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Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are phospholipids and triglycerides an example of?

A

-macromolecules

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2
Q

Describe the difference of an unsaturated and a saturated fatty acid?

A

-if a fatty acid is saturated there are no carbon double bonds in the molecule (it has the full amount of hydrogens) Saturated can be stacked easier as no kink
-if a fatty acid is unsaturated there is a double bond between two of the carbon atoms .This causes a kink where the double bond is.The kink makes the fatty acid more fluid as molecules are further apart.

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3
Q

What makes a Triglyceride?

A

They are made of glycerol and 3 fatty acid chains

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4
Q

How is a triglyceride formed?

A

-a condensation reaction happens between the -COOH group of the fatty acid and and the -OH group of glycerol
-as there are 3 OH groups three fatty acids will bond
-a water molecule is produced and the covalent bond is formed known as an ester bond

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5
Q

Do triglycerides dissolve in water?

A

No as they are non polar

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6
Q

What is the difference between a disaccharide and a polysaccharide?

A

A disaccharide is two monosaccharides while a polysaccharide is many monosaccharides

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7
Q

What groups make up an amino acid?

A

Amino /amine group
Carboxyl group
R group

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8
Q

How is a peptide bond formed?

A

-through a condensation reaction the carbon and nitrogen form a peptide bond
-they are catalysed by enzymes
-all amino acids join together in the same way despite the R group

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9
Q

How is a peptide bond broken?

A

-through a hydrolysis reaction
-enzymes catalyse this

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10
Q

What is the difference between a dipeptide and a polypeptide?

A

-Two amino acids joined together are known as a dipeptide
-Joining a longer chain of amino acids together forms a polypeptide
-A protein may consist of a single polypeptide chain or more than one chain bonded together

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11
Q

What is the primary level of a protein ?

A

-the simplest level
*the sequence of amino acids found in a molecule *
-changing just one amino acid can alter the function of the protein

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12
Q

What are the functions of triglycerides?

A

-energy source
-energy store
-insulation e.g. blubber
-buoyancy
-protection e.g. around delicate organs

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13
Q

How are triglycerides used as an energy source?

A

-they can be broken down in respiration to release energy and generally ATP
-firstly the ester bonds are hydrolysed
-then both glycerol and fatty acids can be broken down completely to carbon dioxide and water

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14
Q

Why are triglycerides used for energy storage?

A

-because triglycerides are insoluble in water they can be stored without affecting the water potential of the cell
-lipids release more energy than glucose due to the higher proportion of hydrogen atoms than carbohydrates and almost no hydrogen

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15
Q

Why are triglycerides used in buoyancy?

A

-because fat is less dense than water

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16
Q

What is cholesterol?

A

-made from 4 carbon based rings or isoprene units
-small and hydrophobic molecule meaning it can sit in the middle of the hydrophobic part of the bilayer

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17
Q

What is cholesterols function?

A

-regulates fluidity of the membrane preventing it from becoming too fluid or stiff
-makes testosterone , oestrogen and vitamin D

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18
Q

What is the secondary structure of an amino acid?

A

-the coiling or folding of an amino acid chain
-The mains forms of secondary structure are:

.alpha helix
-helix is held together by hydrogen bonds between the NH group of one amino acid and the CO group of another. These hydrogen bonds keep it stable

.beta pleated sheet
-chain forms a zigzag and folds over itself
-hydrogen bonds between the NH group of one amino acid and the CO group of another hold the strand together

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19
Q

What is a tertiary structure?

A

-the overall 3d shape of a protein molecule .It’s shape arises due to interactions including hydrogen bonding , disulfide bridges ,ionic bonds and hydrophobic interactions

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20
Q

What is a quaternary structure?

A

-protein structure where a protein consists of more than one polypeptide chain and the addition of a prosthetic group

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21
Q

How does hydrogen bonding occur between water molecules?

