1
Q
Describe a condensation reaction
A
The formation of a polymer through the covalent bonding of two monomers. A water molecule is released in the process.
2
Q
Give an example of a condensation reaction
A
The formation of a disaccharide (maltose) through the bonding of two monosaccharides (alpha glucose). Water is released and the new bond is called a glycosidic bond.
3
Q
Describe a hydrolysis reaction
A
The formation of two monomers through the breaking down of a polymer. Water is added/used
4
Q
Give examples of monomers (3)
A
Monosaccharides (in carbohydrates); amino acids and nucleotides
5
Q
Describe the formation of maltose
A
maltose is a disaccharide formed by condensation of two
alpha glucose molecules
6
Q
Describe the formation of sucrose
A
sucrose is a disaccharide formed by condensation of an alpha glucose molecule and a fructose molecule
7
Q
Describe the formation of lactose
A
lactose is a disaccharide formed by condensation of an alpha glucose molecule and a galactose molecule.
8
Q
What is the difference in structure of alpha and beta glucose?
A
Alpha: the OH group is BELOW
Beta: the OH group is ABOVE
(on the right side of the molecule)
9
Q
How are polysaccharides formed?
Give 2 examples
A
Polysaccharides are formed by the condensation of many glucose units.
• Glycogen and starch are formed by the condensation of
α-glucose.
• Cellulose is formed by the condensation of β-glucose.
10
Q
What is the basic structure of Glycogen?
A
- Chain of alpha glucose monosaccharides joined together
by glycosidic bonds formed from condensation reactions
(shorter chains than starch & more branched) - Branched
11
Q
What is the function of Glycogen?
A
- It serves as a form of energy storage in animals and
bacteria. - It is stored as small granules mainly in the muscles and
liver - It acts as a secondary long-term energy store
- Glycosidic bonds between glucose molecules are
hydrolised to release glucose molecules for respiration
12
Q
Give 3 ways that glycogens structure important in its function.
A
- The highly branched to allow for more sites of enzyme activity = glucose can be released quicker (more branched than starch so quicker release of glucose)
- Insoluble = does not draw water into the cells via osmosis
- It is compact = a lot can be stored in a small space
13
Q
What is the basic structure of Starch?
A
- Long chain of alpha glucose monosaccharides joined together by glycosidic bonds formed from condensation
reactions - Found in plants in the form of small grains
- Two forms: Unbranched (amylose) & branched (amylopectin)
- The unbranched chain is wound into a tight coil (helix) –> very compact
- The branched chain –> quick release of glucose
14
Q
What is the function of Starch?
A
- Energy storage (long term!)
- Plants store starch for times of the year when there’s less
light so the plant still has glucose when photosynthesis is
not possible - Starch in seeds so the plants have energy to grow (before
they can photosynthesise)
15
Q
Why is Starch’s structure important in its function?
A
- It’s insoluble and therefore does not affect water
potential, so water is not drawn into cells via osmosis - It’s large & insoluble so it doesn’t diffuse out of cells
- It’s compact so a lot can be stored in a small space
- When hydrolysed it forms alpha glucose, which is easily
transported and used in respiration - The branched form has many ends which means there
are more sites for enzymes, so glucose monomers are
released rapidly
16
Q
What is the structure of Cellulose?
A
- Made from beta glucose chains
- Straight
- Unbranched
- These chains run parallel to each other allowing
Hydrogen bonds to form cross-linkages between adjacent chains. - There are so many H bonds, this contributes to the
overall strengthening of cellulose - The cellulose molecules are grouped together to form
microfibrils which are then arranged in parallel groups
called fibers
17
Q
What is the function of Cellulose?
A
- Major component in cell walls, e.g it prevents the cell
from bursting when water enters via osmosis. It does this
by exerting an inward pressure that stops any further
influx of water. As a result, the living cells are turgid and
push against each other - making non-woody parts of the
plant semi-rigid. - This is important in maintaining leaves and stems turgid
state so they have the maximum surface area for
photosynthesis
18
Q
Why is Celluloses structure important in its function?
