Chapter 6 Biology - Exchange

Question 1

Equation for diffusion rate?

Answer 1

Diffusion rate = (surface area x difference in conc) / length of diffusion path

Question 2

Organisms need exchange - what are some things that need to be interchanged?

Answer 2

• respiratory gases - oxygen and carbon dioxide
• nutrients like glucose, fatty acids, amino acids, vitamins and minerals
• excretory products like urea
• heat

Question 3

How does an organisms size relate to their SA:V ratio?

Answer 3

The larger the organism, the lower thir surface area to volume ratio

Question 4

How does surface area to volume ratio affect rate of diffusion?
How does this affect metabolic rate?

Answer 4

High SA:V - the diffusion of substances is fast.
Low SA:V - the diffusio
n of substances is slower.

Therefore, the lower the surface area to volume ratio, the lower the metabolic rate

Question 5

What are some features/adaptations of an efficient exchange surface? and examples…

Answer 5

1. Large surface afrea - provides a larger area across which substances can be exchanged.
   E.g root hair cells and folded membranes such as those of the mitochondria
2. Thin - to minimise the diffusion distance. e.g wall of capillaries
3. Good blood supply/ventilation to maintain a steep concentration gradient
   e.g alveoli
4. Partially permeable plasma membrane which controls what substances are exchanged.

Question 6

Why do multicellular organisms require specialised gas exchange surfaces?

Answer 6

Have a smaller surface area to volume ratio so distance that needs to be crossed is larger and substances cannot enter as easily like ina single-celled organism

Question 7

What prevents direct gas exchange in insects?

Answer 7

Insects have high oxygen demands but their tough chitinous external skeleton (exoskeleton) is waterproof and has small SA:V to conserve water so prevents direct gas exchange.

Question 8

Why do insects require gas exchange?

Answer 8

To deliver oxygen to cells - This allows aerobic respiration to occur to release energy for cellular processes.
To remove carbon dioxide from cells - The build up of carbon dioxide produced as a waste product of respiration reduces pH, which can denature enzymes.

Question 9

Name and describe the 3 main features of an insect’s gas exchange system.

Answer 9

Spiracles - external openings of the tracheal system which run into the body of an insect and supply it with the required gases - can be opened or closed by a valve
Tracheae - These are air-filled tubes branching throughout the body. there are multiple tracheae to increase SA
supported by rings to prevent collapse
Trachaeoles - Smaller branches dividing off the tracheae that deliver gases to cells.
highly branched to increase SA

Question 10

Explain the process of gas exchange in insects step by step

Answer 10

Gas enters the tracheal system through open spiracles and then moves in or out of tracheae.
A diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out.
Air is then carried back to the spiracles via the tracheae and released from the body.
Contraction of muscles in the tracheae allows mass movement of these gases.

Question 11

Why can’t fish use thier bodies as an exchange surface?

Answer 11

• They have a waterproof, impermeabe outer membrane so gases cannot diffuse through their skin
• small surface area to volume ratio

Question 12

What are the two main features of a fish’s gas exchange system?
why are they needed?

Answer 12

Gills and Lamellae
to allow fish to efficiently take up oxygen from water and to remove carbon dioxide.

Question 13

Descriobe the structure and of gills and lamellae

Answer 13

Gills - located within the body and are supported by arches. Along arches are gill filaments which are stacked in a pile. These gill filaments have lamellae on them which participate in gas exchange
Lamellae - on gill filaments at right angles and they increase surface area, surrounded by extensive blood vessels
Blood and water flow across them in opposite directions (counter-current exchange system)

Question 14

Adaptations of gills and lamellae

Answer 14

Lamellae;
- provide a large surface area
- thin to minimise diffusion distance
Gills:
- have a rich blood supply to maintain steep diffusion gradients.
- countercurrent flow of blood and water creates even steeper concentration gradients.

Question 15

Overall description of how gas exchange works in fish

Answer 15

Fish opens its mouth and water flows in, fish then closes mouth to increase pressure
Water passes over lamallae and then oxygen diffuses into the bloodstream
Waste CO2 diffuses into the water and flows back out of the gills

Question 16

How does the countercurrent flow system work and how does this benefit the fish?

