bio chapter 12

Question 1

What happens during photosynthesis?

Answer 1

Plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water.

Photosynthesis occurs primarily in the chloroplasts of plant cells.

Question 2

How do plants obtain and transport the substances they need?

Answer 2

Plants use their structure to efficiently obtain raw materials for photosynthesis and transport products for growth.

The transport system includes xylem and phloem.

Question 3

What is transpiration?

Answer 3

Transpiration is the loss of water vapor from the aerial parts of a plant, mainly through the stomata of the leaves.

It is a consequence of gaseous exchange in plants.

Question 4

How is a root hair cell adapted for its function?

Answer 4

A root hair cell has a long and narrow extension with a large surface area to volume ratio (SA:V) to increase the rate of absorption.

It also has many mitochondria for energy release during active transport.

Question 5

What is the pathway by which water is transported into the roots?

Answer 5

Water enters roots via osmosis, moves through the xylem vessels, and is transported to the leaves by transpiration pull.

The process involves a water potential gradient.

Question 6

What factors affect the transpiration rate?

Answer 6

Factors include:
* Humidity of air
* Wind or air movement
* Temperature of air
* Light intensity

High humidity decreases transpiration, while high temperature and light intensity increase it.

Question 7

What is transpiration pull?

Answer 7

Transpiration pull is a suction force that draws water up a plant due to the loss of water vapor through transpiration.

This creates a negative pressure in the xylem.

Question 8

How does water move up a plant?

Answer 8

Water moves up a plant through the xylem vessels, primarily driven by transpiration pull and capillary action.

This movement occurs against gravity.

Question 9

What occurs during wilting?

Answer 9

Wilting occurs when the rate of transpiration exceeds the rate of water absorption by roots.

It results in leaves drooping and decreased photosynthesis.

Question 10

What advantages does wilting provide to a plant?

Answer 10

Wilting reduces the exposed surface area of leaves, leading to decreased transpiration and less water loss.

Guard cells become flaccid, causing stomata to close.

Question 11

How does light intensity affect transpiration?

Answer 11

High light intensity increases the rate of transpiration as stomata open wider, allowing more water vapor to diffuse out of the leaf.

This process enhances photosynthesis.

Question 12

Explain the role of the cuticle in transpiration.

Answer 12

The cuticle is a waxy layer that reduces water loss from the leaf surface, helping to regulate transpiration rates.

It is important for maintaining plant hydration.

Question 13

Fill in the blank: The movement of water out at leaves occurs through _______.

Answer 13

transpiration

Question 14

Fill in the blank: Water enters root hair cells via _______.

Answer 14

osmosis

Question 15

True or False: Transpiration helps cool the plant by removing latent heat.

Answer 15

True

Question 16

What is the significance of maintaining a water potential gradient in root hair cells?

Answer 16

It prevents leakage of cell sap and facilitates the uptake of water and ions via osmosis.

This gradient is essential for efficient nutrient absorption.

Question 17

What happens to the water potential of mesophyll cell sap when water is absorbed?

Answer 17

The water potential of mesophyll cell sap falls, prompting further water absorption from xylem vessels.

This process contributes to transpiration pull.

Question 18

What is the primary role of chlorophyll in photosynthesis?

Answer 18

Chlorophyll absorbs light energy and converts it into chemical energy for the formation of carbohydrates.

This process is essential for the production of glucose and oxygen.

Question 19

What is the word equation for photosynthesis?

Answer 19

Carbon dioxide + Water + Light energy + Chlorophyll → Glucose + Oxygen

In symbols: 6 CO2 + 6 H2O + light energy + chlorophyll → C6H12O6 + 6 O2.

Question 20

List the conditions necessary for photosynthesis to occur.

Answer 20

• Carbon dioxide
• Sufficient water
• Light energy
• Chlorophyll
• Suitable temperature

These factors ensure that photosynthesis can take place effectively.

Question 21

What happens to glucose after photosynthesis?

