cell biology - topic 1 (paper 1)

• All living things are made of cells, which can either be prokaryotic or eukaryotic.
• Sometimes there can be a lower concentration of sugar molecules in the gut than the blood, meaning diffusion cannot take place.
• In the gut, substances such as glucose and amino acids from food have to move from the gut into the bloodstream.
• This requires energy from respiration to work.
• Animal and plant cells are eukaryotic and have a cell membrane, cytoplasm, nucleus containing DNA, and a permanent vacuole.
• Mineral ions are usually in higher concentrations in the cells, meaning diffusion cannot take place.
• Root hairs take up water and mineral ions for healthy growth from the soil.
• Active transport is required to move the sugar to the blood against its concentration gradient.
• 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.
• 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.
• 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, and 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.
• 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.
• 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.
• 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.
• 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.
• The concentration gradient is always steep in the lungs.
• Osmosis in plants can cause the cell to swell, resulting in pressure called turgor, or cause it to become soft and eventually die.
• 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.
• 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 Petri dish should be stored upside down to prevent condensation from the lid landing on the agar surface and disrupting growth.
• In Stage 2 (Mitosis) of the cell cycle, the chromosomes line up at the equator of the cell and cell fibres pull each chromosome of the ‘X’ to either side of the cell.
• The number of bacteria at the end of the growth period can be very large, so it is common for it to be left in standard form.
• In both investigations- growing bacteria and testing the effectiveness of antibiotics- you need to calculate cross-sectional areas (of colonies or inhibition zones).
• A gene is a short section of DNA that codes for a protein and as a result controls a characteristic- therefore each chromosome carries many genes.
• If the microorganisms are bacteria, they can be used to test the effects that different antibiotics have on their growth.
• Sex cells (gametes) are the exception: there are half the number of chromosomes, resulting in 23 chromosomes in total in each gamete cell.
• In Stage 1 (Interphase) of the cell cycle, the cell grows, organelles (such as ribosome and mitochondria) grow and increase in number, the synthesis of proteins occurs, DNA is replicated (forming the characteristic ‘X’ shape) and energy stores are increased.
• There are 23 pairs of chromosomes in each cell of the body, as you inherit one from your mother and one from your father - resulting in 46 chromosomes in total in each cell.
• The investigation involves soaking paper discs in different antibiotics, which are placed on an agar plate with bacteria.
• This involves using the formula πr², where r is the radius of the circle.