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IB Biology > Molecular Biology - 2.3 Carbohydrates and Lipids > Flashcards

Molecular Biology - 2.3 Carbohydrates and Lipids Flashcards

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1
Q

Basic facts of carbohydrates

A
  • Carbohydrates are made of carbon, hydrogen and oxygen ((CH2O)n) and are used to store energy

Three groups of carbohydrates:

  • monosaccharides
  • disaccharides
  • polysaccharides
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2
Q

Monosaccharides (one sugar)

A

Understanding:
Monosaccharides monomers are linked together by condensation reactions to form disaccharides and polysaccharides polymers

Main function = ENERGY SOURCE

Are monomers (single sugar units) also known as reducing sugars and are small enough to pass across the cell membrane 
These monosaccharides may be linked together via condensation reactions

Eg

  1. Glucose (C6H12O6) - made in plants by photosynthesis and used in respiration (in the form D & L Glucose - L is not used by living things)
  2. Fructose (C6H12O6) - made by plants found in fruits and honey
  3. Galacatose (C6H12O6) - produced from the breakdown of lactose
  4. Ribose (C5H10O5) - component of RNA nucleic acid
  • MUST LEARN: formula and structure of Glucose and Ribose

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

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

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3
Q

D and L glucose - Information

A

Glucose is made in the form D & L Glucose:

  • L is not used by living things (not metabolised by them)
  • D glucose comes in 2 forms: alpha and beta
    - Alpha D glucose = starch and glycogen polymers
    - Beta D glucose = cellulose polymer

DIFFERENCE = placement of the hydroxide (on beta it moves so it is closer to the O)

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4
Q

Disaccharides (2 sugars)

A
  • they are produced by combining monosaccharides
  • Disaccharides (two sugar units) are small enough to be soluble in water and commonly function as a TRANSPORT FORM
  1. Sucrose (glucose and frutose)
    Table sugar - it is formed by a condensation reaction in plants
  2. Lactose (galactose and glucose)
    Milk sugar - milk lactose is broken down by the enzyme lactase (in most mammals the production of lactase gradually decreases with maturity - not all have the gene for lifelong lactase production)
  3. Maltose (glucose and glucose)
    Malt sugar - it is the disaccharide produced when the amylase enzyme breaks down the starch polymer. It can be found in germinating seeds
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5
Q

Condensation reactions

A
  • Joining together monosaccharides

Glucose units are joined by removing a molecule of water to form the glycosidic bond

If 2 glucose molecules are joined a disaccharide is formed. If more, then a polysaccharide is formed

Equation:
glucose + glucose -> disaccharide + water

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6
Q

Hydrolysis reactions

A

When a disaccharide is split a water molecule provides the hydrogen and hydroxyl group to break the glycosidic bond

Equation:
Disaccharide + water -> monosaccharide + monosaccharide

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6
Q

Hydrolysis reactions

A

When a disaccharide is split a water molecule provides the hydrogen and hydroxyl group to break the glycosidic bond

Equation:
Disaccharide + water -> monosaccharide + monosaccharide

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7
Q

Disaccharide examples

A
  1. sucrose
  2. lactose
  3. maltose
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8
Q

Polysaccharides (many sugars)

A

Application:
Structure and function of cellulose and starch in plants and glycogen in humans

Polysaccharides are carbohydrate polymers comprised of many (hundreds to thousands) monosaccharide monomers. The type of polymer formed depends on the monosaccharide subunits involved and the bonding arrangement between them

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

Skill:
Use of molecular visualisation software to compare cellulose, starch and glycogen

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9
Q

Polysaccharides - STARCH

A

Long branched (amylopectin) and unbranched (amylose) chains of alpha D glucose

(the way that plants store their carbohydrates - more vertebrates have digestive enzymes that can break starch down)

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10
Q

Polysaccharides - GLYCOGEN

A

Long branched chains of alpha D glucose + (energy storage = animals)

