BIOL 108 Lecture Notes - Lecture 4: Lipid Bilayer, Passive Transport, Facilitated Diffusion

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29 Sep 2017

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Cells must import nutrients and export wastes. The cell membrane is (cid:862)se(cid:373)iper(cid:373)ea(cid:271)le. (cid:863) it controls the passage of substances in and out of the cell. The means used to move substances across membranes depends on two factors: the chemical nature of the solute (hydrophilic or hydrophobic), the relative concentrations of the solute on the two sides of the membrane (the concentration gradient). A phospholipid bilayer is the base fabric of all biological membranes. The hydrophilic (cid:862)heads(cid:863) of the phospholipids face out toward the aqueous surroundings, and the h(cid:455)dropho(cid:271)i(cid:272) (cid:862)tails(cid:863) face in, forming the core of the membrane. Many proteins are also embedded in membranes, and may function as: transport proteins, receptors, enzymes. Again, the means of transport of a molecule or ion depends on two factors: the chemical nature of the molecule/ion. The hydrocarbon core of the phospholipid bilayer (cid:894)the (cid:862)tails(cid:863)(cid:895: allows direct passage of small hydrophobic species, for example o2, co2.

Related Questions

1,Match the descriptions to the type of transport.

- A. B. C.	Water enters a cell because it is hypertonic compared to the extracellular environment, increasing its turgor pressure
- A. B. C.	Water enters guard cells because the guard cells are hypertonic compared to the surrounding cells
- A. B. C.	Potassium ions are pumped into guard cells
- A. B. C.	The motor cells of a Venus fly trap are hypotonic compared to surrounding cells, causing water to leave the motor cells
- A. B. C.	Sugar is loaded into the phloem

A.	Both active and passive transport
B.	Passive Transport
C.	Active transport

2,Describe what is wrong with the following statement and explain why:

All prokaryotic and eukaryotic cells contain plasma membrane, nucleus, ribosomes, organelles, cytoplasm, and cell walls.

What is short-distance transport?

	a,	The movement of solutes from a region of low concentration to a region of high concentration
		b,The movement of water, nutrients, and other substances between cells
c,		The movement of substances from a region of high concentration to a region of low concentration
d,		The movement of water across a semipermeable membrane from a region of low solute concentration to a region of high solute concentration.

What terms describe the movement of water across a semipermeable membrane from a region of high water concentration towards a region of low water concentration (and high solute concentration.)

What is found in the proptoplasm?

Cell wall, cytoplasm, plasma membrane, nucleus, and other cell organelles

Plasmodesmata, cell wall, and plasma membrane

Cell wall, cytoplasm, and plasma membrane

Cytoplasm, nucleus, and other cell organelles

The channels that allow nutrients and protoplasm to pass between plant cells are called _________________.

What happens when a plant cell is placed in a hypotonic solution?

Water will enter the plant cell and the plasma membrane will swell and cell lysis will occur

Water will leave the plant cell and the plasma membrane will pull away from the cell and plasmolysis will occur

Water will enter the plant cell and the plasma membrane will swell and push against the cell wall

Water will leave the plant cell and the plant cell will lose turgor pressure, causing the plant to wilt

________________ transport uses cellular energy.

What molecules make plasma cell membranes hydrophilic on the outside and hydrophobic on the inside?

What type of cells do plants have?

		Bacterial
		Archaeic
		Eukaryotic
		Prokaryotic

Hybridomas are the useful result of a fusion between _______________ and _________________ to obtain hybrid cells that can proliferate and produce _________________ against specific ________________.

	myeloma cells; B lymphocytes; monoclonal antibodies; epitopes
	myeloma cells; T lymphocytes; polyclonal antibodies; antigen
	T lymphocytes; B lymphocytes; monoclonal antibodies; antigen
	T lymphocytes; B lymphocytes; polyclonal antibodies; epitopes

With respect to mammalian cell culture, which of the following statements is true?

	Media used for cell growth contain proteases and a divalent cation chelator to help cells adhere to the surface.
	During the establishment of a cell line, senescence is the last stage of the cell's life.
	Rodent cells cultures undergo spontaneous transformation with similar frequency to human cell cultures.
	Embryonic cell lines do not undergo senescence nor do they have a finite life span.

Epithelial cells have distinct surfaces. Which of these surfaces tends to be involved in secreting proteins out of the cell and into the bloodstream?

	apical
	basal
	All of the answers are correct.
	lateral

Which of the following is NOT true of phospholipid bilayers?

		Phospholipid bilayers separate the cell from the exterior environment as well as from compartments within the cell.
		The interior of phospholipid bilayers is a highly hydrophobic environment.
		Membrane budding requires transient breakages in the bilayer membrane.
		The chemical properties of phospholipids lead to the spontaneous formation of bilayers.

Which of the following is true regarding membrane proteins?

		All peripheral membrane proteins contact the lipid bilayer by covalent attachment to the hydrophilic head groups on membrane lipids.
		Beta strands can assemble into a membrane-spanning barrel structure.
		Lipid-anchored membrane proteins always face the cell exterior.
		A protein with six hydrophobic helices is most likely a lipid-anchored membrane protein.

Which of the following statements is NOT true?

		The three types of lipid anchors responsible for tethering proteins to the bilayer are acylation, prenylation, and ubiquitinylation.
		Movement of lipids from the cytoplasmic to the exoplasmic leaflet of the membrane bilayer requires specialized transport proteins called flippases.
		Glycoproteins are the basis for blood type compatibility between donor and receiver.
		Glycoproteins are always oriented so that the carbohydrate moieties are exoplasmic.

Explain the cell theory; know the three basic tenets of the theory.

All cells have to carry out certain functions, what do all cells have in common?

Compare/contrast an Eukaryotic vs a Prokaryotic cell type.

Understand the concept of selective toxicity. What do all effective targets of an antimicrobial agent have in common? What are some characteristics of Prokaryotic cells that can be targeted?

Explain the unity and diversity of prokaryotic cells in terms of evolutionary theories.

Describe the three basic shapes (morphologies) of bacteria.

What are the functions of the plasma membrane, how does the structure of the plasma membrane aid in carrying out these functions?

Describe the fluid mosaic model of the plasma membrane. Draw out the plasma membrane, include the phospholipid bilayer (indicating polar/hydrophilic and nonpolar/hydrophobic components) and peripheral and integral proteins. Also indicate the intracellular (cytoplasmic) and extracellular regions.

What are the functions of the components of the plasma membrane? Phospholipids, proteins?

Transport. Compare/contrast the following mechanisms of transport in terms of the types of molecules transported, with or against the concentration gradient, if any Energy input is required, if a transport molecule is involved, and if Euk and or Prok use this mechanism.

Osmosis (explain the role of aquaporins)

Diffusion

Facilitated Diffusion

Active transport (proton motive force / ATP binding cassette system)

Group translocation

BIOL 108 Lecture Notes - Lecture 4: Lipid Bilayer, Passive Transport, Facilitated Diffusion

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