BLY Exam 2 Study Guide

What are the 3 main filaments and their structures? (AIM)

• actin: movement and contraction

• intermediate: structure/support

• microtubules: movement, support, transport, organization

What are the characteristics and functions of microtubules?

• structure

• additional functions

• features

• protein functions

• structure: long hollow tubes

• additional functions: organelle movement, DNA separation, move cilia and flagella

• features: directional polarity

• proteins: stability & arrangement

What are the 3 motor proteins & their associations/features?

• kynesin: +, microtubules

• dynein: -, microtubules, slide & bend, move cilia & flagella, not polymerized

• myosin: actin, movement, slides

• all powered by ATP

What are the characteristics and functions of actin filaments?

• structure

• forms

• organization

• binding molecules

• polar or non-polar

• result of hydrolysis

• structure: thin & flexible, helix

• forms: G-actin (individual) and F-Actin (polymerized)

• organized: by cell signals, form cross linked protein networks

• binding molecules: ATP, ADP, myosin, motor proteins

• polar

• hydrolysis leaves ADP and unstable filament

How does cell crawling work?

• actin pushes membrane

• myosin binds to actin & myosin contracts

• lamellipodia & flipodia pull cell forward

How does skeletal muscle contraction work?

1. nerve signal

2. action potential triggers T tubules

3. SER releases Ca2+

4. tropomyosin slides out of the way

5. myosin binds to actin

6. myosin & actin slip n’ slidin’

7. cross bridge cycling causes contraction (CCC)

What are the main characteristics of microtubules?

• stability

• movement (what they move)

• binding molecules

• functions

• polarity and end charges

• dynamic instability: rapid growth & shrinking

• movement: vesicles, organelles, chromosomes

• binds GTP/GDP: hydrolysis leaves unstable filament

• functions: support, transport, organization

• plus & minus end, polar

What are the main characteristics of intermediate filaments?

• attachment & junctions

• nature

• what they form

• structure

• polarity

• transmembrane proteins: form desmosomes & hemidesmosomes

• nature: strong & stable

• form: nuclear lamina

• structure: 2 heads, twist & stack

• non-polar

What are the characteristics, features, and functions of epithelial cells? (LASP)

• regenerative & tightly packed

• simple or stratified

• avascular

• functions: lines, absorbs, secretes, protects

What are fibroblasts? Where are they found? What are the common fibers (CER) and functions?

• cells that produce fibers

• collagen: tensile strength

• elastin: stretch & recoil

• reticular: soft skeleton

What are integrins? What do they interact with?

• transmembrane proteins that connect ECM & cytoskeleton

• interact: collagen & actin

• used by hemidesmosomes

What is the tight junction and what does it do?

• transmembrane proteins that seal & prevent diffusion

• maintain polarity

What is the gap junction and what does it do?

• align adjacent cells

• allows molecules to be exchanged

What do adherens do? (AAA)

• link adjacent actin to plasma membrane

What do hemidesmosomes do?

connect ECM to plasma membrane using integrins

What do desmosomes do?

connect intermediate filaments

What kind of proteins do adherens and desmosomes use?

cadherins

What are cadherins?

proteins that link adjacent cells to plasma membrane

What is the process of transcription?

RNA Poly unwinds DNA, TFIIH initiates transcription thru phosphorylation. TFIID has TATA box and binding site for RNA Poly. mRNA synthesized 5’ to 3’ using DNA 3’ to 5’ strand thru base pairing, then modded post-transcription.

What is the chemical process of translation?

• chemically: charged tRNA lands at A site, c-term polypeptide chain is transferred to tRNA. large unit shifts tRNA PEAP, small realigns complex and tRNA is booted from E site. A site is ready for new tRNA.

• physically: initiation complex gathers everyone (ribosome, tRNA, mRNA), then tRNA & complex scan mRNA for start codon & bind. large unit forms peptides and shifts mRNA 1 codon, small unit matches tRNA anticodon & mRNA codon. tRNA matches amino acid. termination starts when stop codon enters A site and release factors trigger hydrolysis that cleaves tRNA and terminates translation

What are fibrous proteins? Where are they found? Examples?

• filamentous support proteins

• found in: cytoskeleton and ECM

• examples: collagen, elastin, keratin

What are extracellular proteins and their structure?

• proteins outside of cell

• disulfide cysteine -SH groups

How do proteins bind to other molecules (protein-ligand binding)?

noncovalently with lock and key specificity