2.2 - Why is CF mucus so sticky? Flashcards
What is a peptide bond?
bond btwn carbon & nitrogen that joins 2 amino acids tgthr
In what sort of reaction do amino acids join together?
condensation reaction
What are the 5 functions of proteins?
- catalysis (enzymes)
- defence & survival (antibodies)
- transport (carrier proteins)
- structure (collagen etc)
- signalling (receptor proteins for hormones etc.)
What is the protein that when faulty causes CF?
CFTR
What are proteins (structurally)?
polymers of amino acids
Draw the amino acid structure.
check online for answer.
What are the 3 groups of an amino acid?
Amino group
Carboxyl group
Side chain (R group)
What does the R group determine?
what the amino acid is & its properties
How many different types of amino acids are there?
20
What are the 4 different properties that amino acids can have?
- hydrophobic
- hydrophillic
- acidic
- basic
What are the main atoms in an amino acid?
nitrogen, hydrogen, carbon, oxygen & sometimes sulfur
What is the primary strcuture of a protein?
polypeptide chain held tgthr by peptide bonds
What process is used to break peptide bonds?
hydrolysis
What is made when 2 amino acids join together?
dipeptide
What are the 2 secondary structures of a protein? What bonds hold them together? Between which atoms?
alpha helix or beta pleated sheet held tgthr by hydrogen bonds btwn O & H atoms
What will the tertiary structure have, other than secondary structures?
What sort of bonds will a tertiary structure be held together by?
- will have a polypeptide chain “backbone” w one or more secondary structures
- held together by bonds called disulphide bridges, ionic, van de waals attractions & hydrophobic exclusions
How would you define the tertiary structure of a protein?
overall 3D shape of a polypeptide chain
What are disulphide bonds?
bond between 2 sulphur atoms in an R group (that also contain hydrogen) that contains sulphur & amino acids
How are disulphide bonds represented?
S-S
What does the quaternary structure of a protein consist of?
consists of 2 or more identical or different polypeptide chains
What are hydrogen bonds?
covalent bond btwn O & H groups (in R group)
sharing of electrons in a covalent bond is not equal (dipole)
slightly negative oxygen & slightly positive hydrogen
hydrogen bonds = weak bond
Define amino acid.
monomers of proteins
What is a globular protein?
protein where polypeptide chain is folded into a compact spherical shape
What is a fibrous protein?
protein that is un-folded
What provides fibrous proteins with extra strength?
several polypeptide chains cross linked tgthr
Where does an ionic bond occur?
btwn negative R group of one amino acid & a positive R group of another amino acid
Name 4 difference between globular and fibrous proteins.
globular = small, soluble, chains have little repetition & have functional roles
fibrous = long, insoluble and chains have more repetition & have structural roles
What is the acronym to remember the differences between globular and fibrous proteins?
Shape
Purpose
Acid sequence
Durability
Examples
Solubility
What is the different between globular and fibrous proteins in shape?
globular - round & spherical
fibrous - long and narrow
What is the different in the purpose of globular and fibrous proteins?
globular - functional
fibrous - structural
What is the difference in the pattern of the amino acid sequence between globular and fibrous proteins?
globular - irregular amino acid sqnc
fibrous - repetitive amino acid sqnc
What is the different in durability between globular and structural proteins?
howit is affected by different factors etc.
globular - more sensitive to changes in pH, temperature etc.
fibrous - less sensitive to changes in pH, temperature etc.
Name 3 examples of fibrous proteins.
- collagen
- fibrin
- keratin
Name 3 examples of globular proteins.
- enzymes
- haemoglobin
- insulin
What is the difference in solubility between globular and fibrous proteins?
globular - insoluble
fibrous - soluble
What is the function of the cell membrane?
controls what enters & leaves the cell
What 2 substances move into the cell?
oxygen, glucose
What 2 substances move out of the cell?
carbon dioxide & water
What are the 2 parts of a triglyceride lipid molecule?
3 fatty acids & a glycerol
What does hydrophillic mean?
attracted to water
What does hydrophobic mean?
repels water
Define extrinisic & intrinsic proteins.
extrinsic - sit on outside of cell
intrinsic - span cell membrn
define receptor.
organ & specialised cell that can detect change causing stimulus
What is the basic structure of a cell membrane made up of?
phospholipid bilayer
What is the difference between a triglyceride molecule and a phospholipid?