(the way that animals store glucose in muscles and liver - glycogen is insoluble so large amounts can be stored)

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11
Q

Polysaccharides - CELLULOSE

A

Unbranched polymer of beta D glucose + (cell wall structure = plants)

(makes up the walls of plants - humans and most vertebrates are unable to digest cellulose due to the enzymes need to breakdown the beta acetyl linkages that are not found in vertebrates - some bacteria contain these enzymes and are therefore able to breakdown cellulose)

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12
Q

Amylose vs Amylopectin (starch)

A

Amylose

  • helical chains (alpha glucose)
  • energy storage (plants)

Amylopectin

  • Branched chains (alpha glucose)
  • energy storage (plants)
  • has branches approx. every 20 subunits - the branch points have C1-C6 links, non-branched areas have C1-C4 links
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13
Q

Lipids

(you must be able to recognise them!!

A

They are: carbon compounds made by living organisms that are mostly or entirely hydrophobic

  • fats and waxes are solid at room temp + oil is liquid at room temp
  • They are relatively insoluble in water
  • Lipids are important energy storage compounds (fats have the greatest energy per gran of all food types - excess proteins and carbohydrates can be converted to fats for storage)

Main 3 lipid types!!!:

  1. triglycerides
  2. phospholipids
  3. steroids
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14
Q

Triglycerides (lipids)

A

Most common lipid - made of 3 fatty acids joined to a glycerol

Understanding:
Triglycerides are formed by condensation from three fatty acids (2 saturated and 1 unsaturated) and one glycerol

Saturated - all of the covalent bonds are single
Unsaturated - there is one or more double covalent bonds (unsaturated fats tend to be from plants)

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

  • The hydroxyl groups of glycerol combine with the carboxyl groups of the fatty acids to form an ester linkage
  • This condensation reaction results in the formation of three molecules of water
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15
Q

Fatty acids

A

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

Understanding:
Fatty acids can be saturated, monounsaturated or polysaturated

Saturated - all of the covalent bonds are single

Unsaturated - there is one or more double covalent bonds (unsaturated fats tend to be from plants)

mono-saturated - only one double bond

poly-saturated - two or more double bonds

Fatty acids may differ in the length of the hydrocarbon chain (typically 4 – 24 carbons)

(refer to omega 3 vs omega 6 diagrams + info. to see the differences in the position of the double bond.)

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16
Q

Cis + trans unsaturated fatty acids

A

Cis:
cis unsaturated fatty acids hydrogen atoms are bound to the same side of the double bond
(eg. vegetable oils - altered to become: margarine etc)
The hydrogen atoms attached to the carbon double bond are on the same side

Trans:
trans unsaturated fats are bonded to opposite sides (are uncommon in nature but are commonly produced industrially, commonly associated with risk of coronary heart disease)
The hydrogen atoms attached to the carbon double bond are on different sides

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

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

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17
Q

Phospholipids (lipids)

A
  • makes up cell membranes

They are a: important structural component in cell membranes - they are similar to triglycerides but have only 2 fatty acids linked to glycerol with a phosphate group rather than the 3rd fatty acid

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18
Q

Steroids (lipids)

A

All have a similar structure of 17 carbon atoms in 4 rings

Eg.

  1. Cholesterol
  2. Testosterone
  3. Cortisol
  4. Vitamin D2

Notes: one of the rings in vitamin D is broken

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19
Q

Energy storage

A

Application = Lipids are more suitable for long-term energy storage in humans than carbohydrates

Lipids and carbohydrates are used by living organisms as stores of energy:
1g of glycogen is associated with 2g of water: 100g carbs = 1760 kJ, 100g proteins = 1510 kJ, 100g lipid = 4000kJ

==> energy per gram of lipids is double the amount released from a gram of carbohydrates (lipids can be stored and utilised without water so are 6x MORE EFFICIENT)

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20
Q

Body Mass Index (BMI)

A

Skill:
Determination of BMI by calculation or use of nomogram

it is the measure of relative size based on the mass (kg) and height (m).

