Lipids Flashcards
What % of body comprised of fat?
16%.
NB Fats form part of every body cell.
Lipid content can = 70% in severe obesity.
Proteins = 17%
What did Ancel Keys proclaim?
Eating a high saturated fat diet would increase serum cholesterol and consequently lead to heart disease.
What did the Amerian Heart Association recommend post Ancel Keys research?
- Diet low in total fat, especially saturated fat and cholesterol,
- high in carbohydrates from grains
- substituting animal fats for seed oils.
This also resulted in the introduction of statins — one of the most profitable pharmaceutical industry drugs.
What is a cytokine?
Cell-signalling proteins
What lipid found in nerve cell membranes?
Sphingolipids. Found in nerve cell membranes eg myelin.
Functions of white adipose tissue (WAT)?
Complex, metabolically-active endocrine tissue.
- Secretion of hormones, growth factors, enzymes and cytokines and insulin.
- Protection of organ
- Insulation against temperature extremes
- Form of energy storage
EIGHT types of lipids in the body
- Individual fatty acids.
- Triglycerides.
- Phospholipids (in every cell membrane).
- Cholesterol and steroid-based compounds eg oestrogen.
- Sphingolipids.
- Glycolipids — involved in cell identity (like a cell ‘passport’).
- Cerebrosides - Glycosphingolipids found in brain
- Fat-soluble vits — A, D, E, K
Glycolipids?
Involved in cell identity (like a cell ‘passport’).
Cerebrosides?
Glycosphingolipids found in the brain.
FOUR functions of lipids?
- Energy (ATP) production .
- Energy storage — fats are a more efficient form of storing energy reserves than carbs or proteins.
- Cell membrane structure — phospholipids and cholesterol stabilise cell membranes, while allowing a degree of fluidity which is crucial to the function of every cell.
- Thermal insulation in subcutaneous tissue and protection around organs.
- Hormones — progestogens, androgens, glucocorticoids, mineralocorticoids and oestrogens are derived from cholesterol.
- Formation of eicosanoids — signalling molecules involved in a range of processes such as blood coagulation and inflammation.
- Growth and development — brain rich in AA and DHA arachidonic acid (AA) and docosahexaenoic acid (DHA).
- Constituents of nervous tissue structure (sphingomyelin).
- Aid to cell-signalling processes.
- Absorption of fat-soluble vitamins.
What are eicosanoids?
Signalling molecules involved in range of processes such as blood coagulation and inflammation (require lipids).
Too much omega 3?
Cells become too fluid
Chemical structure of fatty acids?
Fatty acids are a type of lipid.Hydrocarbon chains with:
1. an acid group (alpha or carboxylic (-COOH) at one end
2. methyl group (omega) at the other (-CH3)
end
Chemical structure of the FOUR fatty acid types?
- Short Chain Fatty Acids: up to 5 Cs
- MCFA: 6-12
- Long CFA: 13-22
- Very LCFA: >22
Function of medium-chain fatty acids (MCT)?
Travel directly to liver (as do SCFAs) where used to create:
- energy
- ketones.
Can be used as a source of energy before exercise (eg x1 tbsp).
6–12 Cs
What are long and very long chain fatty acids used for?
Build cell membranes.
How are SCFAs produced?
Dietary fibre is fermented in the colon
Name three SCFAs
Most common:
1. Acetate
2. Propionate
3. Butyrate
Importance of butryate?
- SCFA.
- Esp important for colon health because = primary energy source for colonocytes.
- Supports intestinal tight junctions.
- SCFAs are speculated to have a role in microbiota-gut-brain axis crosstalk.
- Butyrate thought to have anti-inflammatory effect on colon.
What one determining factor makes a fatty acid vulnerable?
Number of double carbon bonds.
More double bonds, less stable it is.
Increases susceptibility to oxidation.
What are the three types of fatty acid?
- Saturated: solid
- Unsaturated: liquid, slightly kinky
a)Monounsat’
b) Polyunsat
Saturated fatty acid structure?
- No double carbon bonds (C-C).
- All carbons are saturated with hydrogen bonds.
- Solid at room temp.
Unsaturated fatty acid structure?
