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Topic 2.3 Carbohydrates

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Topic 2.3 Carbohydrates & Lipids What are carbohydrates? Carbohydrates are biological molecules composed of carbon, hydrogen and oxygen. They are mainly used as a ... – PowerPoint PPT presentation

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Title: Topic 2.3 Carbohydrates


1
Topic 2.3 Carbohydrates Lipids
2
What are carbohydrates?
  • Carbohydrates are biological molecules composed
    of carbon, hydrogen and oxygen. They are mainly
    used as a source of energy for living things.
  • Animals consume carbohydrates, use them to fuel
    cellular respiration to produce ATP and can store
    a small amount of the ones they do not use.
  • Plants produce carbohydrates via photosynthesis,
    use them for cellular respiration to produce ATP
    and store the ones they do not use.

3
2.3 (U1) Monosaccharides are linked together by
condensation reactions to form disaccharides and
polysaccharide polymers.
  • Monosaccharides are single unit sugars. Common
    monosaccharides are glucose, fructose and
    galactose.

4
2.3 (U1) Monosaccharides are linked together by
condensation reactions to form disaccharides and
polysaccharide polymers.
  • Disaccharides are double unit sugars composed of
    two monosaccharides held together by an oxygen
    bond created during a process known as a
    condensation reaction.
  • Common disaccharides are maltose, sucrose and
    lactose.

5
2.3 (U1) Monosaccharides are linked together by
condensation reactions to form disaccharides and
polysaccharide polymers.
  • Polysaccharides are many monosaccharides bonded
    together and three examples are starch, glycogen
    and cellulose.

6
2.3 (A1) Structure and function of cellulose and
starch in plants and glycogen in humans.
  • See handout given in class for specific details
    on the function and structure of both
    polysaccharides.

7
2.3 (S1) Use of molecular visualization software
to compare cellulose, starch and glycogen.
  • You are responsible to complete an ICA using
    software known as JMol.
  • It will help you learn more about the molecular
    structure of polysaccharides.

8
Condensation reaction
  • A condensation reaction joins two molecules
    together to form a larger molecule and a water
    molecule is formed as a result.
  • A monosaccharides loses an OH from one end while
    the other monosaccharide loses an H which then
    combine to form a water molecule.
  • Condensation reactions are an anabolic process
    and energy in the form of ATP is used to build
    the polymers.

9
Formation of a disaccharide
10
Lipids
  • Although lipids are a very diverse group of
    carbon containing compounds, they are all
    insoluble in water.
  • One of the principal groups are known as
    triglycerides (i.e., fat in adipose tissue in
    humans and the oil in sunflower seeds).
  • Lipids can be categorized as fats, oils and
    waxes. Fats are solid at room temperature (20C)
    but liquid at body temp (37C). Oils are liquid
    at both temperatures.

11
2.3 (U4) Triglycerides are formed by condensation
from three fatty acids and one glycerol.
  • Triglycerides are formed by a condensation
    reaction that includes one glycerol molecule and
    three fatty acids.
  • Each fatty acid is bonded to the glycerol
    molecule in three condensation reactions
    therefore three water molecules are produced.
  • The bonds are known as ester bonds that form when
    a reaction occurs between the COOH groups of the
    fatty acids and the OH groups of the gylcerol
    molecule.

12
Formation of a triglyceride
13
Functions of Lipids
  • Energy Storage energy can be stored in the form
    of oils in plants and as fat in animals. The
    energy can be release through aerobic cell
    respiration.
  • Heat Insulation heat loss for animals is
    reduced by the fat layer located just below the
    skin.
  • Buoyancy due to the fact that lipids are less
    dense than water they help animals float.

14
2.3 (A3) Lipids are more suitable for long term
storage in humans than carbohydrates.
  • Organisms can store energy in the form of
    carbohydrates and/or lipids.
  • Living organisms tend to use carbohydrates as a
    short term energy storage while lipids are used
    as the long term energy storage.
  • Carbohydrates are stored as glycogen in the
    muscles (2by mass) and liver (up to 150g).
  • Lipids are stored as fats in adipose tissue
    directly under the dermis (on top of muscles) and
    also around various organs such as the kidneys.

