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IB biology > topic 2.3- carbohydrates and lipids > Flashcards

topic 2.3- carbohydrates and lipids Flashcards

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1
Q

give the two main functions of carbohydrates in organisms

A
  • serve as energy sources
  • provide support in structures (eg cell wall)
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2
Q

what elements are carbohydrates composed of?

A

carbon, hydrogen, oxygen

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3
Q

name the three groups of carbohydrates from shortest term energy source and longest term energy source

A
  1. monosaccharides
  2. disaccharides
  3. polysaccharides
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4
Q

define monosaccharides

A

single sugar units

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5
Q

define disaccharides

A

two monosaccharides linked together

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6
Q

define polysaccharides

A

many monosaccharides linked together

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7
Q

give 3 examples of monosaccharides

A

glucose, fructose, galactose

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8
Q

give 3 examples of disaccharides

A

maltose, sucrose, lactose

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9
Q

give 3 examples of polysaccharides

A

starch, glycogen, cellulose

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10
Q

what are the three different types of monosaccharides?

A
  • trioses (monosaccharides with 3 carbon atoms, eg glyceraldehyde)
  • pentoses (monosaccharides with 5 carbon atoms, eg deoxyribose)
  • hexoses (monosaccharides with 6 carbon atoms, eg glucose)
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11
Q

what two features are monosaccharides characterised by?

A
  • a hydroxyl group (OH)
  • a carbonyl group (C=O)
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12
Q

what is the difference between an aldehyde and a ketone?

A
  • aldehyde has variable group R and hydrogen bonded to C
  • ketone has two variable groups R bonded to C
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13
Q

state the general formula for monosaccharides

A

CnH2nOn

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14
Q

what are ribose and deoxyribose?

A

they are pentoses and isomers of each other

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15
Q

what are isomers?

A

molecules with the same molecular formula but different displayed formula

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16
Q

state the 4 important hexoses

A
  • alpha glucose
  • beta glucose
  • fructose
  • galactose
    (all isomers)
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17
Q

what is the reaction forming a disaccharide from a monosaccharide called and why?

A

condensation reaction- water is released

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18
Q

what bond is formed between two monosaccharides when a disaccharide is created?

A

glycosidic bond

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19
Q

what is the reaction breaking down a disaccharide into two monosaccharides called and why?

A

hydrolysis- water is being added

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20
Q

what types of processes are condensation/hydrolysis reactions?

A

condensation- anabolic- energy is used as bonds are being formed
hydrolysis- catabolic- energy is being released as bonds are being broken

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21
Q

what reaction forms polysaccharides from monosaccharides?

A

condensation polymerisation

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22
Q

what are the three most biologically significant polysaccharides?

A

starch, cellulose, glycogen

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23
Q

starch, cellulose, glycogen:
- main similarity?
- two differences?

A

all polymers of glucose but the isomer (alpha/beta) and type of bond (1,4 or 1,6) vary.

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24
Q

how are cellulose chains held together?

A

by the hydrogen bonds formed between hydroxyl groups and hydrogen in parallel chains.

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25
Q

describe a cellulose molecule

A

cellulose is a linear molecule
- 1,4 glycosidic bonds give it its linear structure
- beta glucose molecules ONLY

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26
Q

state the features and functions of cellulose in plants

A
  • cellulose microfibrils have high tensile strength
  • used as basis of plant cell walls
  • prevents cell from bursting due to high water content
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27
Q

what two forms does starch exist in?

A

amylose and amylopectin

28
Q

state the two main similarities between amylose and amylopectin

A
  • both are polymers of alpha glucose and are stabilised by hydrogen bonds
  • both starches are compact, insoluble and easily hydrolysed
29
Q

state the main difference between amylose and amylopectin

A
  • amylose is a straight chain, helix shaped molecule containing only 1,4 glycosidic bonds
  • amylopectin is a branched molecule as it contains both 1,4 and 1,6 glycosidic bonds
30
Q

explain the features and functions of starch in plants

A

molecules are hydrophilic but too large to be soluble in water:
- used as store of glucose in cells where large amounts need to be stored
- made as a temporary store in leaf cells when glucose is being made faster by photosynthesis than it can be exported to other parts of the plant.

31
Q

what is the function of glycogen?

A

storage carbohydrate in animals and fungi

32
Q

describe the structure of glycogen

A
  • polymer of alpha glucose
  • highly branched as it contains 1,4 glycosidic bonds along with many 1,6 bonds.
33
Q

where is glycogen stored in animals?

A

animals- livers and some muscles

34
Q

what are lipids?

A

a diverse group of carbon compounds that share the property of being insoluble in water.

35
Q

state of fats/oils at body and room temperature

A
  • fats are liquid at body temperature but solid at room temperature
  • oils are liquid at both
36
Q

what elements are present in lipids?

A

carbon, hydrogen, oxygen

37
Q

define triglycerides

A

One of the principal groups of lipids

38
Q

how is a triglyceride made?

A

by combining three fatty acids with one glycerol by a condensation reaction

39
Q

what type of linkage is formed between each fatty acid and the glycerol?

