Topic 7- Macronutritents Flashcards
What are 4 chemical groupings are carbohydrates divided up into?
- Monosaccarides
- Disaccarides
- Oligosaccarides
- Polysaccarides
What are monosaccharides and disaccharides general referred to as?
- Sugars
What are oligosaccharides and polysaccharides?
They are composed of longer chains of monosaccharide units bound together by glycosidic bonds. The distinction between the two is based upon the number of monosaccharide units.
Distinction between oligo and polysaccharides?
Oligos typically contain between three and two monosaccharides (e.g. inulin), and polysaccharides contain greater than ten (often hundreds or thousands)
What do polysaccharides represent and what is their function?
They represent an important class of biological polymers and their function in living organisms is usually for structure or storage.
Eg. Starch- a polymer of glucose, is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin
Eg. Glycogen- another glucose polymer thats properties allow it to be metabolised more quickly which suits the lives of moving animals
Eg. Cellulose and chitin- these are examples of structural polysaccharides. Cellulose is used in call walls.
Roles that carbohydrates play in living cells?
- Polysaccarides serve for the storage of energy (starch and glycogen) and as structural components (cellulose)
- The 5 carbon monosaccharide robes in asn important component od coenzymes (e.g.. ATP, FAD, NAD) and the backbone of the genetic molecule known as RNA. The retiled deoxyribose in a component of DNA.
- Saccharides and their derivatives play a key roles in the immune system, fertilisation, blood clotting and development etc.
Are carbohydrates an essential nutrient in humans?
No
Can humans metabolise all types of carbohydrates?
No
What is the recommended percentage amount of daily energy intake that should come from carbs?
45-65%
What are complex carbs?
- They are straight or branched chained of monosaccharides
- The polymers formed and polysaccharides
- There are three main types -> glycogen, starch and fibre
What are the three main types of complex carbs?
- Starch
- Glycogen
- Fibre
What is glycogen?
- It a stored form for short term energy in animals (mainly liver)
- It is a branched glucose chain that can be readily hydrolysed
- Not found in plants and is not a significant food source
What is starch?
- Is a plant form of glucose storages
- Important food source for humans
- Found mainly in seed and underground plant roots\
- Two forms: amylose and amylopectin
What are the two formed of starch and which one is the most rapid to digest ?
- Amylose
- Amylopectin -> is the most rapid to digest
What is fibre?
- Is usually called non-starch polysaccharide (NSP)
- Consists of many compounds with different properties
- Main types include: cellulose, hemicellulose, pectine, gums and mucilages
- Most fibre cannot be digested in th human GI tract
- NSPs have varying bond types and monosaccharide units
- Cellulose in the predominant form of fibre in our diet, and consists of straight chains of glucose
- Cellulose in the building material for plans cell walls.
What are the main types of fibre?
Cellulose, hemicellulose, pectin, gums and mucilages
Where is hemicellulose (a type of fibre) found?
- Cereal fibers
Where are pectins many found (a type of fibre)?
- Fruits, vegetables and form gels in water
What are gums and mucilages composed of?
Wide variety of monosacchardies
What are the water soluble and insoluble fibres?
Water soluble:
- Gums
- Pectins
- Mucilages
- Some hemicellulose
Insolubles:
- Cellulose
- Lignin
- Some hemicellulose
Where are soluble fibres found (give examples)?
Found in plan foods including:
- Legumes
- Oats, chia, barley
- Some fruits and juices
- Certain vegetables such as broccoli, carrots and artichokes
- Root tubers and vegetables like potato and onions
- Psyllium seed husk ( a mucilage soluble fiber)
Where and insoluble fibres found?
- Whole grain foods
- Wheat and corn
- nuts and seeds
- Potato skins
- flax and hemp seed
- vegetables such as beans, cauliflowers, zucchini, celery
- Some fruits including avocado and bananas
- The skins in some fruits including kiwi and tomatoes
Fibre compounds with partial or lower fermentability include?
