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A Level Biology > Unit 1 - Biological Molecules (proteins, enzymes, carbs and lipids)+ some cells > Flashcards

Unit 1 - Biological Molecules (proteins, enzymes, carbs and lipids)+ some cells Flashcards

1
Q

What are monomers?

A

Smaller units from which larger molecules are made

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2
Q

What are polymers?

A

Molecules made from a large number of monomers joined together.

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3
Q

What is a condensation reaction?

A

A reaction that joins two molecules together with the formation of a covalent bond and involving the elimination of a water molecule.

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4
Q

What is a hydrolysis reaction?

A

A reaction that breaks a chemical bond between two molecules and involves the use of a water molecule.

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5
Q

What are amino acids?

A

The monomer from which proteins are made

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6
Q

Describe the general structure of an amino acid.

A

NH2 represents the amine group

Has a central carbon

COOH represents the carboxyl group

R is the residual group which represents a carbon containing side chain.

And a Hydrogen

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7
Q

What are dipeptides

A

When two amino acids are joined together by a condensation reaction a peptide bond is formed and a water molecule is released. The two bonded amino acids is called a dipeptide

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8
Q

How do we test for proteins?

A

Using biuret’s reagent which is pale blue.

In a positive test a purple precipitate forms.

The more amino acids the stronger purple it will be

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9
Q

What are the four levels of protein structure?

A

Primary
Secondary
Tertiary
Quaternary

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10
Q

Describe primary protein structure?

A

Chain of amino acids joined together by peptide bonds to form a poly peptide.

The number and sequence of amino acids determines the tertiary structure and therefore effects the shape of the active site in enzymes.

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11
Q

Describe secondary protein structure?

A

Hydrogen bonds form between amino acids in the chain causing it to coil into an alpha helix or a beta pleated sheet.

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12
Q

Describe tertiary protein structure?

A

This the 3d shape of the polypeptide chain.

Creates a specific shape due to the order and sequence of amino acids in the chain as hydrogen bonds, ionic bonds and disulphide bridges form between R groups.

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13
Q

Describe quaternary protein structure?

A

If proteins have more than one polypeptide chain they are joined together to create a quaternary structure.

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14
Q

What causes the separation of components in chromatography?

A

Size
Charge

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15
Q

Rf =

A

distance molecule traveled / distance solvent traveled

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16
Q

Why draw base line in pencil?

A

Lead is not soluble

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17
Q

Why are the mixtures added repeatedly and dried with a hairdryer?

A

To get a high concentration of the mixture

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18
Q

Why must the solvent be below the baseline?

A

So the mixture doesn’t dissolve into the solvent

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19
Q

Why is the experiment stopped before the solvent reaches the edge of the paper?

A

So we can calculate an rf value

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20
Q

What does standard deviation tell us?

A

The spread of data around the mean

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21
Q

Why is standard deviation better than the range?

A

As the range is affected by anomalies while standard deviation is not

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22
Q

What does it mean if standard deviation bars overlap?

A

The difference in mean could be due to chance-

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23
Q

Define magnification?

A

How many times larger an object appears compared to its actual size

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24
Q

Define resolution?

A

The minimum distance two objects can be apart and still be seen as sperate objects

