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A diagram showing the simplified process of how an enzyme acts in a substrate reaction. The enzyme binds to the substrate, causes a reaction which splits the substrate into two parts and then releases the parts as products.

Enzymes are proteins, which are large molecules that perform many jobs in your body. Enzymes are also catalysts, or substances, that speed up chemical reactions. A chemical reaction is a process in which one or more substances are transformed into one or more different substances.

Enzymes are important for our survival and are involved in many tasks that keep us healthy and active. For example, enzymes help you digest food, build muscles and protect your cells from damage.

E

nzymes interact with specific molecules called substrates. Every enzyme has an active site, which is where the chemical reaction takes place. These sites have unique shapes. Only one specific substrate can bind to an enzyme, just like only one key fits into a specific lock.

When the substrate binds to the enzyme, they form what is called the enzyme-substrate complex. Next, a chemical reaction takes place. When the reaction is complete, the enzyme releases the products of the reaction. A product is a substance that forms during a reaction. After the enzyme releases the products, it is ready to start all over again with another substrate molecule.

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In your own words explain the difference between the two graphs below

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What is the optimal pH for the green enzyme?

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At what temperature will blue enzyme have the highest activity?

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The diagram represents one way an enzyme can be inhibited.
Which statement explains the effect of an inhibitor on an enzyme?

A substrate will be able to bond with the enzyme.

The enzyme will likely be attacked by immune cells.

The enzyme will be unable to produce more enzymes.

A substrate will be unable to attach to the enzyme.

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Match the food to the chemical that it is tested with

Draggable item		Corresponding Item
Glucose		Iodine
Protein		Benedict's
Lipids		Biuret
Starch		Sudan III

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Mya eats pasta for lunch. Pasta is made of mostly starch molecules. For this to be useful to her cells, Mya's digestive system needs to break these starch molecules into:

Glucose

Amino Acids

Oxygen

Fats

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Jack eats fish for dinner. Fish is high in protein molecules. After two hours, Jack's digestive system broke many of these proteins down into:

Glucose

Amino Acids

Oxygen

Fats

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Chris eats a turkey sandwich. Starting at the mouth, what is the path that the molecules take through the body?

Mouth --> Respiratory System --> Digestive System --> Circulatory System --> Cells

Mouth --> Circulatory System --> Digestive System --> Cells

Mouth --> Digestive System --> Circulatory System --> Cells

Mouth --> Respiratory System --> Circulatory System --> Digestive System --> Cells

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What are the tiny air sacs in the lungs called?

Ravioli

Bronchioles

Alveoli

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How does oxygen get into your body?

We absorb it through our skin

We absorb it when we exhale

We Absorb it when we inhale

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The chambers of the heart the receive blood from the body or lungs are the

A. Ventricles

B. Atria

C. Vena Cavas

D. AV valves

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The chambers of the heart that push blood out of the heart to either the body or the lungs are the

A. Ventricles

B. Atria

C. Vena Cavas

D. AV valves

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What side of the heart pumps oxygen poor blood?

Right Side

Left Side

Both sides

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What side of the heart pumps oxygen rich blood?

Right Side

Left Side

Both sides

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Blood flows from the Vena Cavas into the

A. Right Atrium

B. Lungs

C. Left Atrium

D. Aorta

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Blood flows from the Lungs into the

A. Inferior Vena Cava

B. Left Ventricle

C. Left Atrium

D. Aorta

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Which statement correctly shows the path blood travels through the heart.

A. lungs, right ventricle, left ventricle, right atrium, left atrium

B. right atrium, right ventricle, lungs, left atrium, left ventricle

C. left atrium, left ventricle, lungs, right atrium, right ventricle

D. right atrium, left atrium, lungs, right ventricle, left ventricle

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The Arteries the heart , whereas the veins _heart

go to, go to

go to, go away

go away, go to

go away, go away

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The heart pumps blood through a network of tubes inside the body called blood vessels.

Nokorɛ

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What side of the heart pumps oxygen poor blood?

Right Side

Left Side

Both sides

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What side of the heart pumps oxygen rich blood?

