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Cells - Transport 1 (Topic 1.1-11.3) > Unit 3: Membranes > Flashcards

Unit 3: Membranes Flashcards

1
Q

What is water and what is it molecularly composed of?

A
  1. Water is H2O
    - Made of two hydrogens and one oxygen
    - Hydrogens connected to the oxygen in a water molecule by covalent bond
  2. Hydrogens have a positive charge, and oxygen has a negative charge
    - So water is polar (has a charge)
  3. Hydrogens are connected to oxygens in different water molecules by hydrogen bonds (H-bonds)
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2
Q

What are the differences between hydrophilic and hydrophobic substances?

A
  1. Hydrophilic substances are attracted to water
    - Polar substances
    - Can dissolve in water
  2. Hydrophobic substances are repelled by water
    - Non polar substances
    - Cannot dissolve in water
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3
Q

Describe water’s cohesive and adhesive properties.

A
  1. Cohesion
    - Water holds onto itself due to H-bonds
    - This allows some organisms to “walk” on water
  2. Adhesion
    - Water holds onto other (polar) substances due to its polarity
    - Together, adhesion and cohesion are both important in transpiration in plants (moving water from roots to leaves)
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4
Q

Describe water’s thermal properties.

A

Thermal properties (because of cohesion due to H-bonds)

a) It takes a lot of energy to change the temperature of water (= High “specific heat”)
- This makes water a good habitat (it does not change temp a lot)
b) Water makes a good coolant
- When water evaporates, the hottest molecules leave first
- So, sweating cools you down

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5
Q

Describe water’s solvent properties.

A

Solvent properties (because of polarity): It is attracted to other polar things and can dissolve them

  1. Blood is mostly water and can dissolve many things
    - Sugar, amino acids, minerals, oxygen, co2 are soluble
  2. Cytoplasm is mostly water
    - Enzymes (proteins) are mostly soluble
    - So, water is a good medium for metabolic reactions
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6
Q

What substances are transported in blood, and how are they transported?

A

Blood is mostly made of water

  • Small and polar substances can dissolve in water
  • As the blood moves, anything dissolved in it moves too
  1. Glucose, amino acids, oxygen, carbon dioxide, NaCl (salts) and minerals are soluble (small or polar)
    - Can dissolve in blood to be transported
  2. Fats and cholesterol are insoluble
    - They are put in lipoprotein complexes to be transported in blood
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7
Q

Compare the thermal properties of water and methane.

A

Methane vs. Water

  • Non-polar vs. Polar
  • Low boiling point vs. High boiling point
  • Low melting point vs. High melting point
  • Easy to change temp vs. Hard to change temp
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8
Q

What is a phospholipid, and what is its structure?

A

Phospholipids are the building blocks of membranes

  • Phospholipids are amphipathic
  • They have polar and non-polar parts

Phospholipids have two mains parts:

1) Polar phosphate head
- Hydrophilic = attracted to water
- On the outside of a bilayer
- Touching the water of the cytoplasm and the outside
2) Two non-polar fatty acid tails
- Hydrophobic = repels water
- On the inside of a bilayer

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9
Q

What are lipoprotein complexes?

A

Phospholipids in a ball make lipoprotein complexes

  • Phosphate heads on the out of the ball
  • Fatty acid tails are on the inside of the ball
  • Because inside is non-polar, body can put fats and cholesterol inside for transport
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10
Q

How are phospholipids in a membrane arranged?

A
  1. Phospholipids membranes form a bilayer
    - In a bilayer, phospholipids can move around but not flip sides
  2. The phospholipid bilayer is a fluid mosaic model
    - Fluid = Proteins can move around the membrane by sliding between phospholipids
    - Mosaic = The membrane is a mix of phospholipids, proteins, and cholesterol
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11
Q

Describe the proteins present in the phospholipid membrane, and their functions in the membrane.

A

Proteins in the membrane can be:

  1. Integral – Inside the membrane
  2. Peripheral – On the surface of the membrane (inside or outside the cell)

Proteins have many functions in the membrane:

1) Transport
- Channel proteins for facilitated diffusion
- Protein pumps for active transport
2) Receptors
- Receptor proteins to detect internal or external conditions
3) Anchorage
4) Carriers
- Electron carriers for photosynthesis and cell respiration
5) Identification
- Marker proteins (glycoprotein) that identify the cell
6) Enzymes

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12
Q

What is the function of cholesterol in the membrane?

A

Cholesterol maintains the stiffness of the membrane

- Cholesterol is amphoteric, but mainly stays in among the fatty acid tails

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13
Q

What is the Davson-Danielli model of the membrane?

A

This is an old model of the membrane which was disproven

  • No integral proteins in the membrane
  • A full layer of proteins above and below the membrane

Evidence for this model (was misinterpreted)
- Under the microscope they saw two black lines and thought they were proteins (actually phosphate heads in the bilayer)

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14
Q

What is the Singer- Nicolson model of the membrane?

