C1. Homeostasis Basics Flashcards
What is homeostasis?
Changes in your external environment can affect your internal environment -the blood and tissue fluid that surrounds your _____. Homeostasis is the _______________of a stable internal environment. It involves control systems that keep your internal environment roughly constant (within certain limits). This means your internal environment is kept in a state of ___________ _______________(i.e. fluctuating around a normal level). Keeping your internal environment stable is vital for cells to function normally and to stop them being ___________.
Changes in your external environment can affect your internal environment -the blood and tissue fluid that surrounds your cells. Homeostasis is the maintenance of a stable internal environment. It involves control systems that keep your internal environment roughly constant (within certain limits). This means your internal environment is kept in a state of dynamic equilibrium (i.e. fluctuating around a normal level). Keeping your internal environment stable is vital for cells to function normally and to stop them being damaged.
The importance of homeostasis
It’s particularly important to maintain the right core body _____________and ______ __. This is because temperature and pH affect _________activity, and enzymes control the rate of metabolic reactions (chemical reactions in living cells). It’s also important to maintain the right blood glucose concentration because cells need glucose for _______and blood glucose concentration affects the ______ __________of blood
It’s particularly important to maintain the right core body temperature and blood pH. This is because temperature and pH affect enzyme activity, and enzymes control the rate of metabolic reactions (chemical reactions in living cells). It’s also important to maintain the right blood glucose concentration because cells need glucose for energy and blood glucose concentration affects the water potential of blood
Temperature -raising temp
The rate of metabolic reactions increases when the temperature’s increased. More heat means more ________ ________, so molecules move _________. This makes the substrate molecules more likely to _________with the enzymes’ ________sites. The energy of these collisions also increases, which means each collision is more likely to result in a _________.
The rate of metabolic reactions increases when the temperature’s increased. More heat means more kinetic energy, so molecules move faster. This makes the substrate molecules more likely to collide with the enzymes’ active sites. The energy of these collisions also increases, which means each collision is more likely to result in a reaction.
Temperature -too high
But, if the temperature gets too high (e.g. over 40 °C), the reaction essentially _____. The rise in temperature makes the enzyme’s molecules __________more. If the temperature goes above a certain level, this vibration breaks some of the __________bonds that hold the enzyme in its ___shape. The active site changes ________and the enzyme and substrate no longer fit together. At this point, the enzyme is ____________-it no longer functions as a catalyst
But, if the temperature gets too high (e.g. over 40 °C), the reaction essentially stops. The rise in temperature makes the enzyme’s molecules vibrate more. If the temperature goes above a certain level, this vibration breaks some of the hydrogen bonds that hold the enzyme in its 3D shape. The active site changes shape and the enzyme and substrate no longer fit together. At this point, the enzyme is denatured-it no longer functions as a catalyst
Temperature -too low
If body temperature is too low enzyme activity is __________, slowing the rate of ___________reactions. The highest rate of enzyme activity happens at their optimum temperature-about __°C
If body temperature is too low enzyme activity is reduced, slowing the rate of metabolic reactions. The highest rate of enzyme activity happens at their optimum temperature-about 37 °C
Figure 1: Effect of temperature on the rate of a metabolic reaction.
pH
If blood pH is too high or too low (highly alkaline or acidic) enzymes become ____________. The _______bonds and ____________bonds that hold them in their __shape are broken, so the shape of the enzyme’s _______site is changed and it no longer works as a _________. The highest rate of enzyme activity happens at their optimum pH, so this is when metabolic reactions are fastest. Optimum pH is usually around pH 7 (neutral), but some enzymes work best at other pHs, e.g. enzymes found in the stomach work best at a low pH.
If blood pH is too high or too low (highly alkaline or acidic) enzymes become denatured. The ionic bonds and hydrogen bonds that hold them in their 3D shape are broken, so the shape of the enzyme’s active site is changed and it no longer works as a catalyst. The highest rate of enzyme activity happens at their optimum pH, so this is when metabolic reactions are fastest. Optimum pH is usually around pH 7 (neutral), but some enzymes work best at other pHs, e.g. enzymes found in the stomach work best at a low pH.
You can work out the pH of a solution using the following equation:
pH = -log10 [H+]
Examples Maths Skills - Logarithmic Scale
Blood glucose concentration
If blood glucose concentration is too high, the water potential of blood is ____________to a point where water molecules diffuse out of cells into the blood by ________(the diffusion of water molecules from an area of higher water potential to an area of lower water potential, across a partially permeable membrane). This can cause the cells to ________up and ____
If blood glucose concentration is too low, cells are unable to carry out normal activities because there isn’t enough glucose for ________to provide ________.
If blood glucose concentration is too high, the water potential of blood is reduced to a point where water molecules diffuse out of cells into the blood by osmosis (the diffusion of water molecules from an area of higher water potential to an area of lower water potential, across a partially permeable membrane). This can cause the cells to shrivel up and die
If blood glucose concentration is too low, cells are unable to carry out normal activities because there isn’t enough glucose for respiration to provide energy.
Figure 3: Effect of high blood glucose concentration on cells.
Negative feedback
Homeostatic systems involve __________, a __________________system and ____________. _______________detect when a level is too high or too low, and the information’s communicated via the __________system or the ____________system to ____________. The ____________respond to counteract the change-bringing the level back to normal. The mechanism that restores the level to normal is called a negative feedback mechanism
Negative feedback
Homeostatic systems involve receptors, a communication system and effectors. Receptors detect when a level is too high or too low, and the information’s communicated via the nervous system or the hormonal system to effectors. The effectors respond to counteract the change-bringing the level back to normal. The mechanism that restores the level to normal is called a negative feedback mechanism
Figure 4: A negative feedback mechanism.
Negative feedback keeps things around the normal level.
Figure 5: Control of body temperature via negative feedback.
Negative feedback only works within certain limits though–if the change is too big then the effectors may not be able to counteract it, e.g. a huge drop in body ______________caused by prolonged exposure to cold weather may be too _______to counteract.
Negative feedback only works within certain limits though–if the change is too big then the effectors may not be able to counteract it, e.g. a huge drop in body temperature caused by prolonged exposure to cold weather may be too large to counteract.
Figure 6: A positive feedback mechanism.
Figure 8: Positive feedback takes body temperature away from its normal level in people with hypothermia.
