Protein Synthesis Summary

Protein Synthesis 1. The DNA double helix unwinds to expose a sequence of nitrogenous

bases. (A,T,C,G)

2. A copy of one of the strands is made in a process known as transcription. The copy is made of messenger ribonucleic acid (mRNA) which, following transcription, travels out of the nucleus into the main body of the cell, where protein synthesis occurs.

3. The mRNA couples with the protein synthesis apparatus (the ribosome). Another type of RNA, known as transfer RNA (tRNA), brings free amino acids to the ribosome.

4. The anticodon present on the tRNA recognises the codon present on the mRNA, and the ribosome adds the amino acid to the growing chain of linked amino acids (polypeptides), cleaving it away from the tRNA. This process is known as translation.5. As the polypeptide chain grows, it folds to form a protein.

http://www.youtube.com/watch?v=983lhh20rGY

ENERGY RELATED ORGANELLESMitochondria - The Cell's Chemical Furnaces • contains its own DNA, support for Endosymbiosis Theory• singular is "mitochondrion“• 2 membranes, one smooth outer membrane, and an inner

membrane folded into layers called cristae• Cristae has two compartments: the matrix and the inter

membrane space

• function to store energy for cell use. Energy is stored in the form of ATP - adenosine triphosphate

• (Made by cellular respiration… which we will learn later!)

Figure 4.17

Chloroplasts - Where Photosynthesis Takes Place • only found in plant cells• has its own DNA, like

mitochondrion

• functions to convert light energy to carbohydrates

• carbohydrates then broken down in mitochondria to produce ATP

• consists of grana, closed compartments that are stacked

• thylakoids are the individual disk shaped compartments that make up the grana (stack of thylakoids)

• stroma is the fluid surrounded the thylakoids

*Chloroplasts are a type of plastid

Chromoplasts – red, yellow and orange pigmentLeucoplasts – colorless (potatoes)

Endomembrane System• Many of the different membranes of the eukaryotic cell are

part of this system which carry out a variety of tasks in the cell. i.e. synthesis of proteins, metabolism and movement of lipids, & detoxification of drugs and poisons

• The membranes of this system are related either through physical continuity or by the transfer of membrane segments as tiny vesicles (sacs made of membrane)

• This system includes: nuclear envelope, the endoplasmic reticulum, golgi apparatus, lysosomes, various vacuoles, and the plasma membrane

Endomembrane System

Endoplasmic Reticulum

• Extensive network accounting for more than half the total membrane in eukaryotic cells

• Consists of a network of membranous tubules and sacs called cisternae

• The ER membrane separates the internal compartment of the ER, called the ER lumen (cavity) or cisternal space, from the cytosol.

• The ER membrane is continuous with the nuclear membrane

ER cont…

Two types of ER: smooth and rough1. Smooth ER – lacks ribosomes and involved in

diverse metabolic processes such as lipid synthesis, metabolism of carbohydrates, and detoxification of drugs and poisons

2. Rough ER – has ribosomes and is involved in protein synthesis

Figure 4.10a

Golgi Apparatus -- Delivery System

• flattened stacks of membranes

• functions in collection, packaging and distribution of molecules made in the cell and used elsewhere

• front end (cis) faces the ER, and the back end (trans) faces the cell membrane

* folded stacks are called cisternae

• unprocessed proteins enter the Golgi apparatus from ER and proteins are packaged and exported to the nearest membrane

Jobs of the Golgi Apparatus (aka Golgi Complex)1. separates proteins according to their destinations

2. modifies proteins (adds sugar and makes glycoproteins)

3. packages materials into vesicles which are exported outside the cell - secretion

Summary of Endomembrane System

See Handout*

Lysosomes - Intracellular Digestion Centers

• vesicles that are used to digest• contain high levels of degrading

enzymes – low pH(to "lyse" means to dissolve)

• recycle old and worn out cell parts• "suicide sac" - apoptosis (wikipost

HWK)• digest other particles taken in by

phagocytosis http://www.youtube.com/watch?v=m6qJ69wcSnc• found in animal cells  TAY-SACHS disease – missing an

enzyme of the lysosomes that breaks down a fatty substance.  Over time this fat builds up in the brain and nervous tissue, smothering the cells.  Results in degeneration and death.

Vacuoles

Types:1. Food vacuoles – formed by phagocytosishttp://www.youtube.com/watch?v=W6rnhiMxtKU2. Contractile vaculoes – pump excess water out of

the cellhttp://www.youtube.com/watch?v=kkPiRT2ewVA3. In plants & Fungi – Central vacuole: stores food,

nutrients, water and waste…maintains turgor pressure (prefer a hypotonic state)

Mini Quiz1.  What part of the cell produces vesicles for export?

2.  What part of the cell makes proteins?

3.  What part of the cell produces ATP?

4.  What part of the cell transports materials throughout the cytoplasm?

5.  What part of the cell has a cis and a trans face?  

a.  ________________

b.  ________________

c.  _________________

d.  _________________

e.  _________________

f.  __________________

f.

What is this structure? 

Figure 4.7b

Figure 4.10a

What is this structure?

What is this structure?

Figure 4.11

Describe the processes occurring in this image.

Figure 4.13

Figure 4.16b

What is this structure?

What is this structure?

What is its function?  

Find the:

a.  Nucleolus

b.  Centriole

c.  Vesicle

d.  Smooth ER

e.  Lysosome

Summary Video Clip

http://www.youtube.com/watch?v=3jWV568GpkU