- One or more double bonds betewwen carbons
- Liquid at room temperature.
- Slightly kinky - more kinky, easier it is for oxgyengation (bad) to happen.
Mono unsaturated fatty acid structure?
One double bond
Polyunsaturated fatty acid structure?
Several double bonds.
What is an unatural trans fatty acid?
Produced by:
1. high temperatures and
2. hydrogenation ie adding hydrogen atoms which solidifies unsaturated fat.
What is hydrogenaton?
Additon of hydrogen to solidfy an unsaturated fat
Where are unatural trans fats found?
- Margarine
- Processed foods
- Refined vegetable oils
THREE disbenefits of processed trans fats in the body ?
- Stiffens cell membranes, making them prone to oxidation.
- This also alters their protective action and permeability, impeding normal cell function.
- Alters blood triglyceride and cholesterol profile
- Linked to increased risk of CVD, insulin resistance and cancer.
THREE differences between CIS and TRANS fats
Both unsaturated fats.
- Cis fatty acid is bent, whereas trans fatty acid is more linear.
- Cis and trans fats have different properties:
- CIS: H atoms on same side of double bond.
- Trans: H atoms on separate sides of the double bond. - Cis fats make cell membranes more flexibile while trans fats stiffen cell membranes and are prone to oxidative damage making them leaky.
NB Trans fats = unsaturated but behave like saturated fats because of unkinked shape.”
Chat:
Cis and trans fats are types of unsaturated fats that differ in the configuration of their hydrogen atoms around the double bonds in the fatty acid chain.
-
Cis Fats:
- Structure: In cis fats, the hydrogen atoms attached to the carbon atoms in the double bond are on the same side. This causes the fatty acid chain to bend or kink.
- Properties: Because of the kink in their structure, cis fats are typically liquid at room temperature. They are found naturally in various foods, especially in plant oils and fatty fish.
- Health Effects: Cis fats are generally considered healthier than trans fats. Omega-3 and omega-6 fatty acids, which are essential for human health, are examples of cis fats.
-
Trans Fats:
- Structure: In trans fats, the hydrogen atoms are on opposite sides of the double bond, making the fatty acid chain more linear.
- Properties: This linear structure allows trans fats to pack more tightly and be solid at room temperature. Trans fats are rare in nature and are mainly found in partially hydrogenated oils used in processed foods to improve shelf life and stability.
- Health Effects: Trans fats are associated with numerous health risks, including increased LDL cholesterol (bad cholesterol), decreased HDL cholesterol (good cholesterol), and a higher risk of heart disease, stroke, and type 2 diabetes.
The key difference lies in their molecular structure, which significantly impacts their physical properties and health effects. While cis fats are generally beneficial or neutral, trans fats are detrimental to health and are best minimized in the diet.
Conjugated means what?
Stabilised.
Benefits of conjugated linoleic acid (CLA)?
Natural trans fat found in grass-fed meat and dairy products. Helps increase lean muscle mass and decrease body fat.
Most common form of dietary fat?
Triglycerides
Also referred to as triacylglycerols (TAGs).
Major form of how the body stores fat.
Chemical structure of triglycerides?
- Lpid molecules made up of:
- one unit of glycerol
- three fatty acids. - Three fatty acids can differ in length (number of carbon atoms) and degree of saturation (number of hydrogen molecules attached).
High triglycerides in blood lead to which pathologies?
- Atherosclerosis and then…
- Heart disease
- Stroke.
When does the body synthesise triglycerides?
Whenever caloric intake exceeds energy requirements.
Lipogenesis?
Excess dietary energy converted to triglycerides and taken up by adipose tissue.
Acetyl-CoA (via glycolysis) forms palmitic acid (C16).
Three fatty acids bound to glycerol and stored as triglycerides.
Adipocytes are supplied by an extensive network of blood vessels. Acquire triglycerides from circulating lipoproteins, chylomicrons and very low density lipoproteins.
Chylomicron?
Carries tryglycerides from intestines to liver, skeletal muscle and adipose tissue
Where does lipogenesis take place?
- Adipose tissue
- Liver.
