BIOL1004 Study Guide - Final Guide: Membrane Fluidity, Saturated Fat, Red Blood Cell

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Membrane structure and function

Cell membrane

• Cells plasma membrane seperates internal cell functions from the

exterior

• Selectively permeable

• Eukaryotic cells contain membrane bound compartments

• fluid mosaic of lipids and proteins

Phospholipids

• Amphipathic molecules (hydrophilic head, hydrophobic tail)

• Hydrophilic region: glycerol and an additional charged group

• Hydrophobic region: fatty acid

• Spontaneously form bilayers

o To minimise exposure of hydrophobic tails to water molecules and

maximise exposure of hydrophilic heads

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Membrane fluidity

• Membranes need to be fluid to work properly → branch like in structure (like

olive oil)

• Phospholipids can move within the bilayer and spin around their long axis

• Most lipids and some proteins diffuse laterally in the bilayer

• It is very rare for a lipid to flip across a bilayer → the hydrophilic head has to

move through the hydrophobic tails and the water molecules have to be ripped

off the head

• Membranes rich in saturated fat are more fluid than those rich in unsaturated

fat

• At cool temperatures membranes can switch to a solid state

Cholesterol

• Animal membranes contain the steroid cholesterol

• At warm temperatures → restrains movement of phospholipids

• Cool temperatures maintains fluidity by preventing tight packaging

Phospholipidbilayers

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Document Summary

Cell membrane: cell(cid:495)s plasma membrane seperates internal cell functions from the (cid:494)fluid mosaic(cid:495) of lipids and proteins, selectively permeable, eukaryotic cells contain membrane bound compartments exterior. Phospholipids: amphipathic molecules (hydrophilic head, hydrophobic tail, hydrophilic region: glycerol and an additional charged group, hydrophobic region: fatty acid, spontaneously form bilayers, to minimise exposure of hydrophobic tails to water molecules and maximise exposure of hydrophilic heads. Cholesterol: animal membranes contain the steroid cholesterol, at warm temperatures restrains movement of phospholipids, cool temperatures maintains fluidity by preventing tight packaging. Channels: contain a pore through which solutes can diffuse, opening/closure is tightly regulated by specific signals. Carriers: recognize and bind to specific solutes carry them across membrane. Diffusion through lipid bilayer: most biological molecules and ions do not pass through the membrane easily, some drugs pass through easily. Involves: partitioning from water molecules into oily membrane interior partitioning out on the other side of the membrane (must be hydrophobic)

Related Questions

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.

BIOL1004 Study Guide - Final Guide: Membrane Fluidity, Saturated Fat, Red Blood Cell

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