An animal cell has a nucleus, cytoplasm, mitochondria, ribosomes and a cell membrane.
A plant cell has a nucleus, a cytoplasm, mitochondria, ribosomes and a cell membrane. They also have a cell wall, a large permanent vacuole and chloroplasts, which animals cells don't have.
Unicellular means one cell.
Multicellular means multiple cells.
The nucleus contains DNA and controlscellactivity.
The cytoplasm is where chemical reactions occur.
Mitochondria release energy through the process of aerobic respiration.
Ribosomes synthesize (make) proteins.
The cell wall strengthens the cell. Plant cell walls are made from cellulose, while bacterial cell walls are made from murein or peptidoglycan.
The large permanent vacuole contains water, nutrients, waste products, cell sap and more. It also keeps the cell turgid (opposite of flaccid).
Chloroplasts contain chlorophyll which is a green pigment that absorbs light for photosynthesis.
A bacterial cell has a cell membrane, a cytoplasm, a flagella, plasmids, ribosomes and a cell wall. The cell has no nucleus, so it's genetic information is stored in a Loop of DNA.
Eukaryotic vs Prokaryotic Cells
Eukaryotic cells (5 μm - 100 μm) are larger than Prokaryotic Cells (0.2 μm - 2 μm)
Eukaryotic cells contain membrane bound organelles, such as a nucleus, while Prokaryotic cells have no membrane - bound organelles.
In a Eukaryotic cell, genetic material is enclosed in the nucleus, while in a Prokaryotic cell, genetic material is not in a nucleus, but in a DNA loop, which is free in the cytoplasm
Eukaryotic cells divide by mitosis, while Prokaryotic cells divide by binary fission.
Neurone Cell
Function: The cell has extensions and branches, so that it can communicate with other nerve cells, muscles and glands.
Adaptations: The nerve cell is extended, so that nerves can run to and from different parts of the body to the central nervous system. The nerve cell is covered with a fatty sheath which insulates the nerve cell and speeds up the nerve impulse.
Sperm Cell
Function: The head of the sperm cell contains the genetic material for fertilisation.
Adaptations: The acrosome in the head contains enzymes so that the sperm cell can penetrate an egg. The middle part is packed with mitochondria to release energy needed to swim and fertilise the egg.
Muscle Cell
Function: Muscle cells contain filaments of protein that slide over each other to cause muscle contraction.
Adaptations: The arrangement of the filaments causes the banded appearance of heart muscle and skeletal muscle. They contain many well developed mitochondria to provide energy for muscle contraction.
Root hair Cell
Function: The root hair cell has a large surface area to provide contact with soil water.
Adaptations: It has thinwalls so as not restrict the movement of water. It has no chloroplasts because the roots are underground.
Phloem
Function: Dissolved sugars and amino acids can be transported both up and down the phloem.
Adaptations: Companion cells, adjacent to the sieve tubes provide energy required to transport substances in the phloem.
Xylem
Function: Xylem vessels and tubes that carry water and mineral ions up the plant.
Adaptations: There are no top and bottom walls between xylem vessels, so there is a continuous column of water running through them. Their walls become thickened and woody. They therefore support the plant.
Light Microscope
Magnification is the measure by how much the image is enlarged relative to the specimen size. It is determined by the eye piece and objective magnification.
Resolution is the distance that 2 things can be apart and still appear as separate.
History of Microscopy
1590s - Dutch Spectacle maker Zacharicus Janssen experimented with putting lenses into tubes, making the first compound microscope.
1650s - British scientist Robert Hooke observed and drew cells
Late 1600s - Dutch scientist Antonie Van Leevenhoek constructed a microscope with a single spherical lens.
1800s - The optical quality of lenses increased.
Early 1900s - The electron microscope was developed which uses a beam of electrons instead of a light source.
Electron Microscope
Pros and Cons of a Light Microscope VS an Electron Microscope
Light Microscope - Picture is in colour.
Pros:
Easy to use
Relatively cheap
Cons:
Poor Resolution (0.2µm)
Poor Magnification
Cannot study sub-cellular structures (e.g. nucleus, etc.)
Electron Microscope - Picture is in Black and white
Pros:
High Resolution (0.1nm)
High Magnification
Cons:
Hard to use
Expensive
Magnification = Image size / Actual size
Magnification (x times)
Image size (micrometers, µm)
Actual size (micrometers, µm)
Example
Actual size = 0.002mm, Image size = 4.05cm, Find Magnification.
Magnification = Image size / Actual size 4.05cm = 40,500µm
0.002mm = 2µm
Magnification = 40,500 / 2
Magnification = x20,250
Cell cycle
Stage 1 - Interphase
DNA replicates, which forms 2 copies of each chromosome and synthesis of sub-cellular structures
Stage 2 - Mitosis
Nucleus divides
Stage 3 - Cytokinesis
The cell divides into two, forming 2 identical daughter cells, which are also identical to the parent cell.
A chromosome is found in the nucleus and is made up of one molecule of DNA associated with some proteins called histones.
A gene is a small section of a DNA molecule which carries information about a particular characteristic.
New cells are needed for growth, to replace worn out cells and to repair damaged tissue.
Cell division occurs in a stage called mitosis where the cell divides into 2 new genetically identical cells.
A stem cell is an undifferentiated cell that has the ability to differentiate into different types of specialised cells.
There are 3 types of stem cells, embryonic stem cells, adult stem cells and meristem cells.
Meristem Cells
Found in plants in the tip of the roots and shoots of the stem
Differentiates into any cell
The cells function throughout the whole life time of a plant
Embryonic stem cells
Found in the human embryo
Differentiate into any cells
Stop after the baby's death
Adult Stem Cells
Found in the bone marrow
Differentiates only into some cells
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration, without needing energy.
Diffusion only happens in liquids and gases.
Factors affecting the diffusion of particles across a membrane:
Temperature
Surface Area
Concentration gradient
Shorter diffusion pathway
The larger the concentration gradient, the greater the rate of diffusion.
Rate is how much something happens over a certain amount of time.
Often, cells at exchange surfaces have finger-like projections called microvilli to increase surface area to volume ratio.