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IB Biology > 2.3 Carbohydrate and Lipid > Flashcards

2.3 Carbohydrate and Lipid Flashcards

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1
Q

What are carbohydrates made of?

A

Carbohydrates are made of C, H and O (‘carbo’ – contains carbon ; ‘hydrate’ – contains H and O)

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2
Q

What are carbohydrates made of?

A

Carbohydrates are composed of recurring monomers called monosaccharides (which typically form ring structures)

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3
Q

What reaction links monosaccharides?

A

These monosaccharides may be linked together via condensation reactions (water is formed as a by-product)

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4
Q

What bond links two monosaccharides?

A

Two monosaccharide monomers may be joined via a glycosidic linkage to form a disaccharide

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5
Q

What is it called when many monosaccharides join together?

A

Many monosaccharide monomers may be joined via glycosidic linkages to form polysaccharides

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6
Q

What are monosaccahrides? (e.g function)

A

Monosaccharides (one sugar unit) are typically sweet-tasting and function as an immediate energy source for cells

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7
Q

What are examples of monosaccharides?

A

Examples of monosaccharides include glucose, galactose and fructose

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8
Q

What are disaccharides?

A

Disaccharides (two sugar units) are small enough to be soluble in water and commonly function as a transport form

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9
Q

What are examples of disaccharides?

A

Examples of disaccharides include lactose, maltose and sucrose

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10
Q

What is the role of polysaccharides?

A

Polysaccharides (many sugar units) may be used for energy storage or cell structure, and also play a role in cell recognition

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11
Q

What are examples of polysaccharides?

A

Examples of polysaccharides include cellulose, glycogen and starch

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12
Q

What are polysaccharides made of?

A

Polysaccharides are carbohydrate polymers comprised of many (hundreds to thousands) monosaccharide monomers

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13
Q

What does the type of carbohydrate polymer depend on?

A

The type of polymer formed depends on the monosaccharide subunits involved and the bonding arrangement between them

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14
Q

What 3 types of polymers can be made from glucose monomers?

A

Three key polymers can be made from glucose monosaccharides – cellulose, starch (in plants) and glycogen (in animals)

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15
Q

What is cellulose?

A

Cellulose is a structural polysaccharide that is found in the cell wall of plants

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16
Q

What is the structure of cellulose?

A

It is a linear molecule composed of β-glucose subunits (bound in a 1-4 arrangement)

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17
Q

Why can animals not digest cellulose?

A

Because it is composed of β-glucose, it is indigestible for most animals (lack the enzyme required to break it down)

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18
Q

What 2 organisms can consume cellulose?

A

Ruminants (e.g. cows) may digest cellulose due to the presence of helpful bacteria in a specialised stomach

Caecotrophs (e.g. rabbits) will re-ingest specialised faeces that contain digested cellulose (broken down in the caecum)

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19
Q

Where is starch found and what is its function?

A

Starch is an energy storage polysaccharide found in plants

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20
Q

What Is starch composed of?

A

It is composed of α-glucose subunits (bound in a 1-4 arrangement)

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21
Q

What 2 forms does starch take?

A

exists in one of two forms – amylose or amylopectin

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22
Q

What is the structure of amylose?

A

Amylose is a linear (helical) molecule

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23
Q

What is the structure of amylopectin?

A

amylopectin is branched (contains additional 1-6 linkages)

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24
Q

Which form of starch is preferred and why?

A

Amylose is harder to digest and less soluble, however, as it takes up less space, is the preferred storage form in plants

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25
Q

What is glycogen?

A

Glycogen is an energy storage polysaccharide formed in the liver in animals

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26
Q

What is the structure of glycogen?

A

It is composed of α-glucose subunits linked together by both 1-4 linkages and 1-6 linkages (branching)

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27
Q

What molecule is glycogen similar to?

A

It is akin to amylopectin in plants but is more highly branched (1-6 linkages occur every ~10 subunits as opposed to ~20)

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28
Q

What are fatty acids?

