NUTRITION

Section 6 & 7

Define the term ‘nutrition’

The process by which living organisms obtain or make food.

What are the two types of nutrition?

Heterotrophic & Autotrophic Nutrition

What is an ‘autotroph’?

An organism that uses simple inorganic compounds to manufacture complex organic food substances.

State the 3 types of Heterotrophic Nutrition

Holozoic, Parasitic and Saprophytic

Animals, fungi and most bacteria are _______. Humans feed by means of _______ nutrition.

Heterotrophs, Holozoic

What is a saprophyte?

An organism that feeds by obtaining organic food from dead remains of other organisms. They digest the complex organic food outside of their bodies and then absorb the simpler inorganic substances.

What is meant by the term ‘photosynthesis’?

Photosynthesis is the process by which green plants convert carbon dioxide and water into glucose by using sunlight energy absorbed by chlorophyll in the chloroplasts. Oxygen is released as a byproduct

What is the chemical equation for photosynthesis?

6CO2​+6H2​O —→ light energy in chlorophyll = ​C6​H12​O6​ + 6O2​

What occurs in the light stage of photosynthesis?

The light energy captured by the chlorophyll splits water molecules into Hydrogen and oxygen. The oxygen is released as a gas (waste product)

The dark stage of photosynthesis is also called the?

Light Independent Stage

What occurs in the dark stage of photosynthesis?

The hydrogen atoms are used to reduce the Carbon Dioxide molecules to form glucose.

The dark stage of photosynthesis takes place whether or not light is present. However, the dark stage requires ______

enzymes

State the 6 conditions needed for photosynthesis to take place

1. Carbon Dioxide

2. Water

3. Sunlight

4. Enzymes

5. Chlorophyll

6. A suitable temperature (5-40^C)

What is the role of chlorophyll in photosynthesis?

Chlorophyll captures sunlight energy

Label the image of the internal structure of a leaf from A-G

A - Waxy Cuticle

B - Upper Epidermis

C - Palisade Mesophyll Layer/Cells

D - Spongy Mesophyll Layer/Cells

E - Vascular Tissue (Xylem & Phloem)

F - Guard Cells

G - Stomatal Pore

How is the external structure of a leaf adapted to carry out photosynthesis efficiently?

1. The lamina is broad and flat, providing a large surface area to maximize sunlight and carbon dioxide absorption

2. The lamina is thin to allow sunlight energy and carbon dioxide to reach all cells

3. The lamina is held out flat by the veins - maximise sunlight absorption

4. The lamina usually lies at 90 degrees to the sunlight

5. The laminae are spaced out around stems, giving each maximum exposure to sunlight

How is the internal structure of a leaf adapted to carry out photosynthesis efficiently?

• Waxy cuticle - waterproof so prevents excess water loss that is needed for photosynthesis

• Stomatal pores - allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out

• Palisade Mesophyll Cells - Directly below upper epidermis and closest to sunlight, contain large amounts of chloroplasts to maximise sunlight energy absorption, arranged at 90 degrees to the leaf’s surface (allows chloroplasts to move to the top in dim light)

• Intercellular Air Spaces - Diffusion of gases

• Phloem Sieve Tubes - Transport the soluble food made in photosynthesis from the mesophyll cells to other parts of the plant

• Xylem Vessels - Supply all the mesophyll cells with water and mineral ions.

The four main factors that affect the rate of photosynthesis are ______, _____ ______, _______ and ______

light, Carbon Dioxide, Temperature and Water

When does temperature become a limiting factor of photosynthesis?

During winter months in temperate climates

When does water become a limiting factor of photosynthesis?

• Dry season in tropical climates

• When the ground is frozen in temperate climates

What 3 things can happen to the glucose produced during photosynthesis?

1. Used in respiration to produce energy

2. Converted to starch and stored

3. Converted to other organic substances - amino acids, protein, vitamins, etc.

What is Nitrogen used for in plants?

Nitrogen is needed for the formation of proteins used for plant growth and it’s also used to make chlorophyll

State some visible characteristics that can be observed from a plant deficient in Nitrogen

• Stunted growth

• Chlorosis (yellowing of leaves)

• Underdeveloped Leaves

What is Magnesium used for in plants?

To make chlorophyll; magnesium forms a part of the chlorophyll molecule

Outline the steps in testing for Protein in a substance

1. Add an equal volume of sodium hydroxide solution to the substance and shake.

2. Add a few drops of dilute Copper Sulfate Solution and shake.

3. Or add an equal volume of biuret reagent and shake

4. If protein is present the solution will turn purple

______ ______ is used to test for Reducing Sugars

Benedict’s Solution

Explain the necessity for hydrolysis and neutralisation in testing for non-reducing sugars.

Non-reducing sugars, like sucrose, do not react with Benedict’s solution because they do not have the chemical group needed to reduce it. To test for them, the sugar must first be broken down into simpler sugars that can react. This is done by boiling the solution with a little dilute acid, which breaks the non-reducing sugar into reducing sugars — a process called hydrolysis. After this, the solution is acidic, so it needs to be neutralised using an alkali like sodium hydroxide. Once the solution is neutral, Benedict’s solution can be added again and heated. If a non-reducing sugar was present, the test will now give a positive result, usually shown by a colour change from blue to brick red.

