Flashcards in Lecture 12 Deck (29)
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1
What is a carbohydrate
Carbohydrates are large organic molecules
Found in starch and cellulose
Major food source and energy supply for the body
Stored in the liver and muscle as glycogen
Supply carbon for the synthesis of cell components
2
What are carbs used for
The primary way for cells to obtain energy is through the oxidation of carbohydrates – ATP
Example: in the body, glucose is oxidized which release chemical energy (ATP) to do the work within the cells
3
Describe Citric Acid Cycle
Oxidation of carbs
Polysaccharides such as starch and glycogen are first hydrolyzed by enzymes to Glucose
Glucose is transported by blood in animals and cell sap in plants
Glucose is then oxidized to produce carbon dioxide and water
Energy is released in this process which is used for functioning of the cells
Energy can be extracted from carbohydrates, fats and when necessary, proteins
4
What is the structure of a carb like?
Organic compounds containing only C, H and 0
Ratio of carbon, hydrogen and oxygen is 1:2:1
General formula: Cn(H2O)n
Carbonyl group (lone carbon atom double-bonded to an oxygen atom)
Functional groups - an aldehyde (aldose)---(O=CH) or ketone (ketose)----(O=C)
Sugar names usually end in ‘ose’
Carbohydrates means: carbon(Carbo) + water (hydrate)
5
What are some chemical properties of carbs
Reducing substances:
Reduce other compounds
Must contain ketone or aldehyde group
e.g. glucose, maltose, fructose , galactose and lactose
Formation of Gylcosidic bond
With other carbohydrates or non carbohydrates e.g. 2 sugar molecule
6
What are carbs classified as?
Carbohydrates are divided into four types –
Based on the number of sugar units in the total chain
Monosaccharides - single sugar unit
Disaccharides - two monosaccharide units (maltose, sucrose and lactose)
Oligosaccharides - 3-10 monosaccharideunits
Polysaccharides - > 10 monosaccharide units (starch, glucose and glycogen)
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What are Monosaccharides
These are the basic carbohydrates
Most common – Glucose , fructose and galactose
General formula: Cn(H2O)n -simple sugar
n can be 3, 5 , 6 carbon atoms
If n = 3, the sugar is a triose – 3 carbon atoms
If n = 5, the sugar is a pentose – 5 carbons
If n = 6, the sugar is a hexose – 6 carbons
Like Ribose and Deoxyribose in RNA and DNA
8
Describe Complex Carbohydrates with example
Starch e.g. cereals, bread and pasta
Glycogen
Cellulose (form of fiber)
9
What is Ribose?
Simple Sugar
Ribose comprise the backbone of the genetic molecule known as RNA – Ribonucleic Acid
RNA – Single-stranded molecule
Central to protein synthesis
10
What is Deoxyribose?
Simple Sugar
Deoxyribose is a component of DNA –
Deoxyribonucleic Acid
DNA – Double-stranded molecule
Contains the genetic instructions
11
What is Hexose?
The hexose sugars are the most abundant simple sugars and those most frequently found in food
They include the sugars glucose, fructose, and galactose
Glucose (C6H12O6) contain six carbon atoms and an aldehyde group
Monosaccharide molecules can exist in an open-chain (acyclic) and ring (cyclic) form
12
What are Disaccharides?
Simple sugars - found in sweets, jams
Combination of two simple sugars linked by a glycosidic bond (covalent bond)
Involves the elimination of water, from the functional groups only
Produce two monosaccharides when react with water
Common disaccharides:
Maltose ----- 2 D-glucose molecules
Lactose------ glucose + galactose
Sucrose------ glucose + fructose
13
What are Polysaccharides?
Many simple sugars/monosaccharides linked together forming long chains
Important polysaccharides
Starch, glycogen, cellulose
Starch
Humans are able to metabolize
Produced by plants for storage
14
What is Glycogen ?
Composed of a large number of glucose units
Humans store energy/glucose in the form of glycogen
Stored in the liver and muscles
15
What is Cellulose?
Plant stems and leaves
Humans are not able to metabolize
16
What is Glucose Metabolism?
Nervous system – the brain depends on a steady supply of carbohydrates from the extracellular fluid to the tissues for energy
When the glucose concentration decrease, the nervous tissue is incapable of maintaining normal function
17
What are lipids
Main biological function of lipids include energy storage
Lipids are a class of hydrocarbon - containing organic compounds
Contain the same elements as carbohydrates but with much less oxygen
Part of cell membrane
Precursor for steroid hormone
Group of naturally occurring molecules which include triglycerides (fats & oils), phospholipids, fat-soluble vitamins, steroids ….
The most abundant lipids in the body are triglycerides
18
What are lipid (fats)
They are insoluble in water
They are soluble in nonpolar organic solvents (such as ether and chloroform)
Esters of long chain organic acids called fatty acids
Fats are formed by the reaction of fatty acids and glycerol (alcohol)
Glycerol occurs naturally in the body as a component of stored fat
19
What are triglycerides?
Lipids with fatty acid
The major form of fat stored by the body
From the food (fats) we eat as well as being produced by the body
Consist of three molecules of fatty acids combined with a molecule of glycerol
Triglycerides are usually measured along with cholesterol as part of a blood test (Lipid Profile)
20
What are steroids?
Lipids without fatty acids
Functions include:
Form part of the cell membrane
Form part of the bile salts which emulsify fats during digestion
Form the ‘steroid’ hormones
Cholesterol – Found in the cell membranes and transported in the blood
Cortisol – Stress hormone
Aldosterone – Regulates salt excretion
Estrogen, progesterone and testosterone – sex hormones
21
What are Unsaturated Fats ?
They tend to be liquids and are called oils
Fatty acids in these fats have some double bonded carbons
22
What are Phospholipids?
Main Function:
They form the major components of the cell membrane --- Phospholipids and glycolipids
Form lipid bilayers
Structure:
Contain a phosphate group
Esters of glycerol with two fatty acids and one phosphate-nitrogen compound
23
What happens in digestion?
Bile, when secreted into the small intestine, promotes the breakdown of large lipid masses into smaller droplets
Bile is produced by the liver and stored in the gallbladder
Lipase further reacts with the small lipid droplets (fatty acids)
They are later absorbed into the blood stream
24
Where do free fatty acids come from?
They are released when fats are broken down – hydrolysis of fat
They are increased in conditions where sugar is not being used
Low blood sugar; diabetes, starvation, etc
25
What is the structure of a steroid like?
A steroid is a lipid characterized by a carbon skeleton with four fused rings (tetracyclic)
Contain a significant amount of hydrocarbon character
Unlike other lipids they are not esters
26
What is cholesterol?
Part of plasma membrane
Made by the liver
Supplied with food
Must be bound to protein to be transported through the blood (LDL, HDL)
Amphipathic molecule - Polar head, and a nonpolar tail
Insoluble
27
What are ldls
LDLs (low-density lipoproteins) – transport cholesterol from the liver to other cells of body
Tends to deposit cholesterol on arterial walls
28
What are HDLs
HDLs (high-density lipoproteins) – removes cholesterol from dying cells and return it to the liver
Carry cholesterol effectively and can dissolve cholesterol deposits in the arteries
Excess cholesterol deposited on the inside surfaces of arteries, can cause blockages in the flow of blood – create cardiovascular and neurological problems
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