B4: The processes of life

• All living things carry out 7 life processes:

Movement

Respiration

Sense 

Growth

Reproduction

Excretion

Nutrition

• All of these processes depend on chemical reactions in cells and many reactions need energy.
• This energy is released by the 7th life process: Respiration.

• Enzymes- Speed up chemical reactions in cells;natural catalyst.
• They are proteins.
• Genes carry instructions to make them.
• Reacting molecules must fit exactly into the active site of the enzyme.
• Every enzyme has its own shape; the Lock and Key model.

• They work best at their optimum temperature (high rate of reaction)
• Below this temp, they are slow.
• If the temp is too high, enzymes change shape, it no longer catalyses its reaction - It has been Denature.
  

Its activity is a balance between:

• Increasing reaction rate as temp increases.
• Changes to the active site as temp increases above the optimum.

Also work best at their optimum PH. Other PH values change its active site's shape; the protein they break down no longer fits.

• Photosynthesis- plants use sunlight to make their food.

The process:

• Chlorophyll, green pigment, absorbs light energy.
• Energy allow reactions - Carbon dioxide and water become glucose and water; oxygen = waste product.

Photosynthesis also happens in microorganisms such as phytoplankton.

• It is made during Photosynthesis.

3 main uses:

• Made into chemicals plant cells need to grow; Chlorophyll, Proteins & Cellulose.
• Join together to make starch molecules; storage chemical.
• Used in Respiration.

Parts of a plant cell and their function:

• Chloroplasts- contain Chlorophyll and enzymes for Photosynthesis.
• Nucleus- Contains DNA; code for making enzymes and other proteins for Photosynthesis.
• Cytoplasm- Enzymes and other Proteins are made.
• Cell membrane- Controls the diffusion of chemicals, gas and water, in and out of the cell; prevents bigger molecules escaping (Glucose).
• Mitochondria- Where Respiration occurs.
• Vacuole- Contains Glucose molecules, dissolved in water.
• Cell wall- Rigid; made of cellulose.

• Molecules get in and out of cells by Diffusion.
• Diffusion- Movement of molecules from region of high concentration to one of low; Passive process (needs no extra energy).
• Carbon dioxide diffuses into leaves, Oxygen diffuses out of leaves.
• Water enters through a Partially-permeable membrane.
• Water diffuses through Osmosis.
• Osmosis- Movement of Water from a dilute solution to a more concentrated one.
• Minerals enter plants through root cells.
• Active Transport- moves nitrate ions across cell membrane. Energy from Respiration moves the particles from a region of high concentration to lower concentration.

Factors the affect the rate of Photosynthesis:

• Temperature- Faster at higher temperatures.
• Carbon Dioxide concentration- Increasing this speeds up Photosynthesis.
• Light Intensity- Increasing the amount of light, increases the rate of Photosynthesis; up to a certain point.

Different plants are adapted to different light levels. You can investigate this by using:

• Light Metre- Measure light intensity.
• Quadrat(placed at random) and Identification key- Survey plants in sq metre.

• Aerobic respiration releases energy.
• It happens in plants and animal cells and in some microorganisms; it needs oxygen.
• Glucose (C6H12O6) + Oxygen (6O2) = Carbon Dioxide (6CO2) + Water (6H2O)

• Anaerobic Respiration releases less energy than Aerobic respiration.
• It happens in plants and animals cells and in some microorgansims when there is little or no Oxygen:

-In plant roots when the soil is waterlogged.

-In human muscle cells during vigorous exercise.

• Anaerobic respiration in animal cells and some bacteria:

Glucose = Lactic acid

• Microorganisms such as yeast:

Glucose = Ethanol + Carbon Dioxide 

• Anaerobic respiration of yeast produces carbon dioxide which makes bread rise and ethanol for alcoholic drinks.
• Some bacteria produce methane gas which is a useful fuel.

Animal cell

• Cell Membrane- Allows gases and water to pass freely in and out of the cell, controls passage of other molecules.
• Cytoplasm- Where enzymes are made. Where anaerobic reapiration takes place.
• Mitochondria- Contains enzymes for aerobic respiration.
• Nucleus- Holds genetic info for enzymes involved in respiration.

Bacteria cell

• Cell wall
• Cell membrane- Allows water and gases to pass freely and forms a barrier for other chemicals.
• Cytoplasm- Where enzymes are made,location of respiration reactions.
• Strand of circular DNA- Holds genetic info for enzymes involved in respiration.

Yeast cell

• Same as animal cell but with a Cell wall.