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BIO EDEXCEL
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Lecture notes of 22 pages for the course Edexcel at Edexcel (.)
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Differentiation → its the process in where cells become specialized (it is controlled by DNA)Stem cell have the ability to divide many times without becoming differentiated
- Embryonic
- Adult
Nerve cells → specialized to transmit electrical signals quickly
- Axon is long, this allows impulses to be carried along long distances
- Has lots of extensions from cell body (dendrites) so that connections can be formed with other nerve cells
- Nerve endings has many mitochondria which supplies energy to make transmitter chemicals called
neurotransmitters
- Axon is insulated with fatty myelin sheath which insulates nerve cell and speeds up nerve impulses
Muscles cells → specialized to contract or relax for movement
- Lots of mitochondria provide energy from respiration for contraction
- Stores chemical called glycogen that is used in respiration in the mitochondria
Red blood cell → specialized to transport oxygen
- Biconcave disc shape increases surface area for efficient diffusion of oxygen
- Contains hemoglobin which binds with oxygen
- Contains no nucleus so that more hemoglobin can be stored
Ciliated cells → movement of mucus in trachea and bronchi
- Extension of cytoplasm form hairlike structures called cilia which beat and sweep mucus
Sperm cells → reproduction
- Specialized to carry male DNA to egg cell for successful reproduction
- Genetic material is contained in a haploid nucleus in the head
- Streamlined head and flagellum
- Many mitochondria to release energy to swim and to fertilize the egg
- The acrosome has digestive enzymes which break down the outer layer of membrane of the egg cell
Egg cell (ovum) → reproduction
- Contains a lot of cytoplasm that contains nutrients for the growth of the early embryo
- Haploid nucleus contains genetic material for fertilization
- Cell membrane changes after fertilization by single sperm which enables no more sperm to enter
Root hair cell → absorbs water by osmosis and mineral ions by active transport from soil
- Have large surface area to ensure maximum absorption
- Walls are thin to ensure water moves through quickly
- No chloroplasts are present
- Mitochondria to provide energy for respiration for active transport
Xylem vessels → transports water and mineral ions from roots to shoots
- lignin causes cell to die, thus they become hollow and form a continuous tube so water and mineral ions can
move through
- Cells are dead, no cytoplasm is present so more water can flow through
- Walls and thickened by lignin which provides strength
,Phloem vessel → transports sucrose to all parts of plant
- Sieve plates allow movement of substances from cell to cell
- Companion cells supply energy from its mitochondria to phloem vessels so that they are kept alive
Investigating pH & Enzyme Activity
Amylase + starch → maltose
Amylase is the enzyme, it breaks down starch into maltose
Iodine tests for the presence of starch:
- Starch + iodine → blue black color
- Iodine + maltose → stays orange
1. Add iodine into each well of the spotting tile
2. There are 2 tubes, 2cm cubed starch solution and 2cm cubed amylase solution with 1cm cubed buffer
solution
3. Add amylase+buffer into starch solution and start a timer immediately
4. Amylase enzyme starts breaking down starch into maltose
5. After 10 seconds have passed use a pipette to transfer the solution into the frist well
6. First spotting tile changes blue black as starch isn't fully broken down
7. Continue and repeat this for each well every 10 seconds
8. Repeat experiment using different buffer solutions
, Investigating energy content in a sample
1. Use measuring cylinder to measure 25 cm cubed of water, then transfer to a boiling tube
2. Record starting temperature of water using thermometer
3. Record mass of the food sample on an electronic balance or scale
4. Pierce the food with a mounted needle
5. Set fire to the food and hold sample 2 cm away from boiling tube until it has completely burned
6. Record final temperature of water
7. Repeat process with different samples
Larger the increase in temperature, the more energy is stored in the sample
- Incomplete burning → relight food sample until it no longer lights up
- Heat energy may be lost to the surrounding
Gas exchange:
Single celled organisms, can exchange gasses sufficiently by simple diffusion through the cell membrane
Multicellular organisms have exchange surfaces and organ systems that maximize the exchange of materials
[diffusion is a passive process it does not require energy]
Why is the concentration gradient of oxygen inside low? This is because respiring cells cells inside plant use oxygen
Why is the concentration gradient of CO2 inside low? This is because cells that carry out photosynthesis inside plant
use oxygen
Guard cells open and close stomata to control gas exchange and water loss
Guard cells become turgid as water moves into them causing stomata to open
Guard cells become flaccid as water moves out of stomata causing it to close
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