Topic 15: Compartmentalism of cells Flashcards
1
Q
Explain the major functions of the plasma membrane
A
- Cell communication
- via the receptors integrated in the membrane for protein hormones or
- via steroid hormones
- Import/export of molecules or substances
- proteins integrated in the membrane allow substances to move inside like channels, transporters, carrier proteins or aquaporins
- receive hormones and substances via the movement of plasmas membrane
- phagocytosis, pinocytosis, endocytosis, exocytosis
- Shape, size and movement of cell
- integrated proteins attach to cytoskeleton to maintain the structure of cell → able to withstand stress
2
Q
Describe different modes of passive transport
A
- Diffusion: substances move into and out of cell by diffusing with the plasma membrane
- no extra energy input
- along the concentration gradient
- Facilitated diffusion: diffusion via channels or carrier proteins
- for larger molecules
- Osmosis: diffusion of water along the solute concentration gradient
- Hypertonic: the surrounding liquid is higher in solute concentration than outside cell
→ water moves out of cell
→ animal cell shrivels, plant cell plasmolyzes - Hypotonic: the surrounding liquid is lower in solute concentration than inside cell
→ water moves into cell
→ animal cell becomes lysed, plant cell becomes turgid - Isotonic: equal solute concentration
→ equilibrium movement of water into and out of cell
→ animal cell is normal, plant cell is placcid
- Hypertonic: the surrounding liquid is higher in solute concentration than outside cell
3
Q
Describe the active transport
A
- Active transport:
- Against the concentration gradient
- Requires conformational changes of proteins integrated in the membrane → extra energy input
4
Q
Give an example of how a carrier protein goes through conformational change to allow active transport
A
- ATP is broken to release energy and Pi which has negative charge of 2-
- The protein channel in the membrane is usually made up of alpha helix which is rigid and the ends have opposite charge → repel or open to receive substances
- Pi will bind to one of the 2 ends → give the negative charge
- The 2 ends attract and changes the direction of opening the channel → substances move inside
5
Q
Differentiate pinocytosis, phagocytosis, endocytosis and exocytosis
A
- Phagocytosis: engulf large molecules eg. microbes
- Pinocytosis: import small molecules together with fluid
- Endocytosis: materials have to bind to receptors
- the vesicle contains both receptors and materials.
- the vesciles are coated with clathrin
6
Q
Describe how proteins are exported and imported out and into the cell via vesicular transport
A
- Proteins are synthesized by ribosomes integrated in the rough ER whose membranes will surround those proteins, separate from the ER and move to the cis face of Golgi apparatus.
- The Golgi apparatus modify the proteins and pack them in bubbles of membranes called vesicles.
- The vesicles are released from trans face of Golgi will move along the microtubules towards the plasma membrane to fuse and release the proteins.
- The plasma membrane also have receptors to receive proteins, then form a bubble of membrane to bring the proteins inwards. The vesicles will either go to Golgi apparatus or to lysosomes
7
Q
Compare and contrast between the three components of the cytoskeleton
A
- Microtubules: made up of tubulin
+ thickest fiber tissues
+ arranged in a circular and tubular manner
+ extends from the nucleus outwards
+ pathway tracks to which motor proteins bind, hold organelles in place or allow cell movement and vesicle transport - Microfilaments: made up of actin
+ double helix structure
+ wrap around the cell right underneath the cell membrane - Intermediate filaments: made up of keratin - tough and strong proteins
+ keratin filaments form in strings which overlap with each other to form subunits
+ subunits then overlap to form tubes
+ form lattice structure all over cell
+ join junctions and desmosomes together -> strengthen cell
