Unit 4: Animal Structure & Function Nutrients & Food

Food for Growth and Maintenance Nutrients are the chemicals that an organism needs in order to grow, build, and repair tissues, and to produce energy. The nutrients that are important for keeping our bodies healthy are carbohydrates, proteins, lipids (fats), water, minerals, and vitamins.

will stop working properly. What and How Much to Eat? Your body needs six essential nutrients in order to stay healthy: CARBS LIPIDS WATER PROTEIN MINERALS VITAMINS These are the building blocks of life, if any are absent from your diet for too long, your cells will stop working properly.

CARBOHYDRATES Main source of energy for the body Composed of C, H, O atoms Three main types: -monosaccharides – one sugar (ex, glucose) -disaccharides – two sugars joined (ex.sucrose) -polysaccharides – many sugars joined (ex. cellulose) This repeats many times

Polysaccharides Starch (amylose) - made by plants for energy storage - made of branched glucose molecules Cellulose - made and stored in plants, found in cell walls - structural molecules, straight rigid shape - we can’t digest cellulose, but provides bulk (fiber) in our diet Glycogen - made in animal cells (stored in the liver & muscles) for energy -in glycogen, glucose subunits are more highly branched compared to starch molecules - when energy is needed in the body, glycogen is broken down into usable glucose

“Carbs” in Our Diet

PROTEINS key building blocks of cells important structural molecules involved in all metabolic activities, and are used to generate motion. Some proteins serve as hormones—chemical messengers released by cells in the body that influence cellular activity in another part of the body. Main protein functions and examples are listed at right

Protein Structure Proteins are the most complex of all nutrients and are made up of long chains of smaller molecules called amino acids and are highly variable in size and shape There are 20 different amino acids that organisms use to build proteins. The human body can make 12 of these amino acids, but must obtain the other 8 amino acids from food sources, the 8 are called essential amino acids. General Amino Acid Central Carbon Carboxyl Group Amino Group Variable Group

Amino acids join together to form peptide bonds

Protein Sources in Our Diet

LIPIDS Provide a concentrated source of energy for the body They help in the absorption of vitamins, are a main component of cell membranes, and serve as insulation for the body. Certain hormones, including sex hormones (ex. testosterone, estrogen), are lipids

Lipid Structure Fats and oils are made up of three fatty acids bonded to a glycerol molecule, which make up a triglyceride. Triglycerides can be either saturated or unsaturated, depending on the structure of their fatty acid chains. Fatty acid chains Glycerol

Saturated fats, because the are linear, can pack together more neatly, say along the walls of your arteries, and Van der Waals forces keep them together. Unsaturated fats have at least one kink in the chain and can't pack like saturated fats. Read more: http://www.physicsforums.com 

Saturated vs. Unsaturated Fats Saturated fats are usually solid at room temperature (ie butter) and are considered to be less healthy Unsaturated fats are usually liquid at room temperature (ie vegetable oil) and are considered to be more healthy http://www.youtube.com/watch?v=3Gqo3Y6WFYA

WATER Our bodies are 55 – 60 % water Water is needed for chemical reactions, to digest food, and to eliminate waste products. Water is also necessary to maintain your blood volume, to regulate body temperature, and to keep your skin moist. We need about 2L of water per day

VITAMINS Vitamins are organic molecules that the body requires in small amounts as an essential nutrient regulate cell functions, growth, and development are either fat soluble (will dissolve in fats) or water soluble (will dissolve in water).

MINERALS Minerals are elements (ex. calcium, sodium, oxygen, iron, phosophorus) required by the body in small amounts and play a role in cell processes and repair

Factors That Affect Energy Requirements Metabolic rate depends on a number of factors: Body size: The larger the body, the more energy is required to stay alive. Physical activity: Muscle burns more energy than fat, so physical activity requires more energy. Sex: Males are typically larger in size and have a greater proportion of muscle mass than females of the same size, age, and fitness level. Age: Metabolic rate decreases with age (in part due to decreased physical activity and the loss of muscle mass). Hereditary factors: Some individuals have a naturally high metabolic rate. In these individuals, the chemical energy obtained from food is very quickly converted into other forms of energy.

Average Energy Requirements

Measuring Energy and BMR Energy is measured using an SI unit: the joule (J). Joules are small, so we use the kilojoule (kJ) to refer to the energy requirements of people or the energy stored in foods (1 kJ = 1000 J). Another unit is also used - a calorie (small c) is the amount of energy required to raise the temperature of 1 g of water by 1 °C. When referring to food energy, Calorie (big C) is used. One Calorie really means 1 kilocalorie, which is equal to 1000 calories, or 4180 J. The rate at which energy is used by an organism when it is at rest is referred to as the basal metabolic rate (BMR). The BMR is estimated using a calculation that takes into account four variables: height, weight, age, and sex. Males tend to have a higher BMR than females by about 10 %. Energy requirements also depend on activity level.

HEALTHY EATING

Carbs: 45-65% of your daily calories Protein: 10-35% of your daily calories Fats: 25-35% of your daily calories