Carbs

CARBOHYDRATES Carbs, also known as saccharides, are organic molecules that are used as energy sources, structural molecules and as components of other biological molecules. Inorganic and Organic Molecules Even the experts don’t agree on how to define the difference between organic and inorganic substances, but a good, broad definition is as follows. Inorganic molecules are essentially substances that don’t have carbon-hydrogen (C-H) bonds, whereas organic molecules are substances that contain carbon-hydrogen bonds, are found in living things. The major classes of organic molecule include carbohydrates, proteins, lipids and nucleic acids. Carbohydrates The term carbohydrate is actually a descriptor of what these molecules are composed of. They are “carbon hydrates,” in a ratio of one carbon molecule to one water molecule (CH2O)n. You may recognize carbohydrates as source of energy (starch, glycogen), but they fulfill a wide range of roles, including the structural materials of plants (cellulose in plant cell walls) and of some animals chitin of an insect’s exoskeleton. Carbohydrates can also be components of other molecules such as DNA, RNA, glycolipids, glycoproteins, and adenosine triphosphate (ATP) Saccharides The word saccharide is a synonym for carbohydrate and is generally preceded with a prefix indicating the size of the molecule (mono-, di-, tri- poly-). Monosaccharides •

single sugars (one molecule)

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simplest

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examples are glucose and fructose

Disaccharides •

double sugars

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combination of two monosaccharides

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sucrose = glucose + fructose

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lactose = glucose + galactose

Polysaccharides •

polymers composed of several sugars

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can be same monomer (many of same monosaccharide) or mixture of monomers

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glycogen is the major stored carbohydrate in animals

CARBOHYDRATES •

starch is storage polysaccharide of plants. It is a long chain of glucose molecules.

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chitin is a structural carb in some animals

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cellulose is the major structural carbohydrate in plants

Building and Breaking Down Sugars Dehydration and hydrolysis are chemical reactions that make bigger (dehydration) and smaller (hydrolysis). Dehydration Reactions Dehydration is when one molecule contributes a hydrogen (H) and the other a hydroxyl group (OH), therefore the removal of a water molecule (H2O) results in the joining of two smaller molecules. With respect to carbohydrates, dehydration reactions make bigger carbohydrate molecules from smaller sugars. Hydrolysis Reactions Hydrolysis is the reverse of dehydration and is when the addition of a water molecule breaks (lyses) a larger molecule into two smaller molecules. With respect to carbohydrates hydrolysis, the bonds on the larger carbohydrate are broken through the addition of water. One of the smaller molecules receives a hydrogen (H) and the other received a hydroxyl group (OH)

Carbohydrates are an ideal source of energy for the body. This is because they can be converted more readily into glucose, the form of sugar that's transported and used by the body, than can proteins or fats. Even so, a diet too high in carbohydrates can upset the delicate balance of your body's blood sugar level, resulting in fluctuations in energy and mood that leave you feeling irritated and tired. It is better to balance your intake of carbohydrates with protein, a little fat and fibre. There are two types of carbohydrate: complex and simple. Complex carbohydrates Complex carbohydrates are often referred to as starch or starchy foods. They are found naturally in foods and also refined in processed foods. Complex carbohydrates as natural starches are found in: •

bananas

CARBOHYDRATES •

barley

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beans

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brown rice

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chickpeas

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lentils

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nuts

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oats

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parsnips

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potatoes

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root vegetables

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sweet corn

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wholegrain cereals

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wholemeal breads

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wholemeal cereals

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wholemeal flour

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wholemeal pasta

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yams.

Complex carbohydrates as refined starches are found in: •

biscuits, pastries and cakes

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pizzas

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sugary processed breakfast cereals

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white bread

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white flour

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white pasta

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white rice.

Simple carbohydrates Simple carbohydrates are also known as sugars. They also exist in either a natural or refined form. Natural sugars are found in fruit and vegetables. Refined sugars are found in: •

biscuits, cakes and pastries

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chocolate

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honey and jams

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jellies

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brown and white cane sugar

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pizzas

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prepared foods and sauces

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soft drinks

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sweets and snack bars.

Simple carbohydrates (sugar) cause tooth decay. The difference between complex and simple carbohydrates All carbohydrates form glucose when digested. Glucose is transported around the body via blood and taken into cells to be converted into energy. The pancreas gland in your abdomen secretes the hormone insulin which controls the uptake of glucose by your cells. If you have any excess glucose, this is converted into glycogen which is stored in the liver or in fat around the body. When your body needs more energy, a second hormone called glucagon is secreted by the pancreas. This converts the glycogen back into glucose, which is then released into your bloodstream for your cells to use.

CARBOHYDRATES This means the body's glucose (sugar) metabolism is a cycle of glucose, insulin and glucagon reactions. •

The slower the release of glucose and hormones, the more stable and sustainable the energy levels of the body.

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The more refined the carbohydrate, the faster the glucose is released into your blood. This can cause peaks and drops in your blood sugar level, and less stable energy levels in the body.

Complex carbohydrates provide a slower and more sustained release of energy than simple carbohydrates. In their natural form they contribute to long-term good health, appetite control and sustained energy levels. How much do I need? Current advice is that we should get half our energy needs from carbohydrates. According to the British Nutrition Foundation, the average adult's daily diet meets this target with women getting 47.7 per cent of their daily energy from carbs (203g) and men 48.5 per cent (275g). But not all carbohydrates are equal: refined sugars should make up only 11 per cent of your daily diet. For adults, the average intake of refined sugars is slightly higher than this recommended level, with men the worst offenders at 13.6 per cent. The average child's intake is 16 per cent, with the main culprits being fizzy drinks and confectionery. Do carbohydrates make you fat? Eating too much will lead to weight gain, regardless of what foods you get your energy from. Yet while low carb diets have had much publicity, gram for gram carbohydrates contain less calories than fat, protein and alcohol: •

1g carbohydrate contains 3.75 calories.

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1g protein contains 4 calories.

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1g fat contains 9 calories.

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1g alcohol contains 7 calories.

Sugar and starch are found in both healthy and 'unhealthy' foods, so the type of carbohydrates you eat is important for your wellbeing.

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Many foods high in sugar (cakes, pastries, chocolate) are also high in fat or prepared with fat (chips, roast potatoes, sandwiches).

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Starchy foods such as wholegrain bread, pasta etc are rich in fibre, which is essential for digestive health and helps control appetite so you don't feel hungry.

Tips for healthy living •

Your daily diet should be a balance of carbohydrate and protein. As a guide, your plate should contain twice as many carbs as protein.

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Base each of your meals on a complex carbohydrate such as potato, wholemeal bread or brown rice, and include vegetables. Finish the meal with fruit, and this should ensure you get a balance of complex and simple carbohydrates.

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Use high fibre wholegrain cereals as part of your breakfast, and use wholemeal bread for your toast.

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For lunch, choose lean protein such as fish or chicken with only a small amount of carbohydrate to get you through the afternoon.

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Large carbohydrate meals will make you slow and sleepy so save your big pasta meal for the evening.

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Cut down on the amount of refined white flour products in your diet such as white bread, pizza and white pasta and rice. The refining process produces simple carbohydrates and many vitamins and minerals are lost.

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Fruit is naturally high in sugar, which means so are fruit juices and smoothies. In liquid form these sugars can damage your teeth, but these drinks count towards your five a day and contain fibre, vitamins and minerals. To avoid tooth decay, it's best to drink them with a meal.