# Enzymes

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### What are the steps of the scientific method?

1. Observation
2. previous data
3. formulation of a hypothesis
4. observations and/or experimentation
new data
5. conclusion
6. theory

### When does a hypothesis become a scientific theory?

A hypothesis is a statement or prediction based on knowledge where as a scientific theory is supported by a large body of evidence.

### Controlling the variables in a experiment?

This means to keep all variables in an experiment constant except for the one being tested.

### Experimental variable?

The variable in the experiment being tested.

### What is the difference between the dependent and independent variable?

The independent variable is the one that the scientist controls and manipulates. The dependent variable is the one that the scientist does not control. It changes as a result of the independent variable.

### Where do the independent and dependent variables go on a graph?

Independent variable goes on x-axis (horizontal axis)
Dependent variable goes on the y-axis (vertical axis).

### An experiment is done in which cucumbers are given different amount of fertilizer to see how this effects their growth. What is the independent and dependent variable?

Independent variable is the amount of fertilizer. Dependent variable is the amount they grow.

### Control variable?

Any variable factors that you must keep constant so that they do not affect your experiment.

### What are some of the controlled variable in the cucumber experiment?

Amount of water, amount of sunlight, size of original seed etc.

### What is a control setup?

Is the setup that is identical to the experimental setup except that is lacks that factor that you are testing. It is used to compare with the experimental group to see if other factors might be affecting the experiment.

### What is the control setup (or control group) in the cucumber experiment?

A set of cucumbers that do not receive any fertilizer.

### Sample size?

Number of individuals tested.

### Why is it necessary to have a large sample size?

Better represents the population and therefore the results are more meaningful

### Why is it necessary for an experiment to be repeatable?

Gives opportunity for a good average of the results and thus makes the experiment more valid.

### How could you determine whether or not the results of an experiment are reliable?

1. If the results are consistent.
2. Only one variable is being tested once at a time.
3. There is a good control.

### Biochemical reactions?

Reactions that are carried out by living cells.

### Biochemical reaction in mitochondria?

Cellular Respiration:
Glucose + oxygen is turned into ATP (potential energy), carbon dioxide and water.

### Biochemical reaction in chloroplasts?

Photosynthesis:
Solar energy is transformed in chemical energy glucose.

### Exergonic or exothermic reaction?

Chemical reactions that release energy.

### Endergonic of endothermic reactions?

Chemical reactions that absorb energy.

### Cellular metabolism?

The sum of all chemical reactions both endergonic and exergonic that take place in a cell.

### What molecule do living cells use for reactions that require energy input?

ATP which is hydrolised to release energy from the phosphate bond and makes ADP.

### What provides energy for endergonic reactions?

The synthesis of ATP

### Where does the energy for the hydrolysis of ATP come from?

From exergonic reactions.

### Phosphorylation and ATP.

Attachment of phosphate group to ADP to make ATP. Energy is stored in the phosphate bond.

### Enzyme?

Biological catalysts that speed up a chemical reaction.

### Catalyst?

A chemical that speeds up a chemical reaction.

### Do enzymes get used up in a chemical reaction?

NO? They can be used over and over again.

### Substrate or reactant?

The starting material in a chemical reaction.

### Product?

The ending material in a chemical reaction.

### Energy of activation (Ea)?

The energy required to start a chemical reaction.

### Effect of an enzyme on the energy of activation?

Lowers the energy of activation.

### How do enzymes work?

Enzymes work by lower the energy of activation barrier so that the reaction can get started.

### What is a metabolic pathway?

A series of reactions that follow each other.

### What prevents metabolic reactions from running out of control in a cell?

Negative feedback from the products. When there is a sufficient amount of product it blocks the enzymes at the start of the reactions.

### Lock and Key Model of enzymes?

The enzyme and the substrate fit together like a lock that fits a key. this would lower the energy of activation so that the product can form more easily.

### Induced fit model.

In the induced fit model the active site of the enzyme changes shape to accommodate the substrate.

### In what way is the induced fit model different from the lock and key model?

In the induced fit model the enzyme active site changes shape to accommodate the substrate. This does not happen in the lock in key model because the enzyme active site already fits the substrate.

### Why can the enzyme Maltase, which breaks down starch into the sugar Maltose, not also be used to break down the sugar sucrose?

Sucrose has a different shape than starch and therefore does not fit the active site in the enzyme Maltase. Each substrate has its own specific enzyme.

### Factors that effect the rate of an enzyme catalyzed reaction.

1. Temperature
2. pH
3.Substrate concentration
4. Enzyme concentration

### How does temperature effect the rate of an enzyme catalyzed reaction?

As temperature increases, the rate of the enzyme catalyzed reaction also increases because the molecules are moving faster and colliding more frequently. After a certain temperature, the reaction rate decreases because the heat starts to denature the enzyme so that it no longer can function.

### Effect of lowering the temperature below the optimum temperature in an enzyme catalyzed reaction.

molecules move more slowly therefore there are fewer collisions and the reaction slows down.

### The effect of raising temperature above the optimum temperature in an enzyme catalyzed reaction?

The enzyme is a protein and therefore it becomes denatured and the reaction rate slows down.

