Topic 2: Cells and movement Flashcards
What is the level of organization from organelles to an organ system?
Organelles, cell, tissue, organ, organ system
Name all the common features in a cell that plants and animals share
Nucleus - this contains the genetic material of the cell that controls the cell’s activities, surrounded by its own membrane
Cell membrane - a semi-permeable membrane which controls which substances can enter and leave the cell
Cytoplasm - a gel-like substance where most of the cell’s chemical reactions take place, containing enzymes which control these reactions.
Mitochondria - small organelles where most of the reactions for aerobic respiration take place.
Ribosomes: small organelles where proteins are created
Name all the unique features of a plant cell, not shared with animal cells
Chloroplasts - photosynthesis takes place here. They contain a green substance called chlorophyll which gives the plant its color and aids photosynthesis
Cell wall - a rigid structure made of cellulose which surrounds the membrane, giving the cell and plant support and protection.
Vacuole - a large organelle that contains cell sap - a weak solution of sugars and salts - that helps to support the cell
What is diffusion?
Diffusion is the gradual movement of particles from areas of high concentration to areas of low concentration - down the concentration gradient.
Diffusion is a passive process which doesn’t require energy, and takes place in both liquids and gases.
What is osmosis?
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of lower water concentration (still down the concentration gradient)
How is osmosis used?
If a cell is short of water, the sucrose solution within the cell will become concentrated. This will create a concentration gradient which will allow water molecules from outside the cell to move through the partially permeable membrane and into the sucrose solution to dilute it.
If a cell contains excess water, this also creates a concentration gradient which allows the water molecules from the inside of the cell to pass through the partially permeable membrane and out of the cell, balancing out the concentration of water within the cell.
What practical can we conduct to investigate diffusion?
We can use agar cubes and phenolphthalein (a pH indicator) to investigate how acid diffuses into the cubes.
Mix agar jelly with phenolphthalein and dilute sodium hydroxide. Then cut the jelly into equal sized cubes and place them in a beaker containing dilute hydrochloric acid. Phenolphthalein is a pH indicator which is pink in alkaline solutions (sodium hydroxide), and colorless in acidic solutions. When placed in the acid, over a period of time (5-10 minutes), the agar jelly will slowly lose its pink color and turn colorless, as the acid diffuses into the jelly and the phenolphthalein changes color.
What factors affect the movement of substances?
Surface area to volume ratio: objects with a larger surface area to volume ratio will be the best for the movement of substances, as there is more surface area for the substances to move across.
Distance: since cell membranes are very thin, substances can move across them quickly, increasing the rate of the movement of substances.
Temperature: a higher temperature makes the particles move faster, and so they move across membranes much quicker
Concentration gradient: when there is a steep concentration gradient, particles move faster across the membrane of a cell (only affect diffusion and osmosis, not active transport)
What is active transport?
Active transport is the movement of particles against a concentration gradient from an area of LOW concentration to an area of HIGH concentration (against the concentration gradient), using energy released during respiration.
Where is active transport used in our body?
Active transport is used by our gut to transport nutrients into the bloodstream. There is a higher concentration of nutrients in the blood and a lower concentration in the gut, and so active transport is needed to move the nutrients to the blood.
What are specialized cells?
Specialized cells are those which have different cell structures to carry out a particular function
Describe two specialized cells
Red blood cells - these are a concave disc shape and don’t have a nucleus so as to have more space to carry oxygen. They also contain hemoglobin which binds the oxygen to the cell and are smaller than normal cells so as to be able to fit through capillaries and veins.
Sperm cells - these have a tail which helps them move through the body, and contain lots of mitochondria to supply them with energy for the journey. They also have an acrosome which contains enzymes to digest the protective outer layer of the ovum and fuse with it.
What are the advantages of using stem cells in medicine?
The main advantage is that stem cells are able to differentiate into any cell in the body, and so can be used to treat a wide variety of conditions: stem cells can differentiate into skin cells to treat burn victims, or they can differentiate into red blood cells to treat people with sickle cell anemia.
They can also help grow organs and cells in labs to treat patients in need of transplants.
What are the disadvantages of using stem cells in medicine?
Some people argue that using stem cells obtained from embryos is unethical as you are in essence ending a potential human life by using the stem cells needed for that embryo to grow, however this argument is easily countered with the fact that the embryos used to harvest stem cells were going to be disposed of anyway, so using the stem cells is a good way to make sure the potential is not wasted and is used to treat life threatening conditions instead.
