Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > 2 Biological molecules > Flashcards

2 Biological molecules Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Tests for reducing and non-reducing sugars

A
  • Heat a sample with Benedicts reagent in a water bath (if the solution remains blue there is no reducing sugar present)
  • Heat a fresh sample in a water bath for 5 minutes with dilute HCI acid to hydrolyse the non-reducing sugar, then neutralise with sodium hydrogencarbonate and allow to cool
  • Re-test the resulting solution by heating in a water bath with Benedicts reagent which will turn yellow/brown/red due to the reducing sugars made from the hydrolysis of the non-reducing sugar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Semi-quantative Benedicts test on a reducing sugar (can be used to estimate the approximate concentration of reducing sugars in a sample)

A
  • A range of colour standards is produced by preparing a series of glucose solutions of a known concentration
  • An excess of Benedicts reagent is added to the test tubes containing an equal volume of each
  • They are then heated for the same length of time before being cooled to room temperature
  • An equal volume of an unknown sample is then treated in the same way and the colour is compared with that of the colour standards
  • Use a piece of white card placed behind the tubes to make the colours easier to see
  • The test isn’t fully quantitative as you cannot be sure of the actual concentration of the unknown sample
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Further extension (carry out the reducing sugar test and then filter the suspensions)

A
  • The precipitate is then dried and weighed (the greater the mass of the precipitate, the more reducing sugar is present)
  • Alternatively, the filtrate could be placed in a colorimeter (the more intense the blue colour, the less concentrated the reducing sugar)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Monomer

A

a small molecule that can chemically bond with other monomers to form a larger molecule known as a polymer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Polymer

A
  • a large molecule composed of similar repeating subunits called monomers.
  • A polymer is a macromolecule, but not all macromolecules are polymers (lipids arent polymers as they aren’t made up of repeating subunits).
  • Formed by polymerization.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Polymerization

A
  • monomers are chemically bonded together to form a large molecule, known as a polymer.
  • This process occurs through repeated chemical reactions, linking the monomers together in a chain-like structure or in a network.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Macromolecule

A
  • a large molecule, typically composed of thousands or even millions of atoms, that forms when smaller molecules (monomers) chemically bond together.
  • Macromolecules are often polymers, meaning they consist of repeating units of monomers linked together through covalent bonds.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Monosaccharide

A

monomers of disaccharides and polysaccharides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Disaccharide

A

composed of 2 monosaccharides joined by a single glycosidic bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Polysaccharide

A
  • composed of more than 2 monosaccharides, with glycosidic bonds connecting adjacent monosaccharides.
  • They are macromolecules, with some composed of many thousands of monosaccharides.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Glycosidic bond

A
  • the bond formed between the anomeric carbon atom of one sugar molecule and a hydroxyl group of another molecule (often another sugar).
  • This bond forms through a condensation reaction, where a water molecule is eliminated as the bond forms between the two molecules.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Peptide bond

A

bond between amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Covalent bonding

A

atoms share a pair of electrons in their outer shells and as a result the outer shell of both atoms is filled and a more stable compound called a molecule is formed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Ionic bonding

A
  • ions with opposite charges attract one another and this is due to an electrostatic attraction.
  • Ionic bonds are weaker than covalent bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Hydrogen bonding

A
  • occurs when a weak attractive force occurs between an electronegative atom of one molecule and a hydrogen of another molecule that is bonded to an electronegative atom.
  • The electronegative ion has a tendency to attract electrons therefore giving the hydrogen a slightly positive charge.
  • Hydrogen bonding causes water molecules to stick together (cohesion)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Polar

A
  • in a covalent bond when one atom slightly attracts the shared electrons towards its nucleus so that even though the molecule has no overall charge, one atom has a slightly negative charge (delta negative) and the other a slightly positive charge (delta positive).
  • Water is an example.
  • They are hydrophilic.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Non-polar

A

where there is an equal sharing of electrons in a covalent bond and is hydrophobic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Condensation reaction

A

reaction that produces water by removing it (formation of a polypeptide from amino acids and starch from glucose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Hydrolysis reaction

A

reaction that takes in water by adding it to break down a molecule into its constituent parts (polypeptides can be hydrolysed into amino acids and starch into glucose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Anabolism

A

an energy-requiring process in which small molecules are combined to make larger ones.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Catabolism

A

chemical reactions involving the release of energy in the breakdown of larger molecules into smaller ones.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the role of covalent bonds in joining smaller molecules together to form polymers?

