 |
The University of the West Indies Department of Biological and Chemical Sciences |
BL 05B - Preliminary Biology II |
|
The University of the West Indies Department of Biological and Chemical Sciences |
BL 05B - Preliminary Biology II |
HOLOZOIC NUTRITION
Chapter 10, pp 289-290Textbook: most A- level and first year general Bio texts will cover this in sufficient detail.
Examples:
Understanding Biology for Advanced Level by Glenn Toole & Susan Toole (3rd edition)
Biology by Arms and Camp (4th ed.)
Biology by Solomon, Berg & Martin (5th ed.)
Animals are heterotrophs - cannot make their own food from inorganic substances as plants do but must ingest organic molecules from the environment.
Modes of nutrition:
Herbivory - Carnivory - Omnivory -Note - each mode of nutrition has digestive system (mouthparts, gut) modified for handling and digesting the food type ingested.
Digestion - the mechanical and chemical breakdown of food into small organic molecules that can be absorbed from the gut.Nutrients required by animals:
Macronutrients
Uses
1. As energy sources in respiration to produce ATP.
2. To provide carbon (C) atoms that can be used to form other required organic molecules.
- Most common energy source for humans is starch, plants make and store this, found in grains, potatoes, beans.
- Proteins º amino acids º proteins (muscles).
- Fats and oils are important components of cell membranes, cytoplasmic constituents (e.g. mitochondria), insulation (around nerve axons) and steroid biosynthesis (e.g. some hormones).
Storage
- CHO stored as glycogen in muscle & liver.
- Proteins: not stored as such, excess is deaminated converted to amino acids, processed as fat or CHO.
- Fat stored as...fat.
Malnourishment
CHO
Obesity - common diet related problem (excess) in industrialised countries. This is an effect of poor nutrition as are deficiency diseases.
Body mass index (BMI) = wt (kg) / h2 (m)
BMI of 20-25 is ‘healthy’, over 30 is considered obese. (U.N.) [women, models]
Protein
- Deficiency disease is due to lack of essential amino acids. Why?
For humans, essential amino acids are Arg, His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val.
1. Kwashiorkor - mostly growing children; symptoms: skin, retarded growth, lethargy, oedema (swelling of tissues due to fluid retention).
2. Marasmus - deficiency of both total calories and protein º bloated belly, shrivelled skin.
- Both can cause permanent brain damage if not treated early.
- Sources of protein: beans, dairy, meat, & cereals.
How much protein needed per day? About 56 g dry weight (1 lb is about 500 g) - most people eat too much.
Micronutrients
- Substances an organism must have in its diet in small quantities because it cannot make them itself or not as fast as it needs them.
Vitamins (organic compounds)
Minerals (inorganic)
Vitamins
A diverse and chemically unrelated group of compounds. Requirements vary between animal groups, e.g. humans do not make vitamin C as many animals do. In ruminants some vitamins are synthesised by gut bacteria.
Fat-soluble or water-soluble (see table 10.6)
Water-soluble vitamins (B and C vitamins): some are coenzymes needed in metabolism, e.g. riboflavin (vitamin B2, part of FAD - flavine adenine dinucleotide) is a coenzyme in respiration and protein synthesis; niacin (nicotinic acid) is part of NAD+ (nicotinamide adenine dinucleotide) and NADP+ (NAD phosphate).
Fat-soluble vitamins: vitamins A, D, E, K
A (retinol) - part of visual pigment in eye, deficiency = night blindness
D (calciferol) - absorption of Ca and P to build bone, deficiency = rickets
E (tocopherol) - antioxidant, anticancer, fertility.
K (phylloquinones) - necessary for production of blood clotting factors e.g. prothrombin.
vitamin-rich foods: fresh fruits and vegetables
Note: excess of fat-soluble soluble vitamins can be stored in fatty tissue of the body and can accumulate to toxic levels.
Minerals (Table 9.11, p 285)
Elements needed as ions, e.g. sodium may be ingested as sodium ion (Na+) in pot salt (NaCl).
- Some are needed in larger amounts (more than 100 mg per day) than others.
e.g. Sodium (Na) and potassium (K) - vital to the function of each nerve cell and muscle.
Calcium (Ca) - for muscle activity and bone formation (CaPO4).
Phosphorous (P) - is needed for bone formation, nucleotides, energy metabolism, phospholipids.
Also magnesium (Mg), chlorine (Cl), sulphur (S).
Trace minerals (less than 100 mg daily)
e.g. Iron (Fe) - component of heme in haemoglobin.
Iodine (I) - thyroid hormone, thyroxine, which regulates metabolism.
Cobalt (Co) - as a component of vitamin B12 (cyanocobalamin), and red blood cell formation.
Also boron (B), chromium (Cr), copper (Cu), fluorine (F), manganese (Mn), molybdenum (Mo) selenium (Se), and zinc (Zn).
Sources of minerals include: meats, seafood, dairy, whole grains, nuts, legumes, spinach.
Other nutritional requirements: Water & fibre.
NB: Vegetarian diet is associated with decreased risk of heart disease and of some types of cancers.
Audio-visual material available in the LRC:
Kit 20 Digestion
FS 33 What Happens to your Food
VC 41 The Rotten World About Us
VC 1327 Digestion- The New Living Body
Web resources (click on the underlined URL)
Nutrition lectures in Biology 181 at the University of Arizona:
Other
Questions? Comments? Suggest other web links? Email me: lwaterman(at)uwichill.edu.bb
Last modified: February 15, 2008