Biology - Organisation

What is the digestive system?

a group of organs that work together to break down food

What are the stages of digestion?

1. ingestion

2. digestion

3. absorption

4. egestion

What is ingestion?

taking food into the mouth

What is digestion?

mechanical and chemical breakdown of food

What is absorption?

Taking digested food into the blood stream

What is egestion?

removal of undigested waste

what are enzymes?

Biological catalysts that speed up reactions.

They are protein molecules

What does amylase break down?

starch into maltose or glucose

What does protease break down?

Proteins into amino acids

What does lipase break down?

Lipids into fatty acids and glycerol

What are the organs in the digestives system?

1. mouth

2. oesophagus

3. stomach

4. small intestine

5. large intestine

6. rectum and anus

What happens at the mouth?

Food is crushed and mixed with saliva. the saliva contains the enzyme amylase which breaks down carbohydrates into glucose

What happens at the oesophagus?

Peristalsis - muscle contractions move food from the mouth to the stomach

What happens at the stomach?

Food is churned with hydrochloric acid.

Why is food churned in the stomach?

To increase the surface area for enzymes to digest

Why is there hydrochloric acid in the stomach?

To kill pathogens and to provide the optimum temperature and pH for the enzyme pepsin (protease)

What is pepsin?

A type of protease

What happens at the small intestine?

The walls of the small intestine release lipase enzymes to continue the digestive process of proteins and lipids. Nutrients are absorbed into the blood by the villi.

What are the adaptations of the villi?

To increase the rate of diffusion, it has:

- large surface area

- thin (one cell thick)

- good blood supply

Why are villi thin?

to provide a short diffusion distance

Why do villi have a large surface area?

To absorb soluble food molecules by diffusion and active transport

Why do villi have a good blood supply?

the capillaries quickly carries absorbed nutrients away, which maintains a steep concentration gradient, allowing a faster rate diffusion

How are nutrients absorbed into the blood?

diffusion and active transport

What happens at the large intestine?

-The muscular walls of the small intestine squeeze the undigested food into the large intestine

- te large intestine absorbs the water left in the undigested food and it turns into faeces

What happens at the rectum?

Faeces are stored before they are released out through the anus

What happens at the anus?

Faeces leave the body

What is faeces?

Undigested food that forms a waste material.

What is the function of the liver in the digestive system?

it produces bile

Where is bile stored?

In the gall bladder before it's released into the small intestine

What does bile do

- it neutralises stomach acid in the small intestine to create the right alkaline pH for enzymes

- it emulsifies fats, breaking large fat globules into tiny droplets, which increases their surface area for lipase enzymes to digest them more efficiently

What is the function of the pancreas in the digestive system?

- it produces enzymes like lipase, protease, and amylase and releases them into the small intestine to mix with food and bile

-It also secretes bicarbonate to neutralise stomach acid, allowing these enzymes to work effectively

Where is amylase made?

- salivary glands

- pancreas

- small amounts in the small intestine

Where does amylase work?

mouth and small intestine

Where is protease made?

Stomach, pancreas, small intestine

Where does protease work?

stomach and small intestine

Where is lipase made?

Pancreas and small intestine

Where does lipase work?

small intestine

What enzymes does the pancreas make?

protease, amylase, lipase

What enzymes does the small intestine make?

protease, lipase and amylase

What are the two types of enzymes?

catabolic and anabolic

What are catabolic enzymes?

enzymes that break down large molecules into smaller ones

What are anabolic enzymes?

enzymes that build up small molecules to form larger ones

How do enzymes work?

1. Each enzyme has a specific active site to the substrate

2. The substrate fits into the active site

3. The active site binds to the substrate, forming an enzyme-substrate complex

4. The enzyme breaks down and builds up the substrate into a product

5. The enzyme remains unchanged and can be reused

What is the substrate?

The reactant that an enzyme acts on

What type of enzymes are digestive enzymes?

catabolic

What factors affect enzyme activity?

-Temperature

-pH

-substrate concentration

-enzyme concentration

How does temperature affect enzyme activity?

- Enzymes work best at their optimum temperature

- as the temperature increases, the molecules have more kinetic energy, so collisions are more frequent and, so enzyme activity increases

What happens if enzymes get too hot?

They denature and the substrate can no longer fit the active site

What happens if enzymes get too cold?

the rate of reaction is low

What is the optimum temperature for enzymes in humans?

37 degrees

How does pH affect enzyme activity?

- Each enzyme has an optimum pH range

-If it is the wrong pH, the enzyme denatures

What pH does amylase work best at?

pH 7

What pH does pepsin work best at?

pH 2

What pH does lipase work best at?

pH 8

How does substrate concentration affect enzyme activity?