Right Side

Left Side

Both sides

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Blood flows from the Vena Cavas into the

A. Right Atrium

B. Lungs

C. Left Atrium

D. Aorta

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The upper chambers of the heart are the

A. Ventricles

B. Atria

C. Vena Cavas

D. AV valves

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The lower chambers of the heart are the

A. Ventricles

B. Atria

C. Vena Cavas

D. AV valves

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The chambers of the heart the receive blood from the body or lungs are the

A. Ventricles

B. Atria

C. Vena Cavas

D. AV valves

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The chambers of the heart that push blood out of the heart to either the body or the lungs are the

A. Ventricles

B. Atria

C. Vena Cavas

D. AV valves

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What side of the heart pumps oxygen poor blood?

Right Side

Left Side

Both sides

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What side of the heart pumps oxygen rich blood?

Right Side

Left Side

Both sides

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Match the chamber with the correct description

Pumps oxygen poor blood to the lungs
Receives oxygen poor blood from the body

Right Atrium
Right Ventricle

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Match the chamber with the correct description

Receives oxygen rich blood from the lungs
Pumps oxygen rich blood to the aorta

Left Atrium
Left Ventricle

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Match the Vena Cava with the correct description

Brings oxygen poor blood from the lower body (legs and feet) to the heart
Bring oxygen poor blood from the head and upper body to the heart

Superior Vena Cava
Inferior Vena Cava

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Match the structure with the correct description

Wall like structure that prevents oxygen rich and poor blood from mixing
Preven blood from flowing backwards. Found between the atria and ventricles

AV valve
Septum

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Blood flows from the Right Atrium into the

A. Right Ventricle

B. Lungs

C. Left Atrium

D. Left Ventricle

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Blood flows from the Right Ventricle into the

A. Superior Vena Cava

B. Lungs

C. Left Atrium

D. Aorta

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Blood flows from the Lungs into the

A. Inferior Vena Cava

B. Left Ventricle

C. Left Atrium

D. Aorta

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Blood flows from the Left Atrium into the

A. Inferior Vena Cava

B. Left Ventricle

C. Right Atrium

D. Aorta

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Blood flows from the Left Ventricle into the

A. Inferior Vena Cava

B. Pulmonary Artery

C. Right Atrium

D. Aorta

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Oxygen rich blood is pumped out of the heart to the rest of the body by the

A. Pulmonary veins

B. Pulmonary artery

C. Superior Vena Cava

D. Aorta

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Which statement correctly shows the path blood travels through the heart.

A. lungs, right ventricle, left ventricle, right atrium, left atrium

B. right atrium, right ventricle, lungs, left atrium, left ventricle

C. left atrium, left ventricle, lungs, right atrium, right ventricle

D. right atrium, left atrium, lungs, right ventricle, left ventricle

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Gas Exchange in Different Organisms

All living organisms need a way to exchange gases with their environment. This process is essential for respiration, which provides energy for life processes. Different organisms have evolved different gas exchange systems, but they all share common features to allow efficient diffusion of gases such as oxygen and carbon dioxide.

Common Features of Gas Exchange Systems

Although these gas exchange systems are found in different organisms, they share important similarities:

Large Surface Area – This increases the amount of gas that can diffuse at one time.
Thin Surfaces – A short diffusion distance allows gases to move quickly.
Steep Concentration Gradient – Maintained by blood flow in animals or air circulation in plants, ensuring efficient diffusion.

Gas Exchange in Humans

Humans and other mammals have lungs, which contain millions of tiny air sacs called alveoli. These alveoli provide a large surface area for gas exchange. Oxygen from the air we breathe in diffuses across the thin walls of the alveoli into the blood, while carbon dioxide diffuses out of the blood into the alveoli to be exhaled. The alveoli have very thin walls, only one cell thick, ensuring a short diffusion path for gases to move quickly between the lungs and the blood. Additionally, they are surrounded by a dense network of capillaries, which maintain a steep concentration gradient by constantly bringing in blood with low oxygen levels and removing oxygenated blood.

Gas Exchange in Fish

Fish live in water and rely on gills for gas exchange. Gills are made up of many thin filaments covered in tiny structures called lamellae, which increase the surface area for diffusion. Water containing oxygen flows over the gills, and oxygen diffuses into the blood in the gill capillaries. At the same time, carbon dioxide diffuses out of the blood and into the water. Fish use a counter-current flow system, where water and blood flow in opposite directions, maintaining a high concentration gradient for efficient gas exchange. Like alveoli, gills have very thin surfaces to allow gases to diffuse quickly.

