Unit 2 Biology

Animal cells in osmosis

Animal cells can be damaged by osmosis (burst UNLIKE plant cells). They also shrivel if they do not have enough water(UNLIKE PLANT CELLS).

How do proteins enter bloodstream?

Very big and polar (since they are made of amino acids), hence making them too big for channel proteins. They use carrier proteins to pass the membrane and enter the bloodstream. This is active transport: needs NRG.

Besides "bulk" release of molecules out of a cell, how does the response of a target cell to insulin illustrate another important function for exocytosis.

"Exocytosis allows cells to secrete waste substances and molecules, such as hormones and proteins. Exocytosis is also important for chemical signal messaging and cell to cell communication."

What are contractile vacuoles and why are they important for homeostasis in freshwater protists?

"The point of the contractile vacuole is to pump water out of the cell through a process called osmoregulation, the regulation of osmotic pressure. Osmoregulation is the continuous effort to maintain a healthy balance between solvent and solute in the cell. Protists like amoebas take in too much water from their environment during the process of osmosis, water enters the cell along with other needed substances like oxygen. However, the cell needs to expel its excess water or new water and oxygen cannot enter. The excess water and waste products are shunted to the contractile vacuole for storage. When the vacuole is full, it violently contracts and expels the water and waste."

THREE COMPONENTS OF CHANNEL PROTEINS?

- Passive facilitated diffusion only - Small, polar substances - Proteins are SPECIFIC for type of molecule

What can carrier proteins transport? What happens to the carrier after it binds with the molecule?

- Small (ex. ions) OR large substances (ex. glucose) - VERY specific substances can go through certain carrier proteins. There is a receptor site, and the shape of the receptor site must match the substance. - The carrier changes shape

How many micromillimeters are in a millimeter?

1000 um = 1 mm

What is a hormone?

A chemical messenger released into the bloodstream that signals the activity of glands and organs in metabolism, growth, development and homeostasis.

Is exocytosis a passive or active process? Why?

Active - goes from low to high concentration

How does water pass through membrane?

Aquaporins (proteins). They are channel proteins.

How do aquaporins work?

Aquaporins have protein exclusion channels allow H₂O molecules to go by but exclude H⁺ molecules. It does so by forcing the molecules to go down the channels in single file.

Main functions of membrane proteins:

Attachment to the cytoskeleton and extracellular matrix-helps maintain cell shape and stabilizes the location of certain proteins Intercellular joining - membrane proteins of adjacent cells hook together to form various junctions Signal transduction-A mechanism linking a mechanical or chemical stimulus to a cellular response Enzymatic activity-A protein built into the membrane with active site exposed. Cell-cell recognition-Some glycoproteins serve as identification tags that are specifically recognized by other cells. Transport IMPORTANT MOLECULES ACROSS MEMBRANE

Pinocytosis vs Phagocytosis

BOTH ENDOCYTOSIS Pinocytosis ("cell drinking") and phagocytosis ("cell eating")

Why does water flow toward the bloodstream with osmosis?

Bc bloodstream has more molecules (salt, proteins, carbs, lipids) hence making the bloodstream's concentration of water less. Water flows from high to low concentration.

Why is the plasma membrane fluid-like?

Bc cholesterol seperates phospholipids.

Which type of transport protein behaves similarly to enzymes? How so? How do they differ?

Both have specific puzzle-like "active" site for molecule to enter and fit. However, enxymes change chemical nature of molecule whereas carrier proteins don't.

Why, in the absence of insulin, are cells unable to take in glucose from the bloodstream?

Cells obtain energy from glucose or convert it to fat for long-term storage. Like a key fits into a lock, insulin binds to receptors on the cell's surface, causing GLUT4 molecules to come to the cell's surface. As their name implies, glucose transporter proteins act as vehicles to ferry glucose inside the cell

What are the fatty acids? How do they pass through the membrane and into the bloodstream?

Chains of carbon atoms bonded to hydrogen atoms, hence making them nonpolar. They use simple (or regular) diffusion w/out transport protein. This is passive transport.

