Chapter 3 Biological Molecules Flashcards
How is a water molecule structured?
A water molecules is structured in a ‘V’ shape with one oxygen atom bonded covalently to two hydrogen atoms
O / \ H H
What type of molecule is water known as?
Water is known as a polar molecule, this is because it has an uneven distribution of charge due to oxygen being more electronegative than hydrogen. This means that electrons orbit around oxygen more than hydrogen, this unequal share of electrons consequently makes oxygen slightly negative and hydrogen slightly positive. This can be represented with the delta symbol next to the oxygen and hydrogen atoms.
What does waters dipolar nature mean?
Waters dipole nature means that there is an attraction between two different water molecules, this attraction is known as a hydrogen bond (these are weak individually, but in large proportions are very strong) which are represented through dots or lines between the slightly positive hydrogen atom and the slightly negative oxygen atom.
What are some of the principle properties of water?
-Water is polar
-Water is a good solvent, as many ions and covalently bonded polar substances (like glucose) can dissolve in it- this allows chemical reactions to occur within cells as it also acts as a transport medium.
-High specific heat capacity this means water is able to absorb a lot of energy for only a small rise in temperature due to the multiple hydrogen bonds present in water. This is beneficial as it is able to maintain a constant temperature consequently providing a suitable habitat for organisms and enzyme activity. This is also vital for water in the blood plasma because as water passes through active regions of the body, heat energy is absorbed but the temperature remains fairly constant.
-Latent heat of vaporisation, in order for water to evaporate, it must absorb a large amount of energy to break the hydrogen bond. Therefore, this is an advantage for living organisms because only a little water is required to evaporate for the organism to lose a great amount of heat providing a cooling effect.
-Ice is less dense than water because when frozen the hydrogen bonds between the water molecules space out meaning there are more air gaps and allowing ice to float. This is beneficial as it provides a habitat for organisms underneath as well as insulating the underlying water so temperatures remain fairly stable.
-Low viscosity allowing water to flow through small vessels and capillaries
-Cohesive due to hydrogen bonds, this allows water to move through the xylem of plants and through blood vessels in animals. Additionally, this enables surface tension due to hydrogen bonds between the top layer of water molecules allowing insects to float.
-Adhesive as water is able to hydrogen bond to other molecules like cellulose, this allows water to move up through the xylem.
-Translucent which enables water to transmit visible light, so aquatic habitats and organisms are able to survive
What are monosaccharides?
Single units which are used as a primary energy source for fuelling cellular metabolism. For example, glucose and fructose.
All monosaccharides are reducing sugars which means they can participate in reduction reactions.
What is the the structure of the isomer: alpha glucose?
CH2OH
\
H C———————O H
\ / \H \ /
C C
/ \ /OH H \ / \
OH C————————C OH
/ \
H OH
What is the structure of the isomer: Beta glucose?
CH2OH
\
H C———————O OH
\ / \H \ /
C C
/ . /OH H \ / \
OH C———————-C H
/ \
H OH
What is a condensation reaction?
This is when two molecules join to form a larger molecule whilst also releasing water in the process. For example, making bonds between two monosaccharides to form a disaccharide (double sugar molecule joined with a glycosidic bond) as well as producing water
What type of monosaccharide is glucose?
Hexose as it contains 6 carbons
What monosaccharides is the disaccharide lactose made from?
Monosaccharides are: Glucose and Galactose
What monosaccharides is the disaccharide sucrose made from?
Monosaccharides: Glucose and Fructose
What monosaccharides is the disaccharide maltose made from?
Monosaccharide: Glucose and Glucose
What is the chemical test for reducing sugars?
Benedict’s reagent- an alkaline solution of copper(II) sulfate
What is the positive result for reducing sugars?
A brick-red precipitate will be formed after heating as the reducing sugar has reacted with the copper ions in the Benedict’s reagent, resulting in the addition of electrons to the blue Cu2+ ions reducing them to a brick red Cu+ ion.
What is the result of using Benedict’s reagent on non-reducing sugars?
Non-reducing sugars do not react with Benedict’s solution and therefore the solution will remain blue after warming, indicating a negative result. However, if sucrose is first boiled with dilute hydrochloric acid a positive result will be given once warmed with Benedict’s solution. This is because the sucrose has been hydrolysed by the acid to glucose and fructose, both reducing sugars.
What is the test for starch?
The Iodine test is used to test for the presence of starch. A few drops of iodine dissolved in potassium iodide solution are mixed with the sample.
