BM: Carbohydrates Flashcards
1
Q
Why is life based on carbon?
A
Carbon readily forms bonds with other carbons.
This allows sequences of carbon to build up, forming ‘backbones’ upon which other molecules can attach.
2
Q
Carbon-containing molecules are known as what?
A
Organic molecules.
3
Q
What is a monomer?
A
A small, basic molecular unit.
4
Q
A small, basic molecular unit, is also known as what?
A
A monomer.
5
Q
Give examples of monomers?
A
Monosaccharides, amino acids and nucleotides.
6
Q
Monosaccharides, amino acids and nucleotides are all examples of what?
A
Monomers.
7
Q
What do all organisms on Earth contain?
A
A few carbon-based compounds that interact in similar ways.
8
Q
What are polymers?
A
Large, complex molecules composed of long chains of monomers joined together.
9
Q
What elements do all carbohydrates contain?
A
C, H and O.
10
Q
What monomers are carbohydrates composed of?
A
Monosaccharides.
11
Q
Give general properties of monosaccharides:
A
- Sweet- tasting
- Soluble
12
Q
What is the general formula of monosaccharides?
A
‘n’ can be any number from 3 to 7.
13
Q
Give examples of monosaccharides:
A
Glucose, fructose and galactose.
14
Q
What is glucose?
A
A hexose sugar.
A monosaccharide with six carbon atoms in each molecule.
15
Q
What are the two types of glucose?
A
Alpha - α
Beta - β
16
Q
What are isomers?
A
Molecules with the same molecular formula as each other, but with atoms connected in different ways.
17
Q
α - glucose and β - glucose are examples of what?
A
Glucose isomers.
18
Q
Draw the structure of α - glucose:
A
19
Q
Draw the structure of β - glucose:
A
20
Q
What is a condensation reaction?
A
When two molecules join together with the formation of a new chemical bond and the release of a water molecule.
21
Q
What is released when a glycosidic bond is formed?
A
A molecule of water.
22
Q
How are monosaccharides joined?
A
Through condensation reactions.
23
Q
What type of bond joins monosaccharides?
A
A glycosidic bond.
24
Q
Give examples of disaccharides:
A
- Maltose
- Sucrose
- Lactose
25
How is the **disaccharide maltose** formed?
Two α - glucose molecules joined together via a condensation reaction.
26
How is a **the disaccharide sucrose formed?**
Via a condensation reaction between a glucose molecule and a fructose molecule.
27
How is the **disaccharide lactose formed?**
Via a condensation reaction between a glucose molecule and a galactose molecule.
28
How can **polymers** be broken down **into monomers?**
Through hydrolysis reactions.
29
What is a **hydrolysis** reaction?
A reaction that breaks the chemical bond between monomers using a water molecule.
30
What is the **general term** for monosaccharides and disaccharides?
Sugars.
31
How can all **sugars** be classified?
As either:
Reducing
*or*
Non-reducing
32
**Reducing sugars** are what?
All monosaccharides and some disaccharides.
33
All **monosaccharides** and some **disaccharides** are...
... reducing sugars.
34
What is **reduction?**
## Footnote
*What does this mean a reducing sugar is?*
Reduction is a chemical reaction involving the gain of electrons or hydrogen.
## Footnote
*A reducing sugar is therefore a sugar that can donate electrons to another chemical, eg Benedict's reagent.*
35
What is the test **for reducing sugars?**
The Benedict's test.
36
Describe the **Benedict's test** for **reducing sugars:**
* Add Benedict's reagent to the sample - ensure it is in excess.
* Heat it in a water bath that's been brought to the boil.
* If the test's positive a coloured precipitate will form:
* Blue - green - yellow - orange - red, depending on concentration of reducing sugar.
37
Draw a table of **results** for the **reducing sugars** test:
*The higher the concentration of the reducing sugar, the further the colour change goes.*
38
How would you get **more accurate results** in the **reducing sugars test?**
Filter the solution and weigh the precipitate.
39
How do you test for **non-reducing sugars?**
## Footnote
*Eg, sucrose*
* Break them down into monosaccharides
* Get a sample of the test solution
* Add dilute hydrochloric acid
* Carefully heat in a water bath that's been brought to the boil
* Neutralise this with sodium hydrogencarbonate.
* Then, carry out the test for reducing sugars/Benedict's test.
40
What is a **positive result** in the **non-reducing sugars test?**
A coloured precipitate will form - as with the reducing sugars test.
