Short Answer (Exam I)

Front 1

Explain how a Dehydration reaction works and how to identify one

Back 1

One monomer has an -OH group, while another has an -H group

The -OH and -H groups are removed from each of the monomers to synthesize a water molecule

This removal leaves the monomers free to covalently bond with each other

This is identifiable by the synthesis of the water molecule

Front 2

Explain how a Hydrolysis reaction works and how to identify one

Back 2

2 monomers are bonded into a polymer through a covalent bond

An H2O molecule is added to the bond, breaking it apart

Two monomers are then formed, one with an -OH group and one with an -H group

This is identifiable by the loss/addition of the water molecule

Front 3

Explain the process of Osmosis

Back 3

The diffusion of water across a selectively permeable membrane from high to low water potential

Water is separated by a selectively permeable membrane which will only let water molecules pass through it

One side of the membrane has high water potential, where there is a high solute concentration

The water will move across the membrane from the area of high WP to the area of low WP until equilibrium is reached, eg when the concentration of water and total solutes is equal on both sides of the membrane

Front 4

Explain the process of Diffusion

Back 4

Movement of molecules down a concentration gradient until an equilibrium is achieved (ie molecules are distributed equally)

Molecules are moving from areas of high concentration to areas of low concentration

This is passive transport and does not require any input of energy

If the environment is hypotonic, solutes will diffuse into the environment

If the environment is hypertonic, solutes will diffuse into the environment

If the environment is isotonic, then equilibrium is achieved due to the equal concentration of solute in the system and the environment

Front 5

Explain how a protein folds

Back 5

First there is primary structure, which is simply the amino acid sequence of the protein

Then there is secondary structure, which is when H-bonding between R-groups forms one of two structures: an alpha helix or a beta pleated sheet

Tertiary structure is when the protein folds due to hydrophobic and hydrophillic interactions. Hydrophobic regions of the protein fold inward to shield themselves from the water, while hydrophillic regions arrange themselves to face water so that they can interact with it.

Quaternary structure is when multiple protein subunits bond together to form one complete protein

Front 6

Explain how a phospholipid bilayer forms

Back 6

Phospholipids orient themselves so that their nonpolar tails do not interact with water, while their polar heads do interact with water. They do this by isolating their tails by orienting themselves so that their tails face each other, with their heads facing the water. This pattern of bonding continues until a sphere is formed with a membrane formed by a layer of phospholipids 2 phospholipids deep

Front 7

Explain how the Endomembrane system works

Back 7

The endomembrane system is an interconnected series of membrane-bound organelles involved in the synthesis and breakdown of molecules.

This system includes the nuclear envelope, endoplasmic reticulum, golgi apparatus, vesicles and vacuoles, lysosomes, and the cell plasma membrane.

First, ribosomal subunits and mRNA move out of the nuclear envelope (a double membrane made of phospholipids)

Then, we move to the endoplasmic reticulum. In the smooth ER, there are no embedded ribosomes, and the smooth ER functions in lipid synthesis, storage, detoxification.

The rough ER is studded with ribosomes, and functions in membrane and protein synthesis.

Th rough ER forms a glycoprotein through the process of glycosylation, the addition of a short carbohydrate chain to a polypeptide produced by ribosomes. This is then packaged into a transport vesicle, and is sent to the golgi apparatus.

The transport vesicle merges with the golgi, releasing its glycoprotein which is then modified by enzymes. This modified product is packaged into a secretory vesicle, and moves to the cell membrane, where the cell excretes it.

Lysosomes are also part of the endomembrane system, and are involved in the breaking down of molecules. The lysosome merges with an old organelle or ingested food vesicle, and its enzymes "lysozymes" and acidic environment break down the molecules.