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CLS4007-B: Biology (Semester 1) > L3 - Carbohydrates > Flashcards

L3 - Carbohydrates Flashcards

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1
Q

What are carbohydrates?

A

Biological molecules containing carbon (C), hydrogen (H) and oxygen (O) atoms only.

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2
Q

What is the empirical formula of carbohydrates?

A

Cm(H2O)n

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3
Q

What is another term for carbohydrates?

A
  • Saccharides

- Sugars

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4
Q

What 3 things do carbohydrates form?

A
  • Rapid and readily available supply of energy
  • Form part of important molecules in the cell
  • Form markers on the cell surface which aid cell recognition
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5
Q

Describe the 4 classifications of carbohydrates.

A
  • Monosaccharide
  • Disaccharide
  • Oligosaccharide
  • Polysaccharide
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6
Q

Describe the properties of monosaccharides. (x6)

A
  • Single sugar molecules providing instant energy
  • Number of carbon atoms ranges from 3-10
  • Contain aldehyde / ketone and hydroxyl groups
  • Hydroxyl position differs between different sugars
  • Sugars can exist in ‘deoxy’ forms (if hydroxyl, OH is replaced with H)
  • Exist as open-chain or ring (cyclic) structures joined by covalent bond
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7
Q

Name the 3 aldohexose sugars with the chemical formula C6H12O6.

A
  • Glucose
  • Galactose
  • Mannose
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8
Q

What are stereoisomers?

A

Non-superimposable (non-overlapping) mirror images.

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9
Q

What do stereoisomers have in common?

A
  • Same chemical formula

- Same orders and types of bonds

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10
Q

What is different about stereoisomers?

A
  • Different spatial arrangements

- Different biological functions

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11
Q

What is the requirement for stereoisomerisation?

A

Require at least 1 chiral carbon centre.

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12
Q

What two types of stereoisomers are formed, and do they differ?

A
  • D Isomer: OH on bottom chiral centre points to the right

- L Isomer: OH on bottom chiral centre points to the left

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13
Q

When does cyclisation occur?

A

When OH group on the second last carbon reacts with a carbonyl group.

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14
Q

What is the resulting product when an aldose is cyclised?

A

Hemiacetal

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15
Q

What is the resulting product when a ketone is cyclised?

A

Hemiketal

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16
Q

Name and explain why 2 hemiketal / hemiacetal products come about.

A
  • α anomer
  • β anomer
  • OH group can attack planar C=O group from either side
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17
Q

Describe the 4 properties of glucose.

A
  • Primary energy source for live
  • 7 energy rich C-H bonds
  • Bonds broken during cellular respiration
  • Released energy is stored as ATP for use by cell
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18
Q

Describe the 4 properties of fructose.

A
  • Important energy source
  • 7 energy rich C-H bonds
  • Found in fruits, honey, berries and melons
  • Forms a furan-based ring structure despite being a hexose
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19
Q

What is furanose?

A

A 5 membered cyclisation product (pentose sugar).

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20
Q

What are disaccharides?

A

2 monosaccharides linked together.

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21
Q

Describe the formation of disaccharides.

A
  • Formed by dehydration synthesis (condensation reaction) with the removal of H2O
  • Reaction aided by enzymes
  • Molecules joined at OH groups by glycosidic links / bonds
  • Primary function = nutritional source of monosaccharides
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22
Q

Name the constituents of maltose, and the bonds between these.

A
  • 2 glucose molecules
  • Joined at carbons 1 and 4
  • α-1,4-glycosidic link
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23
Q

How else can maltose be generated?

A

Breakdown (hydrolysis) of starch, which is a polysaccharide.

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24
Q

Which enzyme digests maltose?

A

Maltase

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25
Q

Describe maltose metabolism.

A
  • Metabolised by yeast

- Products: ethanol + CO2

26
Q

Name the constituents of lactose, and the bonds between these.

A
  • glucose + galactose
  • Joined at carbons 1 and 4
  • β-1,4-glycosidic link
27
Q

Which enzyme digests lactose?

A

Lactase

28
Q

Name the constituents of sucrose, and the bonds between these.

