Class notes
Edexcel B Biology AS and A2 full notes
- Course
- Institution
Full notes on all the specification points for AS and A2 biology for the exam board edexcel.
[Show more]
Seller
Follow
Elizabethquigg
Reviews received
Content preview
Edexcel Biology B1
,AS
TOPIC 1: BIOLOGICAL MOLECULES
1.1 CARBOHYDRATES
• Know the difference between monosaccharides, disaccharides and polysaccharides.
• Know the structure of the hexose glucose (alpha and beta) and the pentose ribose.
• Understand how monosaccharides (glucose, fructose, galactose) join to form disaccharides
(sucrose, lactose and maltose) and polysaccharides (starch formed from amylose and
amylopectin; glycogen) through condensation reactions forming glycosidic bonds, and how
these can be split through hydrolysis reactions.
• Understand how the structure of glucose, starch, glycogen and cellulose relates to their
function.
1. What elements do carbohydrates contain?
Carbon, hydrogen, oxygen
2. Define monosaccharide
Single sugar monomers
3. What is the general formula for a monosaccharide?
(CH2O)n
4. Define disaccharide
Two monosaccharides joined by a glycosidic bond
5. Define polysaccharide
Polysaccharides are carbohydrate polymers made from many monosaccharides
6. How do polysaccharides differ from sugars?
Polysaccharides are not soluble or sweet tasting
7. What is the structural difference between a monosaccharide, disaccharide and,
polysaccharide?
Monosaccharides are monomers of sugars, disaccharides are composed of two monomers joined
by a glycosidic bond and polysaccharides are composed of a large number of monomers joined
by glycosidic bonds.
8. How many monosaccharides form a true polysaccharide?
More than 10 monosaccharides
9. How many monomers do oligosaccharides contain?
Polysaccharide chains with fewer than 10 monosaccharides but more than 2.
10. How can a variety of polysaccharides be formed?
Changing the type of monosaccharide or changing how the monosaccharides are bonded
together
11. What advantage does alpha glucose lend to polysaccharides?
Alpha glucose polysaccharides are compact so a large amount of energy can be stored in a small
space. Alpha glucose polysaccharides are insoluble in water so do not impact the water potential
of the cell, preventing cytolysis. Alpha glucose polysaccharides are large so do not diffuse out of
the cell. Alpha glucose polysaccharides are easily hydrolysed into alpha glucose molecules when
energy is needed.
12. Define isomer
Isomers are molecules that have the same chemical formula but a different arrangement of atoms
in space.
13. What is the general formula for glucose
C6H12O6
14. What type of substrate is glucose?
Respiratory substrate
15. What does glucose make during cellular respiration?
ATP
16. What is the difference between alpha and beta glucose?
Alpha glucose and beta glucose are both glucose isomers yet they differ in the positioning of the
hydroxyl group. Alpha glucose’s hydroxides and oxygen are parallel, in beta glucose oxygen is
opposite hydroxide.
17. Define triose
Triose is a monosaccharide with the formula C3H6O3
2
,18. What are the roles of glyceraldehyde?
Intermediate in respiration and photosynthesis
19. Define pentose sugar
Pentose is a monosaccharide with the formula C₅H₁₀O₅;
20. What are the roles of ribose?
In RNA, ATP and hydrogen acceptors NAD and NADP
21. Where is deoxyribose found?
In DNA
22. Define pentose sugar
Pentose is a monosaccharide with five carbon atoms.
23. Define hexose
Hexose is a monosaccharide with six carbon atoms, having the chemical formula C₆H₁₂O
24. Draw the structural formula of alpha and beta glucose (textbook page 11)
25. Draw the molecular formula of glucose (textbook page 10)
26. Draw glucose in its skeletal form (textbook page 10)
27. Draw the structure of pentose and rib ose sugars
28. Name three disaccharides
Sucrose, lactose, and maltose
29. How is sucrose synthesised?
Alpha glucose and fructose combine via a glycosidic bond
30. What is the function of sucrose?
Sucrose is transported in the phloem to provide sugars to other parts of the plant.
31. How is lactose synthesised?
Alpha glucose and galactose combine via a glycosidic bond
32. What is the function of lactose?
Lactose is found in mammalian milk to provide energy for infant animals
33. What type of glycosidic bond forms between carbon 1 and carbon 4 in maltose?
1-4 glycosidic bond
34. How is maltose synthesised?
Alpha glucose and alpha glucose join via a glycosidic bond.
35. What is the function of maltose?
Maltose is found in germinating seeds as more complex carbohydrates are broken down for
energy.
