Why are there chemical reactions in cells?
- All living things carry out 7 life processes:
- 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.
What are enzymes?
- 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.
What conditions do enzymes need?
- 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.
What is photosynthesis?
- Photosynthesis- plants use sunlight to make their food.
- 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.
What happens to the glucose?
- 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.
What's in a plant cell?
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.
How do chemicals get into cells?
- 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.
What speeds up Photosynthesis?
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.
How can we investigate Plants and Light?
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.
Why do living organisms need energy?
What is aerobic respiration?
- 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)
What is Anaerobic Respiration?
- 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.
What's in a 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.
- 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.
- Same as animal cell but with a Cell wall.