- cellulose and hemicellulose (polysaccharide)
- lignans, a group pf phytoestrogens
- plant waxes
- resistant starch
Fibre compounds with high fermentability include:
- beta-glucans (poly)
- pectins (hetropoly)
- natural gums (poly)
- Inulins (poly)
- Oligosaccharides
- Resistant dextrins
How are di and polysaccharides formed and broken?
- They are formed by condensation and broken down on hydrolysis
How do sugar units go though condensation?
- They join together through an oxygen linkage by the loss of a water molecule
How do carbs go though hydrolysis?
- Linkages between the sugar units are broken apart by the addition of a water molecule
Digestion and absorption of fibre? (soluble, insoluble, all fibre)
Soluble:
- delays stomach emptying and intestinal transit
- lowers blood cholesterol by bonding to bile
- partially fermented by GI tract bacteria to give short chain fatty acids
Insoluble:
- Accelerates intestinal transit
- Increases faecal weight (binding with water)
All fibre:
- Slows starch breakdown, thus delay glucose absorption and lowering glycemic response
How are starches broken down?
- Carbohydrase enzymes are responsible for the breakdown of starches. They are broken into smaller chains and then to individual monosaccharides
Location of action of starch breakdown?
Mouth: salivary enzyme pytalin attacks starch to form oligosaccharides and some disaccharides
- Stomach: low pH so no carbohydrates activity
- SI (duodenum): disaccharides enzymes on the intestinal wall (sucrase, maltase, lactase ect) convert di to mono
- SI (jejunum): absorption of monosaccharides and the active transport into blood stream
How are carbs metabolised?
- digestible carb is converted to glucose and absorbed into the blood stream
- the liver regulates how much glucose is released into the bloodstream to be delivered to cells for energy metabolism
- excess glucose is converted to glycogen in the lover and used as a short term energy store
- liver glycogen is usually 1/3 of our bodies glycogen stores
- muscle cells store glycogen for tenor own use
What is the first stage of glucose metabolism called?
- Glycolysis
Why is glucose the preferred energy source?
- Due to its simple breakdown
What is glycolysis?
- This is the process where cellular enzymes convert glucose into pyruvate units in the cytoplasm of each cell
- A small amount of energy (ATP) is released by the anaerobic process
What is Glycogenesis?
- This is the formation of glucose from non-carb sources
- Amino acids and glycerol )not petty acids) can be converted into glucose
- Which out sufficient dietary carb intake, dietary protein and body protein (from muscles and organs) can be broken down to glucose to keep blood glucose levels constant
- Fat and protein can be used as energy source directly for most cells but not as easily as carbs
- In the brain, glusoce is the preferred energy source
What is lactic acid formation?
- Is when there is limit oxygen available in cels, not all glucose is converted to acetyl-CoA in the mitochondria
- Pyruvate formed from glucose stayed in the cytoplasm and is converted to lactic acid
- Body cells do not have the enzymes required to break down lactic acid, therefore it is transported to the liver via the blood stream where it is reconverted to glucose
- This is called the Cori Cycle
What is the cori cycle?
- Is part of the lactic acid formation where lactic acid in the cells is transported via the blood stream to the liver to be converted back into glucose
How is glucose converted to fat?
- Excess carbs intake can lead to fat formation
- Carbs are the bodies preferred engird source and will be used preferentially in metabolism
- Excess carbs give rise to production of glycerol molecules and acetal CoA
- Fatty acids can be synthesised from the acetal-CoA, then bonded to the glycerol to form triglycerides
What level is glucose kept constant at?
- 3.5-5 mol/L. BGL breaks after meals but is lowered by isulin
How is blood glucose regulated?
- The pancreatic hormone insulin increases muscle cell uptake of glucose and glycogenesis (conversion of glucose to glycogen) and suppresses gluconeogenesis.
