3.1.2 Carbohydrates Flashcards Preview

Biology 3.1 Biological Molecules Ms Shial > 3.1.2 Carbohydrates > Flashcards

Flashcards in 3.1.2 Carbohydrates Deck (37)
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1
Q

What is a monosaccharide?

A

A single monomer of a carbohydrate

2
Q

What is a disaccharide?

A

Sugar formed when two monosaccahrides are joined by glycosidic linkage (Pair of monosaccharides)

3
Q

What is a polysaccharide?

A

A chain of monosaccharides joined together by glycosidic bonds

4
Q

What is the general formula for monosaccharides?

A

(CH^2O)n where n is ≥ 3 and counts for the number of carbons

5
Q

What can monosaccharides be classified by?

A

the number x of carbons present: 3(triose) 4 (tetrose) 5(pentose) 6(hexose) 7(heptose) etc

6
Q

What are some features of monosaccharides?

A

They are sweet tasting and water soluble. Their atoms usually form a ring and are hydrophilic.

7
Q

What is meant by the term hydrophilic?

A

A substance that is attracted to water and diffuses in water

8
Q

What enables their solubility?

A

They have a large number of OH groups (hydroxyls) and can form hydrogen bonds with H^2O molceules

9
Q

Give an example of some monosaccharides

A

Glucose, fructose, galactose

10
Q

What are the four types of glycosidic bonds?

A

1-2 beta, 1-4 beta, 1-4 alpha 1-6 alpha

11
Q

What are the two forms of glucose and what is the difference?

A

The alpha and beta isomers (isomers have same molecular formula, different arrangement of atoms). In alpha glucose, the hydroxyl group points below the ring while in beta glucose, it points above the ring.

12
Q

What does the energy glucose releases during cellular respiration make?

A

ATP (Adenosine triphosphate) which is the energy currency of the cell, it provides energy for reactions in living organisms

13
Q

What disaccharide is formed by glucose + glucose

A

Maltose

14
Q

What disaccharide is formed by glucose + fructose?

A

Sucrose

15
Q

What disaccharide is formed by glucose + galactose?

A

Lactose

16
Q

How are disaccharides formed?

A

By the condensation reaction between monosaccharides with water as a byproduct

17
Q

What is a glycosidic bond?

A

A type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate

18
Q

How are disaccharides broken down?

A

Through hydrolysis

19
Q

How are polysaccharides formed?

A

When three or more monosaccharides are joined through condensation reactions

20
Q

What monosaccharides make up starch?

A

(Alpha) glucose

21
Q

What makes starch good for storage?

A

It’s helical shape (amylopectin)- which makes it compact and enables it to fold so lots can be stored in a small space.

22
Q

What are the two types of glucose polymer in starch and what is the difference?

A

Amylose and amylopectin. Amylose linked by 1,4-glycosidic bonds and is long unbranched, perfect for energy release. Amylopectin linked by α-1,4-glycosidic bonds and α-1,6-glycosidic bonds and is long and branched and has a helical shape for storage.

23
Q

What makes starch suitable for its role?

A

Insoluble- won’t draw out water easily by osmosis, changing water potential. Large size-doesn’t easily diffuse out of cell. Hydrolysed into glucose- easily transported and regularly used in respiration, Compact- lots stored in small space.

24
Q

What type of cells are starch and cellulose only found in?

A

Plant cells

25
Q

What is the chemical formula of monosaccharides?

A

C6H12O6

26
Q

What is the chemical formula of disaccharides?

A

C12H22011

27
Q

What is the shape of cellulose molecules?

A

Cellulose is a straight chain polymer. Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation

28
Q

What are microfibrils and what’s its purpose?

A

Long, straight cellulose chains joined by hydrogen bonds that provide rigidity for cell

29
Q

(Exam Question) Why is the rise of glucose in the blood slower if the carb is starch rather than sucrose

A

The digestion of starch is more complex than the digestion of sucrose. Sucrose is digested by a one step process involving the enzyme sucrase which breaks it down to form glucose and fructose via hydrolysis. Starch breakdown has broadly two steps. The first involves the enzymes amylase which breaks it down to maltose. The second step results in the production of the final product, glucose, which is formed using maltase which breaks down the maltose to give glucose.

30
Q

Describe the function and structure of cellulose

A

A polymer of beta glucose which gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds up stem). 1)1,4 glycosdic bonds 2) Long unbranched, straight chain molecule 3)Alternate glucose molecules rotated 180degrees 4)H-bond crosslinks between parallel strands form microfibrils- high tensile strength

31
Q

What happens when a polysaccharide is hydrolysed?

A

It is broken down into monosaccharides and disaccharides

32
Q

Describe the test for reducing sugars?

A

Benedict’s Test 1) Add 2cm^3 of the food sample to a boiling tube 2)Add an equal volume of Benedict’s regenant 3)Heat the solution in a water bath for 3-5 minutes 4) Observe for a colour change

33
Q

What do the different colours indicate?

A

Blue- no reducing sugars Green-Low conc of reducing sugars Orange- Moderate Red- High conc.

34
Q

How does the colour change occur?

A

Reducing property of simple carbohydrates. The copper (II) ions in the Benedict’s solution are reduced to Copper (I) ions, which causes the colour change. The blue copper sulphate which is reduced to form an insoluble red precipitate of copper oxide

35
Q

What is Benedict’s solution?

A

A clear blue liquid that changes colour and gives a precipitate depending on how much is reduced

36
Q

What is cellulose? What must be done before condensation reactions can occur to form cellulose?How is the structure of cellulose different to starch? What is structurally different that gives them different physical properties? Why is it impossible for humans to digest food containing cellulose? Cellulose is a major component of…
What does cellulose provide for and how ?

A

Cellulose is formed by beta 1-4 glycosidic linkages and crosslinks, making it rigid. Starch has alpha 1-4 and 1-6 glycosidic linkages without the tight crosslinks of cellulose.

Human digestive enzymes cannot break down the beta 1-4 glycosidic bonds in cellulose as the enzyme that can is absent in humans

37
Q

What is glycogen? Features, why suitable, where made etc

A

Glycogen is found in animals and bacteria but never in plant cells.
Glycogen is very similar in structure to starch but has shorter chains and is more highly branched.
It is sometimes called ‘animal starch’ because it is the major carbohydrate storage product of animals.
Major (but small) stores in liver and muscle cells
Most alpha gluc joined by 1,4 glycosidic bonds, branch point 1,6

• it is insoluble and therefore does not tend to draw water into the
cells by osmosis
• being insoluble, it does not diffuse out of cells
• it is compact, so a lot of it can be stored in a small space
• It is more highly branched than starch and so has more ends that can be acted on simultaneously by enzymes. It is therefore more rapidly broken down to form glucose monomers, which are used in respiration. This is important to animals which have a higher metabolic rate and therefore respiratory rate than plants because
they are more active.