-As substrate concentration increases, enzyme activity also increases because more substrate molecules collide with enzyme active sites

- eventually plateaus when all active sites are saturated, meaning the enzymes are working at full capacity

What does it mean for enzymes to become saturated?

-All the enzyme's active sites are occupied by substrate molecules, reaching the maximum reaction rate and further substrate won't speed things up.

- enzyme concentration the limiting factor.

How does enzyme concentration affect enzyme activity?

-Increasing enzyme concentration increases enzyme activity by providing more active sites for substrate binding, leading to more frequent collisions and faster product formation

-This effect plateaus when all substrate molecules are bound

-making substrate concentration the new limiting factor

-Essentially, more enzymes mean a faster reaction up to the point where they outnumber the available substrate.

What are carbohydrates?

sugars and polymers of sugars

What are simple sugars?

the most basic carbohydrates, made of one or two sugar units

What are the simplest sugars?

glucose, fructose, galactose

What are double sugars?

sugars made of two single sugars like glucose

sucrose, lactose, maltose

What are complex carbohydrates?

long chains of simple sugar units bonded

What are examples of complex carbohydrates?

starch, glycogen, cellulose

What are lipids?

fats and oils

they are the most efficient store of energy in the body

What are lipids used for?

-energy storage

-insulation

-protecting organs

-forming cell membranes

-making hormones

Are lipids soluble in water?

No, they are hydrophobic

What are lipids made from?

-Three molecules of fatty acids joined to a molecule of glycerol

-The glycerol is always the same, but the fatty acids vary

What are proteins?

polymers of amino acids

What are proteins used for?

-repairing cells

-building muscle and bone

-making hormones and enzymes

-boosting your immune system

-supporting organ function

What atoms are carbohydrates made from?

carbon, hydrogen, oxygen

What atoms are lipids made from?

carbon, hydrogen, oxygen

What atoms are proteins made from?

carbon, hydrogen, oxygen, nitrogen

What is blood?

fluid connective tissue

What are the components of blood?

-plasma

-red blood cells

-white blood cells

-platelets

What is the function of red blood cells?

transport oxygen and carbon dioxide

What is haemoglobin?

A large protein that carries oxygen around the body in the red blood cells

What are the adaptations of red blood cells?

- thin membrane

- small and flexible

- biconcave shape

- no nucleus

Why do red blood cells have a thin membrane?

for rapid oxygen diffusion

Why are red blood cells small and flexible?

to navigate narrow capillaries

Why do red blood cells have a biconcave shape?

increase surface area for gas absorption

increase flexibility for fitting through small capillaries

Why do red blood cells have no nucleus?

There is space to contain more haemoglobin molecules.

What are the function of white blood cells?

To fight off pathogens

What are platelets?

fragments of cells that start blood clotting when you get a cut, forming a plug (scab) to stop bleeding and prevent pathogens (germs) from entering the wound

What is plasma?

liquid portion of blood that transports all the blood cells and nutrients, hormones, waste and heat

What are the proportions of blood components

55% is plasma, 45% is RBCs, less than 1% are WBCs and platelets

What are blood vessels?

tubes that carry blood around the body

What are the three types of blood vessels?

arteries, veins, capillaries

What are arteries?

Blood vessels that carry blood away from the heart

What are the key features of arteries?

- thick muscular wall to handle high pressure from the heart

- narrow lumen to keep the pressure high

- no valves (blood is pushed forward by the heart's pumping action

What type of blood do arteries carry?

usually oxygenated blood (except for the pulmonary artery)

What are veins?

Blood vessels that carry blood back to the heart

What are the key features of veins?

- thin walls because the pressure is low

- large lumen allows a large volume of blood to flow back to the heart

-valves to stop blood from flowing backwards

What are valves?

structures that keep blood from flowing backwards

What type of blood do veins carry?

Deoxygenated blood, except the Pulmonary vein

What are capillaries?

tiny blood vessels that connect arteries and veins

What are the key features of capillaries?

- very thin walls (one cell thick) allows for quick diffusion

- connects arteries and veins

- narrow lumen so that red blood cells pass in a single file, maximising contact with the thin walls for better exchange.

- permeable walls that let small molecules like glucose, oxygen, and waste pass through.

- branching creates a large SA of material transfer

Where are capillaries found?

near almost every cell in the body

What is the circulatory system?

The body's blood-transporting system

Summary of the circulatory system

Heart pumps blood through large blood vessels called arteries which branch into smaller and smaller vessels. Smallest vessels are called capillaries. Here blood exchanges substances with surrounding tissues. Blood then flows into larger vessels, called veins, eventually returning to heart.

How does blood flow in the body?

1. lungs

2. left atrium

3. left ventricle

4. the body

5. right atrium

6. right ventricle

7. lungs