Answer 16

Blood and water flow over the gill lamellae in opposite directions to ensure that a steep diffusion gradient is maintained so that the maximum amount of oxygen is
diffusing into the deoxygenated blood from the water. - water is always next to blood with a lower oxygen concentration.
keeps rate of diffusion constant

Question 17

Gas exchange in plants
Adaptations of a leaf for gas exchange

Answer 17

-Thin and flat to provide short diffusion pathway and large surface area to volume ratio
- Stomata - These open when conditions are suitable for photosynthesis, allowing inward diffusion of carbon dioxide and outward diffusion of oxygen, and close to minimise water loss.
- air spaces in the mesophyll to allow gases to move around the leaf easily, facilitating diffusion
-

Question 18

What controls open and close of stomata?
How does this limit water loss?

Answer 18

Guard cells control opening and closing of stomata
Stomata open and close when needed . When closed, limts waterloss as water cannot leave
Some stomata stay open to let oxygen in
- waxy cuticle limits water loss

Question 19

What is the name given to plants adapted to living in dry environments with limited water availability?

Answer 19

Xerophytes

Question 20

What adaptations do xerophytes have to minimise water loss?

Answer 20

1. Thick waxy cuticle - This reduces water loss through evaporation.
2. Rolled up leaves - encloses the stomata on the lower surface to reduce air flow and the evaporation of water and traps a region of still air wiithin the rolled leaf
3. Hairs on leaves - These trap moist air against the leaf surface - reduces the water potential gradient between inside and outside the leaves - less water is lost by evaporation.
4. Sunken stomata in pits or grooves - traps still moist air reduces water potential. - reduce air flow and the evaporation of water.
5. Small, needle-like leaves - These reduce the surface area across which water can be lost.
6. Water storage organs - These conserve water for when it is in low supply.

Question 21

Make flascard on leaf structure with diagram

Question 22

What type of roots do xerophytes have and how does this help them in dry conditions

Answer 22

wide, shallow roots to absorb rain water
deep roots to reach far down water
branch a lot - wide

Question 23

Human gas exchange system
Describe the pathway of air in the human gas exchange system

Answer 23

In through mouth/nasal cavity - trachea - air travels into the two bronchi, with one bronchus going to each lung. - bronchioles - alveoli

Question 24

Structure of lungs

Answer 24

Pair of lobed structures made up of a series of highly branched tubules called bronchioles which end up in tiny air sacs called alveoli

Question 25

Where are lungs located and why? What protects them?

Answer 25

1. Located inside the body inside the chest cavity - air is not dense enough to support and protect delicate lungs 2. Supported and protected by the ribcage Lungs are ventilated by a tidal stream of air ensuring air within them is constantly replenished There is a lubricating substance secreted between lungs and ribs to prevent friction during inhalation and deflation.

Question 26

Describe the structure and function of the trachea

Answer 26

The trachea is the large tube that carries air from the throat down to the lungs. Flexible airway supported by rings of cartilage which prevents the trachea from collapsing as the air pressure inside falls when breathing in Tracheal walls made from muslcle lined with ciliated epithelium and goblet cells

Question 27

Function of ciliated epithelium cells and goblet cells

Answer 27

Goblet cells - These produce and secrete mucus that traps dust and microbes. Cilia on ciliated epithelial cells - These waft the mucus upward to the mouth so it can be swallowed.

Question 28

Describe the structure and functuin of the bronchi

Answer 28

The bronchi are two main branches extending from the trachea that carry air into each lung. Similar structure to the trachea but they are narrower and is 2 of them.Also supported by cartilage rings(amount of cartialge is reduced as bronchi get smaller) and are lined by ciliated epithelium cells. They allow the passage of air into the bronchioles

Question 29

Describe structure and function of bronchioles

Answer 29

They are narrower than bronchi. The bronchioles are smaller airways branching from the bronchi that carry air to the alveoli. Walls are made from muscle lined with epithelial cells - No cartilage Elasticfibres and muscle allows them to constrict/contract and relax easily so they control air flow in and out of the alveoli.

