SECTION B NUTRITION Flashcards
What are carbohydrates?
A carbohydrate is an organic compound that include sugars and starches. They are molecules composed of carbon, hydrogen and oxygen atoms. The ratio of hydrogen atoms to oxygen atoms is 2:1. The simplest carbohydrate molecule has the formula C6H12O6. Carbohydrates are classified into 3 groups.
- monosaccharides
- disaccharides
- polysaccharides
How are disaccharides formed?
Disaccharides are formed through condensation by chemically joining 2 monosaccharide together with the loss of a water molecule.
How are polysaccharides formed?
Polysaccharides are formed by condensation of many monosaccharides (glucose) into straight or branched chains.
What are lipids?
Lipids are fats and oils. Lipids are molecules composed of carbon, hydrogen and oxygen atoms.Each lipid molecule is composed of three fatty acid molecules and one glycerol molecule.
- feel greasy
- insoluble
What are proteins?
Proteins are molecules composed of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur and phosphorous atoms. These atoms form small molecules known as amino acids. Protein molecules are formed by the condensation of many amino acids in long chains. The links between adjacent amino acids are peptide links. The chains fold to give each type of protein molecule a specific shape.
Some proteins are soluble in water = haemoblogin
Others are insoluble = collagen
Reducing sugars
monosaccharides, some disaccharides
example glucose, maltose
Nonreducing sugars
some disaccharides example sucrose
Test?
Positive result?
Reducing sugar
Test = add an equal volume of Benedict’s solution and shake and heat the mixture.
Positive result = an orange-red precipitate forms.
Nonreducing sugar
Test = add a few drops of dilute HCL and heat for 1 minute. Add sodium hydrogen carbonate until effervesce stops. Add an equal volume of Benedict’s solution and shake and heat the mixture.
Positive result = an orange-red precipitate forms. The acid hydrolyzes the disaccharide molecules to monosaccharide molecules. The sodium hydrogen carbonate neutralizes the acid allowing the Benedict’s solution to react with the monosaccharides.
Starch
Test?
Positive result?
Test = add a few drops of iodine solution and shake.
Positive result = solution turns blue-black.
Protein (Biuret Test)
Test?
Positive result?
Test = add an equal volume of sodium hydroxide solution and shake. Add drops of dilute copper sulfate solution and shake or add an equal volume of biuret reagent and shake.
Positive result = solution turns purple
Lipid
Test?
Positive result?
The emulsion test
Test = place 4cm^3 of ethanol in a dry test tube. Add one drop of test substance and shake. Add an equal volume of water and shake.
Positive result = a milky-white emulsion forms.
The grease spot test
Test = rub a drop of test substance onto absorbent paper. Leave for 10 minutes.
Positive result = a translucent mark remains.
What are enzymes?
Enzymes are biological catalysts that speed up chemical reactions occurring in living organisms without being changed themselves.
Why are enzymes important?
Enzymes are proteins produced from amino acids obtained from the diet in animals or manufactured in plants. Without enzymes, chemical reactions would occur too slowly to maintain life.
What are two examples of enzymes?
- Amylase catalyzes the breakdown of starch into sugars (maltose). Amylase is present in saliva, pancreatic juice and germinating seeds.
(amylase) starch ------- maltose
2. Catalase catalyzes the breakdown of hydrogen peroxide into water and oxygen. Catalase is found in most cells and prevents the buildup of harmful hydrogen peroxide which is produced as a by-product of many chemical reactions occurring in cells.
(catalase)
hydrogen peroxide (2H2O2) ------- water (2H2O) + oxygen (O2)
What are 7 properties of enzymes?
- Enzymes are specific meaning each type of enzyme catalyses only one type of reaction.
- Enzymes work best at a particular temperature known as the optimum temperature. This is about 37 degrees C for human enzymes.
- High temperatures denatures enzymes meaning that the shape of the enzyme molecules changes so that they are inactivated. Enzymes start to be denatured at about 40 degrees C to 45 degrees C.
- Enzymes work best at a particular pH known as the optimum pH. This is about pH 7 for most enzymes.
- Extremes of acidity or alkalinity denatures most enzymes.
- The action of enzymes is helped by certain vitamins and minerals example vitamin B helps the action of respiratory enzymes.
- The action of enzymes is inhibited by certain poisons example arsenic and cyanide.
What is nutrition?
Nutrition is the process by which living organisms obtain or make food.
What is autotrophic nutrition?
Autotrophic nutrition occurs in green plants and some bacteria. These organisms are called autotrophs and use simple inorganic compounds, example carbon dioxide and a source of energy like sunlight to manufacture complex organic food substances like carbohydrates, proteins, lipids and vitamins.
What is heterotrophic nutrition?
Heterotrophic nutrition occurs in animals, fungi and most bacteria. These organisms are called heterotrophs and they obtain ready-made organic food from their environment. There are 3 types.
- Holozoic nutrition - occurs in most animals where organisms obtain organic food by consuming other organisms. The complex food is ingested by the organism and then digested into simpler organic substances within the body of the organism.
- Saprophytic nutrition - occurs in fungi and most bacteria. Saprophytes obtain organic food from the dead remains of other organisms. They digest the complex organic food outside their bodies and then absorb the simpler organic substances produced.
- Parasitic nutrition - occurs in some plants, animals, fungi and bacteria. Parasites obtain organic food from the body of another living organism called the host and the host is usually harmed.