What is a positive result of the starch test?
If the solution changes colour from yellow/brown to purple/black then starch is present.
In the starch test, what is iodine dissolved in?
Potassium iodide
What can reagent strips be used to test for?
Test for the presence of reducing sugars, like glucose.
What is the advantage of using reagent strips?
Due to the colour coded chart, the concentration of the sugar can be determined.
What has to happen when two beta glucose molecules combine together?
One of the Beta glucose units has to flip upside down
What is formed when two glucose molecules react together?
A disaccharide which has a 1-4 glycosidic bond
How is starch structured?
Polymer of glucose, which is made up of long chains of alpha glucose molecules.
What is the function of starch?
Energy storage molecule in plants which can be found in chloroplast and concentrated in insoluble starch granules.
Osmotically inactive
What is starch composed of?
Amylose (25%-30%) and Amylopectin (70%-75%)
How is amylose structured?
Made up of long unbranched chains of alpha glucose molecules joined together by 1-4 glycosidic bonds. Coils are induced by the glycosidic bonds.
How is amylopectin structured?
Made up of long branched chains of alpha glucose molecules joined together by a 1-6 glycosidic bond every 23- 30 glucose units, with the rest connected by alpha 1-4 bonds.
What can amylose and amylopectin be broken down by?
Enzyme amylase which hydrolyses the glycosidic bonds.
How is cellulose structured?
Polysaccharide- a large insoluble molecule composed of beta glucose 1-4 glycosidic bonds held together in a bundle of hydrogen bonded Microtubules and fibres.
What is the function of cellulose?
Structural polysaccharide of plants cell wall which is freely permeable to solutes and solvents.
Great tensile strength.
How is glycogen structured?
Large insoluble molecule composed of highly branched chains of alpha glucose molecules.
What is the function of Glycogen?
Storage polysaccharide found in glycogen granules in liver and muscle cells.
Osmotically inactive
Readily converts back into glucose by the influence of the hormone glucagon.
What is the structure of glucose?
A hexose monosaccharide which is a small soluble molecule.
Osmotically active
What is the function of glucose?
Respiratory substrate which is the only fuel for brain cells.
Building blocks for other molecules like starch, cellulose and glycogen.
What are the three important properties of starch and glycogen?
Compact
Free ends for long branching chains means glucose can be added or removed easily
Insoluble
What does a colorimeter measure?
The absorbance and transmission of light.
If a solution is pale, little light will be absorbed, therefore the transmission value will be high while absorbance will be low.
However, if the solution is deeply coloured, more light will be absorbed, therefore the transmission value is low and absorbance value is high.
What disaccharide is a non-reducing sugar?
Sucrose
What are Lipids composed of?
-Built from fatty acid and a glycerol molecule
What are the different types of lipids?
Triglycerides- fats and oils
Phospholipids
Other lipids like:
-Steroids
-Hormones
-Cholesterol
-Waxes
What is the function of lipids?
The function depends on the structure of the lipid, however typically they are used for:
Energy Storage
Metabolic water source
Membrane structure
Water proofing
Insulation
Hormones
What types of lipids contain fatty acids?
Triglycerides
Phospholipids
Waxes
What types of lipids don’t contain fatty acids?
Steroids and Cholesterol
What is the displayed formula of an ester bond?
O — C
||
O
Where is the ester bond formed within a lipid?
Ester bonds are formed between the fatty acids and the glycerol molecule during a condensation reaction
How are saturated fatty acid structured?
The hydrocarbon chain has only single bonds that are in straight chains.
How are unsaturated fatty acids structured?
Contain some carbon atoms that are double bonded with each other.
This unsaturated nature causes kinks in the straight chains which means the molecules cant be packed closely together.
How is a triglyceride lipid structured?
Three fatty acids attached to a glycerol molecule.
How is a phospholipid structured?
Two Fatty acids attached to a glycerol molecule, one of the fatty acids is replaced by the phosphate group.
The Fatty acids are hydrophobic while the phosphate group is hydrophilic.
How are lipids respired?
1-Hydrolysis of ester bonds in triglycerides
2-Glycerol and fatty acids are completely broken down into H2O and CO2
3-This releases energy which is twice as much as the respiration of carbohydrates and release lots of water that is required by some organisms.
What are the advantages of lipids as a storage molecule?
Not water soluble
Don’t effect the water potential of the cell contents
Can be stored in a compact way