Exam Review-BIOCHEMISTRY

Question 1

What is an ISOMER?

Answer 1

substances that have the same molecular formula but different structures or arrangement of atoms
a) structural isomers: same atom bonded differently
b) stereoisomers: atoms bonded in the same way but arranged differently in a 3D space

Question 2

What is a BUFFER?

Answer 2

made up of a weak acid and its salt or a weak base and its salt. Absorbs small additions of acids and bases without allowing a PH change to occur. Ex. acetic acid
When an acid is added to the buffer, acetate ions react with the H3O added to the solution causing the equilibrium to shift to the right
When a base is added to the buffer, the H3O in the equilibrium decreases as it reacts with the OH of the base causing the equilibrium to shift to the left to replace the H3O that is being used up
Buffers resist PH change by shifting equilibrium ( le chatelier’s principle )
Applications: Human blood contains a buffer system that maintains the PH of your blood at 7.5

Question 3

What is a REDOX reaction?

Answer 3

Reactions involving a transfer of one or more electrons from one reactant to another
Oxidation is loss of electrons
Reduction is gain of electrons
Energy is always lost during oxidation and gained during reduction
Application: oxidation of food molecules releases energy used to maintain body temperature and muscle contraction

Question 4

What is a HYDROLYSIS REACTION?

Answer 4

Addition of water to break a molecule into two
Catabolic process (breaking down)
Releases energy

Question 5

What is a CONDENSATION REACTION?

Answer 5

Removal of water molecule to bind two molecules together
Anabolic process (build)
Absorbs energy

Question 6

What is PHOSPHORYLATION?

Answer 6

The transfer of the phosphate group is called phosphorylation
Even Though the human body consumes its own mass in ATP per day a highly efficient recycling system exists in the body whereby catabolic processes provide the energy to reconnect the terminal phosphate ADP molecule as anabolic processes used the energy ATP releases

Question 7

Nucleic Acids:

Answer 7

DNA and RNA are nucleotide polymers
Pyrimidines are the nitrogenous bases with a single ring, Purines have double rings
DNA- deoxyribonucleic acid, RNA- ribonucleic acid
Phosphodiester bonds hold the phosphate group attached to the number 3 carbon of the sugar on the adjacent nucleotide
The two strands of DNA are held together by hydrogen bonds between the nitrogenous bases on adjacent strands
Hydrogen bonds only form properly if one strand is upside down there are said to run Antiparallel

Question 8

LIPIDS overview:

Answer 8

Composed of hydrogen, carbon and oxygen
Lipids can be divided into 3 groups
Fats, oil, waxes
Phospholipids
Steroids
They are an energy source, more difficult to breakdown then carbs

Insoluble in water
Glycerol- carbon chain attached to a hydroxyl group
Fatty acids- hydrocarbon chains containing a carboxyl group at one end
Triglycerides are the most common form of lipid and are composed of a glycerol molecule and three fatty acids
Lipids are produced via dehydration synthesis
Saturated fats have single bonds between carbon atoms (ex lard and butter)
Unsaturated fats will have double bonds between at least two carbon atoms (one double bond ex. oil)

Question 9

What do lipids do?

Answer 9

Aid in vitamin absorption
Insulate the body
Protect internal organs
Are the main component of your cell membrane
Act as raw material when synthesizing hormones and other chemicals needed in the body

Question 10

Cholesterol:

Answer 10

Used by your body to make hormones
Both male and female sex hormones are made from cholesterol
Important part of the cell membrane
Too much cholesterol can combine with other fats to produce plaque which blocks arteries
Compact hydrophobic molecules containing 4 fused hydrocarbon rings and one hydroxyl functional group

Question 11

What are PROTIENS?

Answer 11

Chicken, nuts, beef, fish, tofu
Used to build cell structures and during chemical activities (ex. enzymes)
Not generally used for energy
Composed of hydrogen, carbon, oxygen, nitrogen, and sometimes sulfur
Made up of subunits called amino acids
Sequence of amino acids determines proteins
Many amino acids joined together are known as polypeptide
The molecules are held together by bonds called peptide bonds
8 amino acids are considered essential since our bodies cannot synthesize them we must get them through our diet

Question 12

What is the structure of a protein?