- Glucagon, another pancreatic hormone will increase the rate of glycogen breakdown when blood glucose falls
- Glucose regulation is essential for brain function and basal metabolism
What is the glycemic response to food?
- Different foods will give different blood glucose responses (ie. level of glucose in blood postprandialy) based on the type and amount of carbs they contain
What is glycaemoc index?
- This is a mathematical ration method of comparing the glycemic response of different carbs contain foods
What are the GI ranges (e.g. low, med, high) and give a few examples for each?
- Low GI is below 55: Vegetables, grainy breaks, milk, most fruits
- Medium GI is 56-69: whole wheat products, basmati rise, sweet potato and stable sugar
- High GI is 70 and above: Corn flakes, white bread, jasmine rice, corn flakes
What is glycemic load?
- Whereas GI is a ration of a foods blood glucose raising potential compared with pure glucose (always below 100), The GL takes into account the amount of carbohydrate in the food or even a persons hole diet.
GL = GI x Carb content to food serving / 100
What are proteins?
- Biological compounds consisting of one or more polypeptide typically folded into a global or fibrous form which facilitates a biological function
What to proteins consist of?
- Chains of amino acids which are golden in complex structures. Amino acids are comprised of carbon, hydrogen, oxygen and nitrogen
How many primary amino acids are there?
- 20
How many amino acids contain sulphur which is critical to protein structure?
2
Are most plants limited in some animal acids?
- Yes
What is a polypeptide?
- Is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent animal acid residues
- The sequence of animo acids in a preteen is defined by the sequence of a gene, which is encoded in the centric code
How many essential amino acids are there and why are they essential?
- There are 9 essential amino acids and they are essential as the body cannot synthesis amount to meets the bodies needs.
- If essential amino acids are not supplied by the diet, the body breaks down its own protein to obtain them fro urgent needs
How can non essential amino acids be made by the body?
- These amino acids are still beens but can easily be made by transamination or kept acids in vivo.
What are the 9 essential animo acids?
- histidine
- leucine
- methionine
- threonine
- valine
- isoleucine
- phenylalanine
- tryptophan
- lysine
How are proteins formed?
- The mechanism of protein formation involves an enzyme mediated condensation section that formed a peptide bond between two animo acids
- The -OH group from the acid end and the -H from the amino end (NH2) join and breakaway as H2O, leaving a new word joining the two amino acids
- This process is repeated many times
- Amino and acid terminal groups of the dipeptide can now condense with there amino acids to form a chain, < 100 to > 1000 units long call a polypeptide chain
What are the three uniform classes that proteins can be divided into?
- Globular
- Fibrous
- Membrane
Are globular proteins soluble and what specifically do they often make up?
- They are solvable and often are enzymes
What do membrane proteins often serve as?
- Ofen serve as receptors or provide channels from polar or charged molecules to pass though the cell membrane
Most proteins fold into 3-dimetional structures but biochemist often refer to 4 aspects of a proteins structure. What are they?
- Primary: the animo acid sequence
- Secondary: repeating local structures stabilised by hydrogen bonds. Called helix, beta-sheets and spatial
- Tertiary: is the overall shape of a single protein molecule. Controls the basic function
- Quaternary: Structure formed by several protein molecules. Single protein complex
What are some of the important features of proteins?
- Three-dimentional structure
- Exist in aqueous enviro
- Have both hydro and hydrophilic side chains
- Can have more than one chain
- Chains can fold and twist
- Structure is complex and unique
- 3D structure gives protein is properties
Do dietary proteins provide body protein for human directly and why?
- No, they are too large for direct absorption and if they enter the blood would be seen as a foreign invader. They must be digested and absorbed as animo acids
Digestion of proteins in the mouth?
- No chemical break down occurs in the mouth
Digestion of proteins in the stomach?
