4. Cell membrane and transport

what is the main component of cell membrane?

phospholipid

the cell membrane is said to have a ___________ and is ___________ in thicknesss.

phospholipid bilayer , 7nm

in a cell membrane , the _________ of phospholipids faces outwards and the ___________ of phospholipids faces inwards.

hydrophilic phosphate heads , hydrophobic fatty acid tails

how do we call the cell membrane?

fluid mosaic membrane

what does the mosaic mean in the cell membrane ?

randomly scattered patterns of different molecules

what does the fluid means for cell membrane ?

the components can move throughout the membrane.

state the factors affecting fluidity?

temperature:

increasing temp , increases kinetic energy , increases fluidity and vice versa

length of the fatty acid tails:

long tails , increases entanglement , decrease fluidity vice versa

type of fatty acid tail:
saturated tails are linear → less fluid

unsaturated tails are non linear → more fluid

cholesterol :

type of lipid → 1 hydrophilic head and 1 hydrophobic tail

maintains membrane fluidity

state the components of the cell membrane except form phospholipids?

glycolipids , glycoproteins , transport proteins , cholesterol

what is the role of glycoproteins and glycolipids ?

they act as receptor molecules

what is the roles of transport proteins ?

they allow materials to enter the cell through the cell membrane

outline cell signaling pathway ?

stimulus is received by a receptor

signal is converted to a message

message is transmitted to the effector

a response is triggered

what ligands?

signaling molecules

outline the role of ligands in cell signaling .

ligands are secreted from a cell into extracellular spaces

ligands are transported to the target cell

ligands binds to the surface receptors (glycolipids or glycoproteins)

response is triggered

state the 2 types of diffusion.

diffusion and facilitated diffusion

define diffusion.

the net movement of any molecules or ions from a region of high concentration to a region of low concentration down a concentration gradient until equilibrium is reached

state the factors affecting diffusion . (explain them briefly)

temperature : high temp → high kinetic energy → more diffusion and and the contrary

surface area : high surface area → more diffusion and the contrary

concentration gradient : high gradient → more diffusion and the contrary

Mr of molecules : high Mr → move slowly

what is the point of facilitated diffusion ?

some molecules cannot diffuse through the phospholipid bilayer so they use facilitated diffusion

which molecules cannot go through the bilayer by diffusion?

large polar molecules like glucose and amino acids

ions

what are the two proteins that allows facilitated diffusion ?

channel proteins and carrier proteins

explain channel proteins .

they are water filled pores

they allow charged substances to diffuse

they are gated

controls the exchange of ions

explain the carrier proteins.

they can switch between 2 shapes

they transport glucose and amino acids

define osmosis.

the net movement of water molecules from a region of high water potential to a region of low water potential down a concentration gradient and through a partially permeable membrane

what is the water potential of pure water ?

0 kPa

define active transport.

the net movement of molecules and ions from a region of low concentration to a region of high concentration against a concentration gradient using energy from ATP

state the importance of active transport.

loading of ions from the soil into the roots

loading of sugar for translocation

absorption of some production of digestion into blood stream

reabsorption of useful molecules and ions into the blood after filtration into kidney tubules

how is called the transport of large amount of molecules ?

bulk transport

State the name of bulk transport into and out of the cell.

endocytosis and exocytosis

do bulk transport requires energy? is it active transport?

yes it is active transport

state 2 type of endocytosis.

phagocytosis and pinocytosis

explain phagocytosis.

engulf solid material into cell forming a phagocytic vacuole around the material

explain pinocytosis.

engulf liquids

explain exocytosis.

the substances are packaged into vesicles form the golgi body

vesicles travel to the cell surface membrane

they fuse with it and release their contents outside the cell

what is the tool used to measure the size of an organism ?

surface area to volume ratio

when SAV ratio increases , what happens to the size of the animal ?

volume decreases

when SAV ratio decreases , what happens to the size of the animal ?

volume increases

what happens when a plant cell is placed in pure water ?

water enters the cell from a high water pot to a low water pot into the cell via osmosis through partially permeable membrane

water enters the vacuole of the plant cell , the volume of plant increases

The cell becomes turgid

what happens when a plant cell is placed in a solution with lower water potential than its cytoplasm.

water leaves the plant from high to low water pot by osmosis through partially permeable membrane

volume of plant decreases

protoplast continues to shrink

plasmolysis