Cells at Work

Enzymes are organic catalysts which enable cellular reactions to occur in time spans which enable life to exist. Enzymes Enzymes speed up reactions. The enzyme is not altered in the reaction and can be reused. Reactions can go in both directions enzyme + substrate ↔ enzyme + product

Enzymes are specific for one reaction only because of their key/lock nature. Enzymes are affected by temperature, warmth speeds up most reactions, cold slows them. Too much heat denatures enzymes. (Destroys them.) Enzymes are affected by pH, they work best at the pH which occurs where they work in the body, eg. pepsin works at low pH as it is a stomach enzyme.

Rates of reactions affected by amounts of substrates and products present Co-enzymes may be needed; small molecules, many are vitamins, which need to lock into the enzyme for correct function gy/Biology1111/animations/enzyme.html

All organisms need energy for growth, movement, metabolism, repair and maintenance, reproduction and elimination of wastes.

Energy exists in many forms but cells use chemical energy which is stored in molecular bonds. When the bonds are broken energy is released. Glucose, Fats, and proteins have many energy-containing bonds. Enzymes help with the rate at which molecules are broken down, so that energy can be released quickly.

Green colour in plants signifies cells with chlorophyll, chloroplasts contain chlorophyll and are where photosynthesis takes place; they are in the mesophyll layer of leaves. Like mitochondria, chloroplasts have many layers which increase their surface area for photosynthetic reactions.

Write the chemical equation for photosynthesis and respiration

 An extremely important organelle that will not be found in Prokaryotes, but is found in most eukaryotic cells.  Mitochondria are fairly large organelles which are composed of many layers of folded membrane.  Act as the “Power Plant” of the cell, creating energy for use.

 A mitochondrion’s function in the cell is create energy for use in the cell.  A process called cellular respiration occurs in the mitochondria, involving the breakdown of glucose (sugar).  The glucose is broken apart to produce ATP. This is a usable form of energy for the cell.

 Ribosomes are very tiny organelles which can be found in both prokaryotes and eukaryotes. They are also found within all 5 kingdoms.  These can be freely floating around the cytoplasm, or they can be attached to the endoplasmic reticulum.

 A ribosome’s function in the cell is to synthesize (make) proteins.  Free floating ribosomes normally make proteins which act as enzymes in the cytoplasm.  Ribosomes attached to endoplasmic reticulum normally make proteins that are used in the cell membrane and for export out of the cell.

 Often referred to as simply ER, Endoplasmic Reticulum is a fairly large organelle, which is not found in prokaryotes, but found in most eukaryotic cells.  ER is a large mass of connected membranous sacs called cisternae.  It can be either rough endoplasmic reticulum (with ribosomes attached) or smooth endoplasmic reticulum (no ribosomes attached). (Rough is by far the most abundant type)

 ER has two main functions within the cell: 1.It contains enzymes that assist the ribosomes to synthesize their proteins. 2.It passes the proteins made by the ribosomes onto the Golgi Apparatus.

 The Golgi Apparatus (sometimes known as the Golgi Complex), looks very similar to the ER, and is also made of stacks of Cisternae.  Like the Endoplasmic Reticulum, it is only found in eukaryotic cells.  It doesn’t have Ribosomes attached, so it appears smooth.

 The Golgi Apparatus’ role is to receive the proteins from the ER, sometimes modify them, and package them for transport around the cell.  It moves the proteins around by placing them in small sacs of membrane called Vesicles.  These vesicles can move around the cell, and can also carry proteins out of the cell.

 Ribosomes make the proteins. They are usually passed to ER.  ER sometimes modifies these proteins. Then passes them to the Golgi Apparatus.  Golgi can further modify these proteins, then packages them in vesicles for transport around the cell.

 Lysosomes are small but important organelles, which are found in most animal cells, and in some plant, fungi and protists.  They are essentially vesicles produced by the Golgi Apparatus. (Made of membrane)  They contain powerful digestive enzymes, which are designed to break down materials.

 The lysosomes function is to breakdown unwanted or harmful debris within the cell, including old and worn out organelles.  They do this by fusing with other vesicles that contain unwanted material, and their enzymes begin destroying the material.  Some useful small particles can diffuse back into the cytoplasm, the rest is discarded out of the cell. (“Lyse” means to destroy.)

 Vacuoles vary in size and function, and can be are found in all kingdoms apart from Monera.  They are membrane surrounded organelles that are generally extremely large in plants, but much smaller in other eukaryotic cells  They are usually filled with water or sometimes a sap in plants.

 Vacuoles carry out various tasks: Plants – Normally for Turgor. (physical support) Other kingdoms – Contain food, waste materials, dumping grounds, water balance  Vacuoles are very versatile organelles and their function is generally dependant on the cell type and its requirements.

 Mitochondria turn glucose into ATP. (Sugar into energy)  Chloroplasts is where photosynthesis occurs, and are mainly found in plants.  Lysosomes are the demolition crew of the cell.  Vacuoles vary in size and function. Can be used for food storage, waste dumping, water balance and turgor.

Enzymes in cells. l