A

This is the current accepted model of the cell membrane

  • Phospholipid bilayer where the phospholipid can move in their layer
  • Has integral and peripheral proteins

Evidence for this model:

  • We can now see integral proteins through microscopes
  • Experiment where two cells were merged, and their proteins mixed (showed that phospholipids move)
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15
Q

Why do materials need to move across the cell membrane?

A
  1. Homeostasis
  2. Excretion
  3. Nutrition
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16
Q

What are the definitions of:

  1. Concentration gradient
  2. Permeable?
A
  1. Concentration Gradient = Difference in concentration
    - Down the concentration gradient = from high to low concentration
    - Against the concentration gradient = from low to high concentration
  2. Permeable = allows substances through
    - Cell membrane is semi-permeable
    - Allows small and non-polar particles through, but nothing large or polar
17
Q

What are the 2 main types of transport across membranes?

A
  1. Passive transport: Particle move due to random molecular motion, so the cell does not use energy
    - Simple diffusion (membrane, high to low conc., small non polar particles)
    - Facilitated diffusion (channel, high to low conc.)
    - Osmosis (semi-permeable membrane, low to high solute conc., only water)
  2. Active Transport: Requires energy
    - Active pumping (pumps, low to high conc.)
    - Endocytosis (makes vesicle, particles enter)
    - Exocytosis (uses vesicle, particles exit)
18
Q

What are the 3 forms of passive transport?

A
  1. Diffusion = Movement of particles through the membrane from an area of higher concentration to an area of lower concentration
    - Particles can only diffuse across a cell membrane if they are small and have no charge
    - Examples) O2 and CO2
  2. Facilitated Diffusion = Movement of particles move through a channel protein by from an area of higher concentration to an area of lower concentration.
    - Allows bigger, polar molecules to go through membrane
    - Facilitated diffusion is faster than simple diffusion
    - Channels are specific for one type of particle
    - Examples) Sugars, amino acids, and salts
  3. Osmosis = movement of water through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration
19
Q

What is osmolarity?

A

Osmolarity = The concentration of solutes in a solvent

Solutions can be:

  1. Hypotonic = Has a lower solute concentration than cell
    - Makes cell inflate and burst
  2. Isotonic = Has the same concentration as the cell
    - Cells stay the same size
  3. Hypertonic = Has a higher solute concentration than cell
    - Makes cell deflate
20
Q

How do you determine the osmolarity of a tissue?

A

To determine the osmolarity of a tissue:

  1. Create solutions of different concentrations
  2. Place tissue samples in each solution
  3. Wait for a period of time (a day or more)
  4. Tissue samples will have the same solute concentration as the solution in which it does not change weight = isotonic
    - Tissue samples will lose weight in hypertonic solutions
    - Tissue samples will gain weight in hypotonic solutions
21
Q

What are the 2 forms of active transport?

A
  1. Active Pumping = Moving particles using protein pumps
    - Move particles from an area of lower concentration to an area of high concentration (against diffusion)
  2. Bulk transport = Moving things in vesicles
    a) Endocytosis (particles enter cytoplasm)
    - When the cell membrane pinches in, forming a vesicle around particles that enter the cell
    - New vesicle moves away from cell membrane into the cell
    - Cell gets a little smaller
    b) Exocytosis (particles exit cytoplasm)
    - When a vesicle moves towards the cell membrane and fuses with it, releasing particles outside the cell
    - Cell gets a little bigger
22
Q

Describe the process of exporting proteins in eukaryotes.

A

Exporting proteins in Eukaryotes:

1) Proteins are made by bound ribosomes in the RER
2) Proteins from RER are put in vesicles
3) Vesicles move to and fuse with Golgi apparatus
4) Golgi modifies the proteins
5) Golgi puts proteins in another labelled vesicle
6) Vesicle moves to membrane and fuses with it
7) Releasing proteins outside of cell by exocytosis

23
Q

Compare simple diffusion and facilitated diffusion.

A

Simple diffusion vs. Facilitated diffusion

  • Through membrane vs. Through channel proteins
  • Does not vs. Needs a channel protein
  • Small and nonpolar particles vs. Big and polar as well
  • Slow vs. Fast
  • Both go from high to low concentration
  • Both do not need energy / are passive
24
Q

Compare active pumping and facilitated diffusion.

A

Active pumping vs. Facilitated diffusion

  • Active vs. Passive
  • Pump proteins vs. Channel proteins
  • Low to high concentration vs. High to low concentration
  • Needs energy vs. Does not need energy
  • Both use proteins
25
Q

Compare endocytosis and exocytosis.

A

Endocytosis vs. Exocytosis

  • Particles enter the cell vs. Particles exit the cell
  • Cell gets smaller vs. Cell gets bigger
  • Vesicle is made vs. Vesicle is used up
  • Vesicle moves away from membrane vs. Vesicle moves towards from membrane
  • Both use vesicles
  • Both are active transport (use energy)

Cells - Transport 1 (Topic 1.1-11.3) (4 decks)

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