Chemical Digestion and Enzymes

IntroductionChemical digestion

o Aids in preparing food particles for absorption. o Takes place through the action of . o Large food molecules are chemically changed into smaller molecules

The types of nutrients that are digested through mechanical and chemical action are .

Carbohydrates o Made up of carbon, hydrogen, and oxygen o Quick sources of energy and include both simple molecules (

) and complex molecules ( ) o Common food sources are breads, pasta, and fruit

Proteins o Large complex molecules that contain ______________________________

__________________________________________________________.o Serve as the structural framework of most living tissue and also serve as

enzymes, but are not usually used as an energy source. o Made up of smaller molecules called . o Common food sources include meat, eggs, and nuts.

Lipids o Make up fats, oils, and waxes. o Contain carbon, hydrogen and oxygen. o Capable of storing great amounts of energy in their chemical bonds. o Common food sources include margarine, cooking oil, and animal fat

found in meat.

- biological catalyst that can speed up chemical reactions without being altered in the process.

Grade 11 BiologyUnit 2: Digestion and Nutrition

Digestive EnzymesEnzymes are very specific; they only act on certain molecules called a ___________. Each type of enzyme is very specific in terms of which substrate it will act on. The names for enzymes start with the name of the substrate involved and end in "__________". For example, an enzyme that acts on a protein molecule is a . An enzyme that acts on a carbohydrate molecule is a . And an enzyme that acts on a lipid molecule is a _______.

An analogy that is often used to understand enzyme action is the “____________________“ concept in which the substrate acts as the __________ and the enzyme is the _____________.

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Grade 11 BiologyUnit 2: Digestion and Nutrition

Chemical Digestion in the Human Digestive Tract

Location Secretion Type of Enzyme Action

Mouth Saliva Begins digestion of starch to simple sugars.

Stomach Gastric Juice Begins digestion of proteins.

Small Intestine

Pancreatic Juice

Completes digestion of starch to simple sugars.

Continues digestion of proteins.

Completes digestion of lipids to fatty acids and glycerol with the help of bile.

Intestinal Juice

Completes digestion of proteins to amino acids.

Completes digestion of carbohydrates to simple sugars.

In addition to carbohydrates, proteins, and lipids, nucleic acids are also nutrient molecules that are broken down in the digestive system. When nucleic acids are broken down chemically, the results are nucleotides, which contain nitrogen, phosphorus, and sugars.

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Once nutrient molecules are broken down chemically and mechanically, they are absorbed into the circulatory system. Most absorption occurs in the small

intestine except vitamins, minerals, and water are absorbed in the large intestine.

Grade 11 BiologyUnit 2: Digestion and Nutrition

Factors that Affect Enzyme Action1. ____________

o The pH of a solution refers to how acidic or basic it is. o An enzyme that is structurally changed as a result of pH is said to be

___________________; which leads to a loss of enzymatic activity. o The _________________ in the stomach, _____________, is activated by this

acidic environment and becomes deactivated when it enters the basic environment of the small intestine

o Less acidic environment of the small intestine allows the enzymes produced by the small intestine and pancreas to be more effective in digestion.

2. ________________________o When a food particle is mechanically broken down by chewing it into a

number of smaller particles, the total surface area of exposed particles _________.

o An increased surface area allows more enzymes to act on the food particles.

3. ________________________ o Small organic molecules that are not proteins that help to facilitate the

enzyme-substrate connection and are often produced from various vitamins

o They are located at the active site of the enzyme molecule and facilitate the "lock and key" action of the enzyme and substrate molecules.

o They are not themselves affected by the action of the enzyme on the substrate molecule.

4. ________________________

o Compete with substrate molecules for the active sites of the enzymes. o Binds to the enzyme, rendering the enzyme ineffective on the substrate

molecule that it was designed to act on.

5. _________________________o Most reactions in the human body that involve enzyme activity occur

within a fairly small temperature range — usually from about 30°C to 40°C .

o Temperatures outside of this range can cause denaturation of the enzyme.

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Enzymes are very important in the human digestive system. Their production and accumulation in the body are carefully controlled so that homeostasis is

maintained.

Grade 11 BiologyUnit 2: Digestion and Nutrition

The Liver: Introductiono Almost all the blood circulating from

the intestines to the heart passes through the liver.

o Everything you eat that gets into the bloodstream passes through your liver.

o The liver then either stores nutrients or breaks them down even more.

o The liver transforms nutrients into proteins, fats, and cholesterol and stores vitamins (A, D, K, and B12), minerals, and carbohydrates.

