BIO NOTES YR 11 & 12 Module 1

• Cells are the basic structural and functional unit of all living things.
• The two types of cells are prokaryotic and eukaryotic cells.
• Enzymes have a narrow range of pH which they function most optimally in.
• Excessive alkalinity or acidity can alter the shape of the enzyme.
• Prokaryotic cells have a 0.1 to 5.0 μm diameter and possess four main structures: cell membrane, cytoplasm, ribosomes, and genetic material.
• Prokaryotic cells do not have a membrane-bound nucleus or organelles.
• Most genetic material forms a large loop called the bacterial chromosome, rest is in small circular rings called plasmids.
• Other structures that may be present in prokaryotic cells include cell wall, pili, flagella, and capsule.
• Most prokaryotic cells are unicellular organisms and are divided into two main groups: bacteria and archaea.
• Eukaryotic cells have a 10 to 100 μm size and contain a membrane-bound nucleus and organelles.
• Eukaryotic cells contain various structures such as cell wall, membrane-bound nucleus, organelles, and cytoplasm.
• Cells can be studied using various technologies such as magnification, resolution, light microscopes, fluorescence microscopes, and electron microscopes.
• Light microscopes use a light source that passes through a condenser lens, then through the thin specimen, and are magnified and viewed through the ocular lens.
• Fluorescence microscopes allow viewing of structures beyond the limit of resolution by labeling structures with fluorescent substances and directing fluorescent light through filters that separate it from surrounding light.
• Electron microscopes use an electron beam instead of light and electromagnets instead of glass lenses, and the interaction between electrons and object forms an image.
• Scanning electron microscope (SEM) bombards the specimen with a beam of electrons, causing secondary electrons to emit from surface layers of the specimen, with a resolution of about 10 nm and producing a 3D image.
• Transmission electron microscope (TEM) transmits electrons through the specimen, producing a 2D image with a magnification up to 1,500,000x and a resolution of 2nm.
• Computer-enhanced technology to study cells involves a confocal laser producing an intense beam of light that is focused on one point of the sample, with focusing occurring on many levels, and an image reconstruction program putting together images and creating a 3D image.
• Prokaryotic cells have a 0.1 to 5.0 μm diameter, four main structures: cell membrane, cytoplasm, ribosomes, and genetic material, no membrane-bound nucleus or organelles, most genetic material forms a large loop called the bacterial chromosome, rest is in small circular rings called plasmids, and other structures that may be present include cell wall, pili, flagella, and capsule.
• Eukaryotic cells have a 10 to 100 μm size and contain a membrane-bound nucleus and organelles
• Uncharged molecules (e.g ethanol) can easily penetrate cell membranes because they dissolve in the phospholipid bilayer.
• Exocytosis is used for secreting hormones, neurotransmitters, enzymes and waste products.
• Plant cells carry out cytoplasmic streaming, which is the process of organelles and cytosol flowing around the cell in a circular movement.
• Very large molecules need to be transported via endocytosis or exocytosis.
• The volume is the space taken up by the cell’s internal contents (such as the cytoplasm and nucleus).
• Exocytosis is the process by which substances are transported to the external environment of the cell.
• Cytoplasmic streaming upkeeps a high concentration gradient, allowing rapid diffusion.
• The amoeba sends out membrane projections, changing its shape, and forming a vesicle due to the membrane fusion of the smaller organism’s cell membrane with the projection.
• Water is not lipid-soluble, so it cannot pass through the hydrophobic tails of the phospholipid bilayer, so it must pass through aquaporins.
• The release of insulin by beta pancreatic cells when blood sugar rises is an example of exocytosis.
• The cells of the small intestine obtains fat droplets via endocytosis after a meal.
• Exocytosis involves the fusion of membrane-bound vesicles with the cell membrane, leading to the expulsion of the vesicle’s contents out of the cell.
• Hydrophilic, charged ions (e.g sodium Na+, potassium K+) cannot pass the hydrophobic centre of the membrane.
• Channel proteins specific to each ion allow movement through the membrane.
• Long, flat cells have a higher SA:V ratio than spherical cells with the same volume.
• Equilibrium means there will be no net movement of materials across the cell membrane.
• Large molecules (e.g glucose, amino acids) may need carrier proteins.
• Smaller cells have a higher SA:V ratio.
• A higher SA:V ratio allows for substances to transport in and out of the cell (like obtaining nutrients and removing wastes), while a lower SA:V ratio makes these processes slower because the centre of the cell is further away from its surface.
• Neutral molecules e.g carbon dioxide and oxygen gas are soluble in lipids and have high membrane permeability.