Biological Molecules 1

Question 1

5 properties of water explained

Answer 1

HLHV - provides cooling effect with little loss of water through evaporation.
HSHC - acts as a buffer against temperature change.
Metabolite - used in many metabolic reactions such as hydrolysis and condensation.
Solvent - allows transport of substances/ allows metabolic reactions to occur.
Adhesive - supports columns of water (in plants).
Cohesive - so produces surface tension.

Question 2

Maltose is made of…

Answer 2

2 alpha glucose molecules

Question 3

Lactose is made of…

Answer 3

1 alpha glucose and 1 galactose

Question 4

Sucrose is made of…

Answer 4

1 alpha glucose and 1 fructose

Question 5

Starch properties

Answer 5

1-4 glycosidic bonds, tight, coiled structure so lots of energy is small area, acts as storage for energy in plant, doesn’t affect water potential, cannot diffuse out of cells

Question 6

Glycogen properties

Answer 6

1-4 and 1-6 glycosidic bonds, coiled, branched structure, many branched ends means hydrolysis can occur quicker for energy hungry organs such as the liver and muscles

Question 7

Cellulose properties

Answer 7

made of beta glucose, makes 1-4 glycosidic bonds and every 2nd beta glucose flips 180 degrees, forms a linear structure, which hydrogen bonds to for microfibrils, which form macrofibres

Question 8

Test for non reducing sugars

Answer 8

Boil the solution with blue benedict’s solution and hydrochloric acid, then neutralise with an alkali. Heat in a water bath for five minutes, colour change from blue to brick red/orange.

Question 9

Test for reducing sugars

Answer 9

Add blue bendict’s solution then heat in water bath, colour change from blue to a brick red/yellow/green precipitate.

Question 10

similarities and differences between triglycerides and phospholipids

Answer 10

• both contain ester bonds
• both contain glycerol
• both are insoluble in water
• triglycerides contain 3 fatty acids and a glycerol whereas phospholipids contain only 2 fatty acids with a glycerol and a phosphate head
• triglycerides are hydrophobic whereas phospholipids are both hydrophobic and hydrophilic
• phospholipids can form a bilayer, triglycerides cannot.

Question 11

test for lipids

Answer 11

add ethanol and shake, milky white emulsion appears

Question 12

Meaning of saturated in lipids

Answer 12

Saturated means there is only 1 carbon-carbon double bond and has the most amount of hydrogen it can, tends to be solid at room temperature

Question 13

Triglyceride functions

Answer 13

insulate and protect organs, act as an energy storage and can be broken down to release energy when needed.

Question 14

Phospholipid functions

Answer 14

hydrophilic region faces faces aqueous environments so can form a bilayer, used for cell membranes, allows processes to occur in sub cellular compartments.

Question 15

Test for proteins

Answer 15

add biuret reagent, colour change from blue to lilac

Question 16

General structure from amino acids

Answer 16

Amine group, CH and R group, carboxyl group

Question 17

What is the primary structure of a protein

Answer 17

A specific sequence of amino acids that form peptide bonds between them to form a polypeptide chain.

Question 18

What is the secondary structure of a protein

Answer 18

Long polypeptide chain coils together by forming hydrogen bonds between hydrogen and oxygen groups, forming either an alpha helix or beta pleated sheet.

Question 19

What is the tertiary structure of a protein

Answer 19

Different R groups along the polypeptide chain will form disulfide bridges, ionic bonds, hydrogen bonds and will base the shape of the structure.

Question 20

What is the quaternary structure of a protein

Answer 20

Formed from more than one polypeptide chain and joined and coiled together from the interactions between R-groups.