A
  • Glycosidic bonds that form in carbohydrates
  • Ester bonds in lipids
  • Peptide and disulfide bonds in proteins
  • Phosphodiester bonds in nucleic acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are reducing sugars and what aren’t ?

A

Reducing sugars:
- Glucose
- Fructose
- Maltose

Non-reducing
- Sucrose
- Lactose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How are glycosidic bonds formed by condensation in disaccharides?

A
  • When 2 monosaccharides join, a water molecule is removed (condensation)
  • The disaccharide maltose is produced in a condensation reaction between 2 a-glucose molecules and has reactive groups for the reduction reaction with Benedicts solution and so is, therefore, a reducing sugar
  • In the formation of sucrose, the glycosidic bond is between carbon atom 1 of a-glucose and carbon atom 2 of B-fructose (known as 1,2 glycosidic bond)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How are glycosidic bonds formed by condensation in polysaccharides?

A
  • The monosaccharides are joined by glycosidic bonds that are formed by condensation reactions
  • The resulting chain may vary in length and be branched and folded in various ways
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How is a glycosidic bond broken by hydrolysis in disaccharides?

A
  • When water is added to a disaccharide under suitable conditions, it breaks the glycosidic bond into its constituent monosaccharides (hydrolysis)
  • Sucrose cannot react with Benedicts, so it is a non-reducing sugar. The hydrolysis of sucrose occurs rapidly in the presence of sucrase and without it the breakdown would be very slow.
  • During hydrolysis by boiling with acid, the glycosidic bond is broken to release fructose and glucose, which are both reducing sugars
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How is a glycosidic bond broken by hydrolysis in polysaccharides?

A

When they are hydrolysed they break down into monosaccharides or disaccharides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Starch

A
  • A polysaccharide found in many parts of a plant in the form of small granules or grains
  • Major energy source in most diets
  • As it is a polysaccharide it is a macromolecule which makes it insoluble (suits them for storage)
  • As it is a polysaccharide it is formed by combining many monosaccharide units which are joined by glycosidic bonds that are formed by condensation reactions
  • When they are hydrolysed they break down into monosaccharides or disaccharides
  • It is a mixture of 2 polymers of a-glucose: amylose and amylopectin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What makes starch suited for its main role of energy storage?

A
  • It is insoluble and therefore does not have any osmotic effects within cells and does not diffuse out of cells
  • Starch molecules can be compactly stored within plant cells in structures like plastids (e.g., chloroplasts) and this compact storage allows plants to store a large amount of energy in a relatively small space
  • it can be broken down into glucose molecules relatively easily when needed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Amylose

A
  • Composed of 200-5000 glucose units which are joined in a straight chain by a-1, 4 glycosidic bonds
  • This chain is then wound into a tight helix which makes it more compact and therefore it can be stored more efficiently as it takes up less space
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Amylopectin

A
  • Composed of 5000-100 000 a-glucose units which are joined to each other by a-1,4 and a-1,6 glycosidic bonds
  • Branched and so has many free ends that amylase (the enzyme that catalyses the hydrolysis of starch) can work on simultaneously (meaning that glucose monomers are rapidly released)
  • When hydrolyzed it forms glucose which is easily transported and readily used in respiration to provide ATP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Glycogen

A
  • Similar to amylopectin in structure, but has shorter chains and is more highly branched
  • Major carbohydrate storage product of animals and it is stored as small granules (mainly in muscle and liver cells)
  • Has a-1,4 and a-1,6- glycosidic bonds between monomers
  • Its structure suits it for storage for the same reasons as starch, but it is more highly branched and so has more ends that can be simultaneously acted on by enzymes and is, therefore, more rapidly broken down to release energy
33
Q

How does cellulose differ from starch and glycogen

A

Made from monomers of b-glucose rather than a-glucose

34
Q

Cellulose

A
  • Makes up 20-50% of plant cell walls
  • Rather than forming a coiled chain like starch, cellulose has straight, unbranched chains and these run parallel to one another, allowing hydrogen bonds to form cross-linkages between adjacent chains
  • While each individual hydrogen bond adds very little strength to the molecule, the overall number of them makes a considerable contribution to strengthening cellulose
  • The cellulose molecules are grouped to form microfibrils arranged in parallel groups called fibers.
  • Within the microfibril, the individual linear cellulose molecules start and end in different places so that they overlap, and this contributes to the strength of the microfibril as well as the cellulose fibrils laid down at different angles.
  • With many –OH groups, cellulose can form hydrogen bonds with water and so the molecule is hydrophilic, however, due to the large size of the molecules cellulose is insoluble
35
Q