A

-water consists of two hydrogen atoms each covalently bonded to one oxygen atom
-because the oxygen atom has a greater number of positive protons in its nucleus this exerts a stronger attraction for the shared electron
-so the oxygen atom becomes slightly negative and the hydrogen atoms become slightly negative. This makes water polar
-This causes water to form hydrogen bonds between the slightly negatively charged oxygen of one atom and the positively charged hydrogen of another

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22
Q

Why is water a liquid at room temperature?

A

-as the water molecules constantly move around they continually make and break hydrogen bonds
-these hydrogen bonds make it more difficult for the molecules to escape and become a gas
-water also has a low viscosity so it can flow easily

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23
Q

What is the result of water being a liquid at room temperature?

A

-provides habitats for living things in rivers, lakes and seas
-forms a major component of tissues in living organisms
-provides a reaction medium for chemical reactions
-provides an effective transport medium .e.g. in blood and vascular tissue

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24
Q

Why is ice less dense than water?

A

-water becomes more dense as it gets colder until about 4 degrees Celsius . As it goes from 4 degrees Celsius to freezing point because of its polar nature, the water molecules align themselves in a structure which is less dense than liquid water

25
Q

What is the result of ice being less dense than water?

A

-aquatic organisms have a stable environment in which to live through the winter
-ponds and other bodies of water are insulated against extreme cold. The layer of ice reduces the rate of heat loss from the rest of the pond

26
Q

Why is water a good solvent?

A

-because water is polar the positive and negative parts of the water molecule are attracted to the positive and negative parts of the solute.
-the water molecules cluster around these charged parts of the solute molecules or ions and will help to separate them and keep them apart
-at this point they dissolve and a solution is formed

27
Q

Because water is a good solvent:

A

-molecules and ions can move around and react together in water .e.g.in the cytoplasm which is mainly water
-molecules and ions can be transported around living things whilst dissolved in water

28
Q

Why does water have high surface tension and cohesion?

A

Cohesion -the hydrogen bonding between the molecules pulls them together

Surface tension-the water molecules at the surface are all hydrogen bonded to the water molecules beneath them and hence more attracted to the water molecules beneath than to the air molecules above .Meaning the surface of the water contracts and gives the surface of the water an ability to resist force applied to it

29
Q

Because of surface tension and cohesion in water :

A

-columns of water in plant vascular tissue are pulled up the xylem tissue together from the roots
-insects like pond-skaters can walk on water

30
Q

Why does water have a high specific heat capacity( amount of energy needed for a change of temperature )?

A

-Water molecules are held together quite tightly by hydrogen bonds
-therefore you have to put in a lot of heat energy to increase their kinetic energy and temperature
-so water does not heat up or cool down easily

31
Q

What is the result of waters high specific heat capacity?

A

-provides a stable temperature for enzyme controlled reactions in prokaryotes and eukaryotes
-provides a stable environment for aquatic organisms

32
Q

Why does water have a high latent heat of vaporisation?

A

-because the molecules are held together by hydrogen bonds a relatively large amount of energy is needed for water molecules to evaporate

-therefore water can help cool living things and keep their temperature stable e.g sweating

33
Q

What do you use to test for starch?

A

-add iodine solution to sample
-if starch is present you will see a colour change of yellow-brown to blue-black

34
Q

How to test for reducing sugars?

A

-take a food sample dissolved in water and place it in a boiling tube
-add roughly equal volume of Benedict’s solution
-heat sample for 3minutes in a water bath at 80degrees Celsius
-brickred precipitate indicates presence of a reducing sugar

35
Q

How to test for non-reducing sugars?

A

-first test a sample for reducing sugars to check there are none there in the first place
-take a separate sample and boil it with hydrochloric acid to hydrolyse the sucrose into glucose and fructose
-cool the solution and use sodium hydrogencarbonate solution to neutralise it
-test for reducing sugars again
-a positive result indicates that non reducing sugar was present in the original sample

36
Q

What is the positive result for the lipid emulsion test ?

A

Cloudy white emulsion

37
Q

What is a positive result from the biuret test for proteins?

A

A lilac colour

38
Q

What is the R group in a protein?

