Cells And Organisation

• Light microscopes can magnify up to about 2000 times and have a resolving power of 200nm.
• Electron microscopes magnify up to about 2 million times and have a resolving power of about 0.2nm.
• Magnification in a light microscope is calculated by the equation: magnification = size of image / size of real object.
• All animal cells have a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes in common.
• Plant cells have a permanent vacuole, a cellulose cell wall and chloroplasts in addition to the features common to all animal cells.
• This reduces the amount of carbon dioxide that can diffuse into the leaf, preventing photosynthesis.
• The shape of stomata changes during hot conditions, causing the plant to close its stomata to reduce water loss by transpiration.
• Eukaryotic cells contain their genetic material enclosed in a nucleus.
• Prokaryotic cells contain their genetic material in a single DNA loop or may contain small rings of DNA called plasmids.
• All bacteria are prokaryotes.
• As an organism develops, cells differentiate to form different types of cells.
• As an animal cell differentiates to form a specialised cell, it acquires different sub-cellular structures to enable it to carry out a certain function.
• Plant cells may be specialised to carry out a particular function.
• Examples of specialised animal cells include nerve cells, muscle cells and sperm cells.
• Animal and plant cells may be specialised to function within a tissue, an organ, organ system or whole organisms.
• Examples of specialised plant cells include root hair cells, photosynthetic cells, xylem cells and phloem cells.
• Diffusion is the spreading out of particles of any substance, in solution or a gas, resulting in a net movement from an area of higher concentration to lower concentration, down the concentration gradient.
• The rate of diffusion is affected by the difference in concentrations, the temperature, and the avaliable surface area.
• Dissolved substances such as glucose and urea, and gases such as oxygen and carbon dioxide move in and out of cells by diffusion.
• Osmosis is the movement of water, from a dilute to a more concentrated solution through a partially permable membrane.
• Differences in the concentration of solutions inside and outside a cell cause water to move in or out of the cell by osmosis.
• Animal cells can be damaged if the concentration outside the cell changes dramatically.
• If the concentration of solutes in the solution outside the cell is the same as the internal concentration, the solution is isotonic to the cell.
• If the concentration of solutes in the solution outside the cell is higher than the internal concentration, the solution is hypertonic to the cell.
• If the concentration of solutes in the solution outside the cell is lower than the internal concentration, the solution is hypotonic to the cell.
• Osmosis is important in plant cells to maintain turgor in plant cells.
• Active transport moves substances from a more dilute solution to a more concentrated solution against the concentration gradient using energy.
• Active transport uses energy released from food in respiration to provide energy required.
• Active transport allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil against a concentration gradient.
• Active transport enables sugar molecules, used for cell respiration, to be absorbed from the lower concentrations in the gut, into the blood where the concentration of sugar is higher.
• The function of the nucleus is to enclose the genetic material.
• The cytoplasm is where chemical reactions take place.
• The cell membrane controls the molecules that can enter and leave the cell.
• Some people have ethical or religious objections to theraputic cloning.
• The heart is an organ consisting mainly of mucle tissue which pumps blood around the body.
• Therapeutic cloning could be useful for a range of medical conditions such as diabetes or paralysis.
• The heart has four chambers: the right and left atria and the right and left ventricles, which are separated from each other by valves.
• The coronary arteries branch out of the aorta and spread out into the heart muscle to provide oxygen to the muscle cells of the heart.
• The cell also grows and copies its internal structures such as its mitochondria and ribosomes.
• The stem cells in bone marrow differentiate to form cells found in our blood.