Functions of cellulose

A
  • The cellulose cell wall is freely permeable, allowing materials to access the cell surface membrane and allowing the movement of water along the cell walls of adjacent cells
  • Performs a mainly structural role by providing rigidity to the plant cell wall, which prevents the cell from bursting as water enters via osmosis
  • The cellulose cell wall exerts an inward pressure that stops further influx of water and as a result living plant cells are turgid and push against one another, making herbaceous parts of the plant semi-rigid (important in maintaining stems and leaves in a turgid state so that they can provide the maximum surface area for photosynthesis)
36
Q

Triglycerides (fats and oils)

A
  • Fats are solid at room temperature (10-20 degrees Celsius), whereas oils are liquid
  • They have 3 fatty acids combined with a glycerol
  • Each fatty acid forms an ester bond with glycerol in a condensation reaction and in a hydrolysis reaction a triglyceride produces glycerol and 3 fatty acids
37
Q

The structure of triglycerides related to their functions

A
  • High ratio of energy-storing carbon-hydrogen bonds to carbon atoms- excellent source of energy and they therefore supply many hydrogens for the reduction of NAD (molecule involved in the production of ATP)
  • Low mass to volume ratio- makes them good storage molecules, because much energy can be stored in a small volume (beneficial for animals)
  • Being large, non-polar molecules- they are insoluble in water and as a result their storage does not affect the water potential of cells
  • High ratio of hydrogen to oxygen atoms- triglycerides therefore release water when oxidized and therefore provide an important source of water (important for organisms in dry deserts)
38
Q

Fatty acid

A
  • All fatty acids have a carboxyl group (-COOH) with a hydrocarbon chain attached (this chain may have no double bonds=saturated because all the carbon atoms are linked to the maximum possible number of hydrogen atoms)
  • 4 types: saturated, unsaturated, mono-unsaturated and polyunsaturated
39
Q

Saturated

A

fatty acid chains that have no double bonds, because all the carbon atoms are linked to the maximum possible number of hydrogen atoms

40
Q

Unsaturated

A

fatty acid chain that contains one or more double or triple bonds between carbon atoms and result in fewer hydrogen atoms attached to the carbon atoms

41
Q

Mono-unsaturated

A

if there is a single double bond in the chain

42
Q

Polyunsaturated

A
  • if more than one double bond is present in the chain
  • The kinked shape of polyunsaturated fatty acids means that molecules don’t fit as closely together therefore the intermolecular interactions are weaker and unsaturated fatty acids therefore have a lower melting point
43
Q

Structure of phospholipids

A
  • Similar to lipids except they that one of the fatty acid molecules is replaced by a phosphate molecule
  • Fatty acid molecules are hydrophobic, while phosphate molecules are hydrophilic and are attached to a glycerol molecule (which is also hydrophilic)
44
Q

Arrangement and function of phospholipids

A
  • The inside and outside of the cell are watery and the phospholipids in the cell surface membrane form a double layer
  • The hydrophilic heads pointing into either the watery environment outside the membrane or the watery medium inside the cell
  • The hydrophobic tails point into the middle of the membrane to form a hydrophobic core
  • This bilayer arrangement makes cell surface membranes fluid and easily crossed by lipid-soluble substances
45
Q

How do the structures of fatty acids and phospholipids differ?

A
  • in phospholipids, one of the fatty acid molecules is replaced by a phosphate molecule
  • fatty acid molecules are hydrophobic, while phosphate molecules are hydrophilic and are attached to a glycerol molecule (which is also hydrophilic)
46
Q

Structure of an amino acid

A
  • Amine group (-NH2)
  • Carboxyl group (-COOH)
  • Hydrogen atom (-H)
  • R-group
47
Q

Why are amino acids amphoteric?

A

the carboxyl group is acidic and the amino group is basic therefore amino acids are amphoteric (both an acid and a base) and can act as buffer solutions when it comes to pH

48
Q

Formation of a peptide bond (via condensation by removal of water)

A

Amino acid monomers combine to form dipeptides by the removal of a water

  • Water is made by combining an –OH from the carboxyl group of one amino acid with an –H from the amino group of another amino acid
  • The 2 amino acids then become linked by a covalent bond between the C atom of one amino acid and an N atom of the other
49
Q

Breakage of a peptide bond (via hydrolysis by addition of water)

A

The peptide bond of a dipeptide can be broken by hydrolysis (addition of water)