36. Define glycosidic bond
A covalent bond formed between two monosaccharides by a condensation reaction
37. What is phosphorylase?
Phosphorylase is an enzyme that catalyses the phosphorolysis of the glycosidic bond
38. How do glycosidic bonds join monosaccharides?
A condensation reaction forms water as one oxygen and two hydrogen atoms are removed from
monosaccharides, this forms a covalent bond joining the two monosaccharides.
39. How can disaccharide be split up?
Hydrolysis reaction
40. Why does a hydrolysis reaction split up a disaccharide?
A hydrolysis reaction requires water, as one oxygen and two hydrogens are added to the
disaccharide, this breaks the glycosidic bond and results in two monosaccharides.
41. What are the functions of glucose?
• Glucose is the main source of energy in respiration
• Glucose is used as building blocks for larger carbohydrates
42. How does the structure of glucose relate to its function?
Glucose is small so can be easily transported in and out of carrier proteins
Glucose is soluble so can be easily transported around an organism
Glucose is less reactive than other monosaccharides so breakdown must be catalysed by
enzymes, this means that the rate of reaction can be controlled effectively.
43. Define residue
When monomers link together in a polymer, the resulting molecule is a residue
44. What is the difference between anabolic and catabolic reactions?
Anabolic processes use simple molecules within the organism to create more complex and
specialised compounds.Catabolic processes break down complex compounds and molecules to
release energy.
45. What is the polysaccharide energy store for plants?
3
, Starch
46. Where is starch commonly found?
Photosynthesising cells in leaves and storage cells in seeds and storage organs.
47. What is the polysaccharide energy store for animals?
Glycogen
48. What is starch made from?
Amylose and amylopectin
49. Why does starch not change the water potential of a cell?
It is insoluble
50. What type of glucose makes up starch, alpha or beta glucose?
Alpha glucose
51. How are alpha glucose monomers removed from glycogen and starch?
Hydrolysis
52. How does the structure of starch relate to its function?
Starch is composed of 2 different polysaccharides, amylose and amylopectin. Amylose is a long
chain of αlpha-glucose monomers joined by 1,4-glycosidic bonds. The chain coils in a spiral
shape held together by hydrogen bonds. The helix shape makes starch well suited to energy
storage as it is compact, so it takes up little space in the cell, and not very soluble in water, so it
does not affect the water potential of the cell. Amylopectin is a branched-chain of αlpha-glucose
monomers joined by 1,4-glycosidic bonds and 1,6-glycosidic bonds. The 1,6-glycosidic bonds
form the links which make branches. The branches mean there are many glucose molecules
accessible on the end of chains which can be easily broken off by hydrolysis for use in respiration.
Therefore amylopectin can provide a rapid supply of energy. Branching also makes it compact, it
takes up little space in the cell.
53. What are amyloplasts?
An organelle that stores starch as compacted, dense insoluble grains
54. What are the functions of amyloplasts?
Amyloplasts store starch to ensure that the plant always has a sufficient supply of energy
55. Define amylose
Amylose is a long chain of alpha glucose molecules joined by 1,4 glycosidic bonds
56. What type of glycosidic bonds join together monomers in amylose?
1,4 glycosidic bonds
57. What is the shape of amylose?
Amylose coils into a compact helix shape held together by hydrogen bonds.
58. What binds to the end of amylose accessible ends?
Amylase
59. How many accessible ends does amylose have?
Amylose has two accessible ends where each amylase enzyme can bind to
60. What effect does the breakdown of amylose have?
Because amylose only has two accessible ends, it can only be broken down slowly.
61. Define amylopectin
Amylopectin is a long chain of alpha glucose molecules joined by 1,4 and 1,6 glycosidic bonds.
62. What is the shape of amylopectin?
Amylopectin is a branched structure
63. What effect do 1,6 glycosidic bonds have on amylopectin?
The additional 1,6 glycosidic bonds cause amylopectin to have side branches with more
accessible ends.
64. How does the shape of amylopectin relate to its function?
Amylopectin contains 1,4 glycosidic bonds and 1,6 glycosidic bonds, this means that it has a
branched structure with more accessible ends. This means that during respiration, amylopectin is
easily broken down by enzymes when glucose is needed.
65. Why is amylopectin more easily broken down than amylose?
Amylopectin contains 1,4 glycosidic bonds and 1,6 glycosidic bonds, this means that it has a
branched structure with more accessible ends. This means that during respiration, amylopectin is
easily broken down by enzymes when glucose is needed. Amylose only contains 1,4 glycosidic
bonds, so only has two accessible ends for each amylase enzyme to bind to. Due to fewer
accessible ends than amylopectin, amylose is broken down more slowly than amylopectin.
66. Where is glycogen found in the body?
Glycogen is found in cells with a high metabolic rate
67. What is the structure of glycogen?
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Elizabethquigg. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.38. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
75632 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now