- Stomach HCL denatures protein
- Stomach lining cells secrete inactive enzyme pepisonogen
- Stomach HCL converts pepsinogen into its active form pepsin
- Pepsin cleaves peptide bonds to give smaller polypeptide chains
How does protein digestion happen is the SI?
- Shorten polypeptides enter the small intestine
- Pancreatic and instetinal protests, hydrolyse the chain to smaller units
- Intestinal surface enzymes break more peptide bonds to liberate individual amino acids
- Free amino aids are transported by active transport across intestinal cells into the blood sand then into cells for later use
What are the main uses of synthesised proteins in the body?
- Replacement of proteins deteriorating with time
- Structural purposes such as growth and remain of tissues
- Enzymes
- Hormones
- Fluid balance
- Acid-base balance
- Antibodies for immune function
- Transport
- Blood clotting
Proteins as enzymes?
Proteins that catalyse chemical reaction including anabolic enzymes and catholic enzymes
How are proteins used in fluid balance?
- The help regulation quality of fluid in the blood, cells and interstitial space
- By making and keeping proteins, cells attract water. Water follows proteins via osmosis
How are proteins used in acid-base balance?
- Proteins act as acid-base buffers
- The take up or release H+ from the body fluids
- Inder acidic conditions there are many H= ions in the fluid. Protein absorbed the H+ making less H+ available in the fluid and pH rises. Under alkaline conditions pH is hugh so there are few H+, so proteins release H+ and Ph is lower.
Proteins as antibodies?
- Antibodies are large proteins produces by the immune system to inactivate foreign substances that could be harmful
Proteins as hormones?
- These hormones are chemical messenger molecules produces in endocrine glands e.g. pituitary as well as some organs (pancreas)
Proteins as transport proteins?
- they can be either fixed or moving
- Transporting substances into or out of cells
- Also carier proteins in blood for transporting lipids, fat soluble vitamin and minerals
- Proteins attacked to lipoprotein particles
Proteins in the process of blood clotting?
- During blood vessel injury, the structural protein collagen is exposed
- Platelets adhere to the exposed collagen
- Substances are secreted that induce platelets to aggregate and initiate a cascade of reaction leading to the formation of a blood clot
- This reaction involves numerous proteins
- Process results in formation of fibrin stands (protein) that cross link platelets and red blood cells to form a stable clot
- Fibrinogen and prothrombin are clotting factor proteins found in blood
How does protein contribute to body energy and fat?
- Animo acids not required to structural/functional processes can be used for energy via acetyl-CoA and the TCA cycle.
- If not used as an energy source or in other body processing, they are converted to fatty acids, combined with glycerol and stored as body fat
- Some are converted to ketone bodies as a source in energy for the brain and nerves during carbohydrate shortage or energy restricted diets (starvations). This is termed ketosis.
What is ketosis?
- Ketosis is a state of elevated levels of ketone bodies in the blood. Ketone bodies are formed by ketogensis when the liver glycogen stores are depleted. The ketone bodies (acetoacetate and beta-hydroxybutyrate) are used for energy by some cells of the body such as the brain
- Ketosis leads to a lowered pH and disturb the acid/base balance in the body
- Glucose production from glycerol and amino acids cannot supply the adequate energy to the brain thus the need to convert faye acids to keno bodies
- Ketone bodies are converted to acetal/CoA for energy production in the brain
- A good shower them emergency meshing to full brain but develops into ketoacidosis if prolonged
- Ketone bodies are acids
Whats is the sequence of event in protein synthesis?
- Segment of nuclear DNA contain a code that determines that order of amino acids in a protein
- Code is carried to make ribosomes in the cytoplasm
- Ribosomes make the protein from the animo acids
- Is a non essential amino acids is not the, the cell makes it from other animo acids
- If an essential animo said is not there the cell breaks down structural proteins
- Once proteins are make they are transferred to the endoplasmic reticulum (EPR_ where is it stored, activated and releases when needed.
What is protein quality?
