3.3.1 Exchange

Question 1

Describe the structure of an insects gas exchange system

Answer 1

Insects have small openings in their exoskeletons called spiracles, small tubes called tracheae divide into even smaller tubes called tracheoles. The ends of the tracheoles are filled with liquid when the insect is at rest.

Question 2

Describe the relationship between size of organism and surface area to volume ratio

Answer 2

The larger the organism, the smaller the surface area to volume ratio

Question 3

Explain why larger organisms need specialised gas exchange systems

Answer 3

Because they have a smaller surface area to volume ratio so can’t absorb all the gases they need by simple diffusion so they need a specialised system to provide short diffusion pathways, large surface area and maintained concentration gradients

Question 4

Describe the structure of fish gills

Answer 4

Fish have many gill filaments, each covered in many lamellae providing a large surface area for gas exchange. The blood in the capillaries flows in the opposite direction to the water.

Question 5

Explain why a counter-current flow more efficient than co-current flow in fish gills

Answer 5

Because the blood continues to pass water which has a higher oxygen concentration, so the concentration gradient is maintained along the whole length of the gill filament

Question 6

How do insects limit water loss from their bodies?

Answer 6

They are covered in a water proof exoskeleton and can control the opening and closing of spiracles

Question 7

Describe the process of gas exchange in leaves

Answer 7

Air diffuses into the stomata and into the spongy mesophylly layer where it surrounds the cells, CO2 diffuses into cells and oxygen diffuses out creating a concentration gradient between the inside and outside of the leaf, this causes CO2 to continue to diffuse into the leaf and O2 to diffuse out.

Question 8

Explain why having hairs under leaves, rolled leaves helps a xerophytic plant to survive

Answer 8

This traps a layer of humid air near the stomata so there is a low water potential gradient between the air inside and outside of the leaf. This means that less water is lost by the plant.

Question 9

List 4 adaptations of xerophytic plants

Answer 9

Less stomata, smaller leaves, rollled leaves, hairs under leaves, stomata in pits or grooves

Question 10

What is tidal volume?

Answer 10

The volume of air in breathed in and out at each breath at rest

Question 11

How do you calculate Pulmonary ventilation?

Answer 11

PV = Tidal volume x breathing rate

Question 12

What is breathing rate?

Answer 12

Number of breaths are taken per minute

Question 13

Describe inhalation

Answer 13

Diaphragm contracts, external intercostal muscles contract, chest volume increases, pressure in chest decreases, atmospheric pressure forces air into lungs, lungs expand to equalise pressure

Question 14

Describe exhalation

Answer 14

Diaphragm relaxes, external intercostal muscles relax, chest volume decreases, pressure in chest increases and air is forced out of lungs until air pressure inside and outside chest is equal

Question 15

State two substances produced by the stomach

Answer 15

Hydrochloric Acid, protease enzymes, mucus lining

Question 16

How is the ileum adapted to efficiently absorb nutrients?

Answer 16

It has folded inner walls (villi) with millions of microvilli providing a very large surface area. It also has membrane-bound dissacharidases, protein channels and carrier proteins on it’s epithelial cells

Question 17

Name the three major types of enzymes and where they are produced in the human digestive system

Answer 17

Proteases - stomach and pancreas (SI), Carbohydrases (Amylase) - saliva and pancreas (SI), lipases - panceas (SI)

Question 18

State the products of lipid digestion

Answer 18

Fatty acids and glycerol

Question 19

State the products of protein digestion

Answer 19

amino acids

Question 20

State the products of starch digestion

Answer 20

alpha glucose (maltose first, then alpha glucose)

Question 21

Explain how starch is digested in the human digestive system

Answer 21

Starch begins to be hydrolysed into maltose by salivary amylase, this process stops when the food reaches the stomach (amylase denatured by low pH), then pancreatic amylase continues hyrdolysing starch into maltose. When it reaches the ileum, maltose is hydrolysed into alpha glucose by membrane-bound maltase enzymes. The alpha glucose is then absorbed into the epithelial cells of the ileum lining.

Question 22

State the monosaccharides that make up sucrose

Answer 22

glucose and fructose

Question 23

State the monosaccharides that make up lactose

Answer 23

glucose and galactose

Question 24

What do the three types of peptidases do?

Answer 24

Endopeptidases hydrolyse peptide bonds in the central part of a polypeptide. Exopeptidases hydrolyse bonds at the ends (terminal amino acids), dipeptidases hydrolyse the bond between two amino acids

Question 25

Describe how lipids are digested and absorbed in the human digestive system

Answer 25

Lipids are hydrolysed by lipase and emulsified by bile salts to form micelles (monoglycerides and fatty acids in lipid droplets), micelles release monoglycerides and fatty acids at the ileum lining where they diffuse into the epithelial cell. They are immediately reformed into triglycerides by the smooth ER and packaged in protein to form chylomicrons. These are released by exocytosis into the lacteals of the lymphatic system

Question 26

label this

Answer 26

Question 27

Answer 27

Question 28

Answer 28

Question 29

Answer 29

Question 30

Answer 30

Question 31

Answer 31

Question 32

Answer 32

Question 35

Answer 35