50
Q

Primary structure of a protein

A
  • The sequence of amino acids found in its polypeptide chains
  • This sequence determines its properties and shape
51
Q

Secondary structure of a protein

A
  • The shape that the polypeptide chain forms as a result of bonding between the hydrogens of the amino group and the oxygens of the carboxyl group
  • This may be an alpha-helix or beta-pleated sheet
52
Q

Tertiary structure of a protein

A
  • Due to the coiling and folding of the polypeptide chain into a specific 3D structure
  • All four types of interactions (disulfide bridges, ionic bonds, hydrogen bonds, and hydrophobic interactions) between the R-groups contribute to the maintenance of the tertiary structure
53
Q

Quaternary structure of a protein

A
  • Arises from the combination of a number of different polypeptide chains and associated non-protein (prosthetic) groups into a large, complex protein molecule.
54
Q

Effects of extreme temperature and pH on a protein

A
  • can cause the tertiary or quaternary structure of a protein to be disrupted (denaturation) and this is because hydrogen or ionic bonds between R-groups of amino acids may be broken.
  • Depending on the extent of the disruption, a protein may be partially denatured and may function less well or be fully denatured and lose its function completely.
55
Q

The types of interactions that hold protein molecules in shape:

A
  • hydrophobic interactions
  • hydrogen bonding
  • ionic bonding
  • disulfide bridges
56
Q

What bonds are individually the strongest?

A
  • peptide
  • disulfide
57
Q

Hydrophobic interactions

A
  • formed between non-polar R-groups (repel water) such as those on tyrosine and valine
  • these interactions may twist/fold the polypeptide chain so that they take up a position further away from the watery medium
58
Q

Hydrogen bonding

A
  • formed between electronegative oxygen atoms on CO groups and electropositive H atoms on NH groups.
  • Their individual bonds are weak, but together are an important factor in maintaining the tertiary structure
59
Q

Ionic bonding

A
  • between NH3 + and COO- ions on amino acids such asparagine and acid ones such as aspartic acid
  • form electrostatic bonds due to their mutual attraction.
  • Can be broken due to pH changes.
60
Q

Disulfide bridges

A
  • found between sulfur atoms in the molecules of the amino acid cysteine
  • are covalent bonds which form strong links which make the tertiary structure of a protein very stable.
61
Q

Comparison of fibrous and globular proteins

A

in notes

62
Q

Structural features of haemoglobin related to its ability to carry oxygen

A
  • 4 polypeptide chains, 2 identical a-globin polypeptides of 141 amino acids each and 2 identical B-globin polypeptides of 146 amino acids each.
  • Each polypeptide chain is folded into a compact shape and all 4 are linked together to form an almost spherical haemoglobin molecule
  • Hydrophobic interactions between amino acids with non-polar (hydrophobic) R-groups within the haemoglobin molecule to help maintain its precise shape (helps it to carry oxygen)
  • Amino acids with polar (hydrophilic) R-groups in the molecule tend to orientate themselves to point outwards which enables haemoglobin to be soluble and mix readily with a watery medium (cytoplasm of red blood cell)
  • Associated with each polypeptide is a haem group which contains a ferrous (Fe2+) ion which is a non-protein group (prosthetic group) and they form an integral part of the molecule
  • Each Fe2+ ion can combine with a single oxygen molecule making it 4 O2 molecules which can be carried by a single haemoglobin molecule
63
Q

Haemoglobin + oxygen=

A

oxyhaemoglobin (changes colour from purple to bright red)

64
Q

Globular proteins such as haemoglobin have …

A
  • a very specific shape and even a slight chain to it can result in the molecule being much less efficient.
  • A slight alteration in shape as a result of a mutation in one of the genes coding for the globin chains makes it far less able to transport oxygen (sickle-cell anemia)
65
Q

Fibrous protein collagen (arrangement of collagen molecules to form collagen fibres)

A
  • Found in tissues requiring physical strength (tendons, walls of blood vessels, bone and fibres that hold teeth in place)
  • Collagen is extremely strong and stable
  • It has a very high tensile strength and is able to withstand immense pulling forces without stretching
  • At the same time it is flexible, so that while the collagen in a tendon transmits the pull of a muscle to the bone without stretching it so that it can still bend around a joint as it flexes during movement
66
Q