The liver also plays the role of a filtering system. Toxic substances, including alcohol, are transformed into less harmful substances.

The Role of the Liver in HomeostasisGlucose is necessary for cells to produce ATP. The amount of ATP that the body needs at any one time changes; therefore, the body needs to be able to store glucose when it is not needed, but release glucose when it is needed.

o Two hormones responsible for controlling the concentration of glucose in the blood are ______________ and ____________, which are produced in the _________________.

o The liver also plays an important role in blood glucose control. It is here that excess glucose is stored in the form of __________________.

o When you eat a meal, blood glucose levels start to ________. When they reach a certain concentration, receptors in the pancreas stimulate the production of ______________. This hormone reaches the liver, which then converts blood glucose into glycogen. Blood glucose levels ________ and return to a _________.

o If blood glucose levels drop below a certain level, receptors in the pancreas stimulate the production of ___________. This hormone reaches the liver, which then converts glycogen into glucose. Glucose is released into the bloodstream and blood glucose levels _________ until they return to a ____________________.

Negative Feedback MechanismThe maintenance of adequate blood glucose levels is an example of a negative feedback mechanism.

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Grade 11 BiologyUnit 2: Digestion and Nutrition

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Grade 11 BiologyUnit 2: Digestion and Nutrition

Digestion and NutritionIntroductionThere are six basic types of nutrients (carbohydrates, lipids, proteins, vitamins, minerals, and water) used by the human body. Some of the uses that your body makes of nutrients are ___________________ and others are ____________________ in nature.

Carbohydrateso Used by the cells of the body to produce _________________. o The human body cannot produce its own carbohydrates and must rely on

eating other organisms to acquire them. o Primary source of energy for humans, supplying 50 to 80% of the total

energy required. o Provide short-term energy to cells through the process of cellular

respiration.

There are 3 main types of carbohydrates

1. Monosaccharides o ______________________________________o Most common is glucose which provides energy for

cellular respiration and the production of ATP and fructose which is found in fruit

2. Disaccharides o _________________________________o Made by joining together simple sugars with

chemical bonds. o Most common are sucrose (white table

sugar), and lactose (dairy products)

3. Polysaccharides o Complex sugars made of many simple sugars joined by

__________________.o Several hundred glucose molecules join together to form ________________

which are the primary form of storage carbohydrate used by plants.

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Sucrose

Grade 11 BiologyUnit 2: Digestion and Nutrition

o ___________________, which is found in the cell wall of plants, is the fibre we need in our diets; which our digestive system requires to function correctly.

Food Sources of CarbohydratesSimple Carbohydrates

o Usually sweet-tasting like cookies, candy, pop, pastries, fruits, and juices. o Good sources of carbohydrates, but do not always contain vitamins or

minerals. o Considered “__________________________”

Complex Carbohydrateso Starchy carbohydrates take _______________ to be digested than simple

carbohydrates and therefore provide a more ________________________ source of energy for the body.

o Complex carbs, are found in breads, pasta, rice, and potatoes and most vegetables like corn, tomatoes, carrots, and lettuce

Lipids (Fats)o Are only used for _____________________ when the supply of carbohydrates in

the bloodstream is _____________o Difficult to break downo Stored source of ____________________ energy for the bodyo About ______________ as energetic as one gram of carbohydrateo Important in helping the body absorb vitamins effectivelyo Key structural components of cell membranes, a form of insulation for the

body and serve as protection for delicate vital organso The raw material from which ____________________ are producedo An important component in the transmission of nerve impulses in the

nervous system

Cholesterolo ____________________________ that occurs naturally in the bodyo Produced by the ________________ and is transported by the blood to cells o Found in all animal products o Very important component of _________________________________. o The body processes cholesterol in the diet in different ways, depending

on what type of food contained the cholesterol that was ingested. There are two types of cholesterol in the blood:

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Grade 11 BiologyUnit 2: Digestion and Nutrition

1. LDL ( ________” cholesterol)o ______________________________________o Can accumulate on artery walls and restrict blood flow. o Liver maintains a "normal" level of cholesterol by removing excess

LDL from the blood

2. HDL ("__________” cholesterol) o ______________________________________o Lowers blood cholesterol by carrying LDLs back to the liver which

can break down the LDL moleculeo The level of HDL in the blood can be increased if you decrease the

amount of saturated fat in your diet and if you increase your physical activity.

o HDL can reduce the risk of heart attack and stroke

Comparison between Unsaturated and Saturated Fats

Unsaturated Fats Saturated Fats

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Grade 11 BiologyUnit 2: Digestion and Nutrition

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It is recommended that no more than 30% of your total energy intake should be in the form of lipids, since lipid molecules store about twice as much

chemical energy as carbohydrate molecules.

