BIOLOGY module 2 Flashcards
what is the charge of oxygen in a water molecule?
- slightly negative
- the hydrogen atoms are more positive therefore creating uneven distribution of charges (polar molecule).
describe how hydrogen bonds in water.
- hydrogen bonds form between neighbouring hydrogen and oxygen atoms of adjacent water molecules.
why is ice less dense than liquid water?
- the orientation of hydrogen bonds causes molecules to push further apart compared to average water molecules.
what are the advantages to living organisms of ice being less dense then water?
- ice floats and forms an insulating layer on the top of water sources such as ponds.
- this maintains a constant temperature for organism.
why is water a good solvent?
- its polar so other charged molecules are attracted to it
why is waters high specific heat capacity useful for organisms?
- it has high resistance to sudden temperature changes so …
- it can provide a constant temperature for aquatic organisms
- used as a coolant to buffer temperature changes during chemical reactions.
why is water cohesive and adhesive?
- water is cohesive because the hydrogen bonds mean water molecules are attracted to one another.
- it is adhesive because it can be attracted to other water molecules.
why is it useful that water is cohesive and adhesive?
- water acts as a good transport medium
- also means it can move upwards through narrow tubes by capillary action. eg transport of water to leaves.
what are three examples of hexose monosaccharides?
- glucose, fructose and galactose
what is a hexose monosaccharide?
- has 6 carbons
what are pentose monosaccharides?
- one with 5 carbons
what are 2 examples of pentose monosaccharides?
- ribose and deoxyribose
what is the difference between alpha and beta glucose?
- the OH group is below carbon 1 on alpha, and above it on beta
why is glucose soluble in water?
because it contains an OH group which makes it polar
what is the bond between two monosaccharides called?
glycosidic bond
what is the disaccharide version of alpha glucose called?
maltose
what is the reaction that creates water called?
condensation reaction
what is the addition of water to a disaccharide to split it into two monosaccharides called?
hydrolysis
what is the test for reducing sugars?
Benedict’s test
what is Benedict’s reagent?
an alkaline solution of copper sulphate
what colour would blue Benedict’s reagent change to if reducing sugars are present?
red/orange
are all monosaccharides reducing sugars?
yes
are most disaccharides reducing or non reducing?
non- reducing
why does Benedict’s reagent turn red when reducing sugars are present?
because the blue Cu2+ions have an electron added to form brick red Cu+ ions (will reduce the copper causing oxide precipitate)
what is the method for testing for a reducing sugar?
- add 2cm cubed of sample
- add 2cm cubed Benedict’s reagent
- place the test tube in an 80 degrees water bath.
what is the ethos for testing for a non reducing sugar?
- confirm that same is not a non reducing sugar
- add 2cm cubed of food sample into test tube
- add 2cm cubed of hydrochloric acid
- place in 80 degrees hot water bath for 5 minutes
- remove and slowly add sodium hydrocarbonate until the solution is neutral
- restest the solution using Benedict’s test
how can you make Benedict’s test quantitative?
use a colorimeter to test the transmission of red light in the solutions. more reducing sugars = more red light
what are 2 examples of biosensors?
pregnancy test and blood sugar monitor
what is an analyse in a biosensor?
the sample containing the molecule you are testing for
what is the receptor in the biosensor?
the part which interacts with the molecule you are testing for
what is the transducer in a biosensor?
detects the change in the receptor and provides a response.
what does the display in a biosensor do?
gives a visual representation of the change in the receptor.
what colour does iodine change to in the presence of starch?
becomes black because iodine molecules become trapped int the helix of the starch.
what is the polysaccharide version of beta glucose?
cellulose
which two polypeptides make up starch?
amylose and amylopectin
what percentage of starch is amylose and what percentage is amylopectin?
20-30% amylose
70-80% amylopectin
what type of glucose are amylose and amylopectin made up of?
alpha glucose
what general structure are cellulose molecules?
long, unbranched chains of beta glucose
why are cellulose molecules straight?
the bonds between the glucose molecules are straight.
every other glucose monomer in the chain is flipped over in relation to its neighbors
what are the strong fibres formed by cellulose chains held together by hydrogen bonds called
microfibrils
why is cellulose suitable for use in cell wall?
its microfibril structure makes it strong enough to provide structural support for cell walls
what are some properties of cellulose?
strong, insoluble, hard to break down into fibrous form.
what is alpha glucose stored as in animals and fungi?
glycogen
why is starch used to store glucose?
