Chapter 2 - Cells and Organelles Flashcards
cell membranes contain three main things:
phospholipids, proteins, cholesterol
Membrane proteins come in two types:
integral (transmembrane) and peripheral
True or false: peripheral membrane proteins extend throughout the entire bilayer
False - only on the periphery, generally hydrophilic
Transmembrane protein function
- transport proteins
2. receptor proteins
transport proteins
move large, polar molecules across the cell membrane since they cannot freely diffuse by themselves
examples of peripheral membrane proteins
adhesion proteins, cellular recognition proteins, receptor proteins
adhesion protein function
attach adjacent cells to other things (like other cells) and they also act as anchors for the cytoskeleton
cellular recognition proteins
peripheral membrane proteins that help cells recognize each other; usuallyt interact with receptor protein; attach to glycoproteins
receptor proteins
receive chemical signals from the extracellular environment that do not need to be transmitted inside the cell
agonist
ligands that bind to a receptor and activate its response
antagonist
ligands that bind to a receptor and prevent it from activating
what kind of molecules can travel directly across the phospholipid bilayer?
small, uncharged nonpolar molecules. ex co2 and o2
simple diffusion
flow of substances down their concentration gradient, does not consume energy. does not use proteins to help particles across membrane
what kind of molecules cannot travel directly across the bilayer?
large hydrophilic molecules
facilitated transport
describes how large, hydrophilic molecules travel across the bilayer through transmembrane proteins (usually uniport, moving in 1 direction)
symport
transmembrane protein that helps several molecules moving in 1 direction
antiport
several molecules moving in opposite directions
symport and antiport are examples of :
secondary active transport
channel proteins
face extra and intracellular of the cell at the same time, usually allow the passage of many small, polar molecules and ions
carrier proteins
change their shape to facilitate the movement of molecules through the protein
porins
channel protein used in passive diffusion because they are usually not specific for just one type of molecule
porins usually allow any ____ molecule that fits to pass through
hydrophilic
aquaporin
type of porin found in kidney and plant roots, allow water to flow more rapidly than is possible through simple diffusion alone
active transport
occurs when particles travel against their concentration gradient and requires energy input
primary active transport
uses the energy released from ATP hydrolysis to pump molecules against their concentration gradient.
example of primary active transport
sodium-potassium (Na+/K+) pump (hydrolyzes ATP)
The sodium potassium pump consumes _ ATP to pump (out/in) _ Na+ and pump (out/in) _ K+
1 ATP; 3 out Na+; 2 in K+
Na+/K+ pump is known as:
an ATPase since it hydrolyzes ATP to pump Na⁺ and K⁺ against their concentration gradients by primary active transport.
secondary active transport
uses energy obtained from a source other than ATP; usually comes from free energy released as other molecules spontaneously flow down their concentration gradients
cytosis
facilitates bulk transport of large, polar (hydrophilic) molecules
2 main types of cytosis
endocytosis; exocytosis
true or false: endocytosis and exocytosis require energy input
true - they are active transport mechanisms
phagocytosis
cell engulfs undissolved materials
pinocytosis
“cellular drinking” - cell will invaginate to engulf dissolved materials (liquids)
receptor-mediated endocytosis
occurs when specific ligand binds to peripheral membrane receptor protein, recruits clathrin
exocytosis is an essential part of ___ ___ from the ____ ____
vesicle secretion; golgi apparatus
nuclear envelope
sets the borders of a eukaryotic nucleus
true or false: nuclear envelope has 1 membrane
false - 2 membranes. 2 phospholipid bilayers (one inner, one outer)
area between outer and inner membrane of nuclear envelope
perinuclear space
nuclear pores
holes in the nuclear envelope; mRNA exits through nuclear pores
what is the nuclear lamina
dense and fibrous network of proteins associated with the inner membrane of the nuclear envelope
nuclear lamina function
provides structural support to the nucleus, also regulated DNA organization, DNA replication, and cell division
nucleolus
dense region within the nucleus where rRNA is produced, site of production of ribosomal subunits
ribosomal subunits contain:
proteins and rRNA
when do ribosomal subunits assemble?
when they are floating in nucleoplasm (exited nucleolus)
when do ribosomal subunits assemble into a complete ribosome?
once in the cytosol
true or false: ribosomes are organelles
false (do not contain a membrane)
eukaryotic ribosome subunits
40S and 60S (assemble into 80S)
typical manipulation to proteins in the rough ER
glycosylation
role of smooth ER
synthesize lipids, steroid hormones, detoxify cells, store ions in some cases
example of cells that contain lot of smooth ER
human liver cells (heavily involved with detoxification)
glycoproteins from the rough ER can undergo ____ in the golgi complex
phosphorylation
