Carbohydrates - EoNS Flashcards by Charlotte Smith

What is the structure of CHO

●Cn:H2n:On
●They can be described as simple or complex
●Simple Carbohydrates - Monosaccharides & Disaccharides
●Complex Carbohydrates - Polysaccharides

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Name three monosaccharides

Glucose, fructose and galactose

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What is the main CHO in the body? What is it essential for and where is it found?

Glucose

●Also called Dextrose or blood sugar – level strictly controlled
●Essential fuel for some organs
●Honey, sugar, fruit & veg

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Where is fructose found?

●Honey, fruit, veg and processed foods & drinks
●High fructose corn syrup - inexpensive sweetening agen

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Where is galactose found?

Part of milk sugar (lactose) in milk

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What are monosaccharides?

Single sugars

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What are disaccharides?

Simple sugars made up of two monosaccharides

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Name three disaccharides?

Lactose, sucrose, maltose

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What makes up lactose and where is it found?

Lactose = glucose & galactose
●main carbohydrate in milk
●Present in milk and milk products, including chocolate & biscuits

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What makes up maltose and where is it found?

Maltose = glucose & glucose

●Produced whenever starch is broken down during digestion or during the fermentation process to produce alcohol
●in germinating seeds, beer & cereals

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What makes up sucrose and where is it found?

Sucrose = glucose & fructose

●Various forms e.g. table & brown sugar, molasses, golden syrup, honey, maple syrup
●Present in some fruit, vegetables & some grains
●Sugar cane & beet is refined & granulated to form sugar

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What process creates disaccharides?

Condensation reaction

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How do disaccharides break down to form monosaccharides?

Hydrolysis

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What are intrinsic sugars?

Intrinsic – contained within plant cells e.g. apple

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What are extrinsic sugars?

Extrinsic – free sugars e.g. present in milk, honey, foods with added sugar, or milk

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What are Non-milk extrinsic sugars?

Non-Milk Extrinsic Sugars (NMES) are cariogenic & have potentially damaging health effects

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Are the sugars present in honey, syrups and unsweetened fruit juice free sugars?

Yes

Is the lactose in milk and milk products seen as free sugars

Are dried, stewed & tinned fruit seen as free sugars?

How many carbons does a oligosaccharide contain?

3-10

Where in the GI tract are oligosaccharides resistant to digestion?

They are resistant to digestion in upper GI tract. They are digested by bacteria in the colon

Where are oligosaccharides found?

Present in leeks, onions & beans

What are polysaccharides/ complex carbohydrates made up of?

Polymers of glucose units – more than 10 units

Storage form of glucose in the human body is…

Glycogen

The plant storage form of glucose is…

Starch

Plants also contain polysaccharides in the form of…

Fibre

How much glycogen is stored in the liver and muscles?

Approx 450g of glycogen stored in liver & muscles

Where is starch present?

Starch is present in 1. Grains e.g. rice, oats, barley 2. Pulses 3. Roots & tubers e.g. potato 4. Legumes e.g. peas & beans

How are the glucose molecules arranged in starch?

The glucose molecules can either be arranged in a straight chain {Amylose} or a branched chain {Amylopectin}

What is the amylose to amylopectin ratio?

Amylose:Amylopectin 25%:75%

What are the 4 categories of fibre, how easy are they to digest and where are they found?

●Soluble Fibre – in water, easily digested, present in Oats & Barley ●Insoluble Fibre – harder to digest, present in grains & vegetables ●Resistant Starch – small group of starches that are resistant to digestion, undigested until it reaches the colon. Physically inaccessible to enzymes, Plant cell wall, Retrograded by heating and cooling ●NSP has both soluble and insoluble fractions

What are the functions of carbohydrates

●Energy - Blood glucose, Essential fuel for brain (cannot use fat as an energy source) ●Component of cell membranes ●Mucopolysaccharides important in musculoskeletal system

What are the functions of NSP, resistant starch and dietary fibre?

NSP, resistant starch & dietary fibre facilitates movement of contents through gut, soluble fraction of NSP may reduce cholesterol.

Why are the products of starch digestion released slowly?

To maintain blood glucose level

How are CHO stored?

●Glucose in present in plasma (4g) ●Small amount of glycogen in the liver (100g) ●Glycogen also present in the muscles (400g) {Glucose → Glycogen called Glucogenesis}

What happens to excess glucose?

The excess glucose is converted to glycogen, once glycogen stores are full excess converted into fat and stored in adipose tissue

How are monosaccharides digested?

Monosaccharides are easily absorbed – no digestion required

How are disaccharides digested?

Disaccharides split into constituent monosaccharides by brush border enzymes in small intestine

How are polysaccharides digested?

Polysaccharides are hydrolysed in stages to monosaccharides. They cross the gut wall into the bloodstream. This is done by: ●Physical – biting and churning ●Chemical – enzymes Digestibility of starch varies according to the type, composition of the meal and between individuals

How are carbohydrates absorbed?

●Simple diffusion – e.g. fat soluble materials ●Facilitated diffusion – carrier protein e.g. fructose ●Active transport – requires energy e.g. absorption of glucose

How can the body make glucose when there’s an insufficient amount of CHO?

Glucose can be manufactured from proteins and part of fats (gluconeogenesis)

Are fats good at producing glucose?