Respiration, Excretion in humans, Human diet & digestion

What is respiration?

Respiration is a chemical process that breaks down glucose to release energy

Is respiration enzyme controlled?

Yes respiration is controlled by enzymes

Does respiration require oxygen?

Respiration can occur with oxygen aerobically or without oxygen anaerobically

Where does aerobic respiration mainly occur?

In the mitochondria

State two uses of energy from respiration

Muscle contraction and active transport

Give four uses of energy released in respiration

Muscle contraction protein synthesis cell division active transport

Define aerobic respiration

Aerobic respiration is the complete breakdown of glucose using oxygen to release energy

What are the products of aerobic respiration?

Carbon dioxide water and energy

Word equation for aerobic respiration

Glucose plus oxygen produces carbon dioxide plus water

Balanced equation for aerobic respiration

C6H12O6 plus 6O2 produces 6CO2 plus 6H2O

How many marks is the aerobic respiration equation usually worth?

Three marks

Define anaerobic respiration

Anaerobic respiration is the breakdown of glucose without oxygen to release energy

Is anaerobic respiration complete or incomplete?

Incomplete breakdown

Does anaerobic respiration release more or less energy than aerobic?

Less energy

Where does anaerobic respiration occur in humans?

Muscle cells during vigorous exercise

Word equation for anaerobic respiration in animals

Glucose produces lactic acid

What is the only product of anaerobic respiration in animals?

Lactic acid

Is carbon dioxide produced in anaerobic respiration in animals?

No

Word equation for anaerobic respiration in yeast

Glucose produces ethanol and carbon dioxide

Why is yeast respiration useful in baking?

Carbon dioxide makes dough rise

Why is yeast respiration useful in brewing?

Ethanol produces alcohol and carbon dioxide gives fizz

What causes muscle fatigue during anaerobic respiration?

Build up of lactic acid

Why must lactic acid be removed?

It lowers pH and can denature enzymes

How is lactic acid removed from muscles?

It is transported to the liver in the blood

What happens to lactic acid in the liver?

It is oxidised to carbon dioxide and water

Define oxygen debt

The extra oxygen needed to oxidise lactic acid after exercise

Why do breathing and heart rate remain high after exercise?

To repay oxygen debt

Define excretion

Removal of metabolic waste toxic materials and excess substances

Name two organs involved in excretion

Lungs and kidneys

What does the lungs excrete?

Carbon dioxide

Why must carbon dioxide be excreted?

It forms an acidic solution and lowers pH

What do kidneys excrete?

Urea excess water and salts

What is urea?

A toxic waste product formed from excess amino acids

What is the excretory system?

A group of organs that remove waste from the body

Name four parts of the urinary system

Kidneys ureters bladder urethra

Function of the ureter

Transports urine from kidney to bladder

Function of the bladder

Stores urine

Function of the urethra

Releases urine from the body

State two functions of the kidney

Excretes waste and regulates water content

What is a nephron?

A tiny filtering unit in the kidney

How many nephrons are in each kidney?

About one million

Where does a nephron start?

In the cortex

What process occurs in the glomerulus?

Ultrafiltration

Define ultrafiltration

High pressure forces small molecules out of the blood

Name four substances in filtrate

Glucose water urea salts

Why does ultrafiltration occur?

High pressure in the glomerulus

What is Bowman’s capsule?

A cup shaped structure that collects filtrate

Define selective reabsorption

Useful substances are reabsorbed into the blood

Where is glucose reabsorbed?

Proximal convoluted tubule

How is glucose reabsorbed?

By active transport

Why does the proximal convoluted tubule contain many mitochondria?

To supply energy for active transport

Why can glucose not be reabsorbed later?

Transport proteins are only in the proximal tubule

Why is glucose found in urine in diabetics?

Not all glucose can be reabsorbed

How are salts reabsorbed?

By diffusion and active transport

How is water reabsorbed?

By osmosis

Where is water reabsorbed?

Loop of Henle and collecting duct

What organ carries out deamination?

Liver

Define deamination

Removal of amino group from amino acids

Why must excess amino acids be deaminated?

They cannot be stored

What happens to the carbon part of amino acids?

Converted to glycogen

What happens to the nitrogen part?

Converted to ammonia then urea

Why is ammonia converted to urea?

Ammonia is very toxic

How is urea removed from the body?

Excreted by kidneys in urine

State one effect of high urea levels

Cell death

Define egestion

Removal of undigested food

How is egestion different from excretion?

Egestion removes food waste excretion removes metabolic waste

Define a balanced diet

A diet containing all nutrients in correct proportions

Name seven food groups

Carbohydrates proteins lipids vitamins minerals fibre water

What is scurvy?

A disease caused by vitamin C deficiency

State two symptoms of scurvy

Bleeding gums and tooth loss

How is scurvy treated?

Vitamin C supplements

What is rickets?

A disease caused by vitamin D deficiency

State two symptoms of rickets

Soft bones and bone deformities

Why is vitamin D important?

It helps absorb calcium

Name two sources of vitamin D

Sunlight and fish

What is the alimentary canal?

The tube food passes through

Name organs in the alimentary canal

Mouth oesophagus stomach small intestine large intestine

Name four accessory digestive organs

Salivary glands pancreas liver gall bladder

Define ingestion

Taking food into the body

Define mechanical digestion

Breaking food into smaller pieces without chemical change

Define chemical digestion

Breaking large molecules into small soluble molecules

Define absorption

Movement of digested food into blood or lymph

Define assimilation

Use of absorbed food by cells

Function of saliva

Contains amylase and lubricates food

What enzyme is in saliva?

Amylase

Function of the oesophagus

Transports food by peristalsis

Define peristalsis

Wave like muscle contractions pushing food

Function of the stomach

Mechanical digestion and protein digestion

What enzyme digests protein in stomach?

Pepsin

Why is hydrochloric acid important?

Kills bacteria and provides low pH

What is bile?

An alkaline liquid that emulsifies fats

Where is bile produced?

Liver

Where is bile stored?

Gall bladder

What does emulsification do?

Increases surface area of fats

Is emulsification chemical or physical digestion?

Physical digestion

Where are digestive enzymes produced?

Pancreas salivary glands stomach

What does amylase digest?

Starch to maltose

What does protease digest?

Proteins to amino acids

What does lipase digest?

Lipids to fatty acids and glycerol

Where does most digestion occur?

Small intestine