Answer 12

Protein structure:
Primary: sequence of amino acids, changes in the primary structure can alter the proper functioning of a protein molecule, protein functioning is tied to their 3D structure
Secondary: due to calling/ folding caused by hydrogen bonding between the r-groups, this formes what is called an a helix or b pleated sheet
Tertiary: a folded individual peptide is formed, this is due to more bonding or repulsion between the r groups and the polypeptide and its environment
This is stabilizing by: hydrogen bonding, ionic bonds, disulfide bridges
Quaternary: formed by the interactions of 2 or more polypeptides (hemoglobin)

Question 13

An amino acid has…

Answer 13

An amino group
Carboxyl group
Hydrogen
Side chain (r- group)
All 20 amino acids differ in their r-group which makes the amino acid polar, non-polar or electrically charged
Peptide bond- formed by the joining of the amino end of one molecule to the carboxyl end of another via dehydration synthesis

Question 14

What are CARBOHYDRATES?

Answer 14

Ex. potatoes, bread, corn, rice, fruit, pasta
Most important energy source for the body which we get from food
Composed of carbon, hydrogen, and oxygen in the ratio 1:2:1
Composed of single sugar molecules or chains of these sugar molecules
Saccharide means sugar
Most sugars end with ose
Glucose is found in all of your cells and is our primary energy source
Glucose and fructose are the common monosaccharides
Common polysaccharides are starch, glycogen and cellulose
Starch: storage form of carbohydrates in plants
Cellulose: forms cell wall of plants
Glycogen: storage from in animals
All disaccharides and polysaccharides are formed by a process called dehydration synthesis to join many monosaccharides
Maltose: glucose and glucose
Lactose: glucose and galactose
Sucrose: glucose and fructose
Monosaccharides- simple sugars contain either a carbonyl aldehyde or carbonyl ketone and a hydroxyl group ex glucose
Disaccharides- 2 simple sugars bonded together to form a glycosidic linkage ex. Sucrose
polysaccharide - monosaccharide polymer composed of monosaccharide subunits held together by glycosidic linkages. Ex, chitin, amylase
Alpha glucose- the OH lies below the planet of the ring
Beta glucose- the OH lies above the plane of the ring

Question 15

What is an EXERGONIC reaction?

Answer 15

Exergonic (exothermic) reaction: chemical reaction in which the chemical potential energy of the products is less than the energy of the reactants ( energy has been released)

Question 16

What is an ENDERGONIC reaction?

Answer 16

Endergonic (endothermic) reaction: chemical reaction in which the chemical potential energy fo the products is more than the energy of the reactants ( ex, energy has been absorbed )

Question 17

What is an ANABOLIC reaction?

Answer 17

Reactants that produce large molecules from smaller subunits
Ex, anabolic steroids building muscle
Energy is absorbed

Question 18

What is a CATABOLIC reaction?

Answer 18

Catabolic reaction
Reactions that break macromolecules into subunits
Ex digestion
Energy is released

Question 19

Transport across cell membrane
Brownian motion-

Answer 19

the random movement of particles

Question 20

Transport across cell membrane - PASSIVE TRANSPORT

Answer 20

The movement of molecules across a semipermeable membrane that does not require the cell to expend energy
Types of passive transport are diffusion, osmosis and facilitated diffusion

Question 21

Passive transport: DIFFUSION

Answer 21

the movement of particles down a concentration gradient from an area of high concentration to an area of low concentration
Diffusion is caused by molecular collisions
As particles collide they bounce around in all directions and move farther apart with equal frequency
Areas of high concentration will have more collision than areas of low concentration
Diffusion rates are affected by temperature and pressure
Both oxygen and carbon dioxide are free to diffuse across a cell membrane

Question 22

Passive Transport: OSMOSIS

Answer 22

the diffusion of water molecules across a selectively permeable membrane from an area of high concentration to an area of low concentration

Question 23

Passive Transport: FACILITATED DIFFUSION

Answer 23

method of discussion used by molecules that are simply too large to pass through the membrane by diffusing
Specialized transport proteins imbedded in the membrane move the molecules across
Transport proteins only recognize and move one type of dissolved molecule
This process is still driven by a concentration gradient and molecules move from areas of high concentration to an area of low concentration with no use of energy required
Carrier proteins will only accept non charged particles
Channel proteins will accept charged particles
The proteins have a tunnel like shape that only allow ions that are small enough and with the correct charge to pass
A positively charged channel will only allow negatively charged ions to pass and vise versa

Question 24

Structure and function of the cell membrane:

