Week 2 Flashcards
(49 cards)
What is the role of the smooth endoplasmic reticulum ?
Most cell types have relatively little smooth ER (SER)
•Phospholipid, fat and steroid (including sex hormones) manufacturer
•Carbohydrate metabolism
•In hepatocytes, breaks down stored glycogen to release glucose
•Detoxifies lipid-soluble drugs such as barbiturates
–Adds charged water-soluble groups such as sulphate or glycuronic acid
Describe the sarcoplasmic reticulum
Found in muscle cells
➢Network of tubular sacs
➢Transmits electrical signals
➢Sequesters calcium ions from the cytosol
➢The level of intercellular calcium regulates muscle contraction in muscle cells.
What zone shortens within a sarcomere during contraction ?
The H zone/line
What does the release of Ca2+ do in muscle contraction ?
Ca2+ causes a conformational change in troponin, changing of position of tropomyosin, allowing myosin to bind to its binding sites on actin
What is the motor end plate in muscle cells?
It receives the electrical signal, before it travels to the SR and Ca2+ is released
What do proteins have to have to do with
What does a ribosome require of the desired protein (the mRNA) for it to attach to the RER?
A specific signal peptide sequence
What is glycosylation ?
The addition of sugars or oligosaccharides
What face is the receiving side of the Golgi ?
Which is it exit face ?
Cis face
Trans face
Why is glycosylation important for mucus ?
The long oligosaccharide chains are essential for a highly hydrated gel like material
What was found when respiratory cells were looked at in healthy and cystic fibrosis patients ?
There was a lot more mucus in CF patients (more marker MUC5AC in airway )
There was more epithelial B-tubulin in airway of healthy person , less in CF
Roughly how many hydrologic enzymes do lysosomes use ?
What happens when a lysosome fuses with a target ?
60
H+ ions pumped into secondary lysosomes to bring down the pH and activate the enzymes
What is an example of a disease , which is caused by a lysosome disease?
Tay-Sachs - deficiency in hexosaminidase A enzyme leads to the accumulation of the lipid ganglioside , in nerve cells , usually die by 2-3 years old
What are the types of endocytosis ?
Phagocytosis
Pinocytosis
Receptor mediated endocytosis
For protein synthesis in the RER what is the signal sequence cleaved off with ?
The enzyme signal peptidase
What similarities are there between mitochondria and bacteria ?
Own circular genome
Double membrane
Similar in size to prokaryotic cell
Divide by binary fission
What type of cell contains around 2500 mitochondria when most have several hundred?
Liver cells
How are mitochondria moved inside cells?
They are moved by the microtubules of the cytoskeleton
What is the major protein component of the outer membrane of mitochondria ?
Porin —-> large aqueous channels
What are the 3 major types of membrane complexes in the inner mitochondrial membrane ?
- Electron transport chain
- ATP synthase
- Specific transporters of metabolites which vary according to cell/tissue type
What does the mitochondrial matrix contain ?
Enzymes which catalyse Krebs cycle and fatty acid oxidation
Ribosomes
Mitochondrial DNA
What type of phosphorylation does glycolysis generate?
Substrate level phosphorylation
Why is cyanide one of the most dangerous and fast acting poisons ?
It blocks the passage of electrons from one of the cytochromes thereby blocking the electron transport chain
Why is 2,4-Dinitrophenol so dangerous (DNP)?
makes the inner membrane leaky to H+ so that a gradient cannot be established
electron transport chain still works but energy is released as heat
“ Cooks “ you from the inside
