chapter 3

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1

Briefly describe the fluid mosaic model.

the molecular arrangement of the plasma membrane resembles an ever-moving sea of fluid lipids containing a mosaic of many different proteins.

2

Describe five different functions of integral membrane proteins.

Some membrane proteins act as

Ion channels or

Carriers that transport substances across the membrane.

Receptors that allow the cell to respond to various types of ligands.

Enzymes that catalyze specific chemical reactions.

Linker proteins that anchor cells to neighboring structures including other cells.

Cell identity molecules.

3

Briefly describe the driving force for the movement of water across plasma membranes.

Water moves across membranes by osmosis,

which is driven by solute concentration differences across the membrane.

Water moves from the area of low solute concentration to the area of high solute concentrations.

4

List the steps involved in receptor-mediated endocytosis.

The steps involved in receptor-mediated endocytosis include

1)ligand binding

2)vesicle formation

3)uncoating of the vesicle

4)fusion of the vesicle with endosome

5)recycling of receptors to the plasma membrane

6)degradation of the ligand in the lysosome.

5

Briefly state the functions of the rough and smooth endoplasmic reticulum.

The rough endoplasmic reticulum synthesizes glycoproteins, phospholipids and digestive enzymes that are transferred to other cellular organelles, inserted into the plasma membrane, secreted during exocytosis or stored in the lysosomes.

The smooth endoplasmic reticulum synthesizes fatty acids and steroids, detoxifies harmful substances, removes phosphate groups from glucose-6-phosphate, and stores and releases calcium ions that trigger contractions in muscle fibers.

6

Briefly describe how proteins move through the Golgi complex.

Proteins are packaged into transport vesicles by the rough endoplasmic reticulum membrane.

These vesicles enter on the (cis) face of the Golgi complex, and the proteins move through the cisternae, from (cis) face through to exit (trans) face.

Proteins will leave from the (trans) face of the Golgi complex in vesicles that will deliver the protein to plasma membrane, secretory vesicles, or to other organelles in the cell.

7

Briefly explain the difference between transcription and translation.

Transcription is making mRNA from DNA and it occurs in the nucleus, while translation is making a protein from the information in mRNA and happens in the cytosol of the cell.

8

Briefly describe alternative splicing.

Alternative splicing of mRNA is a process in which the pre-mRNA transcribed from a gene is spliced in different ways to produce several different mRNAs. The different mRNAs are used to make different proteins.

9

Define homologous chromosomes.

Homologous chromosomes contain similar genes arranged in the same (or almost the same) order.

10

Compare mitosis to meiosis.

Mitosis is somatic cell division that produces two identical cells with the same number (diploid) and kinds of chromosomes as the original cell.

Meiosis is reproductive cell division that produces cells in which the number of chromosomes in the nucleus is reduced in half (haploid)

11

Compare and contrast primary and secondary active transport.

Both are energy requiring transport processes that are capable of moving substances against their concentration gradients.

Energy obtained from hydrolysis of ATP drives primary active transport, while energy stored in an ionic concentration gradient drives secondary active transport.

12

Describe the difference between the cytoplasm and the cytosol

The cytoplasm is all the cellular material (organelles and fluid) between the plasma membrane and the nucleus, while the cytosol is only the fluid portion of the cytoplasm.