LB145Sec 001-004

Today’s Outline

• HAND IN Homework1– front of classroom.• StudyNotes2 due on Thursday – see website.• Announcements:

– LB145 Tutorial!– Field Trip!

• Review: Membranes• Prokaryotes versus Eukaryotes• Organelles

– Nucleus, RER, Golgi Apparatus, Cytoskeleton, SER, Ribosomes, Lysosomes, Peroxisomes, Vacuoles, Mitochondria, Chloroplasts

• Evaluate Homework

Announcement 1: LB145 Tutorial

• Purpose: to help students catch up!– Weak chemistry background.– A bit lost with where we are right now.

• Format:– Teams of 2-4. Working on problems with the help

of two senior LAs. (subject to change)• Friday 3-5pm in Lab room C-3.• Accommodates 20-25.• Email me to reserve a place – otherwise, first

come, first serve.

Announcement 2: Field Trip

• Field Museum in Chicago• Friday March 22nd: 7am – 12 midnight• Honors option for this course:

the biology of bioluminescence.

• Open to all students, but honors-option students allowed to sign up first. Remaining places determined by lottery.

• Cost: ~$12 per student.

Which of the following statements about saturated phospholipids is true?

a) They are more common in plants than animals.b) They have double bonds in the carbon chains

of their fatty acids.c) They are more fluid at room temperatured) They contain more hydrogen that unsaturated

phospholipids.e) They make membranes more permeable.

Saturated vs. Unsaturated

The Shape of Phospholipids…• Why is one leg of the phospholipid bent?

Forging Ahead:Cells and Organelles

Prokaryotes vs Eukaryotes

Prokaryotes

Structure• Single celled• Plasma membrane• Cell wall• Cilia/flagella (sometimes)

• Simple cytoskeleton (sometimes)

Other features• Plasmids• Ribosomes• Single circular chromosome• Organelles (few and only sometimes)

Eukaryotes

Structure• Single or multicellular• Membrane and wall (sometimes)• Cytoskeleton

Other features• Nucleus• Ribosomes• Many chromosomes• Extensive internal membranes…• Membrane bound organelles

Prokaryotes vs Eukaryotes

- Nucleus- Ribosomes- Rough Endoplasmic Reticulum (RER)- Smooth Endoplasmic Reticulum (SER)- Golgi Apparatus- Peroxisomes- Lysosomes- Vacuoles- Mitochondria- Chloroplasts- Cytoskeleton

Eukaryotes: Organelles to Live By

Discuss:

• Pick three organelles and write down everything you know about them.

• Turn to your neighbor and compare your lists.• Debrief –

The Nucleus

Campbell 8e, Fig. 6.10

The Nucleus

The Nuclear Envelope

Allows movement of molecular structures into and out of the nucleus

• mRNA and other molecules move to the cytoplasm for encounters with ribosomes

• Proteins, both structural and regulatory, are shipped into the nucleus

mRNA is made in the nucleus (Transcription)

mRNA molecules move to the cytoplasm where they encounter ribosomes

Together, mRNA and ribosomes make proteins (Translation)

Ribosomes

Ribosome and rRNA

• rRNA is made in the nucleus.• Small and Large Subunit proteins are transported

INTO the nucleus. Where the ribosome is assembled.(below: protein in purple, rRNA in orange and yellow)

Eukaryotes have FOUR strands of rRNA.

5S5.8S28S

18S

Prokaryotes have THREE strands of rRNA.

5S23S

16S

rRNA and tRNA are made in the nucleus (Transcription)

http://alienvisions.blogspot.com/

rRNA molecules are packaged with proteins to make ribosomal subunits

• Nucleolus site of synthesis

• Ribosomal subunits move to cytoplasm through nuclear pores

tRNA molecules move to the cytoplasm and helps translate mRNA into protein

Keeping RNAs Straight• mRNA

– MESSANGER RNA– Transcribed from DNA in nucleus.– Transported out into cytosol.– Interacts with ribosome where translation takes place and a protein is

formed.• rRNA

– RIBOSOMAL RNA – Transcribed from DNA in nucleus– Binds to large and small ribosomal subunits in nucleus – acts as structural

support.– Exits nucleus (bound to ribosomal subunits) via nuclear pore.

• tRNA– TRANSFER RNA– Transcribed from DNA in nucleus– Exits into cytosol via nuclear pore– Picks up a specific amino acid (covalent bond) in cytosol and transfers it to

growing polypeptide chain.

Write it Down:

• How many different kinds of mRNA do we have?• How many different kinds of rRNA do we have?• How many different kinds of tRNA do we have?

Coming Up:

• StudyNotes #2 is due on Thursday– StudyNotes #2 is due on

Thursday. It’s a big one!7.0, 7.1, 7.2, 7.5

– If you have Freeman 3,the sections are different – see website.

• Homework #2 (Cystic Fibrosis)will be posted tomorrow. (due Tues Jan. 22)

• Exam #1 is on the 24th!