- triglycerides have 3 fatty acids & a glycerol,
- phospholipids replace the 3rd fatty acid with a negatively charged phosphate group, have 2 fatty acids & a glycerol
What is the structure of a phospholipid molecule?
the head is made up of the glycerol & phosphate group & the tail is made up of 2 fatty acids
What is a specific property of the phosphate head of the phospholipid molecule?
hydrophilic (polar)
What is a specific property of the fatty acid tails of the phospholipid molecule?
hydrophobic (non-polar)
What happens when the phospholipids are added to water? Why?
become arranged into a layer where hydrophilic heads are touching water & the tails are facing upwards so there is no contact between hydrophobic tails & water
In the fluid mosaic model, other than the phospholipid bilayer, what else makes up the cell membrane?
proteins, glycolipids, glycoproteins & cholesterol
Where are the 2 place proteins can be found in the cell membrane?
span the membrane (intrinsic) or only within the outer layer (extrinsic)
What is a glycolipid?
lipid which has a short branched carbohydrate chain
What is the function of a glycolipid?
acts as a receptor eg. binding with hormone
What unit of the body has receptors specific to their function? Give examples of this.
cells eg. only liver & muscle cells have insulin receptors
What is a glycoprotein?
protein which has a short branching carbohydrate chain
What is the function of a glycoprotein?
cell receptor on cell surface membrane eg. in HIV cells
Why is a cell surface membrane partially permeable?
hydrophobic fatty acid tails allow non-polar molecules to pass through the membrane but not polar molecules
What types of molecules move through channel proteins?
water molecules & ions
What types of molecules are transported by carrier proteins?
sugars, amino acids & other molecules (not transported by channel proteins)
What is the function of cholesterol in the cell membrane?
stop membrane becoming too rigid or too fluid & stops membrane breaking open
What sort of heads & tails does cholesterol have?
hydrophilic heads & hydrophobic tails
Who made the first development of the fluid mosaic model?
Gorter & Grendel
What did Gorter & Grendel conclude from their research?
cell membrane is made up of 2 layers of lipids, called a bilayer
What did Gorter & Grendel not know about the cell membrane?
that it contained other components including - proteins, glycoproteins, glycolipids & cholesterol
What was the technological development 2 of the fluid mosaic model?
electron microscope evidence
How did electron microscope evidence tell us about the structure of the cell membrane?
by staining tissue, lighter & darker parts of the membrane showed up under the microscope - showing that the cell membrane was made up of more than one component (lipid bilayer)
Who made the 3rd development of the fluid mosaic model?
Danielli & Davson and Robertson
How did Danielle & Davson propose the structure of the cell membrane to be?
lipid bilayer, where 2 layers of polar lipid molecules are facing outwards
& a layer of protein covering surfaces of the membrane, proteins are emebedded into lipids holding the lipids in place
How did Robertson propose the structure of the cell membrane to be?
added to Danielli & Davson’s, where the outer protein layer is a single polypeptide chain & not embedded into lipids & lipids are not held in place
w an inner layer of either protein or sugar
Who proposed the fluid mosaic model of the cell membrane?
Singer & Nicholson
Describe 3 key features of the proteins in the fluid-mosaic model.
- proteins float around in a globular structure
- proteins do not hold lipids in place, so lipids move like a fluid
- proteins are embedded in the membrane, sometime spanning whole membrane
Why did Singer & Nicholson name their model the ‘fluid mosaic model’.
lipids can move like a fluid & proteins are scattered
Who invented the fluid mosaic model?
Singer & Nicholson
Why did Singer & Nicholson call their model the ‘fluid mosaic model’?
lipids can move like a fluid & proteins are scattered
What happens when you mix a polar and a non polar substance together?
substances will repel
Describe 3 main features of proteins the fluid mosaic model.
- proteins float around in a globular structure & don’t form an inner or outer layer
- proteins do not hold lipids in place, lipids move like a fluid
- proteins are embedded in membrane, sometimes spanning the whole membrane
What happens to the amount of pigment released from a beetroot cell as you increase the concentration of alcohol in a solution? Why?
pigment released ↑ - ethanol disrupts hydrophilic/phobic parts of the phospholipid bilayer, because both ethanol & cell membrane are non polar so the lipids will dissolve in membrane
Define diffusion.
net movement of molecules from an area of high concentration to an area of low concentration, down a concentration gradient
What are the 4 factors that affect rate of diffusion?
- steepness of concentration gradient
- temperature
- surface area
- type of molecule or ion diffusing
How does the steepness of concentration gradient affect the rate of diffusion?
bigger the diff. in conc between the 2 side of the membrane, the faster the rate of diffusion
How does temperature affect the rate of diffusion?
higher the temp, the more kinetic enrgy molecules & ions have
molecules move faster so rate of diffusion is faster
How does surface area affect the rate of diffusion?
greater the surface area, the faster the rate of diffusion
bc there is more space for molecules to move across the membrane
How does the type of molecule or ion affect the rate of diffusion?
- large molecules tend to need more energy to move so diffuse more slowly
- non-polar molecules diffuse more quickly bc they r soluble in the non-polar tails
Which substances can enter cell membrane? Which substance leave the cell membrane?