Question 21

What do non-competitive inhibitors do to an enzyme

Answer 21

• bond to allosteric site and change the shape of the active site permanently, so the reaction is irreversible. This cannot be changed by increasing the substrate concentration

Question 22

What do competitive inhibitors do to an enzyme

Answer 22

They bond temporarily to the active site and do not affect the shape, so the reaction is reversible. This can be undone by increasing the substrate concentration

Question 23

What are the steps to induced fit

Answer 23

• active site is not originally complementary to substrate
• active site changes shape to fit to substrate
• enzyme-substrate complex is formed and this distorts the bonds in the substrate

Question 24

What are the 4 factors affecting enzyme activity

Answer 24

pH, temperature, substrate concentration, enzyme concentration

Question 25

Differences between RNA and DNA (SSLB)

Answer 25

- DNA is double stranded, RNA is singularly stranded - DNA contains deoxyribose sugar, RNA contains ribose sugar - DNA is a much larger and longer molecule, RNA is a much smaller and shorter molecule - DNA contains bases adenine, guanine, cytosine and thymine, RNA contains bases adenine, guanine, cytosine and uracil

Question 26

What is the structure of a DNA molecule

Answer 26

- double helix coiled structure - a polymer of nucleotides - nucleotides consists of 1 deoxyribose sugar, phosphate group and 1 nitrogenous base (TGCA) - phosphodiester bonds form between each nucleotide - hydrogen bonds for between complementary bases

Question 27

How is DNA replicated

Answer 27

- DNA helicase unwinds and unzips the double strand structure and breaks the hydrogen bonds between complementary nitrogenous bases - both of these strands now act as template strands - free activated DNA nucleotides in the nucleoplasm form hydrogen with their complementary bases on the template strands - DNA polymerase joins nucelotides by forming phosphodiester bonds between adjacent nucleotides - two identical DNA molecules are formed, consisting of one original strand and one new synthesised strand

Question 28

DNA features and adaptations that relate to function

Answer 28

- sugar-phosphate backbone protects nitrogenous bases - large molecule so can store lots of info - double stranded so semi conservative replication can make identical copies - weak hydrogen bonds between complementary nitrogenous bases so can easily be broken for replication

Question 29

Roles of ATP (MMSA)

Answer 29

- metabolic reactions - movement (muscle contraction) - secretion of products from cells - activation of molecules (phosphorylation)

Question 30

How do disulfide bridges form in tertiary structures of proteins?

Answer 30

- strong covalent bonds - between R groups - of 2 CYSTEINE amino acids

Question 31

What does more cholesterol in the phospholipid bilayer mean?

Answer 31

More cholesterol means less membrane fluidity and more membrane stability and rigidity.

Question 32

Species that have higher body temperatures tend to have a higher cholesterol concentration in their cell membranes. Suggest why.

Answer 32

Higher temperatures increase the kinetic energy of molecules (e.g. phospholipids) in the membrane. If these molecules move too much, the membrane will break apart. Cholesterol helps to stabilise the membrane and reduce the chance of this happening

Question 33

How is induced fit similar to that of lock and key theory

Answer 33

- both have enzyme-substrate complexes form - substrate binds to an active site

Question 34

draw the structure of ATP

Answer 34

compare to notes

Question 35

what are the 2 main functions of ATP

Answer 35

hydrolysis of ATP by ATP hydrolase releases energy as ADP and Pi is formed in a hydrolysis reaction ATP is resynthesised in a condensation reaction by ATP synthase during photosynthesis or respiration

Question 36

what are the roles of ATP

Answer 36

activation of molecules via phosphorylation helps in active transport by providing energy when hydrolysed available for short bursts of energy, such as in anaerobic respiration

Question 37

what is the importance of Fe3+

Answer 37

importance in haem groups in blood haemoglobin, allows oxyhaemoglobin to form when O2 binds to the Fe2+ group

Question 38

what is the importance of Na+

Answer 38

Na+/K+ pump in synaptic transmission

Question 39

what is the importance of phosphate groups, PO4 3-

Answer 39

adds polarity to a phospholipid, allowing bilayers to form and vesicles to transport important substances via exo and endocytosis

Question 40

what is the importance of H+

Answer 40

controls and regulates pH levels in the body, particularly important for enzyme controlled reactions

Question 41

how is cellulose formed

Answer 41

beta glucose molecules joined together in 1-4 glycosidic bonds in a linear structure every 2nd beta glucose molecule flips in order to do this these bond with other linear chains to form microfibrils via hydrogen bonding