BABS1201 Lecture 5: 5. Nutrient and Ion Transport

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rubysalmon926

28 May 2018

School

UNSW, UNSW Sydney

Department

Biotechnology & Biomolecular Sciences

Course

BABS1201

Professor

All

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Nutrient and Ion Transport

Phospholipid bilayer - impermeable to most molecules

proteins play an important role in transport across membrane

TRANSPORTING MOLECULES INTO CELLS

Passive transport - does not require energy

o Requires a concentration gradient

o Creates a net transport of molecules into the cell

• Diffusion

• Facilitated diffusion

o Uses integral proteins to help molecules diffuse down a concentration gradient

o Creates an environment which molecules can diffuse

• Channels - creates holes in the membrane

▪ Consists of many subunits

▪ Is specific to a particular molecule (e.g. Sodium - potassium pumps)

▪ Allows a direct passage from one side of the membrane to the other side of the membrane

▪ Selective - allows the cell to take up and retain the molecules it needs and exclude what is

unwanted

• Water can diffuse across the membrane - but only very slowly because it is polar

• Aquaporins - specific proteins for water

• Faster than carrier proteins

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•

• Carrier proteins - transporters

▪ Alternates between two shapes

▪ Binds to the molecule they transport, changes conformation then releases the molecule

▪ Specific to substrate

• Transport is slower than through channels

▪

• Gated channels - may require another type of molecule to be bound to a specific site before

they function

▪ Neuron transmitters - bind to the channel, opens and allows the movement of molecules -

then closes

▪ Responds to external stimuli

▪

Active transport - requires energy (ATP)

• Maintains the concentration gradient

• Transport is directional and irreversible

• Usually works against the concentration gradient

o Cotransport - transports two molecules simultaneously

o Exchange transporters - transports in both directions

• The energy released by ATP hydrolysis allows transport against concentration gradient

Electrogenic pumps

o Transports one type of ions

▪ Proton pump

• Gives active H+ transport

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Document Summary

Phospholipid bilayer - impermeable to most molecules proteins play an important role in transport across membrane. Passive transport - does not require energy: requires a concentration gradient, creates a net transport of molecules into the cell, diffusion. Cotransport (plants: transports sucrose against the concentration gradient, proton pump - gives active h+ transport, the return of h+ to the cytosol down a concentration gradient drives the uptake of sucrose. Indirect active transport of sucrose: enzymes hydrolysed macromolecules to monomers in the digestive tract, monomers are taken up by cells in the small intestine using both passive and active transport proteins. Is the voltage difference across a membrane: voltage - created by differences in the distribution of positive and negative ions. Neurons (transmission and transport: neurons - transmits signals over long distances to activate other cells, works by de-polarising their membranes, uses the concentration of na+ and k+ ions, na+ - high outside membrane, k+ - low outside membrane.

Related Questions

Read the following scenarios and indicate which of the following processes they describe.

11. Sodium molecules move randomly around a solution of sodium chloride in water, frequently colliding with other sodium ions and chloride ions. secondary active transport diffusion osmosis facilitated diffusion primary active transport

12. Sodium ions (Na+) move through sodium channels in a synthetic membrane. primary active transport secondary active transport facilitated diffusion osmosis

13. Water molecules move into the cytosol of a cell placed in a hypotonic solution. primary active transport secondary active transport facilitated diffusion osmosis

14. Water molecules move into the cytosol of a cell placed in pure water. facilitated diffusion osmosis secondary active transport primary active transport

15. Water molecules move out of a cell placed in a hypertonic solution. facilitated diffusion primary active transport secondary active transport osmosis

16. The action of sodium-potassium pumps moves sodium ions (Na+) out of a cell and potassium ions (K+) into a cell. facilitated diffusion secondary active transport osmosis primary active transport

17. Glucose molecules move into cells lining the intestine against their concentration gradient driven by the movement of sodium ions (Na+) into the cells down their concentration gradient. osmosis secondary active transport primary active transport facilitated diffusion

18. A beaker of water is separated by a selectively permeable membrane that allows the passage of water but not ions. A solution of 4% sodium chloride (NaCl) is placed on one side of the membrane and pure water is placed on the other side of the membrane. The solutions are allowed to equilibrate. At this point, which process is going on? facilitated diffusion osmosis secondary active transport primary active transport

amaranthelk944

1 Which of the following statements is false?

(a) CO₂ and O₂ can diffuse freely across the cell membranes.

(b) The differences in permeability between artificial lipid bilayers and cell membranes arise from variations in phospholipid content.

(d) Cells expend energy in the form of ATP hydrolysis to maintain ion concentrations that differ from those found outside the cell.

2 Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell?

(a) Na⁺

(b) K⁺

(d) Cl^â

3 Pumps are transporters that are able to harness energy provided by other components in the cells and drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________.

(a) active transport.

(b) free diffusion.

(d) passive transport.

harlequinbuffalo618

3. In an aqueous environment, the phospholipids of a membrane____.

a) are arranged in a single layer

b) are arranged in a bilayer with the polar heads of each layerlocated at the surface

c) are arranged in a bilayer with the fatty acid tails locatedat the surface

d) are arranged in a bilayer but the phospholipids have nospecific orientation

e) dissolve

4. which of the following molecules demonstrate dual solubilitycharacteristics

a) sterols only

b) proteins only

c) phospholipids only

d) sterols and phospholipids

e) sterols, phospholipids, and proteins

5. The "mosaic" part of the fluid mosaic model refers to themembrane ____.

a) proteins

b) phospholipids

c) cholesterol

d) functions

e) layers

9. Transport of a molecule across a cell membrane by facilitateddiffusion ____.

a) does not exhibit specificity for a particular type ofmolecule

b) requires the input of energy

c) depends on a concentration gradient

d) goes against the concentration gradient

e) allows non-polar uncharged molecules to diffuse across amembrane

13. A transport system in which transport of an ion in onedirection provides the energy for active transport in the oppositedirection is known as ____.

a) primary active transport

b) active diffusion

c) secondary active transport

d) cotransport

e) osmosis

14. Cells undergo exocytosis ____.

a) to pump protons down a concentration gradient

b) when replicating

c) to secrete protein and wastes from the cell

d) to ingest nutrients

e) as a means of cellular protection

15. What is the molecular basis of familialhypercholestremia?

a) HDL enters cells using a specific receptor on the cellsurface

b) LDL enters cells using a specific receptor on the cellsurface

c) HDL exits cells using a specific receptor on the cellsurface

d) LDL exits cells using a specific receptor on the cellsurface

e) receptor-mediated exocytosis

16. Carrier molecules are utilized for ____.

a) active transport only

b) passive transport only

c) both active and passive transport

d) osmosis

e) transport of all types of molecules

17. All of the following are functions of integral membraneproteins EXCEPT ____.

a) transport of polar molecules

b) reception of chemical signals form other cells

c) cell division

d) recognition of other cells as being "like"

e) cell-cell binding

olivecod348

BABS1201 Lecture 5: 5. Nutrient and Ion Transport

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