### What does it mean to denature an enzyme?

Means the tertiary shape becomes damaged and so it does not function well.

### Do all enzymes function best at the same temperature?

No. Different enzymes have different ideal temperatures. For example, thermophlilic (heat loving) bacteria live in hot environments and have enzymes that function well at very high temperature.

### What is the ideal temperature for most enzymes in the human body?

Close to 37 oC as this is body temperature.

### How does the optimum pH for the enzymes pepsin and trypsin compare?

Optimal pH for pepsin is around 2.
Optimal pH for trypsin is around 8.

### Why are the ideal pH levels for pepsin and trypsin different?

Pepsin functions in the stomach to where pH is low (acidic) due to the presence of the acid HCl.
Trypsin functions in the small intestine where pH is basic (around 8). For this reason their ideal levels for functioning need to be different.

### What happens to reaction rate if pH is too high or too low?

If the pH is too high or too low, the enzyme becomes denatured and the reaction rate slows down because the substrate no longer fits the active site.

### What is the ideal pH level for enzyme catalyzed reactions for most cells in your body?

Close to neutral (pH 7) because most of our body have a neutral pH.

### Effect of substrate concentration on an enzyme catalyzed reaction.

If the substrate concentration is increased, the reaction rate is also increased because there are more substrates to which the enzymes can attach. Eventually the reaction rate reaches a maximum because the enzyme is saturated and their are no more available.

### Effect of enzyme concentration and reaction rate in an enzyme catalyzed reaction?

If the enzyme concentration is increased the reaction rate is also increased because there are more active sites for the substrate to attach. Eventually the reaction rate reaches a maximum because all of the substrate is saturated with enzyme and there is no more substrate available.

### How does the presence of a heavy metal effect an enzyme catalyzed reaction.

The Heavy metal causes the enzyme to become denatured so the reaction rate is lowered.

### Enzyme inhibition?

Prevention of enzyme reactions by competitive and non-competitive inhibition.

### Competitive inhibitor?

A molecule that mimics the substrate and therefore competes for the active site on the enzyme causing the reaction to slow down.

### Non-competitive inhibitor?

A molecule that slows down the rate of an enzyme catalyzed reaction by changing the shape of the enzymes active site. The non-competitive inhibitor does this by attaching to another site on the enzyme.

### What are some ways in which enzyme inhibitors can be bad for humans?

1.Nerve gases used in war bind to active sites which are needed for nerves to work and thus cause paralysis.
2. Lead and Mercury ions (heavy metals) cause denaturation of the enzymes in the human body and thus lower reaction rate. These heavy metals can be found in our food chain (eg. in tuna).

### What are some ways that enzymes inhibitors are good for humans?

1. Antibiotics can be used by inhibiting the enzymes in disease causing bacteria.
2. Using feedback inhibition to prevent metabolic reaction pathways from running out of control.

### What is feedback inhibition?

Cells use enzymes to regulate metabolic pathways. This occurs when a product of the metabolic pathway inhibits a previous reaction by inhibiting the enzyme.This is called feedback inhibition (one of the products is inhibiting a previous reaction).

### How exactly does feedback inhibition work?

In a metabolic reaction, once a sufficient amount of product has been produced, the end product may bond to the first enzyme. This enzyme is inhibited (inactive) until more product is needs. At this stage the enzyme is "released" and the reaction continues. This is a safeguard against a reaction running out of control and producing excess product.

### Coenzyme?

A molecule that assists the enzyme by binding to the active site and helping the substrate fit better.

### How are coenzymes and vitamins related?

Vitamins are organic coenzymes.

### What effect does the concentration of a coenzyme have on the rate of an enzyme reaction that it helps?

The reaction rate increases as the concentration of the coenzyme increases. Eventually a maximum rate is reached because the active sites all become filled. The reaction rate graph looks the same as and enzyme concentration graph or substrate concentration graph.

### What is a hormone?

A chemical messenger that signals the activity of glands and organs in metabolism, growth, development and homeostasis.

### What is a source gland?

The gland that produces the hormone.

### What is thyroxin?

A hormone that is produced by the Thyroid gland?

### Source gland for thyroxin?

Thyroid gland located in the neck region.

### Endocrine gland?

ductless gland secreting hormones into the blood stream.

### Structure of thyroxin?

Derived from the amino acid called tyrosine. It has 4 iodine atoms attached to it. This is why you need iodine in your diet.

### Where can you get iodine in your diet?

From iodized salt. Manufacturers add iodine to our salt because we need it in our diet.

### Hyperthyroidism?

When thyroid is over active and produced too much thryroxin.

### Hypothyroidism?

When the thyroid gland is underactive and produces too little thyroxin.

### What is a target cell for a hormone?

Specific cell on which the hormone will act.

### What are the target cells for thyroxin?

All the cells in the body.

### How does thyroxin effect metabolic rate of cells?

Increases metabolic rate.

Increases.

### Metabolism?

The chain of enzyme catalyzed reactions that occur in the human body that maintain life.

### What is the effect of thyroxin on heat generation by cells.

Increases heat generation.

### What is the function of thyroxin?

Controls homeostasis: eg. normal blood pressure, heart rate etc.

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