Topic 3 - Organisms exchange substances with their environment

Question 1

What is the relationship between size of organism and its SA:V ratio

Answer 1

The larger the organism, the smaller the SA:V ratio

Question 2

What do larger organisms require to obtain the substances they need

Answer 2

Specialised exchange systems eg, lungs

Question 3

state the adaptations to increase the rate of exchange

Answer 3

Large SA:V ratio, short diffusion pathway to minimise, Movement of medium such as blood to maintain a concentration gradient, selectively permeable membranes

Question 4

What do organisms with high metabolic rates require

Answer 4

A greater SA:V ratio to get more oxygen so more respiration can occur

Question 5

What do multicellular organisms have to help aid diffusion

Answer 5

Tissue Fluid

Question 6

What is the exchange system in insects

Answer 6

Spiracles, trachea and tracheoles surrounded by cells

Question 7

What are the 3 ways in which insects have effective exchange

Answer 7

• Diffusion, o2 diffuses in from high to low and o2 is used in cells so constant gradient maintained
• The trachea expand and contract to move oxygen in
• Water in tracheaoles

Question 8

Why is water in tracheoles important

Answer 8

During extensive exercise lactic acid builds up, there is a high water potential In the tracholes to water moves int cells. this decreases volume which decreases air pressure so the atmospheric pressure is greater and air moves in. Greater rate of diffusion since it occurs in the gas phase not liquid

Question 9

What is the structure of the gas exchange in fish

Answer 9

lamellae running perpendicular to filaments with good water supply to maintain concentration gradient

Question 10

What is parallel flow

Answer 10

The blood and water flow in the same direction so concentration gradient is not maintained

Question 11

Explain how countercurrent flow maximise gas exchange in fish

Answer 11

-Blood and water flow in opposite directions
-So blood is constantly passing water with a higher concentration on o2
-so a concentration gradient is maintained
-along the whole length of the gill filament

Question 12

What is the structure of a leaf from top to bottom

Answer 12

Waxy cuticle, upper epidermis, palisade mesophyll, spongey mesophyll, vascular bundle, lower epidermis, stomata and guard cells

Question 13

function of the waxy cuticle

Answer 13

Reduces water loss

Question 14

function of the upper epidermis

Answer 14

Transparent to let light through

Question 15

function of the palisade mesophyll

Answer 15

Lots of chlorophyll so photosynthesis can occur

Question 16

function of the spongey mesophyll

Answer 16

the site of gas exchange with lots of air spaces for a greater surface area

Question 17

function of the vascular bundle

Answer 17

contains the xylem and phloem

Question 18

function of the stomata

Answer 18

Pathway for gases to enter and exit the leaf

Question 19

function of the guard cell

Answer 19

Open and close the stoma

Question 20

What is a xerophyte

Answer 20

A plant which is adapted to live in conditions with little water

Question 21

What are 3 adaptations of xerophytes

Answer 21

Rolled leaves, hairs and stomata located in pits

Question 22

How do these adaptations of xerophytes help reduce water loss

Answer 22

The water vapour leaves via diffusion and is trapped this lowers the water vapour potential gradient between inside and outside of the leaf so less water is lost

Question 23

What is the gas exchange system in humans

Answer 23

Mouth/nose, trachea, bronchi, bronchioles, alveoli, lungs, thorax, diaphragm

Question 24

Explain how the lungs are adapted to allow rapid gas exchange

Answer 24

-Alveoli one cell thick so short diffusion pathway
-The RBC push against the capillary so shorter diffusion pathway
-constant heart beat so blood being pumped which maintains concentration gradient
- RBC slowed so more time for diffusion
-Lots of capillary’s so more diffusion at once

Question 25

describe the process of inhalation in humans

Answer 25

- External intercostal muscles contract so internal intercostal muscles relax - this pushes the ribs up and outwards - diaphragm contracts and flattens - so volume in the thorax increases - So lower pressure in the lungs - so pulmonary pressure is less than atmospheric pressure so air moves in

Question 26

Describe the process of exhalation in humans

Answer 26

- Internal intercostal muscles contract and external intercostal muscles relax - so ribs move inwards and down - diaphragm relaxes so moves up - volume of thorax decreases - pressure in lungs increases - so pulmonary pressure is greater than atmospheric pressure so sir moves out

Question 27

What is physical digestion

Answer 27

Breaking down larger pieces of food into smaller pieces using the mouth and teeth so it is easier to swallow and provides a greater SA for enzymes

Question 28

What is chemical digestion

Answer 28

Hydrolysing large insoluble molecules into smaller soluble molecules so the products of digestion can be absorbed into the bloodstream

Question 29

What organs are involved in the digestion of carbohydrates

Answer 29

Mouth, stomach, pancreas, ileum

Question 30

what happens in the mouth when digesting carbohydrates

Answer 30

Amylase is released by the salivary glands as well as mineral salts to maintain a ph of 7.

Question 31

What does amylase break down starch into

Answer 31

Starch into maltose

Question 32

What happens to amylase in the stomach

Answer 32

The stomach acid denatures the amylase

Question 33

What does the pancreas secrete

Answer 33

Pancreatic juices containing amylase and alkaline salts to maintain a ph 7

Question 34

What does the ileum do in the digestion of carbohydrates

Answer 34

Secretes maltase which is membrane bound

Question 35

What is a disaccharidase and 3 examples

Answer 35

Breaks down disaccharides -maltase -sucrase -lactase

Question 36

What does maltase break maltose into

Answer 36

alpha glucose

Question 37

What does sucrase break sucrose into

Answer 37

glucose and fructose

Question 38

What does lactase break lactose into

Answer 38

glucose and galactose

Question 39

What enzyme breaks down triglycerides

Answer 39

Lipase

Question 40

What are triglycerides broken into by lipase

Answer 40

Monoglycerides and fatty acids

Question 41

Where is lipase produces

Answer 41

Pancreas and small intestine

Question 42

What is emulsification

Answer 42

Large lipid molecules being broken down into micelles by bile salts

Question 43

Where is bile produces

Answer 43

Liver

Question 44

Where is bile stored

Answer 44

Gal bladder

Question 45

what three enzymes are involved in the digestion of proteins

Answer 45

Endopeptidase, exopeptidase and dipeptidase

Question 46

What does exopeptidase do

Answer 46

Hydrolyses the peptide bonds on the outside of the smaller peptide chain forming amino acids and dipeptides

Question 46

What does endopeptidase do

Answer 46

Hydrolyse the peptide bonds in the middle of the peptide chain forming smaller peptide chains

Question 47

What does dipeptidase do

Answer 47

hydrolyses dipeptides into amino acids

Question 48

What is different about endopeptidase and exopeptidase compared to dipeptidase

Answer 48

Dipeptidase is membrane bound

Question 49

Explain how glucose is absorbed into the ileum

Answer 49

There is a higher concentration of glucose in the lumen of the ileum than the epithelial cells so glucose enters via facilitated diffusion. once the concentration of glucose is lower in the lumen of the ileum than not eh epithelial cell the glucose enters via co transport, against a concentration gradient

Question 50

What system are lacteals part of

Answer 50

The lymphatic system

Question 51

What is the process of absorption of triglycerides

Answer 51

There are epithelial cells adjacent to lacteals which drain into capillaries. Micelles contain bile salts, monoglycerides and fatty acids which burst when they come in contact with the epithelial cell. the monglycerides and fatty acids can enter the epithelial cell via simple diffusion since they are lipid soluble. Inside the epithelial cell the monoglycerides and fatty acids are reformed by the SER. these are packaged into vesicles which take them