A

Represents different possible combinations
The properties of the R group will influence the higher level structure of the protein and the properties of the amino acid

39
Q

Each amino acid has a different R group
Describe how these R groups can interact to determine the tertiary structure of a protein

A

R groups are variable.They determine the specific characteristics of each amino acid. They can interact to determine the proteins 3D structure by:
-forming ionic bonds with oppositely charged R groups
-forming S=S bonds (between 2 cysteines )
-any hydrophobic R groups will fold into the centre of the protein (away from water)
-or hydrophilic will fold onto outside towards water

40
Q

Suggest why the student was unsure if the positive result for lipid was correct for the milk sample

A

Milk is already cloudy

41
Q

What 2 monosaccharides make the polysaccharide maltose?

A

α-glucose + α-glucose —>maltose

42
Q

What 2 monosaccharides make sucrose?

A

α-glucose + fructose —> sucrose

43
Q

What two monosaccharides make lactose?

A

α-glucose + β-galactose —> lactose

44
Q

What monosaccharides make cellulose ?

A

β-glucose+ β-glucose —> cellulose

45
Q

What is the function of glycogen?

A

-the main energy storage molecule in animals

46
Q

What is the structure of glycogen?

A

-it’s formed from many molecules of alpha glucose joined together by 1,4 and 1,6 glycosidic bonds
-it has a large number of side branches meaning that glucose and therefore energy can be released quickly
-it is a relatively large but compact molecule, maximising storage space for energy

47
Q

What is the function of starch?

A

-stores energy in plants

48
Q

What is the structure of starch?

A

Starch is a mixture of two polysaccharides called amylose and amylopectin:
• Amylose — amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, as a result of that amylose is coiled and thus it is a very compact molecule meaning it can store a lot of energy
• Amylopectin- is branched and is made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds, due to the presence of many side branches it is rapidly digested by enzymes therefore energy is released quickly.

49
Q

What is cellulose and its structure?

A

Cellulose forms cells wells in plants and it’s composed of long, unbranched chains of beta glucose which are joined by glycosidic bonds. Microfibrils are strong threads which are made of long cellulose chains joined together by hydrogen bonds and they provide structural support in plants cells.

50
Q

What are fibrous proteins ?

A

-has a relatively long/linear chain, is insoluble in water and metabolically inactive, often having a structural role in an organism

51
Q

What are globular proteins?

A

-has molecules of a relatively spherical shape, which are soluble in water, and often have metabolic roles within the organism.

52
Q

What is a prosthetic group?

A
  • a non-protein component that forms a permanent part of a functioning protein molecule.
53
Q

What is the function of collagen?

A

-is a fibrous protein
-to provide mechanical strength
E.g. -cartilage and connective tissue are made from collagen
-tendons are made from collagen and connect muscle to bones, allowing them to pull on bones

54
Q

What is the function and some properties of keratin?

A

-is a fibrous protein
-rich in cysteine so lots of disulphide bridges form between its polypeptide chains and hydrogen bonding makes keratin very strong
-is found wherever a body part needs to be hard (finger nails, hair,horns, hoofs)
-provides mechanical protection and is an impermeable barrier to infection, also it is waterproof so prevents entry of water-borne pollutants

55
Q

What are the functions and properties of elastin?

A

-it is a fibrous protein
-cross-linking and coiling makes the structure of elastin strong and extendible
-found in living things that need to stretch or adapt their shape as part of life’s processes
E.g. skin , lungs,blood vessels

56
Q

What is a conjugated protein?

A

A globular protein with a prosthetic group

57
Q

What is an example of a conjugated protein?

A

Heamoglobin-has a haem group as a prosthetic group

58
Q

What is AB initio protein modelling?

A

-a model is built based on the physical and electrical properties of the atoms in each amino acid in the sequence
-with this technique there can be multiple solutions to the same amino acid and other methods sometimes need to be used to reduce the number of solutions

59
Q

What is comparative protein modelling ?

A

-one approach is protein threading which scans the amino acid sequence against a database of solved structures and produces a set of possible models that would match the sequence.

Biology (10 decks)

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