6.3.5 Chemical digestion

Chemical digestion

Core

• State the significance of chemical digestion in 

the alimentary canal in producing small, soluble 

molecules that can be absorbed

• State where, in the alimentary canal, amylase, 

protease and lipase enzymes are secreted

• State the functions of a typical amylase, a 

protease and a lipase, listing the substrate and 

end-products

Chemical digestion in the alimentary canal turns large insoluble molecules into smaller water soluble molecules by breaking them down with enzymes in the mouth, stomach and small intestine.

Amylase is secreted in the mouth and small intestine

Protease is secreted in the stomach and small intestine

Lipase is secreted in the small intestine

Protease may turn a protein into amino acids

Lipase may turn a fat into fatty acids and glycerol

Amylase may turn Starch into maltose

6.3.4 Mechanical and physical digestion (Unfinished)

Mechanical and physical digestion

Core

• Define digestion

• Describe the role of longitudinal and circular 

muscles in peristalsis

• Outline the role of bile in emulsifying fats, 

to increase the surface area for the action of 

enzymes

Digestion is the breaking down of food molecules into smaller food molecules in the Alimentary Canal. These molecules are broken down from large insoluble molecules into smaller water - soluble molecules using chemical and mechanical processes.

6.3.3 Human Alimentary Canal

Human Alimentary Canal

Core

Define Ingestion

Define egestion

Identify the main regions of the alimentary canal 

and associated organs

Identify the main regions of the alimentary canal 

and associated organs

Ingestion is the taking in of food to the body through the mouth.

Egestion is the passing of food out of the body which has not been digested, it leaves in the feaces through the anus.

Food enters the mouth and is turned into a bolus with the help of Saliva which contains mucus, Amalayse and water. The amalayse breaks down starch in the food into mucusand the mucus lubricates the food so that it can easily pass through the esophagus. Once food is ready to be swallowed, a sphincter muscle covering the esophagus opens and food travels into the Stomach. In the Stomach the food is made into Chyme with the help of protease. The proteins in the food are broken down into smaller and smaller molecules with the help of hydroclhoric acid (which helps the protease to fuction in the correct PH) Once the food has been broken down into chyme it is passed into the Small intestine where Pancreatic juice and bile are secreted. In the Pancreatic juice is an alkaline substance which neutralizes the churn so that amalayse and lipase may work on it. Bile emulsifies the churn, breaking down fats into smaller molecules for the lipase to have an easier job of working on it.

6.3.1 Diet (unfinished)

Diet

Core

• State what is meant by the term balanced diet 

and describe a balanced diet related to age, sex 

and activity of an individual

• Describe the effects of malnutrition in relation to 

starvation, coronary heart disease, constipation 

and obesity

A balanced diet is a diet in which A person is receiving all the nutrients required for proper growth. Different people may have different requirements in terms of their diet, for example a Pregnant women may need to eat more than a man (the average woman requires less than a man, unless pregnant or ill) If a person has a job which requires a lot of movement, then they will obviously need to eat a diet consisting of more carbohydrates, however a person who is sat down for the majority of the day will need to eat less as he will be burning less.

6.2.3 Mineral Requirements

Mineral Requirements

Core

• Describe the importance of:

• nitrate ions for protein synthesis

• magnesium ions for chlorophyll synthesis

Extended

• Explain the effects of nitrate ion and 

magnesium ion deficiency on plant growth

Nitrate ions and Magnesium ions are taken from the soil by either diffusion or active transport. Nitrate ions are primarily used for making proteins whereas magnesium ions are primarily used to produce chlorophyll.

A lack of Nitrate ions will result in not enough proteins being produced, and will result in weak growth/yellow leaves. A lack of Magnesium ions will result in not enough chlorophyll being produced, limiting the rate of photosynthesis and resulting in yellowing between the veins in the leaves of plants.

6.2.2 Leaf Structure

Leaf Structure

• Identify and label the cuticle, cellular and tissue 

structure of a dicotyledonous leaf, as seen in 

cross-section under the light microscope, and 

describe the significance of these features in 

terms of functions, to include:

• distribution of chloroplasts – photosynthesis

• stomata and mesophyll cells – gas exchange

• vascular bundles (xylem and phloem) – transport 

and support

The cuticle prevents water loss via evaporation as it has a waxy layer which prevents water from getting too hot.

Chloroplasts (chlorophyll inside them) trap sunlight and carry out the process known as photosynthesis - more chloroplasts and enough raw materials and light to support them will mean a higher rate of photosynthesis 

Stomata open to allow gases to diffuse inside the plant leaf, the mesophyll cells all contain chloroplast and so C02 which has diffused into the leaf through the Stomata will eventually reach the Mesophyll cells and contribute to photosynthesis.

Xylem are involved in water uptake. There is always a lower pressure level at the top of the Xylem as a result of transpiration, this means that water is constantly moving up the Xylem tubing towards the leaves from the soil/root hair cells.

Phloem transport sucrose around the plant from places of production to sinks.

6.2 Photosynthesis

Photosynthesis

Core

Define Photosynthesis

State the word equation for the production of 

simple sugars and oxygen

Describe the intake of carbon dioxide and water 

by plants

Explain that chlorophyll traps light energy 

and converts it into chemical energy for the 

formation of carbohydrates and their subsequent 

storage

Extended

State the balanced equation for 

photosynthesis in symbols

Investigate and state the effect of varying 

light intensity, carbon dioxide concentration 

and temperature on the rate of photosynthesis 

(e.g. in submerged aquatic plants)

Define the term limiting factor as something 

present in the environment in such short 

supply that it restricts life processes

Explain the concept of limiting factors in 

photosynthesis

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Photosynthesis is the process by which plants produce Carbohydrates from raw materials by trapping light.

Word Equation for simple sugars and oxygen

Carbon Dioxide + Water --------> Glucose + Oxygen

Water is taken from soil by root hair cells, this water travels up the xylem tubing since there is a lower pressure at the top (transpiration causing water on leaves of plant to evaporate meaning there is a lower pressure up, constantly) Carbon Dioxide is taken into the plant by process of diffusion whilst Stomata on the plant leaves are open, the C02 diffuses into the plant leaves and spreads around.

Varying light intensity on a plant may adversely damage it. If an plant only receives a very low level of light, it will not photosynthesize as much as a plant in normal light and this is because there is less light being converted into chemical energy for the plant to actually undergo the process of photosynthesis. Low levels of C02 would also adversely affect the plant as it would be missing one half of the requirements for photosynthesis. Although too much of these two substances would not harm the plant, at a certain point the rate of photosynthesis neither speeds up or decreases. Low temperature means chemical reactions can not take place as fast as normal and so the rate of photosynthesis is decreased, once again though a certain point is reached as temperature increases and the rate of photosynthesis will no longer increase.

A limiting factor is a factor of the environment which has a certain impact on the rate of photosynthesis of a plant. For example C02 and Temperature can be limiting factors if they are low (temp) or sparsely found (levels of C02)