BMI is best proxy for body fat percentage - used as a diagnostic tool (but has many limitations due to age, gender, body shape, muscle mass, etc)

Bod Mass Index = Weight (kg) / Height^2 (m) Final units = kg/m^2

underweight - 18.5 and under
normal weight - 18.5-24.9
overweight - 25-29
obese - 30+

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21
Q

Health claims

A

Application:
Scientific evidence for health risks of trans fats and saturated fatty acids

  • Increase LDL (low density lipoprotein) levels
  • raising blood cholesterol

The mix of fats in the diet influences the level of cholesterol in the bloodstream
Saturated fats and trans fats raise blood cholesterol levels, while (cis) unsaturated fats lower blood cholesterol levels

Application:
Evaluation of evidence and the methods used to obtains the evidence for health claims made about lipids

  • fatty deposits in discussed arteries contain high concentration of trans fats
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22
Q

proteins

A

Improtance:

  1. Structure - forming the structural components eg. keratin
  2. Regulatory - Regulating cellular function - hormones eg. insulin
  3. Contractile - forming contractile elements in muscles eg. actin
  4. Immunological - Functioning to combat invading microbes (antibodies, antitoxins)
  5. Transport - Acting as carrier molecules eg. carry O (haemoglobin)
  6. Catalytic - Catalysing all the biochemical relations in the body eg. amylase
  7. Sensory - Components of the nervous system including receptors and neurotransmitters

Proteins are polymers - ie. large molecules made up of repeated units (unites/monomers are amino acids)

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23
Q

Amino acid structure

A

central carbon atom with an amine (NH2), a carboxyl group (COOH) and an ‘R’ group - each amino acid has a different ‘R’ group

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24
Q

Essential amino acids

A

The 9 amino acids that cannot be made by the body

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25
Q

Amino acid infromation

A

Understanding:
There are 20 different amino acids in polypeptides synthesized on ribosomes
(eg. Serine, Lysine, Proline, Tyrosine, Cysteine)

Amino acids can be found in all living things and are coded for by the DNA sequence in the ribosomes
If many amino acids are joined, a polypeptide is formed.

(there are 2 extra amino acids found in only a few polypeptides in only a few organisms:

  1. Selenocysteine
  2. Pyrrolysine)
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26
Q

Polypeptides

A

The unbranched chain of amino acids - a protein consists of a single functional polypeptide or more usually several polypeptides joined together

If many amino acids are joined, a polypeptide is formed.

Understanding:
Amino acids are linked together by condensation to form polypeptides

Understanding #2:
The amino acid sequence of polypeptides is coded for by genes
(the sequence of the bases determines the sequence of the amino acids. Three bases (a triplet code for one amino acid))

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27
Q

Amino acids in condensation reactions

A

Amino acids are joined by removing a molecule of water - ie a condensation reaction - therefore forming a peptide bond. If two amino acids are joined, a dipeptide is formed.

Equation:
Amino acid + amino acid -> dipeptide + water

Understanding:
Amino acids are linked together by condensation to form polypeptides

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28
Q

Amino acids in hydrolysis reactions

A

When a dipeptide is split a water molecule provides the hydrogen and hydroxyl group to break the peptide bond

Equation:
Dipeptide + water -> amino acid + amino acid

Understandings:
Amino acids can be linked together in any sequence giving a huge range od possible polypeptides

Understandings:
The amino acid sequence determines the 3D (three-dimensional) conformation of a protein.