What is photosynthesis?
Photosynthesis is the process by which green plants convert carbon dioxide and water into glucose by using sunlight energy absorbed by chlorophyll in chloroplasts. Oxygen is produced as a by-product. Photosynthesis occurs in any plant structure that contains chlorophyll.
What are the two stages of photosynthesis?
- The light stage or light dependent stage requires light energy. The light energy is absorbed by the chlorophyll in chloroplasts and is used to split water molecules into hydrogen and oxygen. The oxygen is a waste product and is released as a gas.
- The dark stage or light independent stage takes place whether or not light is present. The hydrogen atoms produced in the light stage reduce the carbon dioxide molecules forming glucose. The dark stage requires enzymes.
What are 6 conditions that are necessary for photosynthesis?
- Carbon dioxide which diffuses into the leaf from the air through the stomata.
- Water which is absorbed from the soil by the roots.
- Sunlight energy which is absorbed by the chlorophyll in chloroplasts.
- Chlorophyll
- Enzymes which are present in chloroplasts.
- A suitable temperature between about 5 degrees C and 40 degrees C so that enzymes can function.
Mineral ions like magnesium Mg2+, iron Fe3+ and nitrate NO3- are indirectly required to manufacture chlorophyll.
Can you list 12 adaptations of leaves for photosynthesis?
Photosynthesis occurs in the leaves of green plants. All leaves consist of a flat part called the lamina. Photosynthesis takes place in the mesophyll cells of the lamina. The lamina is attached to the plant stem by the petiole. Vascular tissue composed of xylem vessels, phloem sieve tubes and companion cells run through the petiole and throughout the lamina in the midrib and veins so that all the mesophyll cells are close to the vascular tissue.
- The lamina is usually broad and flat and this gives it a large surface area to absorb sunlight energy and carbon dioxide.
- The lamina is usually thin and this allows sunlight energy and carbon dioxide to reach all the cells.
- The lamina is held out flat by the veins and this maximizes its exposure to the sunlight.
- The lamina usually lies at 90 degrees to the sunlight and this maximizes its exposure to the sunlight.
- The laminae are spaced out around stems and this maximizes each one’s exposure to the sunlight.
- Waxy cuticle on the outside of both the upper and lower epidermis are waterproof so they can prevent leaves losing water that is needed for photosynthesis.
- Stomatal pores which are present throughout the lower epidermis allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out.
- The palisade mesophyll cells which are directly below the upper epidermis and closest to the sunlight contain a large number of chloroplasts to maximize the amount of light energy absorbed.
- The palisade mesophyll cells are arranged at 90 degrees to the leaf surface to minimize the loss of sunlight energy which occurs as it passes through cells walls and also to allow the chloroplasts to move to the top of the cells in dim light to maximize the amount of light absorbed.
- The intercellular air spaces between the spongy mesophyll cells allow carbon dioxide to diffuse to all the mesophyll cells and oxygen to diffuse away.
- Xylem vessels in the veins running throughout the leaf supply and the mesophyll cells with water and mineral ions.
- Phloem sieve tubes in the veins transport the soluble food made in photosynthesis away from the mesophyll cells to other parts of the plant.
What are four environmental factors that affect the rate of photosynthesis?
The rate of photosynthesis is limited by which of these factors is in the shortest supply. This factor is known as the limiting factor.
- Light limits the rate between dusk and dawn and also during the winter month in temperate climates.
- Temperature limits the rate during the winter month in temperate climates.
- Water limits the rate during the dry season in tropical climates and when the ground is frozen in temperate climates.
- Carbon dioxide limits the rate during the day in most climates since the concentration of carbon dioxide in the air is very low.
What happens to the glucose made in photosynthesis?
- Glucose can be used by the leaf cells in respiration to produce energy.
- Glucose can be condensed to starch by the leaf cells and stored. The starch can be hydrolyzed back to glucose during the night.
- Glucose can be converted to substances like amino acids and protein, vitamins or chlorophyll by leaf cells.
- Glucose can be converted to sucrose and transported via the phloem to other parts of the plant such as growing parts and storage organs where it can be converted to cellulose and used to make cell walls and lipids and stored mainly in seeds.
What are the 6 major mineral ions required by plants?
- Nitrogen in the form of nitrate ions NO3
Functions to make proteins used for plant growth and to make chlorophyll. Deficiency results in poor growth, chlorosis of leaves and underdeveloped leaves. - Magnesium in the form of magnesium ions Mg2+
Functions to make chlorophyll as magnesium forms part of the chlorophyll molecule. Deficiency results in chlorosis of leaves. - Phosphorus in the form of phosphate ions PO4 3-
Functions to make ATP and some proteins. Deficiency results in stunted growth (short stems), dull and purplish green leaves with curly brown edges and poor root growth. - Potassium in the form of potassium ions K+
Functions to help maintain the correct salt balance in cells and to help in photosynthesis. Deficiency results in leaves having yellow-brown margins and brown spots that give a mottled appearance and premature death of leaves. - Sulfur in the form of sulfur ions SO4 2-
Functions to make proteins. Deficiency results in poor growth and chlorosis of leaves. - Calcium in the form of calcium ions Ca2+
Functions to make cell walls in the tip of growing roots and shoots. Deficiency results in poor and stunted growth, death of the growing tips of roots and shoots and poor bud development.
