Biological Molecules, Key Words

Question 1

Polymers

Answer 1

Large, complex molecules composed of long chains of monomers joined together.

Question 2

Monomers

Answer 2

Small, basic molecular units (E.g. Monosaccharides, amino acids, nucleotides.

Question 3

Carbohydrates

Answer 3

Most carbohydrates are polymers. Made from monosaccharides (glucose, fructose, galactose).

Question 4

Glucose

Answer 4

A hexose sugar. Two types - alpha and beta. They’re isomers so they are molecules with the same molecular formula as each other but with the atoms connected in a different way.

Question 5

Condensation reactions

Answer 5

When two molecules join together with the formation of a new chemical bond, and a water molecule is released when the bond is formed. Monosaccharides are joined together by condensation reactions. A glycosidic bond forms between the two monosaccharides as a molecule of water is released. A disaccharide is formed when two monosaccharides join together.

Question 6

Condensation reactions ( forming disaccharides)

Answer 6

Glucose + Glucose -> Maltose
Glucose + Fructose -> Sucrose
Glucose + Galactose -> Lactose

Question 7

Isotonic

Answer 7

Prevents Osmosis –so no lysis/ bursting/shrinking of organelles.

Question 8

Cell membrane

Answer 8

Cell membrane (plasma) – partially permeable. Contain a phospholipid bilayer, intrinsic proteins (span membrane), extrinsic proteins (on surface), cholesterol (stability) & glycolipids (recognition site)

Question 9

Phospholipids

Answer 9

Phospholipids – 2 fatty acids/1 glycerol/1 phosphate.

-hydrophobic tail & hydrophilic head-so form bilayer.

Question 10

Lipid

Answer 10

Lipid soluble molecules, water and other small substances can diffuse through. Water soluble ones & larger molecules (e.g. glucose) can’t.

Question 11

Fluid-mosaic model

Answer 11

In arrangement known as fluid-mosaic model
Fluid à Molecules are moving
Mosaic à made up of proteins and phospholipids.

Question 12

Osmosis

Answer 12

Osmosis – Net movement of water particles from an area of high concentration to low, across a partially permeable membrane. Passive/no carrier proteins/down gradient
Water moves to more negative water potential. More concentrated solution is (i.e. more solutes)= lower the water potential.

Question 13

Diffusion

Answer 13

Diffusion = net movement of particles from an area of high to low concentration. Passive process, down conc gradient.

Question 14

Monomers and polymers

Answer 14

Monomers- individual molecules

Polymer – chains of repeating monomer units

Question 15

Monosaccharides

Answer 15

Monosaccharides (monomers) – sweet tasting, soluble substances (CH2O)n – e.g. glucose
• Monosaccharides join together by condensation reactions & form a glycosidic bond.

Question 16

Disaccharides

Answer 16

Disaccharides – (polymers) 2 monosaccharides joined (e.g. α glucose + a glucose = maltose
Disaccharides – can break into monosaccharides by adding water (hydrolysis rxn) – breaks glycosidic bonds.

Question 17

Polysaccharide

Answer 17

Polysaccharide – many monosaccharides joined in condensation reactions. Insoluble- good for storage (e.g. Starch) Polysaccharides – can break into monosaccharides by adding water (hydrolysis rxn) – breaks glycosidic bonds

Question 18

Common disaccharides

Answer 18

Common disaccharides:

• Maltose (α glucose + α glucose)
• Sucrose (α glucose + α fructose)
• Lactose (α glucose + α galactose)

Question 19

Reducing sugar

Answer 19

Reducing sugars- all monosaccharides and some disaccharides. Can donate electrons (reduce) other chemicals (e.g. maltose, glucose)

Question 20

Non-reducing sugar

Answer 20

Non- reducing sugars- The other disaccharides & all polysaccharides – can’t donate electrons (e.g. sucrose)

Question 21

Starch

Answer 21

Starch (made of alpha glucose chains)
• Branched / coiled / alpha helix, so makes molecule compact and can fit into a small space
• It is insoluble – stops osmosis/doesn’t affect water potential
• Long chain – Can’t cross cell membrane.
• Polymer of alpha glucose so provides glucose for respiration.
• Branched - so glucose is easily released in respiration (more ends for enzyme action).
(monomers linked by glycosidic bonds - condensation reactions)

Question 22

Test for reducing sugar

Answer 22

Test for reducing sugar:

• Add Benedict’s (reagent) and heat
• Turns red/orange/yellow/green

Question 23

Test for non-reducing sugar

Answer 23

Test for non-reducing sugar:

• Add Benedict’s and heat (will remain blue)
• Add hydrochloric acid (which hydrolyses it)
• Add sodium hydrogen carbonate solution (to neutralise HCl)
• Then do test for reducing sugar

Question 24

Test for starch

Answer 24

Test for starch (polysaccharide)

• Add iodine solution
• Turns blue/black

Question 25

Cellulose

Answer 25

Cellulose (B glucose chains)
• Give cell strength because:
• Long, unbranched (straight) chains of B glucose
• Several chains lie side by side (and form microfibrils)
• H bonds hold these chains together. H bonds are strong in large numbers
• cellulose has only 1,4- glycosidic bonds;

Question 26

Glycogen

Answer 26

Glycogen (Alpha glucose chains)
• Shorter, more branched chains than starch à can be hydrolysed to monomers more easily (energy quicker)
• Spiral shape means it is compact and can fit into a small space
• Coiled as opposed to straight.
• glycogen has 1,4- and 1,6- glycosidic bonds

Question 27

Using a calibration curve to find a sugar concentration

Answer 27

Using a calibration curve to find a sugar concentration
• Make different known sugar concentrations
• Use colorimeter to measure absorbance of each concentration and plot calibration curve on a graph
• Find concentration of sample from calibration curve
• You may be given data points plotted on a graph, you would have to draw a line of nest fit to then read off to determine a value.