Question 30

Structure and function of alveoli

Answer 30

Alveoli are tiny air sacs clustered at the ends of the bronchioles. They are surrounded by a network of capillaries so gases can be exchanged between the air in the alveoli and the blood. Between the alveoli are some collagen and elastic fibres, allows the alveoli to stretch as they fill up with air and spring back during breathing out to expel C02 rich air - site of gas exchange Lined w/ epithelial cells

Question 31

Adaptations of the alveoli

Answer 31

- 300 million alveoli in each lung - gives high surface area of 70m^2 - very thin walls - only one cell thick so very short diffusion pathway - large surface area increases rate of gas exchange - dense network of capillaries allows constant blood supply which maintains a concentration gradient - ventilation of air maintains steep diffusion gradient -moist inner surface - This allows gases to dissolve, and lung surfactant helps alveoli remain inflated.

Question 32

What is ventilation?

Answer 32

Ventilation, or breathing, is the constant movement of air into and out of the lungs. It consists of inspiration (breathing in) and expiration (breathing out). It allows air to enter and leave the lungs, providing the body with oxygen and removing carbon dioxide.

Question 33

What are the 3 sets of muscles involved in ventilation?

Answer 33

- The diaphragm -a sheet of muscle that moves the ribcage up and out when it contracts. - The intercostal muscles The external intercostal muscles - These are found between the ribs and pull the ribcage up and out when they contract. The internal intercostal muscles - These are found between the ribs but pull the ribcage down and in when they contract. They have opposite effects on the ribcage

Question 34

What is inspiration? in terms of air pressure Does it require energy?

Answer 34

Inhalation - when the air pressure of the atmosphere is greater than the air pressure inside the lungs, air is forced into the lungs Yes requires energy and is an active process

Question 35

What is expiration? in terms of air pressure Does it require energy?

Answer 35

Exhalation - when the air pressure inside the lungs is greater than he that of the atmosphere, air is forced out of the lungs at rest is a passive process so it does not require energy.

Question 36

Explain the process of inspiration

Answer 36

The external intercostal muscles contract while internal ones relax This pulls the ribs upwards and outwardes which increases the volume of the thorax. The diaphragm contracts and flattens, further increasing the volume of the thorax. This increased volume of the thorax reduces the pressure in the lungs to below atmoshpheric pressure So because atmospheric pressure is greater pressure outside the lungs is greater so air is forces into the lungs to rebalance

Question 37

Explain the process of expiration

Answer 37

The internal intercostal mucles contract, external ones relax This moves the ribs down and in which decreases the volume of the thorax The diaphragm relaxes and unflattens, further decreasing the volume of the thorax This decreased volume increases the pressure in the lungs so it is higher than the atmospheric pressure outisde of the lungs Air is forced out of the lungs to rebalance

Question 38

What happens to elastic tissue in the alveoli during expiration?

Answer 38

Elastic fibres/tissue in the alveoli also shrink and recoil back to their original shape when the thoracic cavity volume decreases. This increases the pulmonary pressure and helps to push air out of the lungs.

Question 39

What is tidal volume?

Answer 39

The volume of air taken in at each breath - at rest

Question 40

What is pulmonary ventilation and how can it be measured?

Answer 40

Total volume of air that is moved into the lungs in one minute Tidal volume x Breathing rate Can also use a spriometer to measure, which records volume changes as a person breaths onto a graph.

Question 41

What is breathing rate

Answer 41

Number of breaths per minute

Question 42

What is vital capacity?

Answer 42

Vital capacity – the maximum volume of air that can be inhaled or exhaled in a single breath.

Question 43

Digestion The human digestive system breaks down food so that it can be absorbed into the body. What are the 2 stages of digestion and explain

Answer 43

1. Physical breakdown - food is broken down into smaller pieces e.g by teeth to increase surface area for chemical digestion 2. Chemical digestion - Enzymes catalyse hydrolysis reactions that break bonds in large insoluble molecules to form smaller soluble molecules.

Question 44

Different structures of the digestive system Order of digestion?

Answer 44

Mouth ➔ oesophagus ➔ stomach ➔ small intestine ➔ large intestine ➔ rectum ➔ anus

Question 45

1. Function of salivary glands? 2. Function of oesophagus?

Answer 45

1. Salivary glands - These secrete saliva containing amylase, which hydrolyses starch into maltose 2. Oesophagus - This transports food from the mouth to the stomach.

