Lecture 1 &2 : Cells and Cell membrane Flashcards
What are the 5 characteristics common to all cells
- Arise from pre-existing cells
- genetic info stored as DNA in chromosomes
- proteins synthesised on ribosomes
- has selectively permeable plasma membrane
- subcellular components suspended in semifluid cytosol
What unit is used to measure cells and organelles
microns - um which is 10^-6 m.
How many nm per um.
1000 nm per um
Why is there a diverse range of sizes
they have to exist in different environments with different functions.
What is an angstrom Ao
10^-10 m. Used to measure molecules
What can you see using a light microscope
Most plant and animal cells (eukaryotic) and nucleus, most bacteria and mitochondrion (prokaryotic)
What can you see using a electron microscope
Smallest bacteria, viruses, ribosomes, proteins and lipids.
How does Light microscopy work
The light source at the bottom is focused on the specimen which is magnified by lens and reflected to the eye.
What is the benefits of Light microscopy
Can view live cell behaviour/ movements in real time - EM kills organisms.
How is the contrast brought out in a light microscopy specimen
Staining cells, using phase contrast or fluorescence
What does an EM use to see stuff and the res between the two types
Electromagnets to focus a beam of electrons through the specimen (Transmission- res 2nm) or onto its surface (Scanning res 10nm)
How does Transmission EM vs Scanning EM work
Transmission: electrons are reflected off of heavy metal stains that stick to internal cell structures. Scanning: electron beams excite electrons from the surface of the cells which are detected to make 3D image of surface.
How does cell fractionation work
Homogenize tissue and cells in test tube to let components loose. Centrifuge many times to isolate cell components based on size and density. First nucleus, mitochondria +chloroplasts, microsomes membrane, then ribosomes, more Gs needed the smaller the component
What is a supernatant vs a pellet
the pellet is the heavy denser bit of the centrifuged substance. The supernatant is the lighter layer.
What makes up phospholipid hyrophilic head and hydrophobic tail?
A choline (small molecule) + phosphate group and glycerol = head attached to two fatty acids = tail.
What makes a tail straight or kinked
Saturated are straight and unsaturated are kinks (has double bonds).
What are the types of membrane proteins
Integral,
Peripheral,
Glycoproteins (receptors, docking) that protrude into the ECM and have carbohydrates on it.
Integrins can sense changes in the ECM and communicate this to the cell through cascades.
In animal cells what are the 3 main components of the ECM
Proteoglycan complex, collagen and fibronectin - linking membrane proteins to collagen. Can allow cell to navigate through tissue.
What are the main functions of membrane proteins
- Transport across the membrane
- Anchor membrane to microfilaments of the cytoskeleton or ECM keep cell shape
- Enzymatic activity
- Receptors for signalling molecules outside and then start a signal transduction pathway
- Cell to cell recognition proteins (glycoprotein)
- intercellular joining (cell junction)
For proteins destined to be embedded in membranes - eg the outer cell membrane what orientation should it have in the vesicles and membraneous structures of the endomembrane system
The inside layer of the membranous structures will eventually fuse with the outer membrane to become the layer facing the outside of the cell while the outside lipid layer of the membranous structures will be the inside lipid layer facing the inside of the cell.
How can the fluidity of the cell membrane of plants and animals in cold temperatures be increased to stop the tails sticking together
Have a high level of unsaturated fats- have kinks that make space so less viscous. Animals especially can have cholesterol between phospholipids in a leaflet to stop tails sticking- not so much plants
What are three types of cytoskeleton filaments and what are the three main functions - esp microtubule
Microtubules, microfilaments and intermediate filaments. They maintain cell shape, faciliate cell movement (pseudopodia, cillia. flagella) and faciliate the movement of components within the cell (vesicles)
How do vesicles move through the cell
vesicles attach on a receptor for a motor protein that uses ATP to move along the microtubule
Where is ribosomal RNA found
nucleolus
In what direction are proteins going through the Golgi to get phosphorylation or carbohydrates added (modification)
from cis to trans face
What does the lysosome contain and what are its two functions
It contains active hydrolytic enzymes that help to digest. It does Phagocytosis: fusing with food vacuole and Autophagy: fuse with damaged organelle
What organelles contain their own DNA and ribosomes
Mitochondria and Chloroplast
Where are chloroplasts found and what is the site of the photosynthetic apparatus
Found in plants and algae cells. Has Thylakoids which are a 3rd membraneous structure like flattened pancakes
How does the flagella/ cillia bend and flex
Cillia and flagellla are extensions of the cell membrane that has 9 microtubules arranged in a circular fashion with 2 in the middle. Cross linking motor proteins between outer microtubule doublets use ATP to walk along the microtubules (one half activated at a time) and cause it to bend.
What are the main features of a prokaryotic cell
Concentrated DNA in a nucleoid, little or no organelles but ribosomes, rigid cell wall, Glycocalyx: outer coating of slime layer or capsule. Fimbrae: extensions for attachment to other bacteria
What are the main differences between Prokaryotic and Eukaryotic cells
Eukaryotic cells have DNA enclosed in membrane bound nucleus but Prokaryotes don’t.
Eukaryotes produce the network of fibres in ECM to support but prokaryotes have rigid cell wall
What are the 3 main differences between plant cells and animal cells
Cellulose cell wall, central vacuole for storage and breakdown of waste products and Chloroplasts.
What are the four things in the endomembrane system that works to transport stuff around the cell?
Nucleus, Smooth and Rough ER and Golgi
What are the 4 cell junctions discussed and which one is only in plants
Tight junctions, Desmosomes, Gap junctions. Plant : Plasmodesmata enables communication between neighbouring cells and spans the cell wall
How does the cell membrane regulate transport inside and out of the cell
Bilayer stops some molecules diffusing over so require transport proteins for active and passive transport. These are selective.
How are large molecules transported across cell membrane
Exocytosis and Endocytosis
Phagocytosis - engulfment of food
Pinocytosis- engulfment of non specific extra cellular fluid
Receptor mediated endocytosis- specific, takes receptors. has coated vesicle
What is smooth ER involved in
Lipid synthesis, detoxification and ca2+ storage
Which is hollow microtubule or microfilament?
microtubule
What are peroxisomes
Organelle that undergoes various metabolic processes, producing H2O2 as a by product which it converts to water
Only animal cells have
centrioles
How are pseudopodia made
From rearrangement of microfilaments of the cytoskeleton
What do TAGs and phospholipids have in common
glyceride backbone
