Lipids and lipoproteins Flashcards
What are fatty acids made up of?
-made up of hydrocarbon chains of various lengths and saturations
-are derived from triglycerides
Describe the structure of lipids?
-consist of fatty acids which always end in both a carboxyl group (COOH) and a methyl group (CHHH)
What are the 3 different types of fatty acid chain length?
- short chain fatty acids (4-8 carbons)
-medium chain fatty acids (10-14 carbons)
-long chain fatty acids (16-22 carbons)
what is the function of chain length of fatty acids?
-determines whether fatty acid can diffuse freely into the mitochondria for energy production
(the shorter the chain, the more easily it can diffuse)
what are 3 different types of fatty acids and provide an example of each?
-saturated (palmitic acid),
-monounsaturated(eg.oleic acid),
-polyunsaturated (eg.linoleic acid)
what is the difference between saturated, monounsaturated and polyunsaturated fatty acids?
-saturated fatty acids-all carbons are saturated (bonded to hydrogen)
-unsaturated fatty acid- double bond- carbon can only have 4 bonds so therefore 2 carbons are left unsaturated where there would be carbon-instead with a double bond
-one double bond-monounsaturated
-more than 1 double bond-polyunsaturated
Describe what contributes to name of fatty acids?
-the position of the double bond
eg. C18: 1 n-9 (oleic acid)
-18= number of carbons
-1= number of double bonds
-9= position of double bond
are lipids insoluble or soluble in water?
- are insoluble due to hydrophobic carbon compounds
what are the 3 different types of lipids?
-monoglycerides- glycerol and 1 fatty acid
-diglyceride-glycerol and 2 fatty acid
-triglycerides= 3 fatty acids + glycerol
What are the different functions of lipids in body?
-fuel and energy source
-helps with the formation of cell membranes
-helps form phospholipid bilayer
-are important in transport of fat soluble vitamins
-important in formation of hormones (help maintain homeostasis)
Describe how lipids act as a source of energy in the body?
-lipids are oxidised via krebs cycle
-breakdown of triglycerides allows ATP to be generated
function of a cell membrane?
control what enters and exits cell and defines the difference between the inside and outside of cell
what are the 3 main types of membrane lipids?
-phospholipids
- glycolipids
-cholesterol
what is the phospholipid bilayer and what are its 4 components?
it makes up membranes
-fatty acid (fatty acid tail is hydrophobic)-tail length can vary due to fatty acid chain length
-phosphate group (phosphate head is hydrophilic)
-backbone (often glycerol)
-alcohol (polar group)
Describe the role of cholesterol within hormones?
- is a component of steroid hormones
-steroid hormones help control metabolism, inflammation, immune functions, salt/water balance, development of sexual characteristics
-steroid hormones are lipid soluble due to cholesterol component meaning they can diffuse freely across membranes to target sites
in what form a re lipids stored as in the body?
-as triglycerides
what sites in the body can lipids be stored in?
-can be stored in adipose tissue-main storage -found under skin, mostly centred around stomach
-Visceral adipose tissue-more dangerous-found around central organs
-Can also be stored in liver and in skeletal muscle in much smaller quantities
Describe how lipids are stored in the adipose tissue?
-When dietary fat is consumed (triglycerides) its broken down into fatty acids and absorbed by adipose tissue so are stored as “neutral lipids”
-adipose tissue can also take up glucose and convert it to neutral fat (de novo lipogenesis)
Describe how fatty acids are transported in the blood?
-during fasting, it causes a blood glucose signals to be sent out due to decrease in blood glucose-this signals(adrenaline) for adipose tissues to release energy (by fatty acids being released into blood)
-Albumin protein in blood- carries fatty acids to required site (muscle tissue) for it to be taken up and used for energy production
describe how lipids are stored in the skeletal muscle and liver?
-Intramuscular triglycerides (IMTG)-fatty acids stored in skeletal muscle
-IMTG are stored next to mitochondria so once broken down they travel directly into the mitochondria and can be oxidised for energy
sate the composition of fat storage in young males and females and elite male and female athletes?
young men-15-20%, young women- 25-33%
-elite athlete male- 3-5%, elite women- 7-10%
what methods can be used to measure fat storage?
-skinfold tests (callipers)
-bioimpedance
-DEXA
where does lipid digestion primarily take place?
-In small intestine
describe the process of lipid digestion?
-process of chewing and acidic conditions in stomach allow lipids to enter the small intestine in form of large lipid droplets
-large lipid droplets are broken down into emulsion droplets thru being mixed with bile salts in small intestine- create emulsion
-emulsion droplets then broken down into micelles by addition of more bile salts, lipase
(lipase is produced by pancreas)
-micelles can then be broken down further to form free fatty acids and monoglycerides which can then be absorbed into blood to be transported to required tissue
what is a micelle and describe its structure?
-is a small membrane bound package of lipid containing free fatty acids and monoglycerides
-monoglycerides and free fatty acids have a hydrophobic core
Describe what happens to free fatty acids and monoglycerides before entering the bloodstream?
-must cross layer of microvilli and epithelial cell before entering bloodstream
-Once in endothelial cell they become packaged into chylomicrons (lipid carrying packages-made up of triglycerides, phospholipids, proteins and cholesterol) thru process of triglyceride synthesis at endoplasmic reticulum
How is cholesterol transported after being in the intestines?
-cholesterol can be transported to liver then to tissues or from tissues back to liver to be converted into bile
-liver can also produce cholesterol itself thru de novo synthesis
How are triglycerides transported after reaching the intestine?
-triglyceride can be transported to liver (where it can be stored) or peripheral tissues (adipose tissue or skeletal muscle) (its stored or used for energy
-During increased energy demand triglyceride stored in liver can be transported to muscle
What do lipoproteins do?
-transport lipids in the blood
describe the structure of a lipoprotein?
-contains a triglyceride core which also contains some cholesterol
-core is surrounded by phospholipid membrane
-contains binding proteins on outside
what are the 4 main types of lipoproteins and what does each one do?
-chylomicron-are largest, but least dense (carry triglycerides from intestine to tissues)
-VLDL- very low density lipoproteins (carry triglycerides released from liver to tissues)
-LDL, HDL (specialised to carry cholesterol)
LDL-carries cholesterol to tissues and macrophages (immune cells)
HDL- transports cholesterol back to liver to be excreted- contain highest protein % of all lipoproteins
what us a consequence of a build up of cholesterol in macrophages?
development of atherosclerosis (plaque formation in arteries)
-caused by LDL
describe how LDL can lead to build up of cholesterol in macrophages?
-LDL can be damaged by toxic and free radical, are then scavenged by macrophages in order to be removed from blood, however once inside macrophage causes it to fill with cholesterol, increases in size, forming a foam cell
Describe how HDL can prevent the build up of cholesterol in arteries?
-HDL can take away excess cholesterol inside arteries back to liver where it can be broken down into bile
-does this by binding to macrophages and absorbing some of the cholesterol, delaying its transformation into a foam cell