Transport Across Cell Membrane Flashcards
What is the model of the cell membrane called
Fluid Mosaic Model
Cellular membranes are formed from
A bilayer of phospholipids
Structure of a phospholipid (detail)
phosphate head - hydrophilic - soluble in water
Glycerol and 2 fatty acid chains - hydrophobic - insoluble in water
Intrinsic proteins are….
Embedded in the membrane
Extrinsic proteins are
Found on the outer or inner surface of the membrane
What 3 types of lipids do cell membranes contain
Phospholipids
Cholesterol
Glycolipids
Is cholesterol found in eukaryotic or prokaryotic membranes
Only eukaryotic
NOT in prokaryotic
What is the function of cholesterol in the cell membrane
Helps maintain membrane stability ( holds the phospholipids together more tightly)
Prevents fluidity under too warm conditions and too ridge under cool conditions
Reduces movement of water soluble chemicals
What is the structure of a glycoprotein
Proteins with a carbon chain attached
What is the function of glycoprotein and glycolipid
Involved in cell signalling
What type of amino acids do intrinsic proteins have
Hydrophobic
What are the two types of intrinsic proteins
Channel
Carrier
Protein channel allows (what goes through)
Protein channels allow polar molecules and ions to diffuse through
How do carrier proteins work
Change shape or position
To transfer molecules or ions from one side to another
Function of glycoprotein x4
Cell recognition
Allow cells to attach to each other
Role in immune system
Receptors for hormones
Define diffusion
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration
What are the 6 factors that affect diffusion
Concentration gradient
Particle charge/size
Temperature
Thickness of exchange surface
Facilitated diffusion
The surface area
What is simple diffusion
When molecules diffuse directly through the cell membrane
Diffusion is a. ….. process this means …
Passive
It does not need metabolic energy
What happens on facilitated diffusion
Hydrophilic substances diffuse across the cell membrane via proteins
What type of protein are carrier and channel proteins
Intrinsic
How do carrier proteins work
Have a binding site for a specific chemical
Tertiary structure of the carrier protein changes
The chemical is then released on the opposite side of membrane
How does a channel protein work
Protein with a pore
Lined with hydrophilic amino acids and contains water
Hydrophilic substances pass from one side to another
Define osmosis
Osmosis is the movement of water molecules from a region of higher water potential to the region of lower water potential through a partially permeable membrane
Define water potential
The likelihood of water molecules to diffuse in or out of a solution
(One that exerts more pressure)
Water potential of pure water
0
What is the unit of water potential
Kilo pascals
kPa
More concentrated solution has
….. water potential
More ….. value
Lower
Negative
Define isotonic
Is when water potential on both sides of the membrane is equal
Define hypertonic
Water moves out
Water potential of the solution is more negative than the cell.
Define hypotonic
Water moves in
When the water potential of a solution is more positive than the cell
Active transport definition
The movement of molecules and ions against the concentration gradient, from a region of low to a region of high concentration. The process requires energy using ATP
How does active transport work
The molecule or ion attaches to receptor site on the carrier protein. (on the side of the membrane where the chemical is at a lower concentration).
ATP bonds to carrier protein
ATP hydrolyses
Phosphate attaches to carrier protein
Protein changes shape and then returns to original shape
Give two functions of the phospholipids in the cell membrane
Allows non-polar molecules to pass through
Gives fluidity/flexibility to cell membrane
Why data in table above is processed results
Calculations are made from raw data they would have found x and y to do calculation
What is the bond between the glycerol and fatty acid chains called
Ester
A prokaryotic cell does not have cholesterol but still maintains shape explain why (2)
Cell is unable to change shape
Due to cell wall
How could a student use cylinders to to cut the potato/carrot etc to ensure it was a fair test
Cut the cylinders from the same area
Cut the carrot lengthways down the root
Other then the membrane outside of the cell where else can you find the membrane x3
Lysosomes and mitochondria and chloroplasts
Which can pass through the cell membrane hydrophilic or hydrophobic
Hydrophobic
Because the centre is hydrophobic
Hydrophilic substances are polar so can’t pass through
What can pass through the cell membrane
Non-polar (centre is non polar hydrophobic)
Water can pass even though polar because they are extremely small
Function of glycolipids
Recognise other cells and determine wether to come into contact
Antigens to determine blood group
Limitation imposed by the nature of the phospholipid bilayer relating to diffusion
The cell membrane contains a hydrophobic core charged particles can’t diffuse through (excluding water)
does facilitated diffusion use energy
NO passive process still diffusion
What is used in co-transport
Sodium-potassium pump which pumps sodium ions out of the epithelial cells into the blood stream
Co-transport in terms of sodium ions
Sodium glucose transporter protein between gut and epithelia cell
Sodium ions diffuse through down their concentration gradient and at the same time glucose (against concentration gradient)
Adaptation of epithelial cells that help with co-transport
Large number mitochondria for potassium-sodium pump
Large number microvilli increase surface area more space for proteins
Blood stream carrier away the glucose maintains concentration gradient for facilitated diffusion.
What type of protein does co-transport use
Carrier protein
Explain the arrangements of the phospholipids in a cell-surface membrane
It is a bilayer
Hydrophobic tails point away FROM WATER / Hydrophilic heads point toward (attracted) TO WATER
Which are polar and non- polar in a phospholipid
Fatty acid- non-polar
Heads + polar
Which protein does co-transport and active transport use
Carrier
Describe how substances can cross the cell membrane
Simple
Facilitated
Osmosis
Active transport
How to do calibration curve
Make solutions of known concentration
Use colorimeter to value each solution and plot calibration curve
Find concentration of sample from calibration curve
