Cell Biology

• Eukaryotic cells contain their genetic material enclosed in a nucleus.
• Animal and plant cells have two other features which are unique to eukaryotic cells: a cell membrane and cytoplasm.
• Prokaryotic cells, such as bacteria, are different from eukaryotic cells as their genetic material is not enclosed in a nucleus and they are much smaller in size.
• The genetic material of prokaryotic cells consists of a single loop of DNA and they may also have small wings of DNA which are called plasmids.
• Prokaryotic cells have a cell membrane and a cell wall.
• The cell membrane of prokaryotic cells is different from the cell membrane of eukaryotic cells as it is not enclosed in a membrane.
• Prokaryotic cells contain cytoplasm.
• The size of cells is measured in units of the metre, but objects and biology are often much smaller than that.
• A German Shepherd is around 1 meter long, and if we divide 1 meter into 100 equal parts, we get 1 centimeter.
• The prefix centi means one hundredths, and one centimeter is one hundredth of a meter.
• Scientists often use standard form, where 1 centimeter is 1 times 10 to the power of minus 2 meters.
• The width of a ballpoint pen is around 1 millimeter, and the prefix milli means one thousandth, so one millimeter means one thousandth of a meter.
• A meter is 1,000 millimeters long, and in biology, one millimetre is pretty big, so scientists work with even smaller sizes.
• If we divide a meter into 1 million equal parts, we get a micrometer, and the prefix micro means one millionth, so one micrometer is one millionth of a meter.
• A typical human cell such as a red blood cell is around 10 to 20 micrometers in size, and biologists find a micrometer a very useful unit especially when looking at cells.
• Cells contain smaller parts such as ribosomes, and we'll look at those in a later video, which means that we need an even smaller unit to talk about the sizes of objects inside cells.
• The final unit we'll look at is called the nanometer, and the prefix nano means one billionth, so one nanometer is one billionth of a meter.
• Proteins and cells are measured using nanometers.
• Order of magnitude is a concept used by scientists to compare the approximate size of different objects.
• An apple and an orange are both around the same order of magnitude.
• A pineapple is around ten times larger than a lemon, making the pineapple one order of magnitude larger than the lemon.
• A dog is around 100 times longer than a woodlouse, making the dog two orders of magnitude longer than the woodlouse.
• The key idea behind order of magnitude is that every order of magnitude is ten times greater than the one before.
• To work out the order of magnitude, count the number of zeros in the number.
• Ten times is one order of magnitude, 100 times is two orders of magnitude, and 1000 times is three orders of magnitude.
• Animal cells are eukaryotes, with their genetic material enclosed in a nucleus.
• The function of the nucleus is to enclose the genetic material.
• Nuclei are normally not that color inside the cell.
• The cytoplasm is a watery solution where chemical reactions take place, including the first stage of respiration.
• The cell membrane controls the molecules that enter and leave the cell.
• Inside the cell, there are smaller structures called mitochondria, where cellular respiration takes place.
• Ribosomes are extremely small and cannot be seen using a light microscope, hence they need to be viewed using an electron microscope.
• Ribosomes are the sites of protein synthesis, which are important as they carry out various functions, such as enzymes.
• The structures in the diagram include the nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.
• Plant cells have a regular shape unlike animal cells which can easily change their shape.
• Plant cells are packed full of green structures called chloroplasts which contain chlorophyll and other sites of photosynthesis.
• Plant cells are surrounded by a cell wall which is made from a chemical called cellulose and strengthens the cell.
• Plant cells contain a large permanent vacuole which is filled with a fluid called cytoplasm SAP because it's packed full of fluid the vacuole helps give the plant cell its shape.
• Most animal cells are specialized, meaning they have adaptations which help them to carry out their particular function.
• Sperm cells are specialized to join with an ovum, a process known as fertilization, where the genetic information of the ovum and the sperm combine.