Describe the ways in which an enzyme interacts with its substrate.

In lock and key hypothesis, the shape and charge of the active site of the enzyme are specific and complementary to the shape and charge of the substrate.

Upon effective collision between the enzyme and substrate, the substrate will bind and form temporary bonds with the enzyme's active site to form an enzyme-substrate complex.

When reaction between substrates finished, products no longer fit into the active site and are expelled.

In induced fit hypothesis, the active site does not initially exist in shape and charge complementary to the substrate. When the substrate binds to the active site, the shape and charge of the active site changes to ensure a better fit.

Cellular Homeostasis

Villi cells in the small intestines:

The villi is part of a villus. The villus contains capillaries. The villus can absorb nutrients from the food in the small intestines, which is then transported to the capillaries. From there, nutrients from the food are transported throughout the body. The villi plays an important role in maintaining cellular homeostasis because without it, the food cannot be transported to the rest of the body and the body cannot maintain a stable amount of nutrients.

Root hair cells in plants:

The root hair cells in a plant work similarly to the villi cells in the small intestines. The root hair cell absorbs nutrients and mineral ions from the soil outside the cell and transports it to the rest of the plant. Also, it has a similar elongated shape as the villi cell, as the larger surface area enables more absorption. The root hair cells play an important role in maintaining cellular homeostasis because without it, the nutrients and mineral ions cannot be transported to the rest of the plant, and the plant would not be able to maintain a stable amount of nutrients.

Journal Question 9 January

During OBS, think about how your body performs the following:

• water regulation
• temperature regulation
• glucose regulation

Our body controls the amount of water within us using a process called homeostasis. This process regulates the water intake and output. The kidneys retain fluid and also remove toxic products such as urea from our bodies (urea is found in urine). The liver regulates the blood sugar and converts nitrogenous waste. It also has a filtering system in which toxic substances are converted to less harmful substances. The brain also plays a part in water regulation, as it sends the signal for when the urine needs to be expelled from the body. 
In order to regulate the temperature of our bodies, a process called thermoregulation occurs. This is when our bodies maintain our original body temperature despite the temperature of the surroundings being very different. This process is also an aspect of homeostasis. The hypothalamus is our bodies' thermoregulation centre. When the body temperature is exceedingly hot, vasodilation and sweating are performed to release some of the heat. When the body temperature is colder, blood flow to the skin is restricted. The hairs on the skin surface are erected to provide better insulation, causing the appearance of "goosebumps". When necessary, shivering also occurs, causing muscle contraction in order to generate heat to our bodies.
During digestion, the digestive system breaks carbohydrates down into glucose. In order to regulate the glucose in the body, the pancreas produces insulin. This insulin enables the cells in the body to utilise the glucose, producing energy which is supplied to the rest of the body. When the blood glucose level falls, alpha cells in the pancreas produce glucagon, a hormone which stmulates the liver to release some of the glycogen present within it, in order to keep the blood glucose level regulated. This is why after about 15 minutes of feeling very hungry, we will start to feel less hungry.

(306 words)

Journal Questions 8 January

Structural Differences Between Plant and Animal Cells:

How can you classify the various organelles in a cell?

• size?

What is lysozyme? Is it found in lysosome?

Word analysis:
Lyso zyme

The word "lyso" is of Greek origin and means "to dissolve".
The word "zyme" comes from the word "enzyme".

A lysozyme is an enzyme that is able to destroy/dissolve the cell walls of certain bacteria. It can thus also be used as a mild antiseptic.

NO, lysozyme is not found in lysosome. Although they sound similar and have similar functions, lysozyme is found in egg whites, sweat, tears and saliva. However lysosome is found in the cytoplasm of cells and is an organelle.