15
2.3 (A3) Lipids are more suitable for long term
storage in humans than carbohydrates.
  • Lipid molecules contain 9 calories per gram
    whereas carbohydrate molecules only carry 4
    calories per gram.
  • This means that lipid stores are less dense (less
    body mass) for the same amount of energy from
    carbohydrates.
  • Stored lipids form pure droplets whereas
    carbohydrates are stored with water so lipids are
    6x more efficient than carbs in the amount of
    energy that can be stored per gram of body mass.

16
2.3 (A3) Lipids are more suitable for long term
storage in humans than carbohydrates.
  • Stored lipids can also act as insulators.
    Carbohydrates do not have a secondary role.
  • Living organisms are able to digest carbohydrates
    easier and more efficiently than lipids which
    means that the energy stored in the molecule can
    be released faster. Consequently it makes carbs
    better for short term storage.
  • It is more difficult for lipids to be mobilized
    and used in cell respiration than carbs. They
    are non-polar and can only be used in aerobic
    respiration whereas carbohydrates are polar, can
    be transportted easily and can be used in both
    aerobic and anaerobic respiration.

17
2.3 (S2) Determination of body mass index by
calculation or use of a nomogram.
  • See handout given in class

18
2.3 (U2) Fatty acids can be saturated,
monosaturated or polyunsaturated.
  • We covered the structure of fatty acids in topic
    2.1 but lets do a quick review.
  • Fatty acids have a carbon chain with hydrogen
    atoms attached by single covalent bonds forming a
    hydrocarbon chain.
  • There is a carboxyl group attached at the end of
    the chain which is the acid component of the
    fatty acid.

19
Differences in Fatty Acids
  • Fatty acids differ in the number of carbon atoms
    in the hydrocarbon chain. Of the fatty acids
    used by living things, most have between 14 and
    20 carbon atoms in the chain.
  • Another difference is the bonds that form between
    the carbon atoms. Some are single bonds between
    the carbon atoms leaving room for 2 hydrogen
    atoms to bond to the carbon while others are
    double bonds leaving less room for hydrogen
    atoms.

20
Saturated Fatty Acids
  • Saturated fatty acids are composed of all single
    covalent bonds between the carbon atoms.
  • This means each carbon atom can bond to two other
    carbons plus two hydrogen atoms.
  • They are considered saturated fatty acids because
    they hold the maximum amount of hydrogen atoms
    possible.

21
Unsaturated Fatty Acids
  • Unsaturated fatty acids contain one or more
    double bonds between carbon atoms in the
    hydrocarbon chain. This means they contain less
    hydrogen than they could hold so they are
    considered unsaturated.

22
Unsaturated Fatty Acids
  • Monounsaturated fatty acid
  • Polyunsaturated fatty acid
  • Fatty acids that contain one double bond between
    carbon atoms.
  • Fatty acids that contain two or more double bonds
    between carbon atoms.

23
2.3 (U3) Unsaturated fatty acids can be cis or
trans isomers
  • Unsaturated fatty acids are also characterized by
    the location of the hydrogen in relation to the
    double bonded carbon atoms.
  • The hydrogen atoms can be located on the same
    side of the two carbon atoms or they can be be
    located on the opposite side.
  • The location of the hydrogen atoms change the
    shape and the characteristics of the unsaturated
    fatty acid.

24
Cis-fatty Acids
  • In cis-fatty acids the hydrogen atoms are on the
    same side of the double bonded carbon atoms.
    This results in a bend in the fatty acid chain
    which does not allow them to pack tightly
    together. This lowers the melting point of these
    fats and they are normally liquid at room
    temperature.

25
Trans-fatty Acids
  • Trans-fatty acids are artificially produced
    through a process known as hydrogenation.
    Hydrogen is added to unsaturated fats to
    partially saturate them to produce solid fats
    such as shortening and margarine.
  • The hydrogen atoms are bonded on either side of
    the double bonds resulting in a straight
    hydrocarbon chain. They can pack tightly
    together and this increases their melting point
    and they are solid at room temperature.

26
2.3 (A2) Scientific evidence for health risks of
trans fats and saturated fatty acids.
  • See ICA completed in class

27
2.3 (A4) Evaluation of evidence and the methods
used to obtain the evidence for health claims
made about lipids.
  • See ICA completed in class.
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