Adaptations of gills
.Large surface area
.Thin membrane
.Efficient blood supply
.Well ventilated (an area of a rich supply of dissolved oxygen)
Do small organisms have either a smaller or bigger surface area: volume ratio?
Bigger surface area: volume ratio
Development of microscopes in late 1600s
van Leeuwenhoek constructed microscopes with a spherical lens. Magnified up to x275
Formula for Magnification FOR A MICROSCOPE
m= eye piece lens magnification x objective lens magnification
Where can we find diffusion occurring in humans? (and explain why is that?
.Gas exchange in the lungs -> (Carbon dioxide diffuses from the blood to the alveoli. Oxygen diffuses from the alveoli to the blood)
.Small intestine -> (Digested food (e.g. glucose, amino acids) diffuses out of the small intestine into the blood)
What should you not do when drawing a diagram of cells?
Overlap
List down the organelles of an animal cell
.Nucleus
.Cell membrane
.Cytoplasm
.Mitochondria
.Ribosomes
What is diffusion?
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration
Do large organisms have either a smaller or bigger surface area: volume ratio?
Smaller surface area: volume ratio
Name the things used for the onion cell experiment
.Small piece of onion
Scalpel/Knife/Blade
.White tile
.Forceps
.Microscope slide
.Coverslip
.Microscope
.Iodine solution
.Ruler
.Safety googles
What is the purpose of a cell wall?
Stabilises the plant
What is osmosis?
The movement of water particles from an area of high concentration to an area of low concentration through a semi-permeable membrane (a membrane with tiny holes)
What is the conversion from metres to centimetres?
x100
What is the conversion from nanometres to micrometres?
/1000
How can we prevent these three hazards in the onion cell experiment?
Iodine solution -> Wear safety googles + gloves for skin protection
.Scalpel/Knife/Blade -> Cut away from your body onto a white tile
.Glass slides and coverslips -> Handle with care + keep away from the edge of the desk
List down the organelles of a plant cell
.Nucleus
.Cell membrane
.Cytoplasm
.Mitochondria
.Ribosomes
.Chloroplasts
.Cell wall
.Vacuole
What is the decending order of units (and also include units beside their names)?
Kilometre (km)
Metre (m)
Centimetre (cm)
Millimetre (mm)
Micrometre (μm)
Nanometre (nm)
What are the two types of electron microscopes?
Scanning Electron Microscope (SEM)
.Transmitter Electron Microscope (TEM)
What is the purpose of a vacuole?
Contains cell sap and water
Development of microscopes in 1800’s
Quality of lenses increased over time and similar to the ones we use today
What is the conversion from micrometres to millimetres?
/1000
Why is the invention of an electron microscope allowed biologists to find so much more about cells?
Bigger magnification
Name the three hazards in the onion cell experiment (also explain its risks)
.Iodine solution -> Irritant and harmful to skin and eyes
.Scalpel/Knife/Blade -> Cause cuts if used carelessly
.Glass slides and coverslips -> Fragile, causing cuts if damaged
Steps to conduct the onion cell experiment
1.Use dropping pipette to put on one drop of water on the slide
2.Seperate one thin layer of the onion
3.Use forceps to put the layer of onion on top of the drop of water on top of the slide
4.Drop a few drops of iodine solution on top of the onion peel
5.Carefully lower the coverslip on top of the slide by placing one edge on the coverslip on the slide and using the forceps to lower the other edge
6.If there is some liquid around the edge of the coverslip, use a piece of paper to soak this up
7.Put the slide on the stage
8.Use the lowest power objective lens by turning the nose piece
9.The end of the objective lens needs to almost touch the stage. Do this by turning the coarse focus knob and judging what is best by only looking from the side
10.Now looking through the eyepiece, turn the coarse focus knob in the direction to increase the distance between the slide and the objective lens until the cells come into focus
11.Rotate the nose piece to use a higher power objective lens
12.Slightly rotate the fine focus knob to make the cells clearer and use the lower power objective lens to look at the cells
13.When you have found the onion epidermal cell, switch to a higher power
14.Make a clear, labelled drawing of some of these cells also including labels for its organelles
15.Write the magnification under your drawing
16.Carefully place a ruler over your completed slide
17. Rotate the nose piece to use medium power objective lens
18.Adjust the position of the ruler until it lines up with a continuous group of cells across 1mm of the ruler. Use the conversion 1mm = 1000 micrometres
19.Count the number of cells across the 1000 micrometre sample
20. Calculate the size of a single onion cell in micrometres using the formula (length of cell in micrometres = 1000 micrometres/number of cells counted in sample). Use this measurement to add to the diagram you have drawn