Answer 21

• Used immediately for cellular respiration
• Converted to starch for short-term energy storage
• Converted to cellulose to form cell walls
• Transported as sucrose
• Used for synthesis of amino acids/proteins
• Stored as fats for long-term energy storage

Glucose serves various roles in plant metabolism and growth.

Question 22

Explain why most forms of life are completely dependent on photosynthesis.

Answer 22

Photosynthesis produces oxygen for other organisms and glucose as a source of chemical energy for consumers, while also removing carbon dioxide from the atmosphere.

This process is vital for maintaining life on Earth.

Question 23

True or False: Increasing light intensity will always increase the rate of photosynthesis.

Answer 23

False

There is a point at which increasing light intensity no longer increases the rate of photosynthesis due to other limiting factors.

Question 24

What are the three limiting factors discussed that affect the rate of photosynthesis?

Answer 24

• Light intensity
• Carbon dioxide concentration
• Temperature

Each of these factors can limit the rate of photosynthesis if not at optimal levels.

Question 25

What is the effect of temperature on the rate of photosynthesis?

Answer 25

Rate of photosynthesis increases as temperature increases towards optimum temperature, then decreases rapidly beyond that. ## Footnote Extreme temperatures can denature enzymes involved in photosynthesis.

Question 26

Fill in the blank: The first quantitative experiment in plant nutrition was conducted by _______.

Answer 26

Jan Baptista van Helmont ## Footnote This experiment helped establish the importance of water in plant growth.

Question 27

What is the role of starch in plants?

Answer 27

Starch serves as short-term energy storage and is converted back to glucose when needed, especially in darkness. ## Footnote It is a polysaccharide that plants synthesize from glucose.

Question 28

How do we know that photosynthesis has occurred?

Answer 28

Presence of starch and oxygen can be tested to confirm photosynthesis. ## Footnote Starch can be tested using iodine, which turns blue-black in its presence.

Question 29

What happens to the rate of photosynthesis when carbon dioxide concentration increases?

Answer 29

Rate of photosynthesis increases as carbon dioxide concentration increases, until it reaches a saturation point. ## Footnote Beyond a certain concentration, other factors may become limiting.

Question 30

What is the significance of removing carbon dioxide from the atmosphere during photosynthesis?

Answer 30

It reduces greenhouse gases in the atmosphere, contributing to climate regulation. ## Footnote This process is crucial for maintaining ecological balance.

Question 31

What happens during photosynthesis?

Answer 31

Plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. ## Footnote Photosynthesis occurs mainly in the chloroplasts of plant cells.

Question 32

How do plants obtain and transport the substances they need?

Answer 32

Through a specialized structure and transport system, enabling efficient uptake of raw materials for photosynthesis and distribution of products for growth.

Question 33

What is the significance of the structure of a dicotyledonous leaf?

Answer 33

The structure allows for efficient photosynthesis, gas exchange, and transport of materials due to features like chloroplast distribution, stomata, and vascular bundles.

Question 34

What are the functions of chloroplasts in a leaf?

Answer 34

Chloroplasts absorb light energy for photosynthesis, converting carbon dioxide and water into glucose and oxygen.

Question 35

What is the role of stomata in leaves?

Answer 35

Stomata regulate the exchange of gases (CO2 and O2) between the leaf and the environment.

Question 36

What is translocation in plants?

Answer 36

Translocation is the transport of food, mainly sucrose, in the phloem tissue.

Question 37

Fill in the blank: The vascular bundle consists of _______ and _______.

Answer 37

xylem; phloem

Question 38

What is the structure and function of xylem vessels?

Answer 38

* Long hollow tubes with no cross-walls * Conduct water and dissolved mineral salts from roots to stems and leaves * Provide mechanical support for the plant

Question 39

What is the structure and function of phloem?

Answer 39

* Elongated living cells separated by cross walls * Transport manufactured food substances (sucrose and amino acids) from green parts to the rest of the plant

Question 40

What is the role of guard cells in plants?