Answer 24

1972- fluid mosaic model was created
Main points of the model
Made up of a phospholipid bilayer
Polar ends attracted to water, non-polar ends are repelled
The bilayer does not dissolve and this creates a border around the cell
Proteins are embedded in the membrane
Proteins and phospholipids can float and move past each other
Below the surface of the membrane exists a cytoskeleton which anchors parts of the membrane
The membrane also contain cholesterol which allows the membrane to function at a range of temperatures
As temp increases cholesterol maintain rigidity
As temp decreases cholesterol keeps the cell fluid
Function:
Gate keeper - the membrane is selectively permeable
Allows only specific molecules to pass across
Permeable: small nonpolar molecules, small polar molecules, large non-polar (hydrocarbons)

Question 25

Bulk active transport
endocytosis :

Answer 25

active process by which cells ingest materials, cell membranes pinches in on itself to create a vesicle which moves into the cell

Question 26

2 types of endocytosis:
a) phagocytosis “cell eating”

b) Phinocystosis “cell drinking”

Answer 26

a) phagocytosis “cell eating”
Movement of large molecules into the cell ex. White blood cells engulf bacterial cells
b) Phinocystosis “cell drinking”
Transport of fluid droplets into the cell ex. Fat droplets entering a cell

Question 27

What is EXOCYTOSIS?

Answer 27

active process by which cells export material, material filled vesicle fuse with cell membrane and contents are released ex. Specialized cells in pancreas secrete the hormone. Exocytosis restores the membrane removed by endocytosis

Question 28

3 different cell environments: Isotonic (the same)

Answer 28

Water concentration inside the cell is equal to the concentration outside the cell
Net movement is 0

Question 29

3 different cell environments: Hypotonic

Answer 29

Water concentration outside the cell is greater than the water concentration inside the cell
As water keeps diffusing into the cell, the cell expands and may burst
Net movement is outside to inside

Question 30

3 different cell environments: Hypertonic

Answer 30

Water concentration inside the cell is greater than the water concentration outside the cell
As water keeps pumping out the cell shrivers and may die
Net movement is inside to outside

Question 31

What is an ENZYME?

Answer 31

Is a protein
Acts as catalyst which speeds up chemical reaction without being consumed
Work on reactants in a chemical reaction the reactant upon which an enzyme acts is called a substrate
Have one or more depressions on their surface called active sites
When the substrate binds to the active site the enzyme can make subtle changes in shape to accommodate the substrate called induced fit
The substrate- enzyme complex is held together by hydrogen bonds and weak ionic bonds

Question 32

How do enzymes speed up reactions?

Answer 32

Causing stress on the bonds of the substrate by bending or stretching existing bonds
Transfering H and OH ions to or from the substrate to aid hydrolysis and condensation reaction
Can accept electrons forming a temporary bond making the substrate less stable

Question 33

What are factors affecting enzyme function?

Answer 33

A) temperature
As temp increases the activity of enzymes also increases up to a certain critical temperature beyond which enzyme function is impaired
Most human enzymes work best between 35- 40 degree
B) PH
Most enzymes have a optimal PH range
There are exceptions, pepsin works optimally at a PH of 2
C) concentration
Increasing substrate concentration increases the rate of reaction this is because more substrate molecules will be colliding with enzyme molecules so more product will be formed
Increasing enzyme concentration will increase the rate of reaction as more enzymes will be colliding with substrate molecules

Question 34

Regulation of Enzyme activity: INHIBITORS

Answer 34

A) inhibitors
Shut down the action of the enzyme
Non competitive inhibitors- bind to locations other than the active site called allosteric sites thus preventing the substrate from binding to the active site by causing a conformational change that alters the active site so that it is no longer an ideal receptacle for the substance
Competitive inhibitors- bind directly to part of or the entire active site by mimicking the shape of the substrate thus preventing the enzyme from accepting the true substance

Question 35

Regulation of enzyme activity: ACTIVATORS

Answer 35

Bind to the allosteric site enhancing the activity of the enzyme by confirming the shape of the enzyme so that the receptacle is a better fit for the substrate

Question 36

Regulation of Enzyme activity: COFACTORS/COENZYMES

Answer 36

C) cofactors/ coenzymes
Located in the active site of the enzyme they attract electrons from the substrate molecule bonds causing them to break
Cofactors- inorganic ions such as copper and zinc
Coenzymes- organic, non-protein molecules

Question 37

What is a SPONTANEOUS/NON SPONTANEOUS change?

Answer 37

spontaneous change: occurs on its own once started
Non-spontaneous change: cannot occur without continual input of energy