3 - Biological molecules Flashcards
what kind of bonding occurs between water molecules, and what feature does this give?
- hydrogen bonds
- cohesion and adhesion
What are the features of water and give an example of how it is useful.
- high specific heat capacity: provides a stable environment for aquatic organisms.
- high latent heat of evaporation: sweating cools down organisms.
- cohesion/adhesion: useful property in the transpiration stream in plants.
- good solvent: internal transport medium, medium for reactions.
- transparent: allows underwater photosynthesis.
- ice is less dense than water: provides a habitat for polar bears, it is an insulating layer for water underneath so aquatic organisms do not freeze.
- surface tension: habitat for pond skaters.
What elements make up carbohydrates?
C, H, O
What elements make up lipids?
C, H, O
What elements make up proteins?
C, H, O, N, S
what elements make up nucleic acids (DNA, RNA)?
C, H, O, N, P
α - glucose
OH groups: down down up down
β - glucose
OH groups: up down up down
What is a hexose monosaccharide?
A monosaccharide with six carbon atoms.
What is a pentose monosaccharide?
A monosaccharide with five carbon atoms.
function of glucose?
- good energy source in animals and plants.
- soluble: easy to transport.
what type of monosaccharide is glucose?
hexose
What is an example of a pentose sugar?
ribose
What bond is formed between monosaccharides, what type of reaction is this, and how does it form?
- glycosidic bonds
- condensation reaction
- H atom from one monosaccharide and OH group from another bond to form a water molecule.
How are bonds between monosaccharides?
- hydrolysis reaction
- addition of a water molecule to break the glycosidic bond.
Reactions of α-glucose with other monosaccharides to produce disaccharides?
glucose + glucose -> maltose
glucose + fructose -> sucrose
glucose + galactose -> lactose
What two polysaccharides make up starch?
- amylose
- amylopectin
amylose
- α-glucose
- 1,4 glycosidic bonds only
- helix structure
- hydrogen bonding further stabilises the molecule
- coiled structure: compact, good for storage
- insoluble
amylopectin
- α-glucose
- 1,4 and 1,6 glycosidic bonds.
- branched structure
- compact, good for storage
- branched structure allows enzymes to easily access the glycosidic bonds: glucose can be released quickly.
- insoluble
glycogen
- α-glucose
- energy store in animals.
- 1,4 and 1,6 glycosidic bonds.
- branched structure, more branching than amylopectin
- compact, good for storage (more compact than amylopectin)
- branched structure allows enzymes to easily access the glycosidic bonds: glucose can be released quickly. (faster than amylopectin).
- insoluble: (does not affect water potential of cell)
- can be broken down quickly
cellulose
- β - glucose
- 1, 4 glycosidic bonds only
- forms straight chains
- adjacent glucose units in alternate orientation.
- cellulose chains make hydrogen bonds with each other, forming macrofibrils.
- macrofibrils combine to form fibres.
- cellulose provides structural support in plant cells.
- insoluble.
test for reducing sugars
- bendict’s solution
- sample in test tube
- add equal vol of benedict’s solution
- water bath 5 mins
- blue to brick red if reducing sugar is present.
test for non-reducing sugars
- remains blue after benedict’s solution added.
- add dilute HCl
- add benedict’s solution
- blue to red.
Example of reducing sugars?
monosaccharides
- glucose
- fructose
- galactose
Example of non-reducing sugars
disaccharides
- sucrose
- maltose
- lactose
Why is dilute HCl added to non-reducing sugars before benedicts?
- hydrolyses the disaccharide into monosaccharides which are reducing sugars (positive result with benedict’s).
Test for starch?
- iodine test
- iodine dissolved in potassium iodide solution mixed with sample
- brown to purple/black (positive result)
what else can be used for the test for reducing sugars?
- reagent strips.
do lipids have polarity? what does this mean?
- they are non-polar molecules
- insoluble in water
What kind of molecules are lipids?
- macromolecules
- built from repeating units/monomers.
- complex molecules with a relatively large molecular mass.
What is triglyceride composed of? What bonds are between these?
- one glycerol
- 3 fatty acids
- ester bonds between them.
- insoluble, non polar
What group are fatty acids in?
- carboxylic acids
How do triglycerides form?
- 3 ester bonds form between the 1 glycerol molecule and 3 fatty acids.
- when they combine, 3 water molecules are produced (condensation reaction) since 3 ester bonds are formed
- the reaction that leads to the formation of the ester bonds is called esterification (condensation reaction).
saturated and unsaturated fatty acids?
saturated: only contain single C-C bonds
unsaturated: contain C=C double bonds.
How do unsaturated fatty acids affect tryglycerides?
- kink/bend in fatty acid
- fatty acids cannot pack as closely together.
- liquid at room temp.
How are triglycerides broken down into glycerol and fatty acids?
- 3 water molecules are supplied to break the 3 ester bonds between the glycerol and fatty acids.
- hydrolysis reaction.