- Refers to the ability of a dietary protein to proved animo acids for the body
- Is a diet is rich in protein it does not necessarily mean that it will supply all amino acids need in adequate amounts
- Many plant protein lack some certain amino acids
- By combining plants food the total overall amino acid requirement can be met
- This is termed complimentary proteins
What are high quality proteins?
- proteins which prove enough for all essential amino acids
Digestibly of proteins?
- Proteins must be digested before they can be a source of amino acids
- The digestibility depends on its source and other foods eaten with it
- Animal proteins are 90-99% digested
- Plant proteins are 70-90% digested (soy and other legumes can be digested more)
What is a military amino acid?
- If one of the 9 essential acids is not supplies in adequate levels in the diet, the body must breakdown existing proteins (e.g.. muscle tissue)to obtain the needed amino acid or stop making the new prtein
- An essentaion amino acids supplied in less that the amount needed to support protein synthesis is call the limiting amino acids
- The 4 morse likely amino acids to be limiting are: lysine, methionine, threonine and tryptophan
What are ways in which protein quality can be determined?
- chemical scoring
- biological value (BV)
- net protein utilization
- protein efficience ration
- protein digestibility corrected amino acids score
What is chemical scoring?
- Involves determining a diets chemical score
- Is the ration of a gram of the milting amino acid in a test diet to the same amount of the corresponding among acids in a reference diet multiplied by 100
What is biological value (BV) of a protein?
- A tease of the promotion of absorbed protein from a food which becomes incorporated into the proteins of the organisms body. Summarises how readily the broken down proteins can be used in protein synthesis an the cells of the organism
What is the protein efficiency ratio?
- Protein efficiency ration (PER) is based on the weight grain of a test subject divided by its intake of a particular food protein during the test period
What is the net protein utilisation?
- The net protein utilisation os NPU is the ration of amino i acids converted to proteins to the ratio of amino acids supplied
What is protein digestibility corrected amino acid score?
- A meths of evaluation the protein bases in amino acids requirement of humans and the ability to dogged it. (Fairly recent methods and is good)
What is protein energy malnutrition?
- Dietary protein deficiency is usually associated with energy deficiency
- One in 4 children world wide is effected
- Children who are very short for their age may have experienced this long tes
- More prevalent in africa and central, south America, south and south east asia
- To forms are called ‘marasmus’ (wasting) and ‘Kwashiorkor’ (oedema_
How can protein excess be dangerous?
How can protein excess be dangerous?
What are lipids?
- They are fats and oils. There are many types and chemical classification is based in their molecule structure.
What are the main dietary lipids?
- Triglycerides
Are all triglycerides digested the same way?
- Yes
What are lipid composed of?
- C. H and O (and P is phospholipids)
What are some of the roles of lipids?
- Storage form of energy in the body
- Structurally important
- Used as hormone
- Carry fact soluble vitamins
- Responsible for aromas, flavours, palatably in foods
Where do most fats and oils come from?
- Most fats come from animal sources
- Most oils come from plan sources
What is structural component of saturated fat that defines it?
- They have no double bonds and higher melting point
How many double bonds does mono saturated fat have?
- One
How many double bonds are in a polyunsaturated fatty acid?
- More then one (tend to be liquid at room temp)
What are the chemical components of a triglyceride?
- They have a glycerol back bone and three fatty acids
How are triglycerides formed?
- They are formed by condensation reaction between glycerol and three fatty acids
Where are cholesterols found?
- Only in animal food
Does dietary cholesterol have much of an effect on blood cholesterol?
- Has very little effect
The liver produces cholesterol and the blood level rises due to saturated fate intake causing the live to make more cholesterol and remove less
Is cholesterol on the body essential?
- Yes
What is an example of a vitamin made from cholesterol?
- Vitamin D
What is the link between cell membranes and cholesterol?
- Cholesterol is a part of the cell membrane structure
What are phospholipids?
