Cell Organelles, Fluid Mosaic Model & Membrane Transport Flashcards
membrane-enclosed sacs that contain DIGESTIVE enzymes which catalyze hydrolysis reactions and break down macromolecules
lysosomes
Whats a carrier protein
a protein that selectively interacts with specific molecules or ions so it can cross the membrane
ex. sodium and potassium pump
Describe the structure of a phospholipid
hydrophilic head (polar) and hydrophobic tails (non-polar)
- the polar heads love water & dissolve
- the non-polar tails hide from water
what is chlorophyll
the photosynthetic pigment found in thylakoids which absorb light energy and use it to convert carbon dioxide and water into energy-rich molecules through redox reactions
what is passive transport
transport/movement which requires NO energy (ATP) to move substances across cell membranes
~ (goes from high concentration to low concentration without any energy)
How does the cell membrane move?
- a membrane is held together by weak hydrophobic interactions between the carbon-hydrogen chains
- most membrane lipids and some proteins drift LATERALLY (side to side)
- molecules rarely flip transversely (flip flop) across the membrane as hydrophilic parts would have to cross the membrane hydrophobic core
a double membrane structure comprised of two phospholipid bilayers that surrounds the nucleus
nuclear envelope
What is plasmolysis?
when a plant in a hypertonic environment goes through water loss, leading the plant to shrivel and its cell membrane to pull away from the cell wall
membrane-bound sacs that contain OXIDATIVE enzymes which break down additional fatty acids and hydrogen peroxide
peroxisomes
What molecules/ions are transported by each transport?
Passive Transport: glucose, amino acids, ions (Na, Ca, etc.)
Primary Active Transport: metal ions (Na, Mg, Ca, etc.)
Secondary Active Transport: sodium ions (ex. sodium-glucose, sodium-amino acid, etc.)
what is active transport
transport from lower concentration to higher concentration which REQUIRES energy (ATP) to move molecules against a concentration gradient
~ particles bind to transport proteins that use ATP to pump them across the membrane (the loss of a phosphate group from ATP to form ADP produces a lot of energy which the cell uses)
Whats the function of the cell membrane
- controls what enters and exits the cell to maintain a balance called homeostasis
- provides protection and support for the cell
- is selectively permeable (allows some molecules in and keeps others out)
What is exocytosis
used to export, or remove large molecules from the cell
~ first, the material is surrounded at the golgi complex making a vesicle
~ next, the vesicle moves to the cell membrane and is expelled
~ ex. pancreas cells make insulin which is dumped into the blood stream
captures light energy from the Sun and stores it in the form of high-energy organic molecules like glucose
chloroplasts
what is the cytoskeleton
the internal network of protein fibers found throughout the cytoplasm which provide structure, shape, support and mobility; also anchors some organelles in place
What happens if the cell membrane is too fluid?
the bilayer permits too many molecules to diffuse across
What is isotonic?
- solutions of equal solute concentration on both sides of the membrane
- no net movement as an equilibrium is reached (ISOS = equal)
What is endocytosis?
used to move large molecules INTO the cell (endo - to enter)
~ material comes to the outside of the cell membrane, the membrane surrounds the material, and then pinches off inside the cell forming a vesicle; this vesicle travels to its final destination
What’s an enzymatic protein
a protein that catalyzes specific reactions (eg. ATP metabolism)
What are the two types of proteins present in cell membranes
1) Integral proteins: span through the bilayer
2) Peripheral proteins: attached to the outer surface
Both of these proteins act to transport molecules
What is diffusion
movement of particles from an area of high concentration to low concentration
~ they reach a dynamic equilibrium
Why is fluidity so important?
to maintain the transport of molecules into and out of the cell
a non-membrane bound structure located within the nucleus that contains RNA, proteins, and chromatin
nucleolus
breaks down high-energy organic molecules and converts stored energy into usable energy; stores released energy for later cell use as well
mitochondria
what are cilia and flagella
appendages that form on the outside of some eukaryotic cells
flagella - one or two longer appendages (like tails; their whip-like movement propels cells)
cilia - shorter appendages (wave-like motion enables the organism to move)
What is tonicity?
the capability of a solution to alter the water content of cells
~ there are 3 outcomes, depending on the solute content of the solution
~ water will diffuse across the membrane in response to establish equilibrium
How does temperature affect fluidity of the cell membrane?