- Kidneys
- Lactating mammary glands
How do we get acetyl-CoA?
Glucose converts to 2 pyruvate then acetyl-CoA
What is lipolysis?
When dietary energy is limited fatty acids from triglycerides mobilised from adipocytes into circulation.
Triglycerides = hydrolysed by lipase into fatty acids and glycerol for use in the body.
Which hormones stimulate lipolysis?
- Adrenaline, noradrenaline (stress hormones)
- Adrenocorticotropic hormone (ACTH).
- Glucagon
- Growth hormone.
- Thyroid-stimulating hormone (TSH} and thyroxine (need T3 to activate the process).
Catabolism?
Breadown
What antagonises the lipolytic effects of hormones?
Insulin
Insulin hinders the lipolytic (lypolysis) effects of hormones such as TSH, ACHT, adrenaline and noradrenaline. Therefore insulin resistance leads to central adiposity.
Describe how fatty acids can be used for energy (catabolism) ie Krebs
- Fatty acids cross the cell membrane, traverse cytosol and reach mitochondria (aided by carnitine).
- Carnitine facilitates transport of fatty acids across mitochondrial membrane.
- Fatty acids undergo beta-oxidation (no pyruvation)
- Broken down into 2-carbon blocks as acetyl-CoA, which is oxidised via the Krebs cycle to waste materials CO2 and H2O.
- Energy then generated using the electron transport chain.
Decarboxy-lation?
Removal of a carboxyl group
What types of food can brain use?
Ketones and glucose
(Brain can’t metabolise fatty acids)
When ketones made?
- When glucose in short supply eg fasting, low carb intake.
- Made at night too.
Ketogenesis definition
Making of ketones
Describe the process of Ketogenesis
Acetyl-CoA converted to the ketone bodies:
- aceto-acetate or
- β-hydroxy-butyrate (β-OHB).
Acetoacetate can undergo decarboxylation to another ketone acetone (sweet-smelling).
Carb threshold for body to shift primary fuel source form glucose to fat?
Carbs restricted to < c. 40 g per day.
Can everyone switch from carb-burning to fat-burning?
Not everyone will be metabolically flexible enough to do ketosis.
Requires transition period. May feel rough. Stricter you are at begtinning the quicker the transition: nausea, blood glucose drops… need to de-mothball beta-oxidation proesses. MCT oil helps in the adaptation process. Drink lots of fluid.
Health benefits of ketosis?
- Weight loss
- Management of epilepsy
- Parkinson’s and Alzheimer’s disease (Type 3 diabetes - frontal lobe can’t use glucose anymore)
Ketoacidosis?
Unstable and dangerous condition that occurs when there is insufficient pancreatic insulin response to regulate serum β-OHB. Lowers blood pH.
Outline lipid digestion
- Gastric lipase in the stomach and pancreatic lipase in the duodenum, act to separate the glycerol and fatty acids/triglycerides to aid digestion.
- This process is facilitated greatly by the emulsifying action of bile, which increases surface area of fat droplets.
- Resulting two free fatty acids and monoglyceride (=glycerol + 1 fatty acid) transported into enterocytes, where they are rebuilt in the cell, packaged into chylomicrons and transported via the lymphatic system to the bloodstream.
- The fatty acids can be used or stored in adipose tissue.
Emulsification?
Breaks down fatty acids… so greater surface area for enzymes to work to break down.
How to optimise lipid digestion?
- Chew adequately
- Avoid drinking with meals.
- Increase bile production by optimising stomach acid levels via zinc and B6-rich foods, bitter foods (eg chicory, rocket)
- Stress management.
- Choleretics (increase bile production) and cholagogues
(increase bile flow); e.g. dandelion, artichoke and turmeric. - Ensure good hydration to support bile flow.
- Increase glycine and taurine, which are components of bile. Good sources = legumes, sea vegetables, spinach and eggs.
- Olive oil can also stimulate bile secretion.
Bile is made of?
Water (97pc)
Bile salts (taurine and glycine)
Cholesterol
What are choleretics and cholagogues?
Choleretics (increase bile production) and cholagogues (increase bile flow); eg dandelion, artichoke and turmeric.