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What is the cytoplasm?◦ Cyto = “cell”◦ Plasma= “liquid substance of the cell”
Cytoplasm?◦ Clear, gelatinous fluid inside the cell
Let’s Recall
Cells need an inside & an outside…◦ separate cell from its environment
◦cell membrane is the boundary
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Cell (plasma) membrane
INfood- sugars- proteins- fats
saltsO2
H2O
OUTwaste- ammonia- salts- CO2
- H2O products- proteins
cell needs materials in & products or waste out
Why have a plasma membrane?◦ Allow nutrients to move in and out of the cell
How does it control how much goes in and out?◦ Selective permeability
Per= “through” Meare= “ to glide”
Therefore, what does it mean?
Plasma Membrane
How do you build a barrier that keeps the watery contents of the cell separate from the watery environment?
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Building a membrane
What substance do you know that doesn’t mix with water?
FATS
LIPIDS
Remember: oil & water don’t mix!!
Membrane is made of special kind of lipid ◦ phospholipids◦ “split personality”
Membrane is a double layer ◦ phospholipid bilayer
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Lipids of cell membrane
inside cell
outside cell
lipid
“repelled by water”
“attracted to water”
phosphate
Cell membrane controls what gets in or out Need to allow some materials — but not all
— to pass through the membrane ◦ semi-permeable
only some material can get in or out
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Semi-permeable membrane
aa H2Osugar lipids salt waste
So what needs to get across the membrane?
O2
What molecules can get through the cell membrane directly?◦ fats and oils can pass directly through
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Crossing the cell membrane
inside cell
outside cell
lipid
salt
aa H2Osugar
waste
but…what about other stuff?
Need to make “doors” through membrane ◦ protein channels allow substances in & out
specific channels allow specific material in & out H2O channel, salt channel, sugar channel, etc.
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Cell membrane channels
inside cell
outside cell
sugaraaH2O
saltwaste
Channels are made of proteins◦ proteins both “like” water & “like” lipids
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How do you build a semi-permeable cell membrane?
bi-lipidmembrane
protein channelsin bi-lipid membrane
Proteins act as doors in the membrane◦ channels to move specific molecules through cell
membrane
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Protein channels
HIGH
LOW
Protein Channels
Integral Proteins Peripheral Proteins
Embedded all the way through the bilayer
Allow ions to pass through the membrane
Bond to only one side of the membrane
Attach to or near integral proteins
Help with ion identification
Other Key Players
Cholesterol Glycolipid and Glycoprotein
Cell signaling Maintains membrane
fluidity Secures Proteins
Lipid or Protein with a carbohydrate attached
Provide energy Cellular recognition
Why do molecules move through membrane if you give them a channel?
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Movement through the channel
?
?
HIGH
LOW