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25
What is an artefact?
Things observed down a microscope that are not part of the cell or specimen you are looking at
26
What is homogenisation?
Proccess of breaking open cells to release its organelles
27
What is ultracentrifugation?
Using centrifugal force to separate organelles
28
What are the two main processes of cell fractionation
Homogenisation Ultracentrifugation
29
Describe the steps of cell fractionation?
Chop the tissue in a cold **isotonic buffer** solution. Then **homogenise** Filter through a gauze to remove large cell debris. Then conduct **ultracentrifugation** using a **centrifuge** First spin at a low speed and the heaviest organelles form a **pellet** at the bottom. The **supernatant** is drained off and then centrifuged again at a higher speed. Process repeated until all organelles are separated.
30
Why is an isotonic solution used in cell fractionation?
To prevent damage to organelles as a result of osmotic processes. **Not damage to cells as they are already homogenised**
31
Why is a buffer solution used in cell fractionation?
Maintains optimum PH and prevents **enzymes** denaturing
32
Why is a cold solution used in cell fractionation?
Prevents **enzyme**activity which could damage the organelles
33
Dilution series formula?
Wanted conc x total volume / conc of stock solution = how much stock solution needed
34
How do enzymes speed up reactions?
They lower the activation energy
35
How does the tertiary structure of an enzyme affect a specific substrate?
The tertiary structure (3d shape) of the enzyme gives the active site a specific shape. It forms a small depression within the molecule that is complimentary to the substrate.
36
What is the lock and key theory?
The first theory: The substrate can only fit into its complimentary active site and when they do a enzyme substrate complex is formed.
37
What is the induced fit hypothesis?
Later scientists realised that enzyme substrate complexes can be formed even when the substrate is not exactly the same shape. When the substrate binds to the active site the active site slightly changes to complete the fit and form the enzyme substrate complex.
38
What factors affect enzyme activity?
Temperature pH Substrate concentration Enzyme concentration
39
How does Temp affect enzyme activity?
RoR increases with temperature as KE increases. More successful collisions so more ESCs After the optimum temperature the bonds that hold the enzymes tertiary structure in place start to break (hydrogen and ionic). When the tertiary structure changes so does the active site so the enzyme denatures.
40
How does pH affect enzyme activity?
All enzymes work best at their optimum pH. Above an below this the OH and H ions disrupt the hydrogen and ionic bonds that hold the tertiary structure together. Therefore the active site denatures and less ESCs can form
41
How does enzyme concentration affect enzyme activity?
More enzymes means more likely a substrate will collide successfully and form a ESC. However if the substrate is limited then there comes a point where the is enough enzyme molecules to deal with the substrate so adding more has no affect.
42
How does substrate concentration affect enzyme activity?
Higher the substrate concentration means the faster the rate of reaction as more substrate means more frequent and successful collisions and therefore more active sites are occupied. This true up to the saturation point where after all the active sites are full so higher substrate concentration doesn't affect the rate of reaction.
43
What is an inhibitor
A molecule that can reduce the rate of an enzyme controlled reaction
44
What is a competitive inhibitor?
Have a similar shape to the substrate molecule so they compete to bind with the active sites. No reaction occurs but they prevent substrates from binding as the active sites are occupied. This is a reversible inhibitor
45
What is a non competitive inhibitor?
Binds to the enzyme away from the active site. Upon binding it changes the shape of the active site which prevents ESCs forming. Increasing the substrate concentration has no effect as they are not competing for active sites
46
Draw an alpha glucose?
47
Draw a Beta Glucose
48
Properties of monosacharrides?
Soluble Sweet tasting
49
General formula of monosacharrides?
n(CH2O)
50
Which sugars are reducing sugars
All monosaccharides Some disaccharides
51
What is a reducing sugar?
A sugar that can donate electrons (to reduce) another chemical
52
What sugars are non-reducing sugars?
All polysaccharides Some disaccharides
53
Test for reducing sugars:
Add food sample in liquid form to a test tube Add equal of benedict's reagent Heat in water bath for 5 mins reducing sugar = blue -> red
54
Which monomers form maltose?
glucose + glucose
55
Which monomers form sucrose
glucose + fructose
56
Which monomers form lactose?
glucose + galactose
57
Maltose, sucrose and lactose are all forms of ...
disaccharides
58
The bond formed between two monosaccharides in a condensation reaction is called a ...
glyosidic bond
59
draw the formation of maltose?
60
Test for non-reducing sugar
- Add equal volumes of the food solution to dilute HCl (will hydrolise any disaccharides present) and place into hot water bath for 5 mins - Add sodium hydrogencarbonate solution until the solution is alkaline (test with litmus) - benedicts reagent doesn't work under alkaline conditions - perform benedicts test