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29
Q

Protein

A

A protein is a functional unit made up of more than one polypeptide chains

Understanding:
A protein may consist of a single polypeptide or more than one polypeptide linked together

Polar = a protein may be polar (eg. contain hydrophilic amino acids), these amino acids on the surface can make them water soluble (eg. some hormones) 
Non-polar = a protein may be non-polar (eg. contain hydrophobic amino acids), these amino acids can make them (proteins) insoluble (eg. lipase enzyme)

^ these 2 properties allow for diff. materials to pass through the protein in cell membranes and the specificity of active sites in enzymes

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30
Q

Protein structure

A

Protein conformation:
The conformation of a protein is it’s three dimensional (3D) structure with is vital to the function of the protein - modification of the proteins occour in the golgi.

Proteins come into two main structural forms:

  1. fibrous proteins
  2. globular proteins

Understanding:
Living organisms synthesize many different proteins with a wide range of functions

Promary protein structure:
- is sequence of a chain of amino acids

Tertiary protein structure:
- occurs when certain attractions are present between alpha helices and pleated sheets

Secondary protein structure:
- occurs when the sequence of amino acids are linked by hydrogen bonds

Quaternary protein structure:
- Is a protein consisting of more than one amino acid chain

31
Q

Fibrous proteins (characteristics)

A
  • Have a structural role (eg. collagen in tissue and bones)
  • Water insoluble
  • though and stretchy
  • composed of long chains of polypeptides
32
Q

Globular proteins (characteristics)

A
  • catalytic (ie. enzymbes), hormones (eg. insulin), transport (eg. haemoglobin) and immunological (eg. antibodies)
  • water soluble
  • Polypeptide chains folded into specific shape
33
Q

Application for/of Proteins

A

Application:

Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk as examples of the range of protein functions

34
Q

Spider Silk

A

Role = structural

Mechanism of action = used to make webs to catch prey. Has a very high tensile strength so difficult to break.

35
Q

Insulin

A

Role = Regulatory
Mechanism of action = Insulin is a hormone that lower blood sugar levels by binding to body cells so that they absorb glucose from the blood.

36
Q

Collagen

A

Role = Structural
Mechanism of action = Has three polypeptide wound together like a rope which prevents tearing in skin, bones, tendons and ligaments.

37
Q

Rhodopsin

A

Role = Sensory
Mehanism of action = A pigment in the retinal cells of the eyes that make the cells light sensitive. Cell is stimulated and sends a nerve impulse to the brain

38
Q

Immunoglobulins

A

Role = Immunological

Muchanism of actions: Antibodies that bond to specific antigens on pathogens owing to specific surface proteins

39
Q

Rubisco

A

Role = Catalyst
Mechanism of actions: Rubisco is an enzyme that catalyses the photosynthetic creation that fixes CO2 from the atmosphere to make sugars

40
Q

Proteomes:

A

Understandings:
Every individual has a unique proteome

A proteome is all of the proteins produced by the cell or an organism

  • the proteins that different cells make maybe different depending on the cells function
  • proteins from cells can be extracted, analysised and identified. the proteome of each individual will be unique (as DNA is unique and DNA codes for proteins)
41
Q

Denaturation of Proteins

A

Understandings:
Denaturation of proteins by heat or by deviation of pH from the optimum

  • this change is normally permanent (due to the 3D structure changing)

Can be caused by: Heat, radiation, detergents, solvents, have metals, pH and other chemicals.

  • the bonds that maintain the secondary and tertiary levels are altered even though the sequence of amino acids is the same https://www.khanacademy.org/science/biology/macromolecules/proteins-and-amino-acids/a/orders-of-protein-structure
42
Q

primary structure of proteins

A

primary structure, is simply the sequence of amino acids in a polypeptide chain. Each chain has its own set of amino acids, assembled in a particular order.

43
Q

secondary structure of proteins

A

The next level of protein structure, secondary structure, refers to local folded structures that form within a polypeptide due to interactions between atoms of the backbone.

Both structures are held in shape by hydrogen bonds, which form between the carbonyl O of one amino acid and the amino H of another.

44
Q

tertiary structure of proteins

A

The overall three-dimensional structure of a polypeptide is called its tertiary structure. The tertiary structure is primarily due to interactions between the R groups of the amino acids that make up the protein.