A
- The beta glucose that cellulose is made from means that
it forms straight unbranched chains; the chains run
parallel and the h bonds formed make it very strong - The molecules are grouped to form microfibrils which in
turn are grouped to form fibres all of which provide even
more strength
19
Q
What is the function of carbohydrates?
A
- Commonly used by cells as respiratory substrates.
- They also form structural components in plasma
membranes and cell walls.
20
Q
What do lipids do?
A
Lipids have many uses, including the bilayer of plasma
membranes, certain hormones and as
respiratory substrates.
21
Q
What do proteins do?
A
- Proteins form many cell structures.
- They are also important as enzymes, chemical
messengers and components of the blood.
22
Q
What do nucleic acids do?
A
- Nucleic acids carry the genetic code for the production of
proteins. - The genetic code is common to viruses and to all living -
organisms, providing evidence for evolution.
23
Q
Describe the process of the Benedict’s test
A
- Add (2cm3) of the sample to a test tube.
- Add an equal volume of Benedict’s reagent.
- Heat the mixture in a gently boiling water bath for 5 minutes.
- If a reducing sugar is present the solution will turn orange- brown.
- The benedict’s test tests for reducing sugars. If present an insoluble red precipitate of Copper (1) Oxide will form.
24
Q
Describe the test for non-reducing sugars? (e.g sucrose)
4 steps
A
- If the Benedict’s test for reducing sugars is negative, there could still be a non-reducing sugar present
1. Get a new sample, add dilute HCL and heat in a boiling water bath (this will break them down into monosaccharides)
2. Neutralise it with a sodium hydrocarbonate (Benedict’s can’t work in acidic conditions)
3. Then, carry out a normal Benedict’s test for a reducing sugar
4. If the test is positive, a coloured precipitate will form. If the test is negative (no colour change) then no sugar at all is present
25
What are 3 features of lipids
- Composed of Carbon, Hydrogen and Oxygen
- They have a lower proportion of Oxygen to Carbon and
Hydrogen than carbohydrates.
- They are insoluble in water
26
What is the function of lipids? (4)
1. energy storage
2. useful for waterproofing
3. insulation
4. physical protection
27
What does saturated mean?
No double bonds
28
What does monosaturated mean?
One double bond
29
What does polyunsaturated mean?
Multiple double bonds
30
Fats are ____ at 10-20oc
Fats are SOLID at 10-20oc
31
Oils are ____ at 10- 20oc
Oils are LIQUID at 10-20oc
32
Give 4 features of triglycerides
- High ratio of energy storing carbon and hydrogen bonds
so when the bonds are broken a lot of energy is released
- Have a low mass to energy ratio
- Large insoluble molecules
- High ratio of Hydrogen to Oxygen, release water when oxidised
33
Describe phospholipids
They're similar to triglycerides except:
- One of the tree fatty acid tails is replaced with a phosphate molecule in the head
- These phosphate molecules are very useful because other molecules can attach to them
34
Describe the test for lipids
The emulsion test:
1. take a completely dry and grease free test tube
2. Add 5cm³ of ethanol to 2cm³ of the sample
3. Shake to dissolve all lipids
4. Add 5cm³ of water & shake
5. A cloudy- white colour indicates the presence of a lipid
6. As control, repeat the procedures using water instead of the sample (solution should remain clear)
35
What are the two types of lipids?
Phospholipids and Triglycerides
36
How is an ester bond formed?
A condensation reaction between glycerol and a fatty acid (RCOOH) forms an ester bond.
37
How are Triglycerides formed?
Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid.
38
Describe the test for starch.
The iodine test:
1. place 2cm3 of the sample into a test tube
2. add 2 drops of iodine solution and shake
3. If starch is present then the solution will turn from yellow/orange to blue/ black.
39
What do starch, glycogen, cellulose and triglycerides all have in common? (1)
They are all insoluble, this means that they don't draw water into cells and cause them to burst.
