Cell Membrane - 2 Flashcards
Roles of the membrane
- Partially permeable barriers
- Sites of chemical reactions
- Sites of cell communication within and between cells
- Compartmentalisation
- Provide the structure of organelles
What is a phospholipid
- Has a hydrophilic head, made of a glycerol with a phosphate group attached
- Hydrophobic tail made of fatty acids
Define the term Hydrophilic
- Uneven charges/polar
- Easily interact with water
Define the term Hydrophobic
- Evenly distributed charges
- Repels water molecules
Define the term Amphipathic
Some parts charged and some not
Components of cells membranes
- Phospholipids
- Channel proteins
- Glycolipids
- Glycoproteins
- Cholesterol
- Extrinsic proteins
What are Integral proteins
- Are carrier molecules or channels
- Help transport ions, sugars and amino acids across the membrane
- Some are receptors for hormones and enzymes
What are Peripheral proteins
- Free on the membrane surface or bound to integral proteins
- May act as receptors
- Many are glycoproteins
What are Glycoproteins and Glycolipids
- Act as a receptor sites
- can assist in binding cells together
- Glycoproteins = carbohydrate + protein
- Glycolipids = carbohydrate + phospholipids
What is Cholesterol
- Lipid with a molecular formula C27H470
- controls membrane fluidity and permeability
- More cholesterol the less fluid and less permeable
Which Factors affect permeability of the memebrane
- Solvents
- Temperature
- Detergents
How do Solvents affect permeability
- Dissolve the lipids in the membrane
How does Temperature affect permeability
- Negative temperatures cause ice crystals to form and pierce the membrane, increasing permeability
- High temperatures increase the kinetic energy and phospholipids move further apart. Proteins denature and fall out leaving large gaps
What is Cell signalling
- How cells communicate with other cells
- need messenger/ signal molecules
- Needs receptors on cell surface
Define Diffusion
- The movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient
- Passive process
What Factors affect diffusion
- Temperature
- Steepness of gradient
- surface area
- Nature of diffusing molecule
Which Particles can diffuse
- Lipid based molecules
- Very small molecules
Particles that cant diffuse
- Large molecules
- Charged particles
What is Facilitated diffusion
- Passive transport
- Involves channel proteins or carrier proteins
- Occurs down the concentration gradient
Define Active transport
Uses energy in the form of ATP to move molecules or ions against a concentration gradient
Define Bulk transport
- Uses membranes to transport large amounts of materials
- Needs ATP
- Two types: Endocytosis (Entering) and exocytosis (Exiting)
Define Osmosis
The movement of water molecules from a region of higher water potential to a region of lower water potential down a water potential gradient, across a partially permeable membrane
What occurs in a Isotonic solution
No net movement
What occurs in a Hypotonic solution
- Water moves into the cell
- Animal cell bursts (Lysis)
- Haemolysis
- Plant cell becomes turgid
- Doesn’t burst due to cell wall
What occurs in a Hypertonic
- Water moves out the cell
- animal cell shrinks
- crenation
- Plant cell becomes flaccid
- Plasmolysis