Gas Exchange in Plants

Plants also need to exchange gases, particularly for photosynthesis and respiration. They do this through tiny openings on the underside of leaves called stomata. During the day, carbon dioxide from the air diffuses into the leaf through the stomata and is used in photosynthesis to produce oxygen and glucose. Oxygen then diffuses out of the leaf into the air. Inside the leaf, spongy mesophyll cells have air spaces that increase the surface area for gas exchange. Like other gas exchange surfaces, these cells have thin walls to ensure a short diffusion distance.

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Why do living organisms need gas exchange?

To produce glucose

To release waste nitrogen

For respiration to release energy

To absorb nutrients

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What are the two main gases involved in gas exchange?

Oxygen and nitrogen

Carbon dioxide and oxygen

Hydrogen and carbon dioxide

Oxygen and methane

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What is the main organ used for gas exchange in humans?

Stomach

Liver

Lungs

Kidneys

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What are the tiny air sacs in the lungs called?

Bronchi

Alveoli

Capillaries

Trachea

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What is the function of alveoli?

To store oxygen

To remove waste products

To increase the surface area for gas exchange

To digest food

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Why are alveoli walls thin?

To store more oxygen

To allow faster diffusion of gases

To make lungs lighter

To prevent gas exchange

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How does blood help in gas exchange in alveoli?

It absorbs carbon dioxide

It maintains a concentration gradient

It creates a barrier to gas exchange

It produces oxygen

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Where does gas exchange occur in fish?

Lungs

Stomata

Gills

Skin

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What are the thin structures in fish gills called?

Bronchi

Lamellae

Stomata

Alveoli

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How does oxygen enter the fish’s blood?

Through the stomach

By diffusion across the gills

Through the skin

By swallowing air

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What structures in leaves allow gas exchange?

Xylem

Phloem

Stomata

Mesophyll

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Which gas enters a leaf for photosynthesis?

Oxygen

Carbon dioxide

Nitrogen

Hydrogen

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Where are stomata mostly found?

On the upper surface of leaves

On the underside of leaves

Inside the roots

On the stem

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Why do gas exchange surfaces have a large surface area?

To allow more gas to diffuse at once

To store oxygen

To keep the organism warm

To prevent diffusion

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Why do gas exchange surfaces need to be thin?

To allow gases to move quickly

To make them stronger

To store gases

To prevent gas exchange

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What helps maintain a steep concentration gradient in gas exchange?

Slow movement of air

Blood circulation or air movement

Thick gas exchange surfaces

Low oxygen levels

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Name the four components of blood:

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Check all the functions of blood

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The clear liquid in which the cells are suspended in is

red blood cells

white blood cells

plasma

platelets

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Which part of blood transports oxygen?

red blood cells

white blood cells

plasma

platelets

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Which part of blood helps with blood clotting?

red blood cells

white blood cells

plasma

platelets

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Which part of blood fights infections?

red blood cells

white blood cells

plasma

platelets

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Move the description/function to the correct component of blood.

helps fight infections
helps with blood clotting
clear, yellowish fluid
lacks a nucleus
contains hemoglobin
transports oxygen

Red blood cell
White blood cell
Plasma
Platelet

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Blood is responsible for transporting oxygen and nutrients throughout the body.

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4. Blood…

in veins carries carbon dioxide and nutrients, while blood in arteries carries oxygen and other wastes.

in veins carries oxygen and nutrients, while blood in arteries carries carbon dioxide and other wastes.

in arteries carries oxygen and nutrients, while blood in veins carries carbon dioxide and other wastes.

in arteries carries carbon dioxide and nutrients, while blood in veins carries oxygen and other wastes.

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What can be used to treat people with coronary heart disease?

Tick two boxes.

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Figure 3 shows the percentages of adults in the UK who have coronary heart disease.
Figure 3

Calculate the difference in the percentage of male and female adults aged 65 and over who have coronary heart disease.

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Which is the correct conclusion for the data in Figure 3 (above)?

Tick one box.

Children do not suffer from coronary heart disease

More males suffer from coronary heart disease than females

More younger people suffer from coronary heart disease than older people

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Suggest two risk factors for coronary heart disease.

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Question 129