A

Fatty acids are long hydrocarbon chains that are found in certain types of lipids (triglycerides & phospholipids)

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29
Q

Can fatty acids differ?

A

YES
Fatty acids may differ in the length of the hydrocarbon chain (typically 4 – 24 carbons) and in the number of double bonds

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30
Q

What are saturated fatty acids?

A

Fatty acids that possess no double bonds are saturated (have maximum number of H atoms)

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31
Q

What are 3 main properties of saturated fatty acids?

A

Saturated fatty acids are linear in structure, originate from animal sources (i.e. fats) and are typically solid at room temperatures

32
Q

What are unsaturated fatty acids?

A

Fatty acids with double bonds are unsaturated – either monounsaturated (1 double bond) or polyunsaturated (>1 double bond)

33
Q

What are the 3 main properties of unsaturated fatty acids?

A

Unsaturated fatty acids are bent in structure, originate from plant sources (i.e. oils) and are typically liquid at room temperatures

34
Q

In what 2 forms can unsaturated fats come in?

A

Unsaturated fatty acids may occur in two distinct structural configurations – cis and trans isomers

35
Q

What does it mean if a fatty acid is cis?

A

Cis: The hydrogen atoms attached to the carbon double bond are on the same side

36
Q

What does it mean if a fatty acid is trans?

A

Trans: The hydrogen atoms attached to the carbon double bond are on different sides

37
Q

Are trans fatty acids common?

A

Trans fatty acids do not commonly occur in nature and are typically produced by an industrial process called hydrogenation

38
Q

What structure do trans fatty acids have?

A

Trans fatty acids are generally linear in structure (despite being unsaturated) and are usually solid at room temperature

39
Q

What are triglycerides?

A

Triglycerides are the largest class of lipids and function primarily as long-term energy storage molecules

40
Q

In what form do animals store triglycerides?

A

Animals tend to store triglycerides as fats (solid)

41
Q

In what form do plants store triglycerides?

A

plants tend to store triglycerides as oils (liquid)

42
Q

How are triglycerides formed?

A

Triglycerides are formed when condensation reactions occur between one glycerol and three fatty acids

43
Q

What happens in a condensation reaction in triglycerides?

A

The hydroxyl groups of glycerol combine with the carboxyl groups of the fatty acids to form an ester linkage

44
Q

What molecule is formed apart from the triglyceride in a condensation reaction?

A

This condensation reaction results in the formation of three molecules of water

45
Q

What two forms can triglycerides take and what does it depend on?

A

Triglycerides can be either saturated or unsaturated, depending on the composition of the fatty acid chains

46
Q

Are any fats (in excess) “healthy?

A

all types of fats consumed as part of dietary intake will cause adverse health effects if taken in excessive amounts

47
Q

What does fat affect in the bloodstream?

A

The mix of fats in the diet influences the level of cholesterol in the bloodstream

48
Q

What 2 types of fats raise blood cholesterol levels?

A

Saturated fats and trans fats raise blood cholesterol levels,

49
Q

What 2 types of fats lower blood cholesterol levels?

A

(cis) unsaturated fats lower blood cholesterol levels

50
Q

Can fats and cholesterol be transported in the blood?

A

NO
Fats and cholesterol cannot dissolve in blood and are consequently packaged with proteins (to form lipoproteins) for transport

51
Q

What do low-density lipoproteins carry?

A

Low density lipoproteins (LDL) carry cholesterol from the liver to the rest of the body

52
Q

What do high density lipoproteins carry?

A

High density lipoproteins (HDL) scavenge excess cholesterol and carry it back to the liver for disposal

53
Q

Are LDL’s or HDL’s “good” for health?

A

Hence LDLs raise blood cholesterol levels (‘bad’) while HDLs lower blood cholesterol levels (‘good’)

54
Q

How do saturated fats affect the level of cholesterol in the blood?

A

Saturated fats increase LDL levels within the body, raising blood cholesterol levels

55
Q

How do trans fats affect the level of cholesterol in the blood?

