Ch. 3 Biochemical, cellular, and organismal responses to climate change

How do chemical reactions correlate with temperatures?

Positively correlated

Describe Q₁₀ relationships

An index of how much faster a reaction rate occurs with an increase of 10°C

If Q₁₀ reaction is 2…

This means that reaction rate doubled with an increase in 10°C

If Q₁₀ reaction is 3….

Then the reaction rate tripled with an increase in 10°C

How to find reaction time?

divide the rate of a process at a temperature by the rate of the same process at a temperature 10° higher

Protein denaturation

Proteins and enzymes denature at high temperatures so once it goes past optimal rate the protein will denature which results in the organism dying.

Heat shock proteins

Highly conservative proteins that are expressed in all organisms under normal physiological conditions that function to maintain regular metabolism

Mediate the repair and degradation of altered or denatured proteins

What happens when HSP’s are under stress?

The expression of these proteins are rapidly upregulated to protect the cell from damage

Stressful conditions like: raised temperatures, pH extremes, osmotic stress, UV irradiation, inflammation, low oxygen, and nutrient deprivation

Example of how organisms respond differently to heat stress?

Juvenile Chinook Salmon experienced heat stress at 21°C

Juvenile Coho Salmon experienced heat stress at 23°C

Effects of temperature on cell membranes

Weak hydrophobic attraction maintains the bilipid layers

Heat disrupts the cohesion, membranes become more permeable to ionic movement

Membranes breakdown at high temperatures

Effects of temperature on photosynthesis

Photosynthesis is the most temperature-sensitive process in plants

3 types of photosynthesis

1. CAM

2. C₄

3. C₃

Different ways plants are affected by temperature

1. Plants grown at higher temperatures have lower concentrations of photosynthetic enzymes in all three types of photosynthesis because Q₁₀ = 2

2. Plants exhibit ‘temperature acclimation’

3. Photosynthesis cannot keep pace with cellular respiration at warmer temperatures

4. C_3, C₄, CAM respond differently to temperature

5. Life cycles exhibit differences in photosynthetic response to temperature

Explain the process of temperature acclimation in plants

The control of photosynthesis output with temperature

As temperatures increase, photosynthetic output drops but then shifts to a different acclimation pattern facilitated by HSPs.

What is the optimal temperature for cell respiration?

45°C or 100°F

Compare and contrast the thermal effects of C₃, C₄, and CAM photosynthesis

C₃ - plants are intermediate (seaweeds, seagrasses), greatest ability to adjust photosynthetic rates, and most diverse of the three groups

C₄ - maintain higher photosynthetic rates at warmer temperatures (Diatoms) compared to C₃ and CAM

CAM - has lowest photosynthetic rates at high temperatures (Warm adapted CAM plants photosynthesize during cool, early morning hours to save water

How does thermal effects on photosynthesis differ between the life cycles of plants?

Annuals are better photosynthesizers at higher temperatures than perennials or evergreens

With C₃ spps, evergreen trees and perennials have better temperature acclimation

Transpiration

Loss of water vapor at the open stomata

Why is thermal regulation critical?

To avoid high temperatures and denatured proteins

Affects of evaporation from the stomata

Cooling of the surface by releasing water molecules with the highest energyT

How does high temperatures cause competition among plants?

The plants compete for water in the soil and utilize more energy to extract water from the moisture-depleted soil