Cell Membrane Flashcards by Marina Garlick

What is Homeostasis?

a constat stae is maintained

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What are the other functions of the cell membrane (minus being semi-permeable)? (3)

provides structual support
recognized foregin materials
communicate with the cells

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What is the lipid bi-layer

the phospholipid’s orgainized ontotowo layers with the hydrophobic tias int eh center and the hydrophilic head facing into and out of the cell.

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What can pass throug the bi-layer? Why?

small and non polar molecules

Becaue the hydropobic tais will repel any polar substance.

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What are the four types of membrane proteins?

cell recognition: identifys the cell as “self”
receptor: receives signals from surroungings
enzymatic: helps with biochemical relations
transport: moves substances in and out of cell

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What is a Membrane Protein?

A prtein that interacs with or ar a part of biological memebranes

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What are the two types of transport proteins?

channel-specific particles or ions move freely in or out of the cell
carrier - selective interacts with only certain molecules.

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What does permeability mean?

movement across the cell membrane

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What is a concentration gradient?

one area has a higher concentration than another

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What is diffusion?

movement of a substance down their concentration gradient

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What is equilibrium?

balanced on both sides

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What is Passive Transport?

no energy required aka diffusion

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What are the two types of passive transport? explain.

facilitated diffusion: movement through channel proteins down a concentration gradient.
osmosis: water diffusing across the cell membrane (need channel protein.)

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What is Hypertonic?

low concerntration of water outside of the cell and a higher concentration of solute.

So water moves out of the cell causing it to shrink

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What is Hypotonic?

a high concentration of water outside of the cell and a lower concentration of solute.

So water moves in of the cell causing it to swell

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What is Isotonic?

equal solute concentration and water moves in and out at equal rates.

What is active transport?

when a substance moves against its concentration gradient. this required a carrier protein and ATP

What do carrier proteins act as?

pumps

What are vesicles?

they import and export very large molecules that can’t cross the cell membrane.

What are the types of vesicles?

exocytosis
entocytosis
- phagocytosis
- pinocytosis

What is exocytosis?

secretion
vesicles fuse to the cell membrane and then releases their particles
thereby extending the cell wall

What is endocytosis?

a portion of the cell membrane pinches off to format vesicle

What is phagocytosis?

large substances like viruses or white blood cells

What is pinocytosis?

liquid of small substances

- loss of membrane balanced by exocytosis

What is receptor-mediated endocytosis?

molecules must bind to specific receptor proteins in order for vesicles to for and enter the cell.

What are the two purposes of DNA replication?

- growth | - repair

What are the four important enzymes in DNA replication? What are their functions?

- DNA helicase: unzips parent strand - DNA primase: creates a stating spot for polymerase - DNA polymerase: bonds new nucleotides - DNA ligase: contents Okazaki fragments and proof reads.

What is semi-conservative replication?

each daughter strand contains one new strand and one parent strand.

Which way do enzymes work? (regarding DNA) | How does this relate to Okazaki fragments

5' to 3' - the primase has to connect in several spots so the polymerase can work 5' to 3' even though the lagging strand's new chain is 3' to 5'

Describe what the cell growth cycle looks like.

- growth one - rest/ chcekpoint (if the cell is not working properly the cell will be told to commit suicide) - growth two - rest/ checkpoint two - prophase - mitosis (PMATC)

What is a Gene?

a segment of DNA that specifies the amino acid sequence of a polypeptide

Is DNA directly in control of protein synthesis? Explain.

No. its code is copied into RNA and then taken out of the nucleus.

What are the three classes of RNA? What are their functions?

- mRNA: takes a message from DNA to the ribosomes - rRNA: makes up ribosomes (along with proteins) mRNA slots into it. - tRNA: carries amino acid to ribosomes.

What is Transcription?

making mRNA from a segment of DNA (in the nucleus)

In Transcription what are the strands involved called?

- sense strand: the strand being used as a template | - non-sense strand: the strand of DNA not being used.

What are the steps in Transcription?

- RNA polymerase binds and unwinds the DNA strand - DNA helix is opened so complementary base pairing can occur - RNA polymerase joins new RNA nucleotides in a sequence complementary to the sense strand of the DNA - creates mRNA