Question 46

1. Function of the stomach? 2. Function of the liver?

Answer 46

1. Produces enzymes. Stores and digests food, especially proteins. Has glands that produce enzymes which digest protein 2. This produces bile salts to aid lipid digestion.

Question 47

1. Function of pancreas? 2. Function of large intestine?

Answer 47

1. This secretes pancreatic juice containing enzymes (proteases, lipases, and amylases). to hydrolyse proteins lipids and starch 2. Absorbs water and stores water

Question 48

Small intestine - Ileum Overall function?

Answer 48

site of further digestion and absorption.

Question 49

What are the enzymes involved in carbohydrate digestion and where are they produced?

Answer 49

Amylase - Produced in salivary glands in mouth and in the pancreas Maltase, sucrase and lactase in lining of the ileum?

Question 50

Which does each enzyme hydrolyse and how does it work? 1. Amylase 2. Maltase 3. Sucrase 4. Lactase

Answer 50

1. Amylase hydrolyses alternate glycosdic bonds of starch to produce maltose. 2. Maltase hydroylses maltose into alpha glucose monosaccharides. 3. Sucrase hydrolyses single glycosidic bond in sucrose to produce glucose and fructose 4. Lactase hydrolyses glycosidic bond in lactose into glucose and galactose

Question 51

Describe the process of carbohydrate digestion

Answer 51

- Saliva enters the mouth from salivary glands and is mixed with food during chewing - Amylase hydrolyses any starch into maltose and also contains mineral salts that help maintain optimum pH for salivary amylase - Food is swallowed, enters the stomach, acid in stomach denatures amylase to prevent further hydrolysis of starch - Pancreatic amylase continues hydrolysis of any remaining starch into maltose - Muscles in intestine wall push food along the ileum, epithelial ining produces maltase, hydrolyses maltose into alpha glucose. Maltase is not released into lumen of ileum but is part of the cell-surface membranes of epithelial cells that line the ileum so referred to as a membrane-bound disaccharide -There is also sucrose and lactose, hydrolysed by sucrase and lactase

Question 52

Lipid digestion Enzyme is lipase Where is it made and where does lipid digestion occur?

Answer 52

Made in the pancreas and digestion occurs in small intestine

Question 53

What bond does lipase hydrolyse and what does this produce?

Answer 53

Hydrolyses ester bond found in triglycerides so forms fatty acids and monoglycerides

Question 54

What needs to happen before lipid digestion?

Answer 54

Bile salts produced in the liver, emulsify lipids into tiny droplets called micelles which increases the surface area of the lipids so action of lipases is sped up

Question 55

Protein digestion What are the enzymes called? What are the 3 different types of peptidases called?

Answer 55

Peptidases(proteases) Endopeptidases Exopeptidases Dipeptidases

Question 56

What is the role of each peptidases? What do they form? 1. Endopeptidases? 2. Exopeptidases? 3. Dipeptidases?

Answer 56

1. Endopeptidases hydrolyse the peptide bonds between amino acids in the middle/ central region of a protein. Forms a series of peptide molecules 2. Exopeptidases - hydrolyse the peptide bonds at the ends of polypeptides to remove terminal amino acids or dipeptides. 3. Dipeptidases - hydrolyses the bond between two amino acids of a dipeptide - breaks down dipeptides into amino acids Dipeptidases are membrane bound

Question 57

The ileum - Structure of the ileum It is adapted to absorb digested food molecules across the epithelial cells that form its lining so nutrients can enter the bloodstream. How is the ileum adapted to increase efficieny of absorption?

Answer 57

- The walls are folded into finger-like villi to increase surface area. - They have thin walls lined with epitheilal cells. Epithelial cells have microvilli to further increase surface area. Thin walls reduces diffusion distance, shorter diffusion distance. - It has an extensive capillary network and a good blood supply to maintain steep diffusion gradients as blood can carry away absorbed molecules and so maintain a diffusion gradient - Villi contain muscle so are able to move which helps maintain diffusion gradient as the movement mixes the contents of the ileum. Ensures that as productsb of digestion are absorbed from food adjacent to the villi, new material rich in products of digestion replaces it

Question 58

How are amino acids and monosaccharides absorbed into the ileum (despite a negative conc gradient)?

