTIVATORS)
- Reaction rates increase in the presence of activators and decrease in the presence of inhibitors.
reduce enzyme activity and come in two types: competitive inhibitors bind to the active site, blocking substrate molecules from the site and thus from taking part in the reaction. Noncompetitive inhibitors do not compete for the active site but rather bind to another part of the enzyme, altering its shape in a way that changes the structure of the active site, reducing or blocking its ability to bind with substrate.
Just as a molecule can bind to an enzyme and inhibit the enzyme’s activity, some cellular chemicals act as activators. Instead of their binding to an enzyme “turning it off,” their binding to the enzyme “turns it on,” altering the enzyme’s shape or structure so that it can now catalyze a reaction.
macromolecules that store information and are made up of individual units called nucleotides.
- have three components:
- a molecule of sugar
- a phosphate group (containing a phosphorus atom bound to four oxygen atoms)
- and a nitrogen-containing molecule
- are able to store information by varying which base is attached at each position in the molecule’s backbone.
- The nucleic acids DNA and RNA are macromolecules that store information in their unique sequences of bases contained in nucleotides, their building-block molecules.Both nucleic acids play central roles in directing protein production in organisms
- the monomer of a nucleic acid
types of nucleic acids
- deoxyribonucleic acid (DNA)
- ribonucleic acid (RNA)
Two sugar-phosphate backbones spiral around each other, forming the vertical structure of DNA. They are connected by the bases sticking out from their sugar molecules.
- DNA bases are connected with hydrogen bonds
- ADENINE (A)-=-(T) THYMINE
- GUANINE (G)-=-(C) CYTOSINE
deoxyribonucleic acid (DNA)
DNA is shaped like a ladder in which the long vertical sides of the ladder are made from a sequence of sugar-phosphate-sugar-phosphate molecules and the rungs are pairs of nucleotide bases. The sequence of nucleotide bases contains the information about how to produce a particular protein.
ribonucleic acid (RNA).
RNA acts as a middleman molecule—taking the instructions for protein production from DNA to another part of the cell where, in accordance with the RNA instructions, amino acids are pieced together into proteins.
- There are three important structural differences between RNA and DNA.
- The sugar molecule in the RNA backbone contains an extra oxygen.
- RNA has only one sugar-phosphate backbone, while DNA has two.
- Instead of thymine,RNA has a similar base called uracil (U).
carbon is a key component of life
4 things about carbon
4th most common element in the universe
2nd most common element in your body
ability to form multiple covalent bonds
forms both organic and inorganic molecules
why is pH important?
- living things are extremely sensitive to changes in pH, and most function best when their pH stays within a specific range
- many biochemical reactions take place only at a certain pH
- strong acids and bases are highly reactive with other substances, which makes them destructive to the molecules in a cell
one chemical subunit of a polymer
molecule made up of individual subunits, called monomers, linked together in a chain