- increasing temperature increases the fluidity of the membrane
- decreasing temperature causes the bilayer to solidify into a gel as the phospholipids pack closer together (solidification causes enzyme deactivation)
What is the function of peripheral proteins?
- involved in cell signaling
- allows the transmission of molecular signals from the cell’s exterior to the interior to initiate a response
- transports molecules & may easily dissociate from the membrane
What’s a channel protein
a protein that allows a substance to move across the membrane
ex. aquaporins allow water to easily diffuse across
What is a proton pump? How does it work?
- ATP is used to transport proteins AGAINST the concentration gradient
- A proton concentration gradient is established across the cell membrane (more charge outside the cell compared to the inside)
- This gradient stores energy (like a battery) for later use; important in cell respiration and photosynthesis
What is the effect of hypotonic and isotonic environments on plant cells?
- most plant cells thrive in a hypotonic environment when the cell wall is turgid and the vacuole is full
- in an isotonic environment, plants become wilted
What’s the main idea of a Sodium/Potassium pump? (“products”)
3 sodiums are released outside; 2 potassiums are released inside
what is facilitated diffusion
when large or hydrophilic molecules are allowed to diffuse through the cell membrane by specialized transport proteins:
~ Channel proteins (hydrophilic)
~ Carrier proteins (specific to a certain solute such as glucose or amino acids; change shape to allow passage)
What is secondary active transport
- indirect use of ATP
- energy is derived secondarily from energy that has been stored in an electrochemical gradient
~ this energy is used to transport a solute by facilitated diffusion from high to low concentration
ex. hydrogen-sucrose pump
what is turger pressure
the force within a cell that pushes the cell membrane against the cell wall
What is osmoregulation? Who uses it?
osmoregulation is the control of water balance
~ animals use this when they are exposed to hypertonic and hypotonic environments for survival
ex. freshwater fish that live in hypotonic environments use their kidneys and gills to prevent excess water buildup in the body
How does the chemistry of fatty acid tails affect fluidity of the cell membrane?
- UNSATURATED hydrocarbon tails increase membrane fluidity because kinks at the carbon-to-carbon double bonds hinder/delay the close packing of phospholipids
- cells may alter membrane lipid concentration in response to changes in temperature
What happens if the cell membrane is not fluid enough?
the bilayer restricts the movement of molecules across
what is primary active transport
- direct use of ATP
- moves ions to establish a concentration gradient between the inside and outside of the cell membrane
- the difference in change results in a voltage (potential difference) across the membrane; this difference is called ELECTROCHEMICAL GRADIENT
what are intermediate filaments
form the internal scaffolding of the nucleus, anchor some organelles, maintain cell shape
INTERMEDIATE THICKNESS
What is cotransport
when active transport of one solute indirectly drives the transport of another
membrane-enclosed sacs that transport and store proteins and other molecules
vesicles
a rigid layer which surrounds a plant, algae, fungal, bacterial and some archaea cells. providing structural support, protection and shape
cell wall
What is osmosis
the passive transport of water across a semi-permeable membrane
~ water moves from higher concentration to lower concentration of H20 OR from lower to higher concentration of dissolved solute (towards the solute because there’s less water there)
a thick fluid that fills the nucleus and helps maintain its shape and function
nucleoplasm
a group of proteins which form openings in the nuclear envelope
nuclear pore complex
What is hypertonic?
- more dissolved solute outside the cell than inside the cell (hyper = above)
- net movement of water out of the cell
Animal = CRENATION
Plant = PLASMOLYSIS
How does the presence of cholesterol affect fluidity of the cell membrane?
