Gas Exchange, Digestion & Absorption

Question 1

Why did elephants have large ears

Answer 1

An adaption to increase surface area for heat loss

Question 2

What is the difference in a mouse and elephants surface area to volume ratio

Answer 2

mice - large
elephant - small

Question 3

How much heat do mice lose?

Answer 3

The mice loses large amount of heat relative to its mass

Question 4

Why do mice respire at a high rate?

Answer 4

Thes loose a large amount of heat so respire at a high rate to maintain a constant body temp thus high uptake if oxygen

Question 5

What is in the gas exchange system ?

Answer 5

• trachea
• bronchi
• bronchioles

Question 6

Describe the gas exchange system

Answer 6

trachea supported by rings if cartilage to prevent it collapsing during pressure changes in ventilation

• trachea divides into 2 bronchi that repeatedly divide into bronchioles

• alveoli at end bronchioles provide large surface area for gaseous exchange

Question 7

How are the alveoli adapted for gaseous exchange?

Answer 7

• shape and large number provide large surface area

• fluid lining alveolus allows gases to dissolve and diffuse across

• two cell layers= short diffusion pathway

• blood capillaries = large SA

Question 8

Whats the function of the circulatory system?

Answer 8

maintain high concentration gradient for gas exchange by transporting deoxygenated blood to lungs and removing oxygenated blood from lungs

Question 9

What is the function of the ventilation mechanism?

Answer 9

continuously provides air with high oxygen concentration and removes air with high carbon dioxide conc
- maintains high concentration gradient for gaseous exchange

Question 10

What is the function of the fluid lining the epithelium of the alveolus?

Answer 10

oxygen in the alveolar air space dissolves in the fluid

Question 11

What are the two cells separating blood and air in the alveoli?

Answer 11

flattened epithelial cells (alveolar wall)
endothelial cells (capillary wall)

Question 12

What is inspiration

Answer 12

breathing in (INspiritation>

Question 13

Describe inspiration.

Answer 13

• external intercostal muscles contact
• rib cage pulled up and out
• diaphragm muscles contract
• diaphragm flattens
• thorax volume increases and pressure decreases
• air enters area of low pressure IN LUNGS

Question 14

Describe Expiration

Answer 14

• external intercostal muscles relax
• rib cage pulled down and in
• diaphragm muscles relax
• diaphragm moves up to dome shape
• thorax volume decreases and pressure increases
• air enters area of low pressure OUT LUNGS

Question 15

What is the equation for pulmonary ventilation

Answer 15

pulmonary ventilation = tidal volume(dm3) x ventilation rate(min-1)

Question 16

What is the ventilation rate?

Answer 16

number if breaths per minute (usually 12-20)

Question 17

What is the tidal volume?

Answer 17

Volume if air normally taken in with each breath ( usually 0.5)

Question 18

What are spiracles?

Answer 18

• tiny holes on opening of tracheae
• have valves that can close ti reduce water loss

Question 19

What are tracheoles?

Answer 19

• branches from the trachea
• thin thus providing short diffusion distance for oxygen
• many = large surface area

Question 20

How dies oxygen enter the insects cell?

Answer 20

• diffuses from air into spiracles along trachea and tracheoles into cells
• CO2 leaves in the reverse path way

Question 21

What happenens during increased activity in insects?

Answer 21

anaerobic respiration creates lactic acid
- lowers WP of cells and water ends in tracheoles move into cells by osmosis

• more air moves along tracheoles

Question 22

How are gills adapted for gas exchange?

Answer 22

• large surface area
  provided by gill filaments which posesss lamellae
• short diffusion pathway
  bc blood and water is separated by two cell layers
  • epithelial layer if lamellae
  • endothelial layer of capillaries

Question 23

Describe the countercurrent system?

Answer 23

blood and water flow in opposite directions

• blood continuously meets water with a higher oxygen conversion
• this maintains a high diffusion gradient along the length of the lamellae

Question 24

How does the ventilation system help gas exchange in fish?

Answer 24

provides continual flow of water over gills
- this brings more oxygen and removes CO2 thus maintaining high diffusion gradient

Question 25

How does the circulatory system help gas exchange im fish?