61
Why are polysaccharides suitable as storage molecules?
Large and insoluble
62
What is starch formed of?
Chains of alpha glucose monosaccharides joined by glycosidic bonds
63
What is starch's main role? Why does its structure suit this? x4
Energy storage in plants Insoluble so unaffected by osmosis Large - doesn't diffuse out of cells Compact - lots can be stored in a small place Branched form has many ends so can be acted on simultaneously by enzymes to release glucose. When hydrolysed it forms alpha glucose which is easily transported and used in respiration
64
Role of glycogen?
Energy/ carb storage in animals and bacteria
65
Why is glycogen suited for its role?
Insoluble so doesn't affect or be affected by osmosis Compact Large and insoluble so doesn't diffuse out of cells Highly branched so the ends can be acted on by enzymes simultaneously so can be rapidly broken down to form glucose monomers to be used in respiration.
66
Structure of cellulose?
Chain of beta glucose Straight and unbranched chains allow hydrogen bonds to form between chains. - sheer number of hydrogen bonds = strength. Cellulose molecules grouped together to form microfibrils which in turn are arranged in parallel groups to form fibres.
67
Structure of glycogen and starch
Coiled chain of alpha glucose joined by glycosidic bonds Note that cellulose is more branched
68
What do hydrogen bonds do to cellulose?
Sheer number makes it very strong
69
What happens to cellulose molecules?
Grouped together to from microfibrils which in turn are arranged into groups called fibres.
70
What elements make up lipids?
Carbon, hydrogen and oxygen
71
Are lipids soluble or insoluble in water?
insoluble
72
Are lipids soluble or insoluble in organic solvents such as alcohols and acetone?
Soluble
73
Whats the difference in the composition of lipids and carbohydrates?
Lipids have a lower proportion of oxygen than carbohydrates.
74
5 roles of lipids?
**Source of energy** - Lipids can be oxidised to release energy **Structural Components** - Phospholipids are used in cell surface membranes **Waterproofing** - Insoluble lipids are used to form water resistant barriers eg. waxy cuticle **Insulation** - Lipids retain heat as they are poor conductors of heat. They also act as electrical insulators in the mylein sheith around nerve cells **Protection** - Fat is often stored around delicate organs such as the kidney
75
Why are lipids not polymers?
They are not made up of repeating monomers They are organic macromolecules
76
Fatty Acid composition?
Carboxyl group (-COOH) Combined with an alcohol (glycerol) called and R group. This is the **hydrocarbon chain**
77
What is a triglyceride?
A type of lipid usually involved in energy storage?
78
Triglyceride composition?
1 glycerol bonds to 3 fatty acids. Each fatty acid forms an ester bond with glycerol in a condensation reaction and therefore each time a water molecule is release
79
Word equation for the production of a triglyceride?
Glycerol + 3 fatty acids -> triglyceride + 3 water molecules
80
The hydrocarbon tail of a fatty acid can be saturated or unsaturated. How does this affect the properties of a lipid?
Unsaturated decreases the boiling point
81
What does mono and polysaturated mean?
Mono = 1 double bond Poly = 2 or more
82
Test for lipid?
Emulsion Food sample Add ethanol Shake Add water Positive result = milky white precipitate
83
How does the structure of a triglyceride make it a good source of energy?
High ratio of energy storing C-H bonds to carbon atoms - the c-h bonds release much energy when broken Low mass to energy ratio meaning much energy can stored in a small volume Large and non polar so are insoluble in water - not affected by osmosis
84
Why do triglycerides no affect osmotic activity in cells?
They are large and non polar so are insoluble. Therefore they do not affect osmosis or water potential in cells
85
Why are lipids a good source of water?
They release water when oxidised due to high ratio of hydrogen to oxygen atoms
86
What is a phospholipid?
A type of lipid used as a structural component in the cell membrane
87
Structural difference between a triglyceride and a phospholipid?
Phospholipid has a **phosphate group** in place of one of the fatty acids.
88
Phospholipid head is .... Phospholipid tail is ....
Head is hydrophilic Tail is hydrophobic
89
Why is a phosphate head of a phospholipid hydrophilic?
It is polar
90
How does a phospholipids structure relate to its function? x2
As the head is hydrophobic and the tail is hydrophilic it forms a phospholipid bilayer. **This means water soluble substances cannot pass through** Phospholipid structure allows them to form **glycolipids** (used for cell recognition) by combining with carbohydrates.
91
How to test for starch?
And iodine to sample in solution Brown/orange to blue/black indicates a positive result
92
What are the two main groups of lipids called?
Triglycerides Phospholipids
93
How would you make a 1 in 1000 dilution of an original liquid?
Add 1 part of the original liquid and 9 parts water to make 10^-1 Mix Repeat using 9 parts water and 1 part 10^-1 solution to make a 10^-2 dilution Mix Then repeat using 9 parts water and 1 part 10^-2 dilution to produce 10^-3 dilution (1 in 1000)
94

A Level Biology (11 decks)

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