Answer 58

Co- transport and faciliated diffusion- go over chapter 4 Move from ileum to epithelial cells, here there is a higher conc than the blood so then diffuse into blood by facilitated diffusion | Amino acids and monosaccharides are transported w sodium ions

Question 59

Why do fatty acids and monosaccharides not require co-transport?

Answer 59

Because they are non polar so they can easily diffuse across the membrane of epithelial cells.

Question 60

Describe the process of fat absorption

Answer 60

- Monoglycerides and fatty acids associate with bile salts - form micelles - Micelles break down into monoglycerides and fatty acids when they come into contact with the epithelial cells . - The Monoglycerides and fatty acids diffuse across cell surface membrane into the epithelial cells - They are transported to the endoplasmic reticulum where triglycerides reform inside the cells’ endoplasmic reticulum. - The triglycerides , starting in E.R and continuing to golgi apparatus, associate with cholesterol and lipoproteins to form chylomicrons - Chylomicrons are move out of the epithelial cells by exocytosis into lacteals, which are lymphatic vessels in the villi - and then chylomicrons into the bloodstream. Triglycerides in the chylomicrons are hydrloyses in the endothelial cells of blood capillaries and then diffuse into cells.

Question 61

What are chylomicrons? What are lacteals?

Answer 61

1. The product of triglycerides associating with cholesterol and lipoproteins. 2. Lymphatic capillaries found at the centre of each villus

Question 62

Sodium potassium pump is required for absorption of amino acids and monosacharrides Respiratory inhibitors such as cyanide reduce respiration in cells. Explain why cyanide would reduce the absorption of monosaccharides in the ileum.

Answer 62

The majority of monosaccharides enter the ileum via co-transport using sodium ions. This requires a sodium ion concentration gradient between the lumen and epithelial cells. The gradient is maintained by the sodium-potassium pump, which requires ATP. Cyanide inhibits respiration, which reduces the release of ATP. This means less ATP is available for the sodium potassium pump. This causes the concentration of sodium ions in epithelial cells to increase, which reduces the sodium ion concentration gradient between the cells and the lumen. This slows the rate of co-transport of monosaccharides into the epithelial cells.

Question 63

Describe how the products of lipid digestion in the lumen enter the lymphatic system.

Answer 63

In the lumen, lipids are broken down into glycerol, fatty acids and monoglycerides. Fatty acids and monoglycerides associate with bile salts, forming micelles. This makes them more soluble in water and they’re transported to the epithelial cell. There, they enter the cell by diffusion. Inside the epithelial cell, the products of lipid digestion are converted back into triglycerides by the endoplasmic reticulum. The endoplasmic reticulum and Golgi apparatus then combine the triglycerides with proteins and cholesterol to form chylomicrons. The chylomicrons are then packaged into vesicles and released into the lymphatic system via exocytosis.

Question 64

Adaptations of epithelial cells for absorption

Answer 64

1. Microvilli to provide large surface area for absorption 2. To maximise the absorption of amino acids and monosaccharides, epithelial cells have a lot of co-transport/channel/carrier proteins. 3.lots of mitochondria- A large number of mitochondria ensures a good supply of ATP for the sodium-potassium pump. This maximises the rate of active transport of sodium ions and therefore the co-transport of amino acids and monosaccharides.

Question 65

Insect gas exchange Tracheal fluid Describe process

Answer 65

Oxygen dissolves into the tracheal fluid before diffusing into the muscle tissue.

Question 66

Adaptations of tracheoles

Answer 66

1. There is a large number of tracheoles that reach into the muscle tissues. This helps ensure a short diffusion pathway and maximises the surface area for gas exchange. 2. The walls of the tracheoles are just 1 cell thick. This also helps ensure a short diffusion pathway for gas exchange.

Question 67

There is a carbon dioxide concentration gradient in an insect gas exchange system. Describe how this gradient is formed.

Answer 67

Aerobic respiration in muscle tissue produces carbon dioxide. As a result, the concentration of carbon dioxide in the muscle tissue is greater than the concentration in the air. So, there is a carbon dioxide gradient from the respiring tissues to the air, and c02 moves down this conc gradient out of the muscle tissue into the tracheoles and then out of the spircales