Topic 2

• The key organelles within the eukaryotic cells are the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, and vacuole.
• The nucleus is where DNA replication occurs and it's a cytotranscription, where mRNA is made, and it contains the DNA which is a genetic code for the cell.
• The nucleolus is the site of RNA production and it's where ribosomes are made.
• The endoplasmic reticulum consists of the smooth and the rough, with the rough endoplasmic reticulum being where protein synthesis occurs due to the ribosomes on the outside, and the smooth endoplasmic reticulum being where the synthesis of lipids and carbohydrates occurs and they also get stored there.
• The Golgi apparatus is a folded membrane making this systemy shape and vesicles will pinch off from those cysteine once whatever it is that's going to be modified has been modified and packaged.
• Lysosomes are bags of digestive enzymes and are often involved in phagocytosis.
• The mitochondria is the site of aerobic respiration and has a double membrane organelle with the outer membrane and the inner membrane, with the inner membrane being where oxidative phosphorylation happens, which is one of the key stages in aerobic respiration.
• Optical microscopes can produce colored images, but they have a lower resolution and cannot observe living samples.
• Electron microscopes can only produce black and white images and require a vacuum to observe living samples.
• The resolution of electron microscopes is higher than that of optical microscopes, allowing for the observation of details within small organelles.
• A scanning electron microscope creates 3D images by beaming electrons onto the surface of the specimen, which are scattered in different ways depending on the contours.
• The formula for calculating magnification is i am, where image size equals actual size times magnification.
• The image size and the actual size in a magnification question must be in the same units.
• The eyepiece graticule, a scale on a glass disc within the optical microscope, can be used to measure the size of objects being viewed.
• Cell fractionation is used to isolate the different organelles for further study.
• The cells need to be prepared in a cold isotonic and buffered solution for cell fractionation.
• Homogenization is the first step in cell fractionation, where the cells are broken open to release the contents and the organelles.
• Ultra centrifugation is the second step in cell fractionation, where the organelles separate according to their size and density.
• Ribosomes are found in prokaryotic and eukaryotic cells because they are not membrane bound and are made up of rrna and proteins, with different sizes including the ats, the largest size ribosome in eukaryotic cells, and the 70s, a smaller sized ribosome found in prokaryotic cells as well as in mitochondria and chloroplasts, where protein synthesis occurs.
• The vacuole, only found in plant cells, is filled with fluid and surrounded by a single membrane called atonoplast, providing support and storing temporary stores of sugars and amino acids.
• Chloroplasts, only found in plants, are the site of photosynthesis.
• Differential centrifugation is a method used to separate organelles based on their densities.
• In the first centrifugation, the nuclei are the most dense, followed by the chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, and finally the ribosomes.
• Eukaryotic cells enter the cell cycle and divide by mitosis or meiosis, while prokaryotic cells replicate by binary fission and viruses do not undergo cell division.
• The cell cycle of eukaryotic cells includes interphase, which is the longest stage, followed by nuclear division, mitosis, and cytokinesis.
• During interphase, the cell is increasing in size and the organelles are doubling.
• In the s phase, dna replication happens.
• During g2, there is further growth and preparation for mitosis, including an error check stage.
• Nuclear division is either mitosis or meiosis, and the final stage of the cell cycle is cytokinesis.
• Mitosis is split into four key stages: prophase, metaphase, anaphase, and telophase.
• During prophase, the chromosomes condense and become visible, and in animal cells, the pairs of centrioles move to opposite poles to create spindle fibers.
• In metaphase, the chromosomes line up in single file along the equator, and the spindle fibers are released from both poles to attach to the centromere and the chromatids.
• During anaphase, the spindle fibers start to retract and pull back towards the centrioles, causing the centromere to divide and the individual chromatids to be pulled to the opposite poles of the cell, separating the chromatids.
• Telophase is the final stage in the cell cycle, where the chromosomes are at each pole of the cell and become longer and thinner, and the spindle fibers disintegrate as the nucleus starts to reform.
• The mitotic index can be calculated by counting the number of cells that are visible in a stage of mitosis and dividing it by the total number of cells present, then multiplying by 100.
• The thylakoid membranes are embedded with proteins and pigments such as chlorophyll, making it the site of the light dependent reactions in photosynthesis.
• The stroma is the fluid parts surrounding the thylakoid membranes, containing enzymes needed for the light independent stages of photosynthesis.
• Cell walls are not found in animal cells but are in fungi and plant cells, providing structural strength to the cells and preventing them from bursting if lots of water moves in.
• The plasma membrane is found in all cells, controlling what can enter and exit the cell.
• Prokaryotic cells, such as bacteria, are much smaller, don't have any membrane-bound organelles, ribosomes, a nucleus, a cell wall, and may contain plasmids, a capsule, and flagella.