- oxygen enters
- CO2 leaves
- glucose enters
- water enters
- nutrient/minerals enters & leaves
- urea leaves
Define osmosis.
net movement of water molecules from an area of high water conc. to an area of low water conc.
across a partially permeable membrane
What is a solute?
solid substance that has dissolves in a solvent (liquid)
What is a solvent?
liquid substance which dissolves a solute
What is a solution?
when a solid dissolves into a liquid
Define hypertonic solution.
concentrated solution
Define hypotonic solution.
dilute solution
Define isotonic solution.
solution w same conc. as cell’s cytoplasm
What happens in an animal cell do in a hypertonic solution?
water moves out of cell, causing cell to shrivel
What happens in an animal cell in hypotonic solution?
water moves into cell, causing cell to bcm lysed
What happens in an animal cell in an isotonic solution?
water will move in & out of cell, cell will stay a normal cell
What happens in a plant cell in a hypertonic solution?
water moves out of cell, cell bcms plasmolysed
What happens in a plant cell in a hypotonic solution?
water moves into cell, so cell swells & bcms turgid
water pressure is high, but cellulose in cell walls means cell doesn’t burst (normal state of plant cell)
What happens in a plant cell cell in an isotonic solution?
water moves in & out of cell, cell bcms flaccid
Define facilitated diffusion.
net movement of large molecules
via channel or transport proteins
across a biological membrane,
from an area of high conc. to low conc, down a conc. gradient
Define active transport.
transport of proteins or ions against the concentration gradient,
from an area of low conc to high conc
it is an active process, which means that it requires energy in the form of molecule ATP
What sort of process is active transport? What does this mean it requires?
active - energy in form of molecule ATP
What do molecules travel via in facilitated diffusion?
carrier or channel proteins (in the cell membrane)
How do molecules travel via channel proteins?
molecules move through channel proteins through the cell membrane
How do molecules travel via carrier proteins?
proteins change shape & molecules bind to a specific site on the protein, so that the protein can transport the molecule across the membrane
Can different types of ions & molecules pass through each protein channel?
no - only 1 type of ion or molecule can pass through a specific protein channel
In terms of channel proteins, what does the rate of facilitated diffusion depend on?
number of protein channels & whether they are open or closed
Why does active transport use energy?
molecules move against conc. gradient
How is ATP produced?
in respiration
Other than moving molecules, what does else is the energy in active transport used for?
make carrier protein change its shape, in order to transfer ions or molecules across the membrane
What is an example of active transport in animals? And in plants?
animals - absorption of prdcts of dgstn
plants - sugar from photosynthesis moving into phloem tissue
What the types of passive transport?
- diffusion
- facilitated diffusion
- osmosis
What types of molecules are moved by diffusion?
small molecules or ions
What types of molecules are moved by facilitated diffusion?
large molecules or ions (any that are specific to protein)
What 2 types of transport require molecules to transported via a protein?
- facilitated diffusion
- active transport
What type of protein is more likely to be used in facilitated diffusion?
channel protein
What type of protein is more likely to be used in active transport?
What are the 2 types of bulk transport?
- exocytosis
- endocytosis
Define bulk transport.
process by which large amounts of substances enter the cell without crossing the membrane
What happens in exocytosis?
large molecules are manufactured in the cell
secretory vesicles carry their the cell’s content to membrane & fuse w membrane, releasing their contents
What happens in endocytosis?
- cell membrane engulfs structures that are too large to fit through pores in membrane proteins
- membrane wraps itself around particles & pinches off cell membrane,
- cell membrane becomes outside of vesicle inside the cell
What are 2 differences between endocytosis and exocytosis?
- endo involves substances entering cells, whereas exo involves substances leaving cells
- exo involves the fusing of vesicles with cell surface membrane, whereas endo involves formation of vesicles from cell surface membrane
What does ENaCs stand for?
epithelial sodium ion channels
What is the apical membrane?
side of cell facing airway
What is the basal membrane?
opposite side of apical membrane
What is the role of chlorine and sodium ions in the membranes of cells?
causes water to enter or leave cells by osmosis & thus keeps mucus lining epithelial cell surfaces runny
What happens in membranes of someone (without CF) with excess water?
- CFTR channel is closed
- Na+ moves out of cell by active transport, so conc inside the cell falls
- Na+ ions now moves out of mucus into cell by faciliated diffusion through ENaC
- There is now an electrical gradient, so Cl- moves in between the gaps of cells
- Na+ & Cl- conc is higher in the tissue fluid & so water moves out of the cell & out of mucus to dilute tissue fluid
what is happening in the membranes of someone with CF?
- CFTR protein is missing or non-functioning so Cl- cannot leave the cells
- ENACs are not blocked so Na+ enters the cells
- Raise level of Na+ draws water & Cl- into the cell & out of mucus
- Mucus is viscous & hard for cilia to move
- Gas exchange is reduced & bacteria build up. Phagocytes are produ
