Unit 3 - Organisms Exchange substances with their environment

Question 1

How have organisms developed to cope with SA difficulties

Answer 1

A flattened shape so no cell is far from the surface
Specialised exchange surfaces with large areas to increase SA volume ratio

Question 2

Feature of specialised exchange surfaces

Answer 2

Large SA relative to volume of the organism with increases rate of exchange
Very thin so that the diffusion distance is short and materials cross rapidly
Selectively permeable to allow materials across
Movement of environmental medium to maintain diffusion gradient

Question 3

describe insect respiratory system

Answer 3

Spiracles lead into trachea which lead into tracheoles

Question 4

Two methods of movement for gases in insects

Answer 4

Diffusion
Ventilation

Question 5

Process in insects during anaerobic respiration

Answer 5

High anaerobic respiratory rate- Lactate moves builds in the muscles
-Reducing the water potential gradient
- Water moves into cells by osmosis
- No longer any water in tracheoles
-Lower diffusion distance for respiratory gases- so higher rate of aerobic respiration

Question 6

Features of gills in fish

Answer 6

• They have lots of small lamellae which means they have large SA: Vol ratio
• The lamella have lots of blood capillaries and a thin surface layer of cells decreasing diffusion distance
• Blood flows in the opposite direction to water flow to maintain a high concentration across the whole lamellae

Question 7

Adaptations of Dicot leaves

Answer 7

• Broad thin leaf- Large SA with a short diffusion distance
• Spongy mesophyll has lots of space- allowing gases to get in and out easily
• Many small stomata so never far from one to allow gases in and out faster
• Spongy Mesophyll have a large SA:Vol Ratio

Question 8

Xerophitic plant modifications

Answer 8

• Stomata sunken in pits
• Presence of hairs creates local humidity
• Stomata on underside of leaf
• Stomata close to midrib
  -Stomata close together
• Thick waxy cuticle
• Thick short leaves

Question 9

Why are the lungs located in the body

Answer 9

• Air is not dense enough to support and protect these structures
  The body would lose lots of water and dry out

Question 10

Alveolar epithelium adaptations

Answer 10

• Red blood cells are slowed
  -Alveoli press against cappilaries
• Thin flattened membranes
• Blood flow maintains conc gradient
• Blood cells flattened against cappilary walls

Question 11

Inspiration

Answer 11

-External intercostal muscles and diaphragm contract
- Ribs are pulled upwards and outwards increasing volume of thorax
- The increased volume causes a reduction in pressure lower then atmospheric pressure
- Air moves into lungs along the pressure gradient

Question 12

Expiration

Answer 12

• The internal intercostal muscles contract
• The ribs move downwards and inwards
• Diaphragm moves upwards
• This decreases volume in thorax and increases pressure in thorax
• Air is pushed out

Question 13

What is the equation for PVR?

Answer 13

Tidal volume* Breathing Rate

Question 14

How does pulmonary tuberculosis affect breathing?

Answer 14

Tubercules form to contain pathogen
Infected tissue forms scars (fibrosis)
This affects SA and tidal volume
Ventilation rate increases to compensate

Question 15

How does fibrosis affect breathing?

Answer 15

Scar tissue formed in lungs from asbestos/ dust
Lungs become thicker and less elastic
Lungs arent able to expand and larger diffusion distance for gases
Increased ventilation rate to compensate

Question 16

How Athsma happens

Answer 16

Airways inflamed and irritated
Smooth muscle in bronchiles contract and mucus is produced
Air flow and FEV reduced

Question 17

Emphysema

Answer 17

Foreign particles trapped in alveoli
Inflammation- attracts phagocytes
Lots of elastin breaks it down- alveoli cant recoil
Decreases- SA:Vol ratio

Question 18

Dissociation curve- When pO2 is high

Answer 18

Haemoglobin has a high affinity for oxygen
Will readily combine/ hold on to oxygen
Thus a high saturation

Question 19

Dissociation curve- When pO2 is low

Answer 19

• Low affinity to O2 releases oxygen rather than combining
• Low saturation of oxygen

Question 20

Bohr effect

Answer 20

When cells respire ppO2 decreases
ppCo2 increases
This increases the rate of oxygen unloading
Thus shifting the curve to the right

Question 21

Arteries properties

Answer 21

Blood from heart
Thick muscular walls
Folded endothelium
Run into arterioles

Question 22

i

Answer 22

i

Question 22

Veins

Answer 22

Take blood back to the heart
Thin muscular walls
Large lumen
Valves stop backflow
Aided by contraction of muscles

Question 23

Capillaries

Answer 23

-Where exchange occurs
intertwined within tissue
One cell thick walls
large network- increases SA:VOL

Question 24

Tissue fluid

Answer 24

Fluid surrounds cells in tissues Comprises of small molecules able to leave the blood

Question 25

Formation of the tissue fluid (Process)

Answer 25

Hydrostatic pressure in the cappilaries forces water into the surrounding area at the arteriole end This causes a decreased water potential in the venule end as the concerntration of ions has increased Water re-enters the cappilaries at the venule end by osmosis Any excess tissue fluid is transported via the lymphatic system into the ciruclatory system.

