Cell vacuole - contains watery sap and helps make the cell firm (plant cell)
Chloroplasts - site of photosynthesis (plant cell)
Mitochondria - site of aerobic respiration (plant + animal cell)
Plant cells have chloroplasts but animal cells don’t as they carry out photosynthesis and also absorb light.
SPECIALISED CELLS
Cells with specialfeatures that make them moreefficient at performing a specificfunction.
Specialised cells:
Palisade cell - plant leaves for photosynthesis.
Egg cells
Ciliated cell - in animal airways to protect lungs from damage.
Root hair cell - large surface area to absorb.
Red blood cell - transport of oxygen, no nucleus, biconcave, haemoglobin.
Sperm cell - lots of mitochondria, fertilise inside egg through enzymes in head.
Nerve cell - carries signals over long distance.
Microscopes
Let us see things we can’t with the naked eye.
Total magnification = eyepiece x objective lens
Biological cell staining is a technique to enable better visualisation of cells under the microscop.
LIGHT microscopes
Limited magnification
Natural colouring unless stained
Used to view dead or alive specimens
ELECTRON microscope
Higher magnification (x2,000,000)
False colouring can be added
Black and white images
Specimens must be dead to view
Diffusion is the movement of particles from an area of high concentration (down concentration gradient) until the concentration are equal.
Diffusion does NOT require energy so it’s a passive process.
Cell membrane is selectively permeable - only allows certain substances to pass through, e.g. CO2 and oxygen.
Visking tubing:
Can be used as a model for cell membrane as has pores, allowing particles that are small enough to pass through pores can diffuse, particles that are too large cannot.
E.g. Glucose and iodine are small so can pass, but starch is too large - starch stays in the tube, iodine diffuses into tube down the concentration gradient, tube turns blue/black
Osmosis is the movement of water molecules from an area of high water concentration to an area of low water concentration, down a water concentration gradient, across a selectively permeable membrane.
Concentration gradient:
The greater the difference in the water concentration on either side of the membran, the steeper the concentration gradient so faster rate of reaction.
If water concentration was equal on both sides of the membrane - no NET movement of water overall.
Flaccid
when a plant cell had lost some water but membrane hasn’t peeled away
Plasmolyed
when a plant cell has lost lots of water and the membrane has peeled away
Turgid
when a plant cell had lots of water and the cell is firm - the vacuole pushes on the cell wall
Tubes of a vegetable can be used to show osmosis - in pure water it will gain length/mass (osmosis into cells), in low salt solution there will be no change (no net osmosis), high salt solution it will lose length/mass (osmosis out of cells).
Active transport:
Moves molecules from an area of low concentration to an area of high concentration - against concentration gradient.
This process requires energy, in form of ATP from respiration - if respiration doesn’t occur, neither can active transport.
Occurs in small intestine and plant roots.
Factor that can affect the rate of respiration:
Temperature
pH
Number of mitochondria
Toxic substances
Similarities and differencies
ROOT HAIR CELLS
Large surface area to increase rate of absorption- water and mineral ions.
They absorb mineral ions by active transport.
Multicellular Organisms
Atoms (oxygen)
Molecules (sugar)
Organelles (nucleus)
Cells (sperm cell)
Tissues (muscle tissue) - group of similar cells with similar functions.
Organs (liver) - consists of several tissues performing specific functions.
Organsystems (digestive system) - consists of number of organs working together to perform an overall function.
Organism
If a diagram is magnified 100 times larger, to calculate the size of the actual cell, you need to make the drawing 100 times smaller.