A
  • glucose + fructose
  • Joined at carbons 1 and 2
  • α-1,2-glycosidic link
29
Q

Which enzyme digests sucrose?

A

Sucrase

30
Q

What is sucrose abundant in?

A

Plants and sap - especially sugar cane and sugar beet.

31
Q

What is a hydrolysis reaction?

A

Cleavage of chemical bonds by the addition of water.

32
Q

Describe the 2 types of glycosidic links and where they occur.

A
  • α-1,4-glycosidic link: At the C1 OH group, below the plane of the glucose ring
  • β-1,4-glycosidic link: At the C1 OH group, above the plane of the glucose ring
33
Q

Why might organisms convert soluble sugars into an insoluble form?

A
  • For storage in the cell
  • For building structures
  • For taking part in cellular processes
34
Q

What is the range of monosaccharides that may be contained within an oligosaccharide?

A

3-20

35
Q

Name the 2 polysaccharide components of starch.

A
  • Amylose

- Amylopectin

36
Q

Describe the 2 polysaccharide components of starch.

A
  • Amylose: long linear chains of α-1,4 linked D-glucose residues
  • Amylopectin: linear chains of α-1,4 linked D-glucose residues joined through α-1,6 linked branch points
37
Q

What shape is the structure of amylose?

A

Coiled

38
Q

What shape is the structure of amylopectin?

A

Brush-like

39
Q

Describe the properties of starch. (x3)

A
  • Main dietary source of carbohydrates
  • Main storage polymer in plants
  • Found in amyloplasts and chloroplasts of plant cells from roots, tubers, seeds and fruits
40
Q

What are amyloplasts?

A

Non-pigmented plant cell organelles that are responsible for synthesis and storage of starch granules through polymerisation of glucose.

41
Q

Which enzymes digest starch, and where are these enzymes found?

A
  • Amylase (in saliva and gut)

- Maltase and Isomaltase (in gut only)

42
Q

What products is starch digested into?

A
  • Dextrins (oligosaccharides)
  • Maltriose
  • Maltose
  • Isomaltose
  • Glucose
43
Q

What links do amylase and maltase break down?

A

α-1,4-glycosidic links

44
Q

What links does isomaltase break down?

A

α-1,6-glycosidic links

45
Q

Describe the structure of glycogen.

A

Complex branched structure of α-1,4 linked D-glucose residues joined through α-1,6 linked branch points.

46
Q

Describe the differences between the structures of glycogen and amylopectin.

A
  • Structure similar to amylopectin

- But branch points occur more frequently (every 8-12 residues instead of 24-30 residues)

47
Q

How much glucose does blood typically contain at any given time?

A

5-6 mMol

48
Q

How does the body maintain (or attempt to maintain) glucose levels in starving/fasting individuals?

A

Converts glycogen stores in the liver and muscle to glucose.

49
Q

What are glycoproteins?

A

Proteins that contain oligosaccharide chains covalently attached to their protein structure.

50
Q

What do glycosylated membranes play an important role in?

A

Immune recognition

51
Q

What do secreted glycoproteins make up?

A
  • Mucins

- Glycocalyx

52
Q

What are mucins?

A

Principle components of mucus by mucous membranes and as component of saliva.

53
Q

What are mucous membranes?

A

Lining of body cavities open to the exterior.

54
Q

What is the glycocalyx?

A

Glycoprotein covering surrounding the cell membranes of epithelial and other cell types, as well as bacteria.

55
Q

What are glycolipids?

A

Lipids that contain oligosaccharide chains covalently attached to their lipid structure.

56
Q

What are glycolipids often associated with?

A

Phospholipids on the outer surface of cell membranes.

57
Q

What do glycolipids usually function as? (x3)

A
  • Recognition signals
  • Attachment factors
  • Membrane stabilisers
58
Q

What are sphingolipids?

A

A sub-type / class of lipids.

59
Q

What 2 types of sphingolipids are there?

A
  • Ceramide (signalling molecule)

- Sphingomyelin (membranes)

60
Q

What 2 types of glycosphingolipids are there?

A
  • Cerebosides (found in muscles and nerves)

- Gangliosides (found in plasma membranes)

CLS4007-B: Biology (Semester 1) (12 decks)

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