- at higher temperatures, cholesterol INCREASES intramolecular forces and holds it more tightly, which REDUCES/DECREASES fluidity
- at lower temperatures, cholesterol molecules PREVENT the close packing of phospholipids into a gel, which INCREASES fluidity
Describe the structure of the cell membrane
- a fluid mosaic (combination of different parts) made up of lipids, proteins, and carbohydrates
- protein molecules are “bobbing” in a fluid bilayer of phospholipids
- carbohydrate marks are present on the surface to identify cell type
What is the endomembrane system? What organelles does it include?
a system within a cell that helps synthesize, modify, and transport cell products and proteins
includes the endoplasmic reticulum, golgi apparatus, vesicles, and the cell membrane
What are some factors that affect fluidity?
Temperature
Chemistry of Fatty acid tails
Presence of cholesterol
Why are proteins the perfect molecules to build structures in the cell membrane?
- protein side chains act as anchors
- within membrane proteins there are:
~ nonpolar amino acids (hydrophobic; anchors proteins into membrane) - on the outer surfaces of membrane:
~ polar amino acids (hydrophilic; extends into extracellular fluid & into cytosol)
What is receptor-mediated endocytosis?
membrane proteins lock onto specific molecules and bring these into the cell
~ ex. insulin
What is hypotonic?
- solution with a lower solute concentration and a higher water concentration
- net movement of water into the cell
- hypo = below
Animal = LYSING
Plant = TURGID
What is bulk vesicle transport
- used to transport larger particles (which cannot fit through an integral protein) into, or out of the cell
~ ex. proteins and polysaccharides - involves rearrangement of the cell membrane into vesicles to get molecules across
a network of protein fibres that provide the nucleus with its internal structure and support
nuclear matrix
Describe the structure of the phospholipid bilayer
phospholipids in the cell membrane are arranged in two layers forming the phospholipid bilayer
~ it has a bimolecular lipid layer that contains proteins
How does the sodium-potassium pump work?
- the pump transports sodium ions out of the cell while transporting potassium ions into the cell
- when the 3 sodiums bind to the pump, a phosphate from ATP also binds which changes the shape of the protein and causes it to face the opposite side (towards the outside)
- after the sodiums are released outside the cell, 2 potassiums bind to the protein/pump, the phosphate that was binded before gets released, and the protein returns back to its original shape
~ the pump then releases both the potassiums into the cell
what are the two types of endocytosis? explain each
1) Pinocytosis (cell drinking): transport of liquids INTO the cell
2) Phagocytosis (cell eating): transport of large molecules/cells INTO the cell
~ ex. macrophages (white blood cells that fight infection by engulfing bacterial cells)
what are microtubules
assist in cell division (spindle formation), maintain cell structure, facilitate movement of organelles
THICKEST FIBRES
What are the different integral proteins?
Channel Protein
Carrier Protein
Cell Recognition Protein
Receptor Protein
Enzymatic Protein
what are microfilaments
assist in cell division (cleavage furrow), involved in muscle contraction, maintain cell shape
THINNEST FIBRES
membrane-bound organelles that store water, ions, sugars, amino acids, and macromolecules
vacuoles
What is a concentration gradient?
a difference between the concentration on the inside of the membrane and the concentration on the outside of the membrane
What’s a receptor protein
a protein that is specifically shaped to a specific molecule
eg. liver stores glucose after insulin binds to cell receptor
a stack of curved membrane sacs that packages, sorts, and distributes substances like proteins and lipids within the cell
golgi apparatus
What happens to cells when the cell membrane does not function properly
the cell’s cellular processes fails which leads to cell death
Whats a cell recognition protein
- also called glycoproteins
a protein that allows the cell to be recognized by the body’s immune system
found on the surface of the membrane; functions is to facilitate cell recognition
glycolipids
cells use this specific type of transport to move gases and small lipid soluble molecules
simple diffusion