Unit 1 - Biochemistry

Question 1

Describe the atom

Answer 1

• Basic unit of life
• Smallest unit of an element that still retains the properties of that element
• Composed of protons/neutrons/electrons

Question 2

What are elements?

Answer 2

• Pure substances consisting of all the same type of atom
• Cannot be broken down chemically into simpler substances
• 90% of an organism’s mass is composed of C, H, O, N

Question 3

What are isotopes?

Answer 3

• Atoms of the same element with different numbers of neutrons, they each have different masses
• Some are radioactive, meaning their nuclei are unstable and always break down

Question 4

What is a compound?

Answer 4

• Chemical combination of 2/more elements in definite proportions
• Chemical/physical properties of a compound are different than the properties of the individual elements that compose them

Question 5

Describe ionic bonds

Answer 5

• Formed when one/more electrons are transferred from one atom to another

Question 6

Describe covalent bonds

Answer 6

• Electrons are shared between atoms instead of being transferred
• Polar: electrons are shared unequally
• Non-polar: electrons are shared equally

Question 7

Which end of an H2O molecule will always have more electrons?

Answer 7

• The oxygen end, as it has a much stronger attraction for electrons

Question 8

What is a hydrogen bond?

Answer 8

• Weak chemical bond formed when a slightly positive hydrogen atom of one molecule is attracted to the negative atom of another molecule
• Single H2O molecule can form 4 w/ each other at one time, which is the cause behind H2O’s unique properties
• They break/reform/form often

Question 9

What happens to hydrogen bonds in the three states of water?

Answer 9

1. Solid state: all molecules are H-bonded, bonds do not break
2. Liquid state: an equal number of bonds are formed/broken at any time
3. Gaseous state: at high temps, H-bonds are completely broken and the molecules escape into the air as a gas

Question 10

What two forces of attraction are present in water molecules?

Answer 10

1. Cohesion: attraction b/w molecules of the same substance
2. Adhesion: attraction b/w molecules of different substances

Question 11

What is a mixture and its two types that are made w/ water?

Answer 11

• Mixture: substance composed of elements/composed that are physically but not chemically combined
  ~ Solution: homogenous mixture w/ a solute and solvent
  ~ Suspension: mixture of water and undissolved materials (ex: blood)

Question 12

What are some ways water makes life on earth possible?

Answer 12

1. Water’s cohesion: at a wide range of temps, cohesion makes water remain a liquid, so it does not turn into a gas or solid
2. Water stabilizes temps on Earth: it can absorb/release large amounts of heat to cool/warm landmasses, like a heat bank
3. Evaporative cooling: property of a liquid where a surface becomes cooler in evaporation, helps plants transpire and animals sweat to keep them cool
4. Water dissolves many substances
5. Surface ice helps insulate bodies of water during the cold to keep organisms alive under the ice

Question 13

What is an acid and a base?

Answer 13

• Acid: solution that forms H+ ions in solution, pH less than 7
• Base: solution that forms OH- ions in solution, pH more than 7

Question 14

What is a buffer?

Answer 14

• Substances produced by cells that prevent sudden changes in pH, to ensure chemical reactions run smoothly

Question 15

What are inorganic vs. organic compounds?

Answer 15

• Organic: compounds containing hydrocarbons and carbon-carbon bonds
  -Inorganic: do not contain carbon

Question 16

What structures can carbon-carbon bonds create?

Answer 16

1. Straight chains
2. Branched chains
3. Rings
   ~ Chains are almost unlimited in size

Question 17

What characteristics of carbon make possible the building of a variety of molecules?

Answer 17

1. 4 valence electrons that form strong, stable covalent bonds
2. Readily forms bonds w/ itself and other elements including sulfur, phosphorus, oxygen, nitrogen, hydrogen
3. Bonds w/ itself to form straight/branched chains or rings
4. Chains are almost unlimited in size
5. Tendency to bond w/ itself results in variety of organic molecules
6. 3-D shape determines the properties/functions of the molecule within living systems
7. Do not dissolve readily in water
8. Readily available and abundant
9. Only carbon has these characteristics

Question 18

Define a macromolecule

Answer 18

• Larger molecule made of smaller molecules
• 4 types: proteins, lipids, carbs, nucleic acids
• Polymerization: large compounds are built by the joining together of many smaller molecules

Question 19

What is a monomer vs. a polymer?

Answer 19

• Monomers: smaller repeating subunit of molecules that make up polymers
• Polymer: Long molecule consisting of many monomers linked by covalent bonds

Question 20

Explain condensation reactions

Answer 20

1. Attaches monomers together to form a polymer
2. Two molecules are covalently bonded to one another through the loss of a water molecule
3. Each monomer contributes part of the water molecule lost (H and OH)
4. Cell must expend energy to carry out condensation
5. Enzymes are required

Question 21

Explain hydrolysis reactions

Answer 21

1. Polymers are broken down into monomers
2. Reverse of condensation
3. Water is used to break down the polymer and the water breaks the bond linking each monomer
   4.

Question 22

Describe carbohydrates

Answer 22

• Made of C, H, O in a 1:2:1 ratio
• Examples: sugars, starches, cellulose
• Known as quick-energy foods as they immediately supply energy for cellular activities
• Two functions: main energy source for most living things, structural purposes for some
• Monomers are simple sugars like glucose
• Classified by their number of sugar molecules (mono, di-saccharide)

Question 23

What are isomers?