List 2 chemical properties of monosaccharides and disaccharides

Have a sweet taste

Soluble in water

List the 3 monosaccharides

1. Fructose

2. Glucose

3. Galactose

List the 3 disaccharides

1. Maltose

2. Sucrose

3. Lactose

Disaccharides are formed by chemically joining two monosaccharide molecules via a process called ________

dehydration synthesis OR condensation

__________ is the process used to split disaccharide/polysaccharide molecules

Hydrolysis

A lipid molecule is composed of 4 smaller molecules: ___ Fatty Acid molecules and 1 ______ molecule

3; glycerol

State 1 examples of a soluble protein and 1 example of an insoluble protein

Soluble - haemoglobin, albumin

Insoluble - collagen

What is mechanical digestion?

The breaking up of large pieces of food into smaller pieces. It gives digestive enzymes a larger surface area to act upon and makes food easy to swallow.

Mechanical digestion begins in the ______ where it is carried out mainly by the ______

mouth;teeth

List the 4 types of teeth in a human

1. Incisors (8) - to cut food, to bite of food

2. Canine (4) - to grip and tear food

3. Premolars (8) - To crush and grind food

4. Molars (12) - To crush and grind food

A tooth is divided into 2 parts: the _____ and the ______

root and the crown

Why are fibres important in the structure of a tooth?

To anchor the tooth in the jawbone and to allow slight movement for shock absorption

What is an enzyme?

Enzymes are biological catalysts that speed up chemical reactions occuring in living organisms without being changed themselves.

State FOUR properties of an enzyme

1. Enzymes work at a particular temperature knows at the optimum temperature

2. Enzymes are specific - each only catalyzes one type of reaction

3. High temps denature enzymes

4. Enzymes work best at an optimum pH (pH 7)

5. Extremes of acidity or alkalinity denature most enzymes

6. The action of enzymes is inhibited by certain poisons

State the name of the enzyme found in saliva and its use

Salivary Amylase - breaks down starch into maltose

Name 2 enzymes found in the stomach and their uses

1. Pepsin - begins the breakdown of protein into peptides

2. Rennin - produced in infants to clot soluble proteins in milk so protein is retained in the stomach

Where is bile stored?

In the gall bladder

Organic bile salts are used to emulsify lipids. What is meant by this?

They break down lipid droplets into smaller droplets increasing their surface area for digestion.

List the 3 digestive enzymes in Pancreatic Juice and their uses

1. Pancreatic Amylase - continues to breakdown starch into maltose

2. Pancreatic Lipase - digests lipids into fatty acids and glycerol

3. Trypsin - continues to break down protein into peptides

State 3 enzymes found in intestinal juice

Maltase, Sucrase Lactase, Peptidase

List THREE ways that the ileum is adapted to efficient absorption

1. It is very long providing a large surface area for rapid absorption

2. Its inner surface has thousands of villi - surface area

3. Each villus has a network of capillaries and a lacteal inside. These provide a means of rapidly transporting products of digestion

4. The wall of each villus known as the epithelium, is only one cell thick

5. The epithelial cells have microvilli

What is the function of the lymphatic vessel in the villi

To transport fatty substances to the blood before it enters the heart

List 4 substances that are absorbed in the ileum

• Water

• Vitamins

• Minerals

• Monosaccharides

• Fatty acids & glycerol

• Amino Acids

What two things are absorbed in the colon?

Water and mineral salts

What does the term ‘assimilation’ mean?

The process by which the body uses the products of digestion.

What happens to excess amino acids when they’re absorbed by the body

When excess amino acids are absorbed by the body, they can't be stored like fats or carbohydrates. Instead, the liver breaks them down in a process called deamination. This removes the part of the amino acid that contains nitrogen, which is turned into urea and passed out of the body in urine. The rest of the molecule can be used for energy or turned into fat and stored.

Two hormones secreted into the blood by the pancreas are responsible for blood sugar control. They are _______ and ______

glucagon and insulin

What happens in the body when blood sugar falls?

The pancreas secretes glucagon which stimulates the liver to convert stored glycogen back to glucose for respiration.

What happens in the body when blood sugar rises?

The pancreas secretes insulin which stimulates body cells to absorb glucose for respiration. The liver converts excess glucose to glycogen and stores it.

State 3 uses of lipids in the body

1. To make cell membranes of newly formed cells

2. To provide energy when carbohydrates have been used up

3. For storage

4. For insulation

What is Xerophthalmia and what nutrient deficiency is it cause by?

Xerophthalmia is when the eyes fail to produce tears leading to a dry damaged cornea and sometimes blindness. It is caused by a Vitamin A deficiency

State 1 function of Vitamin B1 in the body

• Important for the proper functioning of the nervous system

• Aids in respiration to produce energy

List 3 symptoms of scurvy

• Swollen, red, gums

• Loose teeth

• Wounds do not heal

• Red-blue spots on the skin

State two benefits of a vegetarian diet?

1. The diet is low in saturated fats and cholesterol, therefore vegetarians are less prone to obesity, heart disease, hypertension, diabetes and gall stones.

2. The diet is high in dietary fibre, therefore, vegetarians are less likely to suffer from constipation, colon cancer, and certain other types of cancer