Grade 11 BiologyUnit 2: Digestion and Nutrition

Proteinso Primary __________________________ component of all cells o Broken down by your digestive system into _____________________________

molecules which are then rebuilt into other proteins.o Muscle, cartilage, ligaments, skin, and hair are all examples of protein

molecules. o Smaller protein molecules also play vital roles as hormones, antibodies,

enzymes, and hemoglobin. o Vary in size and shape which allows for incredible diversity of functions

performed by proteins

Amino Acidso 20 amino acids o 9 of them cannot be made by the human body and

are referred to as the __________________________ _________________ because they must be eaten.

o All 20 "building blocks" allow the synthesis of all of the many proteins that your body manufactures.

Example of the amino acid glycine:

Food Sources of Proteins

Complete Proteins Incomplete Proteins

Vitaminso ____________________ substances (must

contain a carbon chain) that are needed in very small amounts.

o Part of the structure of many ____________.

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It is recommended that you consume 0.8 - 1.5 grams of protein per kilogram of body weight. People who are on a vegetarian diet need to pay special attention to the foods they eat to make sure that they acquire adequate amounts of all

amino acids.

Grade 11 BiologyUnit 2: Digestion and Nutrition

o If your diet is deficient in a certain vitamin, the result could be an enzyme deficiency that can in turn cause serious health problems.

o Are chemicals that are necessary for normal growth and _________________________.

o Some vitamins are required for the chemical reactions that result in the release of energy from carbohydrates, fats, and proteins.

In all, there are 13 vitamins; that are divided into two groups:

i. Fat-soluble vitamins (______________________________) are not as readily excreted from the body stored in the liver

ii. Water-soluble vitamins (________________________________) can become depleted more quickly leading to a deficiency must be included regularly in your diet

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Grade 11 BiologyUnit 2: Digestion and Nutrition

Minerals

Unlike vitamins, minerals are ______________________ — that is, they are not based on a carbon chain. Most minerals are molecules of a single _______________. Minerals do not provide ____________________ for the body, but they do play very important roles in many cellular reactions. For example, minerals are vital in maintaining nervous system functions, water balance, and skeletal health.

There are about 16 essential minerals. o ______________ is found in table salt and helps maintain proper blood

pressure. o _____________________ is found in bananas and keeps nerves and muscles

working properly. o ______________ is found in dairy products and is needed to build strong

bones. o ____________ is found in red meats and wholegrain vegetables; it is very

important in the production of red blood cells.

Watero Water is an essential component of ____________________ — the intracellular

fluid that makes up all ____________. o Water is an important _________________ because most chemical reactions in

the body occur between molecules that are dissolved in it. o Water is also an important lubricant and bathes body cells. o Water is a ________________ component of blood and _______________ vital

nutrients and unneeded wastes throughout the body. o Water also serves an important role in ________________________________.

Water is acquired in many ways. Drinking water is the most obvious way that you obtain water. However, many foods have a high water content, such as fruit and vegetables. Also, many cellular processes involve the production of water. For these reasons, it is suggested that you drink about 8 cups of water or other non-caffeinated fluids per day to maintain adequate hydration.

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This number is the actual amount (quantity) of the nutrient in the specific amount of food. Even if the nutrient amount is zero, it is listed.

The % Daily Value (%DV) gives a context to the actual amount of a nutrient. It indicates at a glance how much of a nutrient is in the specific amount of food.

The facts table lists calories and some core nutrients.

All the information in Nutrition Facts is based on a specific amount of food.

Grade 11 BiologyUnit 2: Digestion and Nutrition

Dietary Decisions

Labels on packaged foods are helpful in that they tell you what vitamins, minerals, and nutrients are contained in the foods that you buy. An informative label might look like this:

Dieticians of Canada have identified a list of "Guidelines for Healthy Eating":

1. Enjoy a variety of foods.2. Emphasize whole grain cereals, breads, other whole grain products,

vegetables, and fruit.3. Choose lower-fat dairy products, leaner meats, and foods prepared with

little or no fat.4. Achieve and maintain a healthy body weight by enjoying regular physical

activity and healthy eating.5. Limit salt, alcohol, and caffeine.

They stress that there are no "good" or "bad" foods. Consumers do not have to give up foods that they like but instead try to achieve variety and moderation in their diet.

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