They are similar to triglycerides but have only two fat acid attached to a glycerol backbone. The thirst position is occupied by a combined phosphate/base group of which there are 4 types
What are fatty acids?
Organic acids contain a fatty chain of CH2 ground that are highly non-polar (repel water)
Characteristics of fatty acids?
- Only contain C, H, O
- Terminal groups are -CH3 and -COOH
- The chains consist of multiple -CH2 units, except where double bonds are located and the chain units have one less H atom (is CH not CH2)
- Naturally occurring fatty acids have an even numbered carbon chain and generally range from 4-26 carbons
What does saturation mean?
- It mean the maximum number of hydrogen atoms bonded to each carbon
- If a double bond is inserted between each carbon then 2 Hs have to be lost, and the fatty acid is no longer saturated with hydrogens
- If one double bond is present the fatty acid is a monounsaturated fatty acid. If two or more double bonds are present it is a polyunsaturated fatty acid
What is hydrogenation?
In the margarine industry, vegetable oils containing MUFA and PUFA are hydrogenated to make the mixture contain more saturated fatty acids which make it more solid
What are the main PUFA subgroups?
Omega- 3 and Omega- 6
Others include omega 7 and 9
What variation is there in PUFA families?
- Location os double bonds as well as with number. This effects the behaviour of fatty acids in the body and how it is metabolised
Why are lipids harder to digest?
- Lipids do not mix well in the aqueous environment of the GI tract where lipase enzymes are located. A number of process are therefor required for lips digestion and absorption
How does the mouth help with lipid digestion?
- Hard fats are softened by the temperatue
How does the stomach help with lipid digestion?
- Linited hydrolysis of triglycerides by lipase. Some milk TG converted to diglycerides and a fatty acid
How does the SI help with lipid digestion?
- Fat globules emulsified by bile
- Bile is release from the gall bladder under control of the hormone cholecystokinin (CKK) released from he duodenum into the blood
What is the role of bile?
- Bile os used to emulsify fat
- Bile is a mixture of liver produced substances, the main ingredient (bile acids) are made form cholesterol
- The active form is a bit salt or acid that is combined with an animo acid group
The process of lips absorption?
- One lips are broken down the smaller units, glycerol and smaller fatty acids can enter the intestinal lining.
- Some TG are not fully broken down and form monoglycerides
- These mono glycerides an long chain fattya acids are large in a molecular scale. There are more water insoluble and form circular complexes call micelle that then enter intestine cells
- Monoglycerides and longer chain fatty acids then combine with cholesterol and proteins to form chylomicrons in the mucosal cells
- Chylomicrons ever the lymph in the villi where they reach the circulatory system at the thoracic dict and subclavian vein in the upper chest region
What are lipoproteins?
- These are transport vehicles from lipids around the body. They have a polar group on the particle surface and the outward facing polar regions if the phospholipids allow the lipoprotein to be suspended in a water environment. The more non polar substances including triglycerides and cholesterol can stay in the interior of the particle away from contact with water.
What are the 4 types of lipoproteins?
- Chylomicrons
- VLDL
- LDL
- HDH
LDL in the modern wester diet?
- In todays western diets there is excess LDL cholesterol being transported around the body. The high amounts of LDL are loosely correlation with increased CHD rates
- As cholesterol in HDL is being removed to the liver. High HDL cholesterol is correlated with lower CHD death rates
- A high LDL:HDL ration can lead to negative health effects
Lipids and energy?
- Some energy used by cells comes from triglycerides, these are delivered by chylomicrons directly from food from the intestines or VLDL from liver storage
Energy from storage fat on the body?
- Much larger energy store then liver and muscle glycogen, supplying approx 60% of the bodies energy at rest
- Hormin sensitive lipase in adipose cells hydrolyse TG when energy is required. Glycerol and fatty acids formed are transported back into the blood cells requiring energy
- Fatty acids are oxidised to carbon dioxide and water releasing bond energy through the TCA cycle and ETC
