1. long term energy storage
Lipids
long term energy storage
concentrated energy

2. Lipids: Fats & Oils

3. Lipids Lipids are composed of C, H, O Insoluble in water
long hydrocarbon chains (H-C)
Insoluble in water
“Family groups”
Fats &Oils
Phospholipids
Steroids & Waxes
Do not form polymers
big molecules made of smaller subunits
not a continuing chain
Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties

4. Functions of Lipids
Structure: Phospholipids are a main component of cell membranes
Hormonal signaling: Steroids are involved in hormonal signaling (e.g. estrogen, progesterone, testosterone)
Insulation: Fats in animals can serve as heat insulators while sphingolipids in the myelin sheath (of neurons) can serve as electrical insulators
Protection: Triglycerides may form a tissue layer around many key internal organs and provide protection against physical injury
Storage of energy: Triglycerides can be used as a long-term energy storage source
What happens when you add oil to water
Why is there a lot of energy stored in fats?
• big molecule
• lots of bonds of stored energy
So why are we attracted to eating fat?
Think about our ancestors on the Serengeti Plain & during the Ice Age. Was eating fat an advantage?
Lipids are normally used for long-term energy storage whereas carbohydrates are used for short-term energy storage
The lipids that are used are fats. They are stored in specialized groups of cells called adipose tissue. Adipose tissue is located immediately beneath the skin and also around some organs including the kidneys.

5. Fats & Oils Structure: glycerol (3C alcohol) + 3 fatty acids
fatty acid = long HC “tail” with carboxyl (COOH) group “head”
Look at structure… What makes them hydrophobic?
Note functional group = carboxyl
condensation

6. Building Fats & Oils Triacylglycerol (Triglyceride)**
3 fatty acids linked to glycerol
ester linkage = between OH & COOH
hydroxyl
carboxyl
BIG FAT molecule!!

7. Condensation Condensation enzyme enzyme enzyme H2O H2O H2O H2O
Pulling the water out to free up the bond
enzyme
H2O
enzyme
H2O

8. Saturated fats All Single Bonds No C=C double bonds
(saturated with single
bonds)
No C=C double bonds
long, straight chain
most animal fats
solid at room temp.
contributes to cardiovascular disease (atherosclerosis) = plaque deposits
Mostly animal fats

9. Unsaturated fats C=C double bonds in the fatty acids plant & fish fats
vegetable oils
liquid at room temperature
the kinks made by double bonded C prevent the molecules from packing tightly together.
Mostly plant lipids
Think about “natural” peanut butter:
Lots of unsaturated fats Oil separates out
Companies want to make their product easier to use:
Stop the oil from separating Keep oil solid at room temp.
Hydrogenate it = chemically alter to saturate it
Affect nutrition?

10. Saturated vs. unsaturated

11. Saturated, monounsaturated or polyunsaturated?
2.3.2 Fatty acids can be saturated, monounsaturated or polyunsaturated.
Saturated, monounsaturated or polyunsaturated?
Q1 Oleic Acid
Q2 Caproic Acid
Q3 α-Linolenic Acid

12. 2.3.2 Fatty acids can be saturated, monounsaturated or polyunsaturated.
Q1 Oleic Acid 1 double bond therefore monounsaturated
Q2 Caproic Acid no double bonds therefore saturated
Q3 α-Linolenic Acid 3 double bonds therefore polyunsaturated
n.b. the term saturated refers to whether more hydrogen can be added to the fatty acid. A double bond can be replaced if two hydrogen atoms are added. If there are no double bonds a fatty acid is said to be saturated as no more hydrogen atoms can be added.

13. Cis - isomers Trans - isomers
2.3.3 Unsaturated fatty acids can be cis or trans isomers.
Cis - isomers
Trans - isomers
Very common in nature
Rare in nature – usually artificially produced to produce solid fats, e.g. margarine from vegetable oils.
the hydrogen atoms are on the same side of the two carbon atoms
the hydrogen atoms are on the opposite side of the two carbon atoms
The double bond causes a bend in the fatty acid chain
The double bond does not causes a bend in the fatty acid chain
Therefore cis-isomers are only loosely packed
Trans-isomers can be closely packed
Triglycerides formed from cis-isomers have low melting points – they usually liquid at room temperature
Triglycerides formed from trans-isomers have high melting points – they usually solid at room temp.

14. ??? ??? 2.3.3 Unsaturated fatty acids can be cis or trans isomers.
Q1 trans or cis isomers?
???
???

15. 2.3.3 Unsaturated fatty acids can be cis or trans isomers.
Q1 trans or cis isomers?

16. Q2 trans or cis isomer of α-Linolenic Acid?
2.3.3 Unsaturated fatty acids can be cis or trans isomers.
Q2 trans or cis isomer of α-Linolenic Acid?

17. Q2 trans or cis isomer of α-Linolenic Acid?
2.3.3 Unsaturated fatty acids can be cis or trans isomers.
Q2 trans or cis isomer of α-Linolenic Acid?
All 3 double bonds are cis, each one causes a bend in the fatty acid chain.

18. Peanut-butter can separate!
Unsaturated
Saturated
Is this peanut butter made up of more saturated or unsaturated fats? How can you tell?

19. It’s just like a penguin…
Phospholipids
Structure:
glycerol + 2 fatty acids + PO4
PO4 = negatively charged
It’s just like a penguin…
A head at one end
& a tail at the other!