Answer 25

**Provides continual flow of blood** through respiratory surface to **absorb oxygen and remove CO2** - maintaining high diffusion gradient

Question 26

Which structures are involved in gas exchange in plants?

Answer 26

stomata and mesophyll cells and air spaces between them

Question 27

What are stomata?

Answer 27

pores in the epidermis of leaves that surrounded by guard cells - gases diffuse in and out the stomata - leaves are thin = short diffusion pathway

Question 28

whats the function of mesophyll cells?

Answer 28

provide large surface area for gas exchange

Question 29

Whats the function of amylase?

Answer 29

hydrolyses starch into maltose

Question 30

How is food broken down during chewing?

Answer 30

saliva contains salivary amylase which breaks down starch - only a small amount is broken down as chewing is a short process

Question 31

How dies chewing speed up hydrolysis if starch?

Answer 31

breaks down food to smaller pieces which increases the surface area

Question 32

How dies the pancreas aid in breaking down the remainder if the starch?

Answer 32

- releases pancreatic juice into **small intestine** which contains enzymes pancreatic amylase this hydrolyses the remaining starch

Question 33

Where does the complete hydrolsis of starch occur?

Answer 33

In the ileum

Question 34

What do membrane bound disaccharides do ?

Answer 34

*Maltase and other disaccharides* **form the cell membrane** of epithelial cells that line the ileum

Question 35

Which enzyme hydrolyses lipids?

Answer 35

lipase (hydrolyse the ester bonds in lipids)

Question 36

Where is lipase secreted from?

Answer 36

The pancreas into the small intestine

Question 37

How do bile salts increase the rate of hydrolysis of lipids?

Answer 37

- they emulsify lipids causing them to form droplets - this increases surface area for hydrolysis

Question 38

What hydrolyses proteins?

Answer 38

endopeptides exopeptides dipeptidases

Question 39

How do Endopeptidases work?

Answer 39

They hydrolyse the INTERNAL peptide bonds between amino acids to form short amino acid chains

Question 40

How do exopeptidase work?

Answer 40

- they hydrolyse peptide bonds at either end if a polypeptide so individual amino acids are removed

Question 41

What is the final stage of protein digestion

Answer 41

Breaking down dipeptides to single amino acids - enzyme dipeptidase found in epithelial cells of the ileum - hydrolyse dipeptide

Question 42

How is the ileum adapted for absorption?

Answer 42

- **large surface** area due to long length villi and microvilli - **villi** contain **blood capillaries** that absorb monosaccharides and aminos, this maintains high diffusion gradient - **lacteals** in villi absorb digested lipids that also maintain high diffusion gradient for absorption - **many mitochondria** to provide ATP for active transport

Question 43

How do villi increase absorption?

Answer 43

Villus wall contain a single layer of **epithelia cells** providing **short diffusion pathway**

Question 44

Outline the absorption digested of lipids?

Answer 44

- bile salts emulsify lipids droplets - bile salts combine with monoglycerides and fatty acids to firm micelles - micelles transport MG and FA to surface of epithelial cell - micelles break down and release FA and MG and they diffuse thru epithelial cell - FA and MG recombine in smooth ER - packaged in protein and phospholipid by golgi and form CHYLOMICRONS - Chylomicrons absorbed into lacteals which drain into blood

Question 45

How are monosaccharides and aminos absorbed?

Answer 45

*they’re at a high concentration in lumen of ileum so they will be absorbed **down a concentration gradient by facilitated diffusion**

Question 46

How are monosaccharides and aminos transported?

Answer 46

by co-transport against a concentration gradient

Question 47

How is glucose taken up by co-transport?

Answer 47

- Na+ actively transported out epithelial cells into blood to ensure low conc of sodium in epithelial cell - high conc of sodium will be in lumen - so there will be a conc gradient for sodium ions to diffuse into cell - Na+ diffuse into epithelial cell from lumen with glucose via a co transport protein by facillitated diffusion - glucose enters blood by facillitated diffusion

Question 48

Define digestion

Answer 48

process where large molecules are **hydrolysed** by enzymes to produce small molecules that can be absorbed

Question 49

Where is the endopeptidase Pepsin secreted from?

Answer 49

cells lining the stomach

Question 50

Where are exopeptidases secreted from?

Answer 50

pancreas