Why do we need to eat???

Objectives:1. Explain the importance of digestion in providing

nutrients needed for energy and growth.2. Explain what energy is and how it is measured.3. State what nutrients our bodies need to grow, heal and

regulate other body processes

Energy• We basically eat so that our bodies can use the food

to make energy and carry out all the processes that keep us alive and healthy.

• Our bodies use energy for everything…– Moving– Breathing– Sleeping– Even thinking uses energy!!!

Energy

• When we eat and digest food we convert food energy into chemical energy.

• That chemical energy is converted by the cell into other forms of energy– Kinetic energy: Movement– Heat energy: Maintain constant body temperature in

endothermic/warm blooded animals• Endothermic animals require more energy to keep

their bodies warm.

Metabolism• Defined as the sum of all chemical reactions that

occur with in the cells of your body.– catabolism (breaking large molecules into smaller ones)– Anabolism (uses energy to build large molecules from

smaller ones)• Energy requirements determined…– Body mass (more cells = more energy)– Amount of muscle– Activity level– Rate of metabolism: rate as which the body converts

stored energy into working energy

So how much energy do you need???

• The more active you are, the more energy you need. – Muscle activity

• The more active your cells are the more energy they need to function. Therefore they need more food!!!

Basal Metabolic Rate

• Defined as the minimum amount of energy we need to ‘just survive’. (BMR)

• Balancing Energy: We have to balance the amount of energy we take in and the amount of energy we expend.

• If energy in = energy out body mass stays the same• If energy in > energy out body mass increase• If energy in < energy out… you get the picture

BMR

• BMR for females = [655 + (9.6 x mass in kg) + (1.8 x height in cm) –

(4.7 x age in yrs)] x 4.18• BMR for males = [66 + (13.7 x mass in kg) + (5.0 x height in cm) –

(6.8 x age in yrs)] x 4.18Calculate your BMR!!

Calculating Energy

• Energy is measure in J or kJ (1 kJ = 1000 J)• In Canada we usually look at Calories (sometimes

referred to as kcal)…• Calorie: 1 Cal = 4.2 kJTry to find out how much energy (how many calories) you would need to do three of the activities listed on table 2 (page 232)1 kg = 2.3lbs

But what do we need to eat???

• 3 Macromolecules: – Carbohydrates– Lipids– Proteins

• Essential Nutrients: – Vitamins– Minerals

• like carbohydrates, lipids and proteins, vitamins are considered to be organic compounds because they contain carbon and hydrogen atoms.

• they are required in the body in small amounts for metabolic purposes in the cell, but the body cannot produce them even in these small amounts

Vitamins

• unlike carbohydrates, lipids, proteins and vitamins, minerals are considered to be INORGANIC compounds which provide essential elements to the body in ionic form

• like vitamins, they are also required in the body in small amounts for metabolic purposes in the cell.

Minerals

Energy comes in many forms…

Energy in our food is chemical energy and it is locked inside nutrients that we eat, like carbohydrates, lipids, proteins and vitamins and minerals.When we digest our food, enzymes in our body break these nutrients down into raw materials that can be absorbed by our cells. These raw materials are used by the cell to make energy, aid cellular processes, build or repair tissue or help make compounds needed for growth.

Your Task

• Read through page 230-236• Answer the questions on your hand out ‘Food

Energy and Nutrients’

Primary Function:• many vitamins participate in key chemical

reactions of the body as components of coenzymes (which act as enzyme helpers)

• some B vitamins are coenzymes in cellular respiration (ENERGY PRODUCTION)

• other vitamins are required for synthesis of important molecules such as DNA

Vitamins (cont’d)

Other Functions:• most vitamins are involved in maintenance of

cells & tissues in the body• a lack of a vitamin will lead to a deficiency

disease

Vitamins (cont’d)

• Examples of deficiencies- Vitamin A – healthy eyes, skin and hair; deficiency –

night-blindness- Vitamin B (niacin) – needed for cellular respiration;

deficiency - pellagra- Vitamin C – maintenance of capillaries, bones and teeth;

deficiency - scurvy- Vitamin D – development and maintenance of bones

and teeth; deficiency – rickets (bowed legs)

Vitamins (cont’d)

• many vitamins protect cells from free radicals• free radicals are molecules that are by-products of cellular

metabolism• free radicals are unstable molecules that carry an extra

electron – e.g. O2 - and OH-

• these extra electrons can attach themselves to other molecules in the cell and damage them– ( eg. lipids associated with the plasma membrane, DNA or proteins )

• may cause inflammation or even cancer (DNA damage)

Vitamins as Antioxidants

Functions: • some minerals are components of large molecules e.g.

Iron (Fe) in hemoglobin• some minerals form parts of cells or tissues e.g.

calcium salts form the matrix of bone tissue• some minerals help maintain fluid balance in the

blood e.g. Na+• some minerals are used to create electrical impulses

in nerves and muscles e.g. Na+, K+, Ca+

Minerals (cont’d)

Plenary

1. What does basal metabolic rate mean?2. What are some factors that affect energy output?3. Why do young children require less food energy?4. What are vitamins and what are they used for?5. What are minerals and what are they used for?6. What are amino acids?7. Explain what energy is and how it is measured.8. State what nutrients our bodies need to grow, heal

and regulate other body processes

Enzyme Action

Objective1. Review what enzymes are and how they work.2. Discuss the factors that affect enzyme action

3. Plan/Review an investigation that will allow us to observe/determine how temperature and pH affects enzyme activity.

Break down of the Macromolecules (AMYLASE)CHO’s ------digested to------ MONOSACCHARIDES(starch) (glucose)

(PEPTIDASE)PROTEIN -------digested to--------- AMINO ACIDS

(BILE) (LIPASE)FATS ---emulsified----digested to --- GLYCEROL & FATTY ACIDS

Enzymes are proteins that allow chemical reactions in the body to happen by speeding them up and/or allowing them to occur at a lower temperature (body temperature)Enzymes are specific - the active site of an enzyme has a specific shape that matches up with only one kind of molecule (like a key in a lock); because they are specific we need many thousands of them to aid in the many chemical reactions that occur throughout the body

ENZYMES

‘Lock and Key’

Enzymes are sensitiveThe rate at which an enzyme works best is affected by two things…

Temperature: Higher temperatures result in greater enzyme activity…however, temperatures which are too high can cause enzymes to denature (Recall what this means.)

pH: Some enzymes work best at a high pH (basic) and some work best at a low pH (acidic)

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The Plan….