Unit 1 Topic 2 - Multicellular organisms

Question 1

Define stem cells

Answer 1

Unspecialized cells that have capacity to develop into many different cell types under special conditions

Question 2

What are the two main properties of stem cells?

Answer 2

self-renewal (ability to got through several cell cycles without further differentiation) and potency (ability to differentiate into specialized cell types)

Question 3

Explain the relationship between the structural features and efficient gas exchange in alveoli

Answer 3

Alveoli are microscopic round sacs that have four main structural features, which ensure they have efficient gas exchange.

1. Moist surfaces enables oxygen entering the body to dissolve into the bloodstream, without this moisture, oxygen would not be able to cross the membrane and quickly dissolve into the bloodstream.
2. The lungs are covered in Alveoli. The shape and frequency of alveoli in the lungs, increases the surface area to volume ratio which in turn increases the diffusion rate. This ensures that oxygen and carbon dioxide can diffuse in and out rapidly, which is vital to maintain efficiency of bodily functions.
3. Each Alveoli have thin membranes which are approximately one to two cells thick this results in high permeability as there is less distance for the gas to travel in and out of the bloodstream, resulting in high diffusion rates.
4. Lastly, each alveoli is covered by capillaries, which maintains the concentration gradient, whereby molecules move from high to low concentration. Blood pumped towards the lungs is high in carbon dioxide and each alveoli is high in oxygen. This ensures that oxygen is diffused into the bloodstream and carbon dioxide is diffused into the lungs and exhaled through the mouth. These four structural features on the alveoli ensure that the body maintains high levels of oxygen in the blood and remove carbon dioxide from the body efficiently.

Question 4

Explain structure and function of capillaries

Answer 4

Capillaries are very thin and are only 2-layer thick - easy for water, oxygen, carbon dioxide, ions and nutrients to pass through

Question 5

What is the structure and function of villi?

Answer 5

absorption occurs via osmosis, diffusion and active transport. Villi are located in the small intestine where digested food is absorbed across the walls into blood capillaries. Villi contain projections called microvilli which increase surface area for the absorption of food

Question 6

What is the role of enzymes amylase, protease and lipase in chemical digestion?

Answer 6

amylase - chemically digest carbohydrates
protease - digest proteins into amino acid monomers
lipase - chemically digest lipids

Question 7

What are nitrogenous wastes produced by breakdown of proteins?

Answer 7

ammonia, urea, uric acid and creatine

Question 8

What is the function of glomerulus in the nephron and its function in the production of urine?

Answer 8

The glomerulus is the capillary knot found in Bowman’s capsule through which ultrafiltration of blood into the nephron of the mammalian kidney occurs. It begins the urine production process as blood pressure in the glomerulus pushes water and solutes through a filtration membrane.

Question 9

What is the function of Bowman’s capsule in the nephron and its function in the production of urine?

Answer 9

The area of the kidney in which ultrafiltration of blood occurs. It creates a urinary space through which filtrate can enter the nephron and pass to the proximal convoluted tube

Question 10

What is the function of the proximal convoluted tubule in the nephron and its function in the production of urine?

Answer 10

the tubule of the kidney nephron arising from Bowman’s capsule and leading to the Loop of Henle; responsible for the reabsorption of glucose, sodium chloride and water

Question 11

What is the function of distal convoluted tubule in the nephron and its function in the production of urine?

Answer 11

part of the nephron which joins the loop of Henle to the collecting duct; responsible for the reabsorption of sodium, potassium, phosphate and calcium ions under the control of ions

Question 12

What is the function of loop of Henle in the nephron and its function in the production of urine?

Answer 12

are between proximal and distal convoluted tubules of the nephron in kidney; is a counter-current multiplier whereby high salt concentration in the tissue fluid is maintained, resulting in diffusion of water from the filtrate to the surrounding blood capillaries

Question 13

What is the function of collecting duct in the nephron and its function in the production of urine?

Answer 13

a duct in which waste materials from each nephron in the kidney drain

Question 14

What is ultrafiltration?

Answer 14

the removal of most of the plasma and its contents from a capillary under high pressure

Question 15

What are the three main functions of the nephron?

Answer 15

1. Blood is filtered
2. required molecules and water is reabsorbed
3. unwanted waste molecules is secreted

Question 16

Describe the role of stomata and guard cells in controlling movement of gases in leaves

Answer 16

Stomata control water loss and gas exchange by opening and closing. They allow water and oxygen out and carbon dioxide in.
Guard cells surround each stoma and as they lose water they become straighter and the pore closes

Question 17

Explain the relationship between photosynthesis and main tissues of leaves (spongy and palisade mesophyll, epidermis, cuticle and vascular bundles)

Answer 17

Photosynthesis occurs in mesophyll (divided into two layers - upper palisade layer and lower spongy layer)
The mesophyll is located between the upper lower layers of the leaf epidermis.
The cuticle protects the mesophyll after photosynthesis

Question 18

Contrast structure and function of xylem and phloem tissue

Answer 18

Phloem - is living tissue, responsible for transporting food and other organic materials through sieve tubes
Xylem - is the complex tissue of plants, responsible for transporting water and other nutrients to the plants

Question 19

Explain how water and dissolved mineral move through xylem

Answer 19

root pressure causing water to move a limited distance up the stem until counteracted by the force of gravity
transpiration causing loss of water from the stomata of the leaves
cohesion between the water molecules forming the thin water columns in the xylem

Question 20

What are factors that influence the rate of transpiration?

Answer 20

light - stomata open in light and close in dark
temperature - increase temp increases rate of transpiration
humidity - increase humidity decrease rate of transpiration
wind - wind increase transpiration by removal of water around stomatal pore

Question 21

What is translocation?

Answer 21

Movement of organic molecules throughout the plant. Occurs in the sieve tubes of the phloem.