40
Phospholipids have fatty acid tails that are _____
| and phosphate molecules (in the head) that are _____
Phospholipids have fatty acid tails that are HYDROPHOBIC
| and phosphate molecules (in the head) that are HYDROPHILIC
41
What does hydrophobic mean? Give an example
- The molecule is repelled by water (they will 'hide' from
water) .
- fatty acid tails in phospholipids
42
What does hydrophilic mean? Give an example
- The molecule is attracted to water
| - phosphate heads
43
List 3 differences between a triglyceride molecule and a phospholipid molecule
1. Triglyceride molecules have 3 fatty acid tails whereas in phospholipid molecules one of the tails has been replaced by a phosphate molecule (which is in the head).
2. Triglyceride molecules have NO phosphate group whereas Phospholipids contain ONE phosphate group.
3. Triglyceride molecules are NON - POLAR whereas phospholipid molecules are POLAR, they have hydrophobic tails and a hydrophilic head.
44
What are the components of proteins?
Amino acids
45
What is the formula for the amino group?
(-NH2)
46
What is the formula for the carboxyl group?
(-COOH)
47
Describe the components of an Amino acid.
- At the center is the alpha carbon, everything branches off of this
- One side is a solitary hydrogen
- One branch is the amino group
- The opposite branch is the carboxyl group
- The fourth group is the R group (variable group)
48
How many amino acids are common in all organisms? and how do they differ?
- There are twenty amino acids that
are common in all organisms
- They differ only in their side group (R group)
49
What bond does the condensation reaction between two amino acids form?
It forms a peptide bond
50
How are dipeptides formed?
Dipeptides are formed by the condensation of two amino acids.
51
How are polypeptides formed?
Polypeptides are formed by the condensation of many amino acids.
52
A functional protein may contain one or more polypeptides. TRUE/ FALSE
A functional protein may contain one or more polypeptides. TRUE
53
Describe the polymerisation of amino acids
Polymerisation:
Through a series of condensation reactions, many amino acid monomers can be joined together. The resulting chain of many hundreds of amino acids is called a polypeptide.
54
What forms the primary structure of a protein?
The sequence of amino acids (joined by peptide bonds) in a polypeptide chain forms the primary structure
55
What does the primary structure (of a protein) determine?
The primary structure determines the ultimate shape and functionality of the protein
56
Describe the secondary structure (of a protein)
- It occurs as Hydrogen bonds (weak) between the
+Hydrogen of the -NH (amino) group and the -Oxygen of
the -C=O (carboxyl group)
- These Hydrogen bonds are strong enough to twist the
polypeptide chain into a 3D sheet
- E.g the alpha helix or beta pleated sheet
57
Describe the tertiary structure (of a protein)
- Further twisting of the secondary structure
- Can be complex and is specific to the protein
- Plays a significant role in determining the behaviour of
the protein
58
Describe disulfide bonds, in what structure?
Fairly strong, not easily broken
| In the tertiary structure
59
Describe Ionic bonds, in what structure?
- Form between any carboxyl and amino groups not involved in peptide bonds
- Weaker than disulfide bonds
- Easily broken by changes in pH
In the tertiary structure
60
Describe Hydrogen bonds
Numerous but easily broken
61
Which structure do small proteins stop at?
Tertiary
62
Describe the quaternary structure (of a protein)
- Multiple polypeptides bond together
| - There may also be non-protein (prosthetic) groups associated with the molecules: e.g the iron-containing haem group
63
Describe the test for proteins.
The biuret's test:
1. Place the sample in a test tube and add an equal volume of sodium hydroxide solution at room temp
2. Add a few drops of very dilute (0.05%) copper (II) sulfate solution and mix gently
3. If the solution turns purple peptide bonds are present (= a protein). If no protein is present the solution will remain blue
64
What does an enzyme do?
Enzymes lower the activation energy needed for molecules to collide and change their atom arrangement, without being used up
65
What are the conditions required for normal chemical reactions?
- The free energy of the products must be less than that of the substrates
- The reactants must collide with enough energy to change the arrangement of their atoms to form the products
- The activation energy
66
What structure do the properties of an enzyme relate to?