Also important to tertiary structure are hydrophobic interactions, in which amino acids with nonpolar, hydrophobic R groups cluster together on the inside of the protein, leaving hydrophilic amino acids on the outside to interact with surrounding water molecules.

+ Disulfide bonds

45
Q

How heat denatures proteins

A

Heat causes vibrations within the protein molecules that break the intramolecular bonds and causes the conformation to change

(eg. heating egg protein changes alters to dissolve albumin into an insoluble form. Causing the egg white to become a white solid)

46
Q

How pH denatures proteins

A

pH also causes the intramolecular bonds to break and causes the conformation to change

47
Q

✨Water✨

A

Water is the medium of life

Understanding:
Water malecules are polar and hydrogenbonds form between them.

Water is a polar molecule

48
Q

Polar and non-polar molecules

A

Polar molecules and ions dissolve together - stick to one another (eg. water and sugar)

Polar and non-polar molecules do not dissolve together - do not stick to one another (eg. water and oil)

49
Q

Hydrophilic

A

(water attracting)

they stick to the water molecule. Ionic and polar compounds are hydrophilic and dissolve in water because they molecules are more attracted to water than they are to each other (eg. salt)

Understandings:
Substances can be hydrophilic or hydrophoblic

50
Q

Hydrophobic

A

(water “repelling”)

They do not dissolved in water because the molecules are more attracted to each other than they are to water (eg. oil)

Understandings:
Substances can be hydrophilic or hydrophoblic

51
Q

Blood Transport and Solubility

A

Blood transports are a varity of substances. Most are in the blood plasma - the mode of transport depends on its solubility in water

52
Q

Modes of transport for ____ in relation to their solubility in water

= MTRSW

A

Application:
Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in relation to their solubility in water.

53
Q

Why is water the universal solvent?

A

Because it dissolves almost all chemicals

54
Q

Sodium chloride (salt) (MTRSW)

A

Substance = Sodium chloride (salt)

Solubility = soluble in water as polar Na and Cl ions

Method of Transport in Blood = Dissolved in plasma

55
Q

Glucose and Amino acids (MTRSW)

A

Substance = Glucose and Amino acids

Solubility = polar substances

Method of Transport in Blood = Dissolved in plasma

56
Q

Oxygen (MTRSW)

A

Substance = Oxygen

Solubility = non-polar, doesn’t dissolve well in plasma

Method of Transport in Blood = Carried by red blood cells attached to haemoglobin

57
Q

Cholesterol and fats (MTRSW)

A

Substance = Cholesterol and fats

Solubility = non-polar and insoluble in H2O

Method of Transport in Blood = Carried by small droplets called lipoproteins

58
Q

Properties of water

A

Understanding:
Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water

NEED TO KNOW:

  1. Adhesion
  2. Cohesive
  3. Solvent
  4. Thermal properties

(EXTRA: density, viscosity, transparency, sound transmission - won’t be marked for!!!)

59
Q

Adhesion - property of water

A

Explaination:
Water molecules will form intermolecular association with polar and charged molecules. Attraction to charged or polar surfaces allows water to flow in opposition of gravitational forces (capillary action)

Significance for life:
This capillary action is necessary to allow water to be transported up plant stems via a transpiration stream

-> also relates to: waters role as a transport medium (due to it being a universal solvent)

60
Q

capillary action

A

Attraction to charged or polar surfaces allows water to flow in opposition of gravitational forces

It is defined as the movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension - google definition

61
Q

Cohesive - property of water

A

Explanation:
Water molecules stick to each other because of the hydrogen bonds that form between molecules. These bonds allow water to resist low levels of external force (surface tension)

Significance for life:
The high surface tension of water makes it sufficiently dense for certain smaller organisms to move along its surface

-> also relates to: waters role as a transport medium (due to it being a universal solvent)

62
Q

surface tension

A

These bonds (hydrogen bonds) allow water to resist low levels of external force

“The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules.” - google definition

63
Q

Solvent - property of water

A

Explanation:
Many substances dissolve in water due to its polarity, including those of ions or polar molecules

Significance for life:
Medium for chemical relations. Transports substances eg. CO2, O, salts, sugars, etc.