A

Trans fats increase LDL levels and decrease HDL levels within the body, significantly raising blood cholesterol levels

56
Q

How do unsaturated (cis) fats affect the level of cholesterol in the blood?

A

Unsaturated (cis) fats increase HDL levels within the body, lowering blood cholesterol levels

57
Q

What is the risk of high cholesterol?

A

High cholesterol levels in the bloodstream lead to the hardening and narrowing of arteries (atherosclerosis)

58
Q

What will happen when there are high levels of LDL in the blood?

A

When there are high levels of LDL in the bloodstream, the LDL particles will form deposits in the walls of the arteries

59
Q

What does the accumulation of fat in the arteries cause?

A

The accumulation of fat within the arterial walls lead to the development of plaques which restrict blood flow

60
Q

What is the final result of high blood cholesterol?

A

If coronary arteries become blocked, coronary heart disease (CHD) will result – this includes heart attacks and strokes

61
Q

What are the 2 main health claims about lipids in the diet?

A

Diets rich in saturated fats and trans fats increase the risk of CHD

Diets rich in monounsaturated and polyunsaturated (cis) fats decrease the risk of CHD

62
Q

Where is the evidence for the effect of fats on the body gathered?

A

Epidemiological studies comparing different population groups

Intervention studies that monitor cohorts following dietary modifications

Experimental designs utilising animal models or data based on autopsies

63
Q

Lipids and health counter and pro arguments?

A

Evidence Supporting Health Claims

A positive correlation has been found between the intake of saturated fats and the incidence of CHD in human populations

Counter: 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)

Intervention studies have shown that lowering dietary intakes of saturated fats reduces factors associated with the development of CHD (e.g. blood cholesterol levels, blood pressure, etc.)

Counter: Validity of intervention studies is dependent on size and composition of cohort, as well as the duration of the study

In patients who died from CHD, fatty deposits in diseased arteries were found to contain high concentrations of trans fats

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

Evidence Against Health Claims

Proportion of saturated and trans fats in Western diets has decreased over the last 50 years, but incidence of CHD has risen

Counter: Increased carbohydrate intake may cause detrimental health effects associated with CHD (e.g. diabetes, obesity)
Counter: Incidence of CHD dependent on a myriad of factors besides dietary intake (e.g. exercise, access to health care, etc.)

64
Q

In what 5 ways do lipids and carbohydrates differ in function?

A 
Storage
Osmolarity
Digestion
ATP yield
Solubility
65
Q

In what way do lipids and carbohydrates differ in terms of storage?

A

lipids are more suitable for long-term energy storage

66
Q

In what way do lipids and carbohydrates differ in terms of osmolarity?

A

lipids have less of an effect on the osmotic pressure of a cell

67
Q

In what way do lipids and carbohydrates differ in terms of digestion?

A

carbohydrates are easier to digest and utilise

68
Q

In what way do lipids and carbohydrates differ in terms of ATP yield?

A

(lipids store more energy per gram

69
Q

In what way do lipids and carbohydrates differ in terms of solubility?

A

carbohydrates are easier to transport in the bloodstream

70
Q

What is the BMI?

A

The body mass index (BMI) provides a measure of relative mass based on the weight and height of the individual

71
Q

What is the formula for BM!?

A

BMI = mass in kg/ height in m ^2

72
Q

What do BMI values range from?

A

BMI ranges from underweight to obese, according to predetermined values based on an average adult population

73
Q

When are BMI’s not valid?

A

BMI values are not a valid indicator for pregnant women or professional athletes with atypical muscle / fat ratios

74
Q

Can BMI’s by themselves be used as a diagnostic tool?

A

BMI calculations should not be used as a diagnostic tool and should be used in conjunction with other measurements

75
Q

What is another way to calculate body mass index?

A

An alternative way of calculating body mass index is by using an alignment chart (nomogram

76
Q

What is a nonogram?

A

Nomograms display height and weight on perpendicular axes and then assign BMI values to colour coded regions

IB Biology (38 decks)

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