Answer 23

• Monosaccharides w/ the same formula but different arrangement of atoms
• This difference makes only small changes in the chemical properties of the sugars
• The changes are recognized by enzymes/proteins and can then therefore have major biological effects

Question 24

What are the different types of isomers?

Answer 24

1. Structural: compounds have the same atoms bonded in a different way
2. Stereoisomers: same atoms are bonded in the same way, but arranged differently in space
   ~ Geometric: different physical but similar chemical properties
   ~ Optical: similar physical and chemical properties, only cell proteins/enzymes can distinguish them

Question 25

What is the difference b/w an alpha and beta glucose?

Answer 25

• Alpha: OH groups are on opposite sides of the molecule
• Beta: OH groups are on the same side of the molecule

Question 26

What are polysaccharides and their function?

Answer 26

• Are made of 3/more monosaccharides
• Used as storage material and can be hydrolyzed to provide free sugars for energy
• Can also be used as building material or for protection

Question 27

What are the most common polysaccharides?

Answer 27

1. Starch: used for excess glucose storage in plants only
2. Glycogen: used for excess glucose storage in animals only, produced in the liver
3. Cellulose: structural polysaccharide found in the cell wall of plants to give them strength, also found in wood/paper

Question 28

What is amylopectin?

Answer 28

• Type of starch and polymer made of glucose molecules
• Consists mainly of a(1-4) links but also has branches made w/ a(1-6) links
  ~ Branches produce a compact structure that can rapidly be broken down for energy

Question 29

What is cellulose?

Answer 29

• Found in plants only, makes tough cell walls
• Structural function
• Composed of long glucose chains held together mainly by B(1-4) linkages-these links allow for inter/intra chain H-bonds

Question 30

Why can’t we break down cellulose?

Answer 30

• No mammal makes the necessary enzymes for breaking down cellulose
• Animals that do consume lots of cellulose have symbiotic bacteria that helps them digest it - We still need cellulose to stimulate secretion of mucus in the lining of the digestive tract

Question 31

What is chitin?

Answer 31

• Used by arthropods to build their exoskeleton

Question 32

What are lipids?

Answer 32

• Large, nonpolar organic molecules
• Higher ratio of C and H than O, so they can store more energy per gram
• Insoluble, hydrophobic
• Ex: fats, oils, waxes
• Diverse in form/function

Question 33

List the types of lipids

Answer 33

1. Steroids
2. Fatty acids
3. Phospholipids
4. Waxes

Question 34

Name the differences b/w saturated and unsaturated fats

Answer 34

• Saturated: no C-C double bonds, solid at room temp
• Unsaturated: at least 1 C-C double bond, liquid at room temp

Question 35

What is a triglyceride?

Answer 35

• Composed of 3 fatty acids attached to 1 glycerol

Question 36

What is a phospholipid?

Answer 36

• Composed of 2 fatty acids and 1 glycerol
• Structural component of cell membrane, forms bilayer to separate the inside/outside of the cell

Question 37

What are steroids?

Answer 37

• Lipids w/ a 4 carbon ring framework
• Can be used to treat inflammation (ex: asthma)
• Anabolic steroids mimic male sex hormones to build muscle mass
  ~ Used by cancer/AIDS patients, abused by others
• Ex: cholesterol, vitamin D2, cortisol, testosterone

Question 38

What are waxes?

Answer 38

• Waterproof, form protective coatings on outer surfaces such as feathers, leaves, fruits exoskeletons, etc.
• Contain fatty acids

Question 39

What are proteins?

Answer 39

• Macromolecules made of C, O, H, N
• Monomers are amino acids (20 of them, either essential/non-essential)

Question 40

What does the basic structure of an amino acid consist of?

Answer 40

1. A carboxyl group (COOH)
2. A single H atom
3. An amino group (NH2)
4. An R group (rest of molecule)
   ~ All are covalently bonded to central C atom

Question 41

What is a peptide bond?

Answer 41

• A covalent bond formed b/w the carboxyl group of one amino acid and the amino group of another amino acid through a condensation reaction

Question 42

What is a dipeptide?

Answer 42

• Two amino acids joined by a peptide bond

Question 43

What is a polypeptide?

Answer 43

• Long chain of amino acids joined by peptide bonds (sequence of amino acids determines protein and its function)

Question 44

What is a functional protein?

Answer 44

• A macromolecule that consists of one/more polypeptide chains folded, coiled, and twisted into specific shapes
• A protein’s function is determined by its unique 3D shape as well as its ability to recognize and bind to some molecules

Question 45

What are some uses for proteins?

Answer 45

1. Enzymes
2. Hormones
3. Transport proteins
4. Contractile proteins
5. Antibodies
6. Membrane proteins
7. Structural proteins

Question 46

What are enzymes?

Answer 46

• Proteins that speed up chemical reactions of a cell
• Without them, reactions would be too slow for the cell to survive

Question 47

What is the equation for an enzyme-substrate reaction?

Answer 47

• Enzyme + Substrate –> E.S Complex –> Unchanged Enzyme –> New Product
• Reactions depend on a physical fit b/w the enzyme + substrate

Question 48

What are nucleic acids?

Answer 48

• Large and complex organic molecules that store/transfer vital info to the cell
• Contain the elements C, H, O, N, P
• DNA (nucleus) and RNA (cytoplasm–>ribosomes)
• Monomers are nucleotides