A

an ester bond

40
Q

what is the function of triglycerides?

A
  • energy stores
  • do not conduct heat well- insulators eg blubber
41
Q

what are fatty acids?

A

long hydrocarbon chains with a carboxyl group (COOH) at one end

42
Q

how do you calculate BMI?

A

mass in kg/(height in metres)^2

43
Q

what are the units for BMI?

A

kg m^-2

44
Q

state the relationship between BMI and a person’s status

A

below 18.5- underweight
18.5-24.9- normal weight
25.0-29.9- overweight
30.0 or more- obese

45
Q

what is a saturated fatty acid?

A

a fatty acid with single bonds between all of its carbon atoms, that therefore contains as much hydrogen as it possibly could.

46
Q

what is an unsaturated fatty acid?

A

a fatty acid that has one or more carbon - carbon double bonds, that therefore contains less hydrogen than it could

47
Q

what is the difference between a monounsaturated fatty acid and a polyunsaturated fatty acid?

A

a monounsaturated fatty acid has one carbon-carbon double bond
a polyunsaturated fatty acid has more than one carbon-carbon double bond

48
Q

what are cis-fatty acids?

A

unsaturated fatty acids where the hydrogen atoms are on the same side of the two carbon atoms that are double bonded.

49
Q

what are trans-fatty acids?

A

unsaturated fatty acids where the hydrogen atoms are on different sides of the two carbon atoms that are double bonded.

50
Q

explain the features of cis-fatty acids

A
  • there is a bend in the hydrocarbon chain at the double bond
  • triglycerides containing these fatty acids are less good at packing together in regular arrays, so this lowers the melting point = usually liquid at room temp
51
Q

explain the features of trans-fatty acids

A
  • do not have a bend in the hydrocarbon chain at the double bond
  • triglycerides containing these fatty acids are good at packing together in regular arrays, so this raises the melting point = usually solid at room temp
52
Q

are lipids or carbohydrates more suitable for long term energy storage in humans?

A

lipids

53
Q

why are lipids more suitable for long term energy storage in terms of mass than carbohydrates?

A
  1. amount of energy released in cell respiration per gram of lipids is double the amount released from a gram of carbohydrates
  2. fats form pure droplets in cells with no water associated, but each gram of glycogen is associated with about 2g of water
    => lipids 6x more efficient in the amount of energy that can be stored per g of body mass (less body mass added)
54
Q

why are lipids more suitable for long term energy storage in terms of secondary roles than carbohydrates?

A
  • lipids are poor conductors of heat so can act as insulators
  • fat is liquid at body temp so it can also act as a shock absorber for organs
55
Q

why is glycogen ideal for short term energy storage?

A
  • can be broken down into glucose rapidly and then transported easily to where its needed.
  • fats in adipose tissue cannot be mobilised as rapidly
  • fatty acids can only be used in aerobic respiration
56
Q

which fats have positive effects on the body?

A

Unsaturated cis fats:
- increase HDL levels within the body, lowering blood cholesterol levels

57
Q

which fats have negative effects on the body?

A

Saturated fats:
- increase LDL levels within the body
Trans fats:
- increase LDL levels and decrease HDL levels within the body

58
Q

what do LDLs and HDLs do and stand for?

A
  • HDLs (high density lipoproteins) scavenge excess cholesterol and carry it back to the liver for disposal, so lower blood cholesterol levels
  • LDLs (low density lipoproteins) carry cholesterol from liver to rest of body, so raise blood cholesterol levels.
59
Q

what are the health risks of high blood cholesterol levels?

A

atherosclerosis- narrowing and hardening of arteries
CHD- due to the accumulation of LDL particles in walls of arteries

60
Q

describe the correlations between fats and CHD

A
  • A positive correlation has been found between the intake of saturated fats and the incidence of CHD in human populations
  • In patients who died from CHD, fatty deposits in diseased arteries were found to contain high concentrations of trans fats
61
Q

counter the claim ‘a positive correlation has been found between the intake of saturated fats and the incidence of CHD in human populations’

A

certain populations do not fit this trend (e.g. the Maasai tribe in Africa have a fat-rich diet but very low rates of CHD)

62
Q

counter the claim ‘in patients who died from CHD, fatty deposits in diseased arteries were found to contain high concentrations of trans fats’

A

genetic factors may play a role (e.g. blood cholesterol levels only show a weak association to dietary levels)

63
Q

state 3 general counter claims for fats

A
  • validity of intervention studies is dependent on size and composition of cohort, as well as the duration of the study
  • increased carbohydrate intake may cause detrimental health effects associated with CHD (e.g. diabetes, obesity)
  • incidence of CHD dependent on other factors besides dietary intake (e.g. exercise, access to health care, etc.)
64
Q

sucrose

A

alpha glucose and fructose

65
Q

maltose

A
  • 2x alpha glucose (same way up)
  • alpha 1,4 glycosidic bond
66
Q

lactose

A
  • beta glucose and galactose
  • upside down to each other
  • beta glycosidic bond

IB biology (60 decks)

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