The properties of an enzyme relate to the tertiary structure of its active site and its ability to combine with complementary substrate(s).
67
Describe the induced fit model of an enzyme.
- The active site forms as the enzyme and substrate interact
- The enzyme is flexible and can mold itself around the
substrate, like a glove & a hand
- The enzyme has a certain general shape (like a glove)
but this alters in the presence of the substrate
- The enzyme puts a strain on the substrate molecule - this
distorts a particular bond or bonds in the substrate and
consequently lowers the activation energy needed to
break the bond(s)
68
For an enzyme to work, it must:
- Come into physical contact with the substrate
| - Have an active site that fits the substrate
69
What are the two main categories of proteins?
Fibrous & Globular
70
What functions do fibrous proteins have? and give an example.
Fibrous proteins have structural functions. E.g Collagen, it is found in tendons which join muscles to bones
71
Describe fibrous proteins
- Long parallel chains
| - Chains are linked by cross- bridges and so form very stable molecules
72
Describe collagens protein structures (5)
1. Primary structure - unbranched polypeptide chain
2. Secondary structure - very tightly coiled
3. High concentration of amino acid - glycine helps close
packing
4. The tertiary structure is twisted into a second helix
5. Its quaternary structure is made up of three polypeptide
chains wound together (in the same way as in rope)
73
What happens when an enzyme is breaking down a substrate?
During breaking a subsrate the enzyme puts strain on the substrate, reducing the energy needed to break the molecule
74
What happens when an enzyme is forming a substrate?
The enzyme holds the substrate molecules close enough to overcome repulsion between the molecules
75
What does an increasing temp mean for an enzyme assisted reaction?
- Higher temp = the substrate molecules have more kinetic energy = more successful substrate-active site collisions
- However if the temp gets too high the vibrations break the bonds in the enzyme, meaning its active site shape will change so that a specific substrate will no longer fit, this is called denaturing
76
What is the optimum pH for MOST body enzymes? give an exception
7pH
| E.g Pepsin- its optimum pH is 2
77
What is the optimum temp for most body enzymes?
37c
78
What happens to the enzyme if the pH drops below or exceeds the optimal pH?
The H+ or OH- ions interfere with the ionic and hydrogen bonds in an enzyme's tertiary structure, which changes its shape. It is denatured.
79
Describe Competitive enzyme inhibition
- When a molecule other than the enzymes specific substrate is complementary to the active site of the enzyme
- If the competitively inhibiting molecule forms a complex with the enzymes active site, then the active site is occupied and the usual substrate cannot form the intended enzyme-substrate complex
80
Describe Non- Competitive enzyme inhibition
- Some inhibiting molecules do not occupy the active site
- They attach to the enzyme elsewhere and change its shape, distorting the shape of the active site and preventing an enzyme substrate complex
81
What does increasing the conc. of substrates or enzymes do to the rate of reaction? What happens to the conc. of enzymes?
Increasing the conc. of substrates or enzymes increases the rate of reaction.
- However, because enzymes are not used up their conc. will not change throughout the reaction.
- Therefore the decrease in rate of reaction in enzyme assisted reactions is due to the substrate being used up.
82
Name 3 monosaccharides
- Glucose
- Galactose
- Fructose
83
Name 3 disaccharides
- Maltose
- Sucrose
- Lactose
Biology A1 & A2
flashcards
Decks in class (19)
# Cards
-
Statistics26
-
1A: Biological molecules83
-
1B: More Biological molecules60
-
2A: Cell structure & division65
-
2B: Transport across cell membranes25
-
2C: Cell recognition & immunity70
-
3A: Exchange154
-
3B: Mass transport151
-
4A: Genetic information43
-
4B: Diversity, Classification & Variation101
-
5A & B: Energy transfers165
-
6A: Stimuli and response73
-
6B: Nervous coordination87
-
6C: Homeostasis82
-
7A: Inheritance45
-
7B: Populations & evolution38
-
7C: Populations in Ecosystems50
-
8A: Mutations and gene expression47
-
8B: Genome projects & Gene technologies0