20. Phospholipids Hydrophobic or hydrophilic? fatty acid tails =
PO4 head =
split “personality”
hydrophobic
hydrophillic
“attracted to water”
Come here, No, go away!
interaction with H2O is complex & very important!
“repelled by water”

21. Phospholipids in water
Hydrophilic heads “attracted” to H2O
Hydrophobic tails “hide” from H2O
can self-assemble into “bubbles”
bubble = “micelle”
can also form a phospholipid bilayer
early evolutionary stage of cell?
water
bilayer
water

22. Why is this important? Phospholipids create a barrier in water
define outside vs. inside
they make cell membranes!
Tell them about soap!

23. Steroids Structure: 4 fused C rings + ??
different steroids created by attaching different functional groups to rings
different structure creates different function
examples: cholesterol, sex hormones
cholesterol

24. Cholesterol Important cell component animal cell membranes
precursor of all other steroids
including vertebrate sex hormones
high levels in blood may contribute to cardiovascular disease

25. Cholesterol Important component of cell membrane
helps keep cell membranes rigid.

26. From Cholesterol  Sex Hormones
What a big difference a few atoms can make!
Same C skeleton, different functional groups

27. Carbohydrates vs. Lipids for energy storage

28. Reasons for using lipids for long-term energy storage…
2.3.7 Lipids are more suitable for long-term energy storage in humans than carbohydrates.
Reasons for using lipids for long-term energy storage…
The amount of energy released in cell respiration per gram of lipids is more than double that for carbohydrates (and protein): 9 Cal/g v. 4 Cal/g
Lipids add 1/6 as much to body mass as carbohydrates: fats are stored as pure droplets whereas when 1g glycogen is stored it is associated with 2g of water. This is especially critical for active animals as energy stores have to be carried.

29. Why is glycogen is needed at all?
2.3.7 Lipids are more suitable for long-term energy storage in humans than carbohydrates.
Why is glycogen is needed at all?
This is because glycogen can be broken down to glucose rapidly and then transported easily by the blood to where it is needed
Fats in adipose tissue cannot be mobilized as rapidly
Glucose can be used either in anaerobic or aerobic cell respiration whereas fats and fatty acids can only be used in aerobic respiration

30. Wallet Bank You are paid in cash Spend it! easy to get to, An analogy:
2.3.7 Lipids are more suitable for long-term energy storage in humans than carbohydrates.
Glycogen is the medium-term energy storage molecule in animals. It is stored in the liver and muscles. The energy stored in glycogen is more readily available than the energy stored in fat.
Glucose in the bloodstream is for immediate use and will either be used in respiration to yield ATP or converted to glycogen or fat
Wallet
easy to get to,
would be too big if you put in all your money
An analogy:
Put it in your
(Glycogen)
You are
paid in cash
Deposit in the
(Glucose)
Bank
(Fat)
Can put lots of money here, more of a hassle to get it back out
Spend it!
(Respiration)

31. 2.3.6 Scientific evidence for health risks of trans fats and saturated fatty acids.
There have been many claims about the effects of different types of fat on human health. The main concern is coronary heart disease (CHD). In this disease the coronary arteries become partially blocked by fatty deposits, leading to blood clot formation and heart attacks.

32. 2.3.6 Scientific evidence for health risks of trans fats and saturated fatty acids.
A positive correlation has been found between saturated fatty acid intake and rates of CHD in many studies.
Correlation ≠ causation. Another factor, e.g. dietary fiber could be responsible.
There are populations that do not fit the correlation such as the Masai of Kenya. They have a diet that is rich in meat, fat, blood and milk. They therefore have a high consumption of saturated fats, yet CHD is almost unknown among Masai.
Diets rich in olive oil, which contains cis-monounsaturated fatty acids, are traditionally eaten in countries around the Mediterranean. The populations of these countries typically have low rates of CHD and it has been claimed that this is due to the intake of cis-monounsaturated fatty acids.
Genetic factors in these populations could be responsible.
There is also a positive correlation between amounts of trans-fat consumed and rates of CHD.
Other risk factors have been tested, to see if they can account for the correlation, but none did. Trans-fats therefore probably do cause CHD.
In patients who had died from CHD, fatty deposits in the diseased arteries have been found to contain high concentrations of trans-fats, which gives more evidence of a causal link.

33. 2.3.8 Evaluation of evidence and the methods used to obtain the evidence for health claims made about lipids.
Evidence for health claims comes from research. Some of this research is more scientifically valid than others.
Evaluation = Make an appraisal by weighing up the strengths and limitations
Key questions to consider for the strengths are:
Is there a correlation between intake of the lipid being investigated and rate of the disease or the health benefit?
If mean values are being compared how different are they? Has this difference been assessed statistically?
How widely spread is the data? This can be assessed by the spread of data points or the relative size of error bars. The more widely spread the data the smaller the significance can be placed on the correlation and/or the conclusion.
Key questions to consider for the limitations are:
Was the measure of the health a valid one? Cholesterol levels in blood are more informative than BMI
How large was the sample size?
Does the sample reflect population as a whole or just a particular sex, age, state of health, lifestyle or ethnicity?
Was the data gathered from human or animal trials? If only done of animals how applicable are the findings?
Were all the important control variables, e.g. level of activity, effectively controlled?
Were the levels and frequency of the lipids (or substance studied) intake realistic?
How rigorous were methods used to gather data? e.g. If only a survey was used how truthful were respondents?

34. Which health claims are valid?
2.3.8 Evaluation of evidence and the methods used to obtain the evidence for health claims made about lipids.
Which health claims are valid?

35. Let’s build some Lipids!