Cell biology - 1

• All living things are made of cells, which can either be prokaryotic or eukaryotic.
• Animal and plant cells are eukaryotic and have a cell membrane, cytoplasm, nucleus containing DNA, and a permanent vacuole.
• Bacterial cells are prokaryotic and have a cell wall, cell membrane, cytoplasm, single circular strand of DNA and plasmids.
• Organelles are structures in a cell that have different functions.
• Prefixes go before units of measurement (such as ‘metres’) to show the multiple of the unit.
• Mineral ions are usually in higher concentrations in the cells, meaning diffusion cannot take place.
• This requires energy from respiration to work.
• Active transport is required to move the sugar to the blood against its concentration gradient.
• In the gut, substances such as glucose and amino acids from food have to move from the gut into the bloodstream.
• Sometimes there can be a lower concentration of sugar molecules in the gut than the blood, meaning diffusion cannot take place.
• Root hairs take up water and mineral ions for healthy growth from the soil.
• In animal and plant cells, the nucleus contains DNA coding for a particular protein needed to build new cells, is enclosed in a nuclear membrane, and controls what enters and leaves the cell.
• In animal and plant cells, the cytoplasm is a liquid substance in which chemical reactions occur, contains enzymes, and organelles are found in it.
• In animal and plant cells, the cell membrane controls what enters and leaves the cell, and organelles are found in it.
• In bacterial cells, the cell membrane controls what enters and leaves the cell, and organelles are found in it.
• In bacterial cells, the cell wall provides strength to the cell, is made from cellulose, and is found within the cytoplasm.
• In bacterial cells, the nucleus does not contain DNA coding for a particular protein needed to build new cells, is not enclosed in a nuclear membrane, and does not control what enters and leaves the cell.
• In bacterial cells, the cytoplasm is a liquid substance in which chemical reactions occur, does not contain enzymes, and organelles are found in it.
• Having an efficient blood supply or being ventilated in animals creates a steep concentration gradient, so diffusion occurs faster.
• Water is able to move across cell membranes by osmosis, the movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrane.
• The concentration gradient is always steep in the lungs.
• Active transport is the movement of particles from an area where they are in lower concentration to an area where they are in higher concentration- against their concentration gradient.
• Water moves from a dilute solution to a concentrated solution because it moves from an area of high water potential to low water potential, down the concentration gradient.
• Water flows in one direction and blood flows in the other in fish, maintaining a steep concentration gradient as the concentration of oxygen is always much higher in the water.
• Active transport requires energy from respiration, which is why it is called active.
• Placing potato tubers (cylinders) in different concentrations of sugar solution results in different volumes of water moving in or out of the tubers, affecting its mass.
• A dilute solution of sugar has a high concentration of water and a high water potential, while a concentrated solution of sugar has a low concentration of water and a low water potential.
• Osmosis in animals can cause the cell to burst if the external solution is more dilute, or cause it to shrivel if the external solution is more concentrated.
• The lungs constantly supply oxygen to make the blood from alveoli and capillaries oxygenated, by exchanging it for carbon dioxide that can be breathed out.
• Osmosis in plants can cause the cell to swell, resulting in pressure called turgor, or cause it to become soft and eventually die.
• In bacterial cells, the mitochondria are where aerobic respiration reactions occur, providing energy for the cell, and ribosomes are found on a structure called the rough endoplasmic reticulum.
• The greater the temperature, the greater the movement of particles, resulting in more collisions and therefore a faster rate of diffusion.
• Having a large surface area provides a short diffusion pathway, allowing the process to occur faster.
• Villi in the small intestine have a single layer of surface cell.
• This takes place across the surface of millions of air sacs called alveoli, which are covered in tiny capillaries, which supply the blood.
• If this is large, the organism is less likely to require specialised exchange surfaces and a transport system because the rate of diffusion is sufficient in supplying and removing the necessary gases.
• This is because more particles are randomly moving down the gradient than are moving against it.
• Water which has oxygen passes through the mouth and over the gills.
• In the leaves of the plant there are many different tissues to aid with gas exchange.
• The stomata are controlled by guard cells, which change the size of the stomata based on how much water the plant received (the guard cells swell with lots of water and make the stomata larger).