Cell Physiology Flashcards
(51 cards)
What short term describes the plasma or cell surface membrane?
A phospholipid bilayer
The plasma membrane is primarily composed of a phospholipid bilayer, which is essential for cell function.
What does the term, hydrophobic, mean in relation to phospholipids?
Hydrophobic means the fatty acid tails are water repelling or water hating and they will only mix with lipid
This property is crucial for the formation of the lipid bilayer.
What does the term, hydrophilic, mean in relation to phospholipids?
Hydrophilic means the phosphate heads are water loving and will not mix with lipid
This allows the phosphate heads to interact with the aqueous environment.
What term is used to describe the arrangement of all the molecules in the plasma membrane?
Fluid Mosaic Model
The model illustrates the dynamic nature of the plasma membrane.
Describe the fluid mosaic model.
The phospholipids move laterally or sideways, making the structure FLUID: the proteins are irregularly arranged like a MOSAIC, ‘floating’ amongst the lipids.
This model highlights the flexibility and variability of the membrane structure.
What are transmembrane, extrinsic, and intrinsic proteins?
Transmembrane - the proteins go right through the bilayer
Extrinsic - the proteins are attached peripherally
Intrinsic - the proteins are embedded within one of the layers
These proteins play various roles in cellular functions.
What is the GLYCOCALYX?
This is the outer layer of our cell membranes, made up of glycoproteins (carbohydrate plus protein) and glycolipids (lipid and carbohydrate), and unique to everyone.
The glycoalyx can act as antigens or receptor sites on the cell surface.
Fill in the blank: The phospholipids move laterally or sideways, making the structure ______.
FLUID
True or False: The glycoproteins and glycolipids in the glycoalyx are the same for every individual.
False
The glycoalyx is unique to each individual, contributing to cellular identity.
What are some types of proteins found in the plasma membrane?
- Integral protein
- Peripheral protein
- Channel protein
- Alpha-helix protein
Each type of protein has specific functions, such as transport and signaling.
What is the role of cholesterol in the cell membrane?
Increases the forces of attraction between the fatty acid tails, making the membrane structure more stable
Cholesterol contributes to the fluidity and stability of the membrane by preventing the fatty acid chains from packing too closely together.
What roles do the proteins in the cell membrane have?
- Stability and support by anchoring phospholipids
- Enzymes
- Receptor sites (having a complementary shape to attaching molecules such as hormones)
- Transport - carriers and channels
- Cell recognition
- Antigens in immune response
Proteins in the cell membrane perform various essential functions that facilitate cellular communication and transport.
Define diffusion.
The net movement of particles down a concentration gradient, from a higher to a lower concentration, until concentrations are equal.
Diffusion is a passive process that does not require energy.
What sorts of molecules can diffuse directly through the phospholipid bilayer?
- Lipid soluble, hydrophobic molecules such as steroids and glycerol
- Small uncharged molecules, such as water and carbon dioxide, which move through gaps
These molecules can easily pass through the lipid bilayer due to their compatibility with the membrane’s hydrophobic core.
What does PASSIVE mean?
The process does not require energy (ATP).
Passive transport relies on concentration gradients to move substances across membranes.
What factors speed up diffusion?
- Steeper concentration gradient
- Short distances (i.e. thin membranes)
- Smaller size of molecule
- Higher temperature (molecules have more kinetic energy)
- Greater surface area
These factors enhance the rate at which molecules move from areas of higher concentration to areas of lower concentration.
What types of molecules cannot diffuse across the membrane?
- Water soluble, hydrophilic or polar molecules such as glucose, amino acids and ions
These molecules require specific transport mechanisms to cross the lipid bilayer.
How do water soluble, hydrophilic and polar molecules get across the membrane?
- Channel proteins (which may be gated): Used for diffusion of ions/charged/polar molecules
- Carrier proteins: Have specific binding sites and following binding they change shape and release the molecule on the other side of the membrane
These proteins facilitate the transport of molecules that cannot pass through the lipid bilayer directly.
What is ACTIVE TRANSPORT?
The energy-requiring transport of molecules against a concentration gradient using carrier proteins.
Example: Active transport of minerals into root hair cells
Why does active transport require oxygen?
Active transport requires energy in the form of ATP, which is made during aerobic respiration, and aerobic respiration requires oxygen.
What is OSMOSIS?
The DIFFUSION of water molecules from an area of higher water potential to an area of lower water potential through a partially/selectively permeable membrane.
What are the two types of transport for moving substances that are too large to move through the membrane or which have to be moved in BULK?
- Endocytosis
- Exocytosis
Describe EXOCYTOSIS.
Secretory vesicles pinch off the Golgi and move towards the cell surface membrane, merge with the cell membrane, and release their contents outside of the cell.
Describe ENDOCYTOSIS.
A section of the cell membrane surrounds the substance, forms a vesicle/vacuole, pinches off, and moves into the cytoplasm where it fuses with lysosomes.