- because amylose and amylopectin are insolubles so the glucose won’t interfere with osmosis
- Starch is also a quick molecule to break down to access the glucose needed for energy release.
what is general structure of amylose?
a tight unbranched helix with 1,4 glycosidic bonds
what is general structure of amylopectin?
a long, tight helix structure with branches
1,4 and 1,6 glycosidic bonds
what is the general structure of glycogen?
similar to amylopectin but has a lot more branches.
why does glycogens structure make it suitable to storage?
it is compact like amylopectin because it is coiled. its many branches also allow energy to be released quickly making it suited to more active animals.
which carbon do branches occur from in starch and glycogen?
carbon 6
what are some uses of fat in organisms?
protection around organs, shock absorption, buoyancy in aquatic animals, insulation, making hormones, making up cell membranes and storing energy.
what are two types of lipids?
phospholipids and triglycerides
are phospholipids polar
partially - they have polar head (phosphate group) and a non polar tail (the fatty acids)
what is structure of triglyceride?
a glycerol with three fatty acids (hydrocarbon chains with carboxyl group) joined by glycosidic bonds
where are triglycerides found?
in bloodstream
why are triglycerides insoluble in water?
because of non polar tails
what is structure of a phospholipid?
a glycerol, two fatty acids and a phosphate group.
what is the main use of triglycerides and why?
energy storage because their hydrocarbon tails contain lots of energy.
what is the test for lipids?
the emulsion test
what result indicates the presence of lipids when using the emulsion test?
a milky emulsion forming
how would you conduct a test for lipids in a food solution?
- add 2cm cubed of ethanol to either a liquid sample or add the ethanol to a solid sample, crush it and pipette the ethanol into a separate test tube.
- and 2cm cubed of water to this ethanol and shake gently
- observe the appearance of the test tube content.
why can ethanol form emulsion?
because it is non polar
why do unsaturated fats tend to be liquid rather than solid at room temperature?
because the double bonds cause a kink in the hydrocarbon chain so the molecules can’t pack together as closely
what type of alcohol is cholesterol?
a sterol alcohol
where is cholesterol made?
mostly liver and intestines
what are some functions of cholesterol?
adds stability to the cell membrane involved in the production of steroid hormones, vitamin D and bile
what is the structure of cholesterol?
a polar hydroxyl group and 4 carbon rings and a hydrocarbon chain tail both of which are non polar.
what is the structure of an amino acid?
an amine group, a carbon with a hydrogen and an R group attached and a carboxyl group.
what is the bond between two amino acids in a dipeptide called?
a peptide bond
which part of the amino acid bond together to form a dipeptide?
the H of one amine group and the OH of the others carboxyl group.
what is the primary structure of a protein?
the sequence of amino acids in a chain
what is a polypeptide formed of?
two or more amino acids
what is a protein formed of?
two or more polypeptides
what is the secondary structure of a protein?
an alpha helix or a beta pleated sheet formed by hydrogen bonds forming between NH and CO groups in a chain.
what is the tertiary structure of a protein?
the overall three-dimensional arrangement of its polypeptide chain in space
The bonds in the tertiary structure of a protein involve disulfide bonds bridge, hydrogen bonds between R groups, ionic bonds between oppositely charged R groups, and hydrophobic interactions.
how are hydrophobic and hydrophilic R groups arranged in the tertiary and quartenary structure of proteins?
hydrophobic groups on inside nd hydrophilic on outside
what forms the quaternary structure of a protein?
the association of several protein chains or subunits into a closely packed arrangement.
what is a conjugated protein?
a protein which contains a non protein group called a prosthetic group as part of its quaternary structure
what is the structure of a globular protein?
compact and round in shape
what is a simple protein?
one without a prosthetic group
what is it called when a prosthetic group is key to a proteins function?
a cofactor
what are three examples of conjugated proteins?
haemoglobin(contains 4 iron harm groups), lipoproteins (contain a lipid) glycoproteins (contain a carbohydrate)
what is general structure of a fibrous protein?
very repetitive primary structure leading to long, strong, organised rope like structures which are not folded into 3D shape
why are fibrous proteins insoluble?
because they have many hydrophobic R groups in their component amino acids