Answer 40

Guard cells control the size of stomatal openings, regulating gas exchange and water loss.

Question 41

How does carbon dioxide reach mesophyll cells in a leaf?

Answer 41

* Diffusion via CO2 concentration gradient * Dissolves in thin film of water on mesophyll cells * Diffuses into mesophyll cells

Question 42

How does water enter a leaf?

Answer 42

Water and mineral salts leave xylem vessels and move from cell to cell via osmosis.

Question 43

What adaptations do leaves have for photosynthesis?

Answer 43

* Thin leaf blade for short diffusion distance * Large surface area for maximum light absorption * Transparent waxy cuticle to allow sunlight penetration

Question 44

What are the adaptations of xylem for transport?

Answer 44

* Lignin deposits to strengthen walls * Hollow structure to reduce resistance to water flow

Question 45

What are the adaptations of phloem for transport?

Answer 45

* Companion cells provide energy for active transport * Sieve tube cells have thin cytoplasm for rapid flow of food substances

Question 46

True or False: The palisade mesophyll contains the most chloroplasts in a leaf.

Answer 46

True

Question 47

What is the mechanism for the opening and closing of stomatal pores?

Answer 47

* Turgidity of guard cells changes based on water potential * Increased glucose concentration leads to water entering guard cells, making them turgid and opening stomata

Question 48

What is the role of the cuticle on a leaf?

Answer 48

The cuticle is a waxy layer that prevents excessive water loss while allowing sunlight to penetrate.

Question 49

Fill in the blank: The spongy mesophyll contains _______ for _______ exchange.

Answer 49

intercellular air spaces; gas

Question 50

What is the process of phloem loading?

Answer 50

Sugar is actively transported from photosynthesizing leaf cells to the phloem, and water follows by osmosis.

Question 51

What happens during phloem unloading?

Answer 51

Sugar is unloaded at the sink, and water returns to the xylem.

Question 52

What does the ringing experiment demonstrate?

Answer 52

It shows the transport of sugars in the phloem by observing changes in the plant after removing a ring of bark.

Question 53

What substances are primarily transported in the xylem?

Answer 53

Water and mineral salts.

Question 54

What substances are primarily transported in the phloem?

Answer 54

Sucrose and amino acids.

Question 55

how does air movement affect transpiration rate

Answer 55

In moving air, the water vapour will be swept away from the leaf (decreasing the humidity around it). The steep concentration gradient of water vapour between the leaf and the surrounding increases the rate of diffusion of water vapour out of the leaf. → Transpiration rate increases In still air, the water vapour accumulates around the leaf (increasing the humidity around it). The smaller concentration gradient of water vapour between the leaf and the surrounding reduces the rate of diffusion of water vapour out of the leaf. → Transpiration rate decreases

Question 56

how does humidity affect transpiration rate

Answer 56

More humid = more water vapour in the air (moist air). The smaller concentration gradient of water vapour between the leaf and the surrounding reduces the diffusion of water vapour out of the leaf. → Transpiration rate decreases Less humid = less water vapour in air (dry air). The steeper concentration gradient of water vapour between the leaf and the surrounding increases the diffusion of water vapour out of the leaf. → Transpiration rate increases

Question 57

how does temperature affect transpiration rate

Answer 57

At higher temperature, moisture on the mesophyll cells evaporates into the intercellular air space more quickly. The steeper concentration gradient of water vapour between the leaf and the surrounding increases diffusion of water vapour out of the leaf. → Transpiration rate increases At lower temperature, moisture on mesophyll cells evaporates into the intercellular air space more slowly. The concentration gradient of water vapour between the leaf and surroundings decreases, rate of diffusion of water vapour out of leaf decreases. → Transpiration rate decreases

Question 58

how does light intensity affect rate of transpiration

Answer 58

At high light intensity, stomata open. More water vapour diffuses out of the leaf. → Transpiration rate increases. At low light intensity, stomata close. Less water vapour diffuses out of the leaf. → Transpiration rate decreases.