Microscopes Flashcards
Light microscopes
Can magnify up to 1500 times and allows you to see individual animal and plant cells along with the organelles inside them.
- If the cells have been stained you can see the dark coloured Nucleus surrounded but the light coloured cytoplasm
- Tiny mitochondria and the black line of the cell membrane are also visible
- In plant cells., the cell wall, chloroplasts and the vacuole can be seen
Electron microscopes
Can magnify objects more than 50000 times.
Allows greater detail than a light microscopes.
Allows you to see the structured details inside the organelle such as the mitochondria and chloroplasts. ]The image recorded is called am electron micro-graph.
The nucleus
Control centre of the cell.
Contains DNA, which is the coded information needed for the making of proteins.
During cell division the chromosomes carrying the long DNA molecules coil up becoming shorter and thicker and visible with a light microscope.
Electron micro graphs show that theres a double membrane.
Mitochondria
The size of a bacteria
Can be seen with a light microscope but electron microscope is needed so they can be seen in detail.
Each mitochondrion has a smooth outer membrane and a folded inner membrane.
There job is to capture the energy in glucose.
Aerobic respiration: GLUCOSE+OXYGEN= CARBON DIOXIDE + WATER+ (ENERGY)
This ends up in molecules of ATP
ATP
ATP is used in the cell to provide the energy for muscle contractions. active transport and building large molecules from small ones
Cell walls - PLANTS
relatively rigid for support for the cell
consists of bundles of long straight cellulose molecules.
cellulose molecules lay side by side to form microfibrils.
What is the structure of a cell surface membrane?
Very thin structure around an individual cell
1. Electron micrographs show that the cell surface membrane consists of a double layer of phospholipid molecules tightly packed together.
2. bigger protein molecules are embedded in the phospholipid molecule.
3. Some proteins go through the membrane and some only go halfway.
4. membranes surrounding the organelles inside the cell have the same structure.
Membrane is partially permeable
Diffusion
The particles of liquids and gases are constantly moving about. #Movement is from high concentration to low.
Particles diffuse through the cell membrane as long as they are small enough to pass through the small gaps between the phospholipid molecules.
H2O, O2, CO2 can do this
Cell doesnt need to provide any energy for this process.
Osmosis
The diffusion of water acrsoss a partially permeable from a region of high concentration of water molecules to a lower concentration of water molecules.
The cell does not need to provide energy.
The concentration of water molecules is also referred to as water potential.
Facilitated diffusion
- Glucose and many other water soluble molecules are too big to diffuse across the membrane by themselves. They must be helped my a carrier protein.
- Each substance has its own carrier protein.
- This causes the protein to change shape, allowing the glucose to diffuse through it into the cytoplasm of the cell. The cell doesn’t prove any energy.
- Mineral ions such as potassium and sodium have electrical charge son them so they need help across the membrane, therefore specific channel proteins in the membrane allow them to diffuse through.
Active Transport
- When a cell needs to move a substance across the membrane from a region of low concentration to a region of higher concentration, IT MUST PROVIDE ENERGY.
- The substance fits into a specific carrier protein, the molecules of ATP provide the energy to change the shape of protein.
- As the shape changes the protein actively transports the substance across the membrane.
- These special carrier proteins are sometimes called ‘pumps. because theyre moving substances against the concentration gradient .