Structural features that allow collagen to form collagen fibres

A
  • Primary structure is a repeat of the amino acid sequence glycine-proline-alanine which forms an unbranched polypeptide chains.
  • The collagen molecule is made up of 3 of these polypeptide chains wound in a triple helix that is held together by hydrogen bonds between the peptide bond NH of glycine and a peptide C=O (carbonyl) group of amino acids in the adjacent polypeptide
  • As every 3rd amino acid is the relatively small and compact glycine molecule, the triple helix produced is very tightly wound, while larger amino acids will produce a more loosely wound one and therefore a less strong triple helix
  • The triple-stranded molecules run parallel to others and form stronger units called fibrils which form collagen fibres
  • The collage molecules found in the collagen fibres/fibrils are held together by cross-linkages formed by covalent bonds between lysine amino acids of adjacent molecules which adds strength and stability to the structure
  • Where one collagen molecule ends and where the next begins are spread out throughout the structure (if they weren’t arranged like this they would be prone to breaking under tension)
67
Q

How is water formed?

A
  • Made up of 2 hydrogen atoms and 1 oxygen atom which forms a triangular shape
  • The molecule has no overall charge, however, the distribution of negatively charged electrons is uneven as the oxygens atoms pull them away from the hydrogen atoms, therefore the oxygen atom has a slightly negative charge (δ-), while the hydrogen atoms have a slightly positive one (δ+)
  • The molecule has both positive and negative poles and is therefore dipolar
68
Q

Hydrogen bonding

A

the attractive force between these opposite charges

69
Q

Cohesion

A

the tendency of water molecules to stick together due to hydrogen bonding

  • The positive pole of one water molecule is attracted to the negative pole of another water molecule
  • Although each hydrogen bond is weak, together they form forces that cause cohesion of the water molecules
70
Q

A water molecule: (drawing)

A

in notes

71
Q

Water molecules showing hydrogen bonding

A

in notes

72
Q

Roles that water plays in living organisms

A
  • Solvent action
  • High specific heat capacity
  • Latent heat of vaporization
73
Q

Solvent action

A
  • As water is a dipolar molecule, other polar molecules and ions readily dissolve in water
  • Water is used for transport (sugars in blood/phloem), removal of wastes (ammonia, urea), secretions (digestive juices, tears), and as an environment in which enzyme reactions can take place in
74
Q

Specific heat capacity

A

the amount of energy needed to heat a given mass of water

75
Q

Water has a high specific heat capacity, because:

A
  • Water molecules are cohesive and it takes more energy (heat) to separate them than would be needed if they did not bond to one another, therefore the boiling point of water is higher than expected
  • Without its hydrogen bonds water would be a gas (water vapor) at temperatures commonly found on earth
  • For the same reason it takes more energy to heat a given mass of water (high specific heat capacity)
  • Acts as a buffer against sudden temperature changes for organisms that live in water, because it helps to regulate temperature and avoid extremes and helps maintain the internal cellular environment remain constant
76
Q

Latent heat of vaporization

A

the amount of heat energy required to evaporate one gram of water

  • Due to hydrogen bonding between water molecules it requires a lot of energy to evaporate one gram of water(latent heat of vaporisation)
  • Evaporation of water is effective in cooling mammals as body heat is used to evaporate the water
  • Evaporation of water from surfaces of mesophyll cells within the leaves of plants cools it down when the external temperature is high
77
Q

Examples of the importance of water

A
  • Metabolism (water is used in hydrolysis, acts as a medium for reactions to take place in and raw material in photosynthesis)
  • Solvent (dipolar, therefore other polar molecules and ions readily dissolve in water)
  • Support (not easily compressed and therefore is used in the hydrostatic skeleton of earthworms, in the amniotic fluid to support fetus, and in creating turgor pressure of leaf cells for support)
  • Other (its evaporation to create a cooling effect and is involved in cell elongation and expansion in plants)
  • Environment for living organisms (acts as a buffer, larger bodies of water hardy ever freeze, transparent therefore plants can photosynthesis and it is a dense medium so provides support for organisms in water
78
Q

Lactose-free milk

A
  • Lactose is a non-reducing sugar
  • Lactase can be immobilised on sodium alginate beads when milk is poured over the beads and the lactase breaks the lactose down
  • The milk that is produced is lactose-free
79
Q

How to determine whether any lactose has been broken down in the lactose-free milk?

A
  • Test for a reducing sugar (as lactose is a disaccharide and would be broken down into two simple sugars: glucose and galactose which are reducing sugars)
  • Heat/boil with Benedicts solution and look for colour change to orange or (yellow/green/brick red)
  • As lactose is a non-reducing sugar and therefore needs to be hydrolysed before it will react with Benedicts

Biology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions