B4 - The Processes of Life - Revision Cards in GCSE Science

Enzymes

Need to be at a specific constant temp to work at optimum
Changing temp causes a change in rate of reaction
High temp increases rate
If temp is too high, bonds holding enzyme together break, changing shape of active site
Substrate no longer fits and enzyme stops working - Denaturing
Enzymes also have an optimum pH
If pH is too low or too high, interferes with bonds therefore changes shape of active site.

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Series of chemical reations that use energy from sunlight to build large food molecules in plant cells and phytoplankton
Carbon Dioxide+Water------>Glucose+Oxygen
6CO2 + 6H2O------->C6H12O6
Sunlight absorbed by chlorophyll which is found in chloroplasts
Allows energy to be used to convert carbon dioxide and water into glucose
Glucose is:
- converted to chemicals needed for growth e.g. cellulose for cell walls, protein, chlorophyll
- converted into starch for storage
- used in respiration to release energy
Glucose and nitrates taken up by roots are used to synthesise amino acids which are assembled into proteins
Oxygen is a waste product

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1) Not enough light slows down rate of photosynthesis
As light level is increased, rate increases steadily - upto a certain point
Beyond that, there will be no difference as either temp or CO2 will be the limiting factor

3)Temperature has to be right
If temp is limiting factor it is too low - enzymes work more slowly at low temp
If plant is too hot, enzymes will denature
Enzymes denature at 45C

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Respiration - release of energy by breaking down large food molecules
Aerobic respiration uses oxygen and occurs in animal and plant cells and some microorganisms
Glucose+Oxygen----->Carbon Dioxide+Water (+Energy Released)
C6H12O6+6O2----->6CO2+6H2O (+Energy Released)
Aerobic resp happens in mitochondria - has enzymes for aerobic respiration

Energy released speeds up reactions such as:
Movement - Energy needed to make muscles contract
Active Transport - Uses energy to move substances in and out of cells
Synthesis of large molecules - Large molecules/polymers made by joining smaller molecules which require energy. Glucose is joined to make starch and cellulose. In plant and animal cells and microorganisms, glucose and nitrogen joined to make amino acids -> proteins

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Occurs when there is little or no oxygen available
Occurs in human cells during vigorous exercise (body can't supply enough oxygen to muscle cells), plant cells in waterlogged soil and bacteria in wounds
Anaerobic respiration releases less energy than aerobic
Glucose----->Lactic acid + ENERGY

Fermentation used by some microorganisms - breaking down sugars into other products
Glucose----->Ethanol+Carbon Dioxide + ENERGY
1) Biogas - Fuel used for heating and lighting. Microorganisms ferment plant and animal waste containg carbs. Biogas made of methane and CO2
2)Bread - Made using yeast----->Ferment the carbs in flour and release CO2, causing bread to rise
3)Alcohol - Yeast ferment sugar to form alcohol (ethanol). Sugar used in production comes from grapes and barley.

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Diffusion - Passive (no energy needed) movement of chemicals from a high to low conventration
In photosynthesis:
Water taken up by plant roots
CO2 enters plant leaves by diffusion
Oxygen leaves by diffusion
Osmosis - Movement of water from a dilute (high concentrated) to a concentrated solution (low concentration)
Chemicals separated by partially permeable membrane - lets water pass through but keeps other chemicals in or out
Movement of water into plant roots from soil and across roots occur by osmosis
Active Transport - Uses energy from respiratation to transport chemicals across cell membranes from area of low concentration to high concentration
Minerals such as nitrates taken up by plant roots use active transport. Concentration of minerals in root cells is higher than in the soil around them.

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1) Identification Key - used to identify plants by answering a series of questions. Start at Q1 and answer narrows down your options
2)Quadrat - Square frame divided into a grid of 100 smaller squares. Put on the ground a number of times so an average is taken, or at random in a location if there is no obvious change in distribution of plants
If there is an obvious change, quadrat should be used along a line called a transect
3) Light Meter - Light intensity needs to be measured if you were comparing plants in areas with different levels of light

Trees, bushes and hedges can cast shade on an area and can therefore affect growth of plants around them
There may be a correlation between distance from a tree and growth of other plants
Other factors may be involved such as competition for nutrients

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