64
Q

Thermal properties - property of water

A

Explanation:

Due to hydrogen bonding water has high mp and bp - high latent heat of vaporisation and high specific heat capacity

65
Q

Thermal properties - property of water

A

Explanation:
Due to hydrogen bonding water has high mp and bp - high latent heat of vaporisation and high specific heat capacity

Significance for life:
Water is a liquid in most Earth environments. Water remains at a relatively stable temperature Aquatic environment temps don’t change much. Heat can be lost my EVAPORATION (ie. hence an effective coolant when water evaporates as sweat)

66
Q

Thermal properties of water and methane

A

Methane = similar mass/size to H2O

Methane is non-polar and it has a similar molecular mass to water but has weak intermolecular forces (rather than hydrogen bonds)

67
Q

Specific heat capacity

A

Amount of heat absorbed per gram when temperature increased by 1°C (J/g/ °C)

Water = 4.2
Methane = 2.2

Application:
comparison of the thermal properties of water with those of methane

68
Q

Latent heat vaporisation

A

The amount of energy needed to convery 1g of liquid to a gas (J/g)

Water = 2257
Methane = 760

Application:
comparison of the thermal properties of water with those of methane

69
Q

!!!!
Application:
Use of water as a coolant (due tot he thermal properties of H2O)

(4.5 points)

A

mechanism of the evaporation of water as sweat employed by humans as a means of cooling down.

  1. The change of water from liquid to water (evaporation) require energy
  2. the energy comes from the surface of the skin with it is hot, when swat evaporates skin is cooled
  3. Water has a high specific heat capacity, so it absorbs a lot of thermal energy before it evaporates
  4. Therefore, water functions as a highly effective coolant, making it the principal component of sweat
70
Q

Habitat (water)

A

Water can maintain a stable temp (eg. oceans and lakes do not change temperature dramatically) due to the specific heat capacity of water (ie. NOT endangering aquatic life)

DO NOT TALK ABOUT: density, visability, etc.

71
Q

LDL

A

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

  • Saturated fats increase LDL levels within the body, raising blood cholesterol levels
  • Trans fats increase LDL levels and decrease HDL levels within the body, significantly raising blood cholesterol levels
72
Q

HDL

A

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

  • Trans fats increase LDL levels and decrease HDL levels within the body, significantly raising blood cholesterol levels
  • Unsaturated (cis) fats increase HDL levels within the body, lowering blood cholesterol levels
73
Q

Health Risks of High Cholesterol

A

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

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

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

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

74
Q

The differences between Lipids and carbohydrates as they both function as energy storage molecules in humans

A

Storage (lipids are more suitable for long-term energy storage)
Osmolality (lipids have less of an effect on the osmotic pressure of a cell)
Digestion (carbohydrates are easier to digest and utilise)
ATP Yield (lipids store more energy per gram)
Solubility (carbohydrates are easier to transport in the bloodstream)

Mnemonic: SODAS

75
Q

Storing energy as carbohydrates

A

is similar to keeping the cash in a wallet

  • It is easier to carry around (monosaccharides and disaccharides are water soluble)
  • It is readily accessible (carbohydrates are easier to digest)
  • You cannot carry as much (carbohydrates store less energy per gram)
76
Q

Storing energy as lipids

A

(i.e. triglycerides) is similar to keeping the cash in a safe

  • It is not viable to carry around (triglycerides are insoluble in water)
  • It is harder to access (triglycerides cannot be easily digested)
  • You can keep more cash in it (triglycerides store more energy per gram)

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