Question 26

Step 1- Atrial systole

Answer 26

Ventricles relaxed and atria contract Increases pressure in atria, forcing blood into the ventricles AV valves forced open When pressure increases in ventricles- AV valves forced shut

Question 27

Step 2-Ventricular systole

Answer 27

Ventricles contract Increases pressure in ventricles relative to atria AV valves forced shut Semi lunar valves open

Question 28

Step 3- Diastole

Answer 28

All muscles relax Pressure in pulmonary artery and aorta is greater than ventricles so SL valves shut AV valves open

Question 29

Arethroma formation

Answer 29

Damage is caused to endothelium (e.g by blood pressure) White blood cells and lipids clump under lining This builds up an arethroma over time (Plaque)

Question 30

Arethromas can lead to

Answer 30

Aneurysms Swelling in vessel Thrombosis- Clot Myocardial infarction- Death of heart muscle cells

Question 31

Risk factors for cardiovascular disease

Answer 31

High colesterol/ poor diet Cigarette smoking High blood pressure

Question 32

What does the xylem transport?

Answer 32

Mineral ions and water

Question 33

What does the phloem transport?

Answer 33

Sugars and organic substances

Question 34

Transpiration process

Answer 34

Water evaporates from the leaves at the top of the xylem Water diffuses out of spongy mesophyll cells into the airspace This causes water to exit from xylem to surrounding cells by osmosis Due to cohesion water is pulled with the gradient towards the leaf Water enters the root by osmosis as the water concerntration gradient increases

Question 35

Factors affecting transpiration rate

Answer 35

Light Temperature Humidity Wind

Question 36

Potometer experiment

Answer 36

Cut shoot underwater at a slant- to prevent air from entering xylem and at a slant to increase SA. Assemble potometer underwater Check apparatus is air and watertight Dry leaves and allow potometer to acclimatise Record starting position of air bubble Rectod time and distance moved

Question 37

Translocation process

Answer 37

Active transport is used to actively load solutes from companion cells into the sieve tubes of the phloem at the source This lowers water potential inside the sieve tubes, so water enters the tubes by osmosis Creating a higer hydrostatic pressure At the sink end, solutes diffuse into the companion cells as they're being used Decreases the water potential in cells so water leaves seive tubes by osmosis Lowers pressure at the sink Results in a pressure gradient from source to sink. Solution moves down hydrostatic pressure gradient.

Question 38

Digestion of carbs

Answer 38

Amylase breaks down starch into maltose in saliva and pancreas Once starch is hydrolysed, it is broken down by enzymes in the ileum.

Question 39

Digestion of lipids

Answer 39

Bile salts in the liver emulsify the lipids Lipase made in the pancreas hydrolyses the lipids in the small intestine

Question 40

Digestion of proteins

Answer 40

Endopeptidases and exopeptidases both break peptide bonds between amino acids sequencially.

Question 41

Where are endopeptidases found?

Answer 41

Synthesised in the pancreas and secreted into the small intestine.

Question 42

Where are exopeptidases found?

Answer 42

Cell surface membrane of epithelial cells in small intestine

Question 43

How is each biological molecule is absorbed?

Answer 43

Glucose/ Galactose/ Amino acid---- cotransport Frustose----> Facilitated diffusion Lipids------> simple diffusion through phospholipid bilayer

Question 44

Role of micelles in absorbtion of lipids

Answer 44

Aid the transport of monoglycerides to the surface of the epithelial cells

Question 45

Role of bile salts

Answer 45

Increases the surface area of lipids that bile salts can work on- emulsification

Question 46

Why are arterioles useful

Answer 46

They can cut off blood supply to specific organs. E.g stomach during excercise

Question 47

Three adaptations of tracheoles

Answer 47

Thin walls- Short diffusion distance Large network- Large SA to vol ratio Fluid in end of tracheoles which moves out during anaerobic respiration- increasing rate of diffusion

Question 48

Role of micelles

Answer 48

Question 49

Role of Aorta recoiling

Answer 49

Smooths blood flow

Question 50

Describe and explain effect of increasing PPCO2 on dissociation of oxyhaemoglobin

Answer 50

Decreases haemoglobins affinity to O2 By decreasing blood PH