## Footnote
*If the test's negative, the solution will stay blue, which means the sample does not contain any sugar (either reducing or non-reducing).*
41
What type of data does the **Benedict's test produce?**
Semi-quantitative, so an approximate estimate of reducing sugar in the sample can be made.
42
Name **three polysaccharides:**
Starch, glycogen and cellulose.
43
What is **starch?**
A polysaccharide.
It is the main storage material in plants.
44
Where do **plants** get their energy from?
## Footnote
*When they have excess of this, what do they do?*
Get energy from glucose.
## Footnote
*They store excess glucose as starch, which can be broken down when needed.*
45
What is **starch** a **made** of?
Two polysaccharides of alpha-glucose.
## Footnote
*Amylose and amylopectin.*
46
What is **amylose?**
A long, unbranched chain of alpha-glucose.
47
Describe the **shape** of **amylose** and **explain** how this relates to its function:
* Coiled structure (due to the angles of the glycosidic bond).
* This makes it compact, so it is great for storage because you can fit a lot of it in a tight space.
48
What is **amylopectin?**
A long, branched chain of alpha-glucose.
49
Describe the **shape** of **amylopectin** and **explain** how this relates to its **function**:
* It has lots of side branches.
* These many side branches can all be acted on by enzymes simultaneously, meaning starch can be broken down for quick energy release.
50
Describe how the **structure of starch** makes it **adapted to its function:**
* Insoluble in water, so does not affect the water potential or cause cells to swell via osmosis.
* Large and insoluble so doesn't diffuse out of cells.
* Compact (amylose) so lots can be stored in one place.
* When hydrolysed it forms alpha glucose, which is easily transported and readily used in respiration to make energy
* The branched form means it has many ends, which can be acted on enzymes simultaneously meaning glucose monomers are released rapidly
51
What is **glycogen?**
The main energy storage material in animals.
52
What is the **test for starch?**
Iodine test.
53
Describe how you would perform the **iodine test for starch:**
* Add iodine dissolved in potassium iodide solution to the test sample.
* Shake or stir.
54
What would a **positive result be** in the iodine test for starch?
When starch is present, the sample changes colour from **browny-orange** to a **dark, blue-black colour.**
55
Describe the **structure of glycogen:**
Alpha-glucose molecules joined by glycosidic bonds.
Very similar to amylopectin, however it is even more highly branched .
56
Where do **animals** get their energy from?
## Footnote
*How do they store this when they have excess?*
They get their energy from glucose.
When they have excess, they store it as glycogen.
57
Draw **starch:**
58
Draw **glycogen:**
59
How does the **structure of glycogen** mean it is **adapted to its function?**
* More highly branched than starch and has more ends that can be simultaneously acted on by enzymes
* So more rapidly broken down to form glucose monomers, that can be used in respiration.
* *Important for animals which have higher metabolic and respiratory rates than plants, because they are more active.*
* Insoluble and so tends not to draw water into cells by osmosis.
* Does not diffuse out of cells, and so is ideal for storage, as it is insoluble.
* Compact, so a lot can be stored in a small place.
60
What is **cellulose?**
The major component of cell walls in plants.
61
What is **cellulose made of?**
Long, unbranched chains of beta-glucose.
62
What **forms when beta-glucose molecules** bond?
Straight cellulose chains.
These run parallel to each other, allowing hydrogen bonds to form cross-linkages between adjacent chains.
*These are known as microfibrils.*
63
What are **microfibrils?**
Parallel chains of beta-glucose, joind via hydrogen bonds.
## Footnote
*They group together to form fibres.*
64
Draw **cellulose:**
65
What is the **function of glycogen?**
It is the stored version of glucose, which is used in animals to facilitate respiration.
66
What is the role of **cellulose?**
* Cellulose adds structure and rigidity to plants.
* Prevents plants cells from bursting as water enters via osmosis.
* It does this by exerting an inward pressure that stops any more water from entering
* So, living plant cells are turgid and push against each other
* This is important in making stems and leaves turgid, so that they provide the maximum surface area for photosynthesis.
* It can only be broken down by enzymes produced by certain bacteria or fungi
* So, only certain animals, like termites or cows (which harbour this bacteria in their gastrointestinal tracts) can digest and utilize cellulose as an energy source.
67
How does the **structure of celluose** relate to its function?
* Made of β-glucose so form long, straight, unbranched chains
* Chains run parallel to each other and are cross-linked by hydrogen bonds which add collective strength
* Molecules are grouped to form microfibrils, which are then grouped to form fibres, which provide even more strength.