How does temp, molecular size, and concentration gradient affect rate of diffusion? BE ABLE TO EXPLAIN THIS AT THE LEVEL OF A MOLVEULE (ANSWER ON THIS QUIXLET DOES NOT DO THAT)

Concentration gradient: High to low means faster. Smaller the molecule, faster the diffusion happens Higher temperatures (warmer) increase the energy and therefore the movement of the molecules, increasing the rate of diffusion. Lower temperatures (colder) decrease the energy of the molecules, thus decreasing the rate of diffusion.

What type of cellular transport is based on the random movement of particles?

Diffusion and facilitated diffusion

Diffusion vs. Osmosis

Diffusion is movement of solutes, membrane is permeable to solute and solvent Osmosis is movement of solvent, membrane only permeable to solvent

Why does diffusion result is dynamic equilibrium? Why use the word "dynamic?"

Diffusion will continue until the concentration gradient has been eliminated. The end result of diffusion is an equal concentration, or equilibrium, of molecules on both sides of the membrane. Dynamic equilibrium only occurs in reversible reactions, and it's when the rate of the forward reaction is equal to the rate of the reverse reaction. These equations are dynamic because the forward and reverse reactions are still occurring, but the two rates are equal and unchanging, so they're also at equilibrium.

What type of cellular transport occurs across the cell membrane?

Diffusion, facilitated diffusion, and active transport

Types of passive transport

Diffusion, osmosis, facilitated diffusion

What is the advantage of exocytosis with vesicles VS transport proteins?

Exocytosis allows for: - More molecules to be transported at a time (bigger bulk transport) - Larger molecules can be transported (insulin is a protein MUCH larger than glucose, so whereas glucose can fit into carrier proteins, insulin cannot, therefore reasoning for why insulin needs exocytosis).

Types of active transport

Exocytosis, and Protein Pumps - Lower Concentration to Higher Concentration ALSO Endocytosis (phagocytosis and pinocytosis)

Is facilitated diffusion or simple diffusion faster? Are they solute specific?

FD is faster than SD AND SD isn't solute specific whereas FD ALWAYS is.

What type of cellular transport involves molecules and/or ions?

Facilitated diffusion and active transport

What type of cellular transport involves proteins in the cell membrane?

Facilitated diffusion and active transport

What is microvilli?

Fingerlike extensions of the plasma membrane that increase the surface area for absorption.

Why is membrane described as fluid mosaic?

Fluid/liquid: bc the lipid bilayer is a liquid structure bc of the types of molecules that make up the cell membrane. Also, bc membrane has many types of molecules that float along with the lipids. Mosaic part is the carbohydrate molecules that act like identification cards that can help individual cells to identify one another NOTE: a mosaic is a picture/painting made from severla small bits of different colored pieces

How is insulin released?

Higher concentrated blood glucose signals pancreas cells to release insulin by exocystosis w/ vesicles.

Hypertonic vs Hypotonic vs Isotonic

Hypertonic: solution with high concentration solute on outside. Net movement of water is outward. Hypotonic: solution with lower concentration solute (lower on outside). Net movement of water is into the cell. Isotonic: When cell is in solution that has same concentration of water and solutes, so there is no net movement (cells retain normal shape).

What solution causes osmosis?

Hypo and hypertonic

Plant cells in hypo vs hypertonic environments What is plasmolysis?

Hypo: Water gives plant structure, giving it a stronger shape and making its cell wall more rigid. Filled central vacuoles help the plant stay upright. Hyper: Wall doesn't shrink, but membrane dies. Plasmolysis happens. Plasmolysis: the breaking away of the plasma (cell) membrane from the cell wall.

What solution causes a cell to swell?

Hypotonic

Where do amoebas and paramecium live and "why?"

In fresh water, meaning there is LESS CONCENTRATION OF SOLUTE. They live there so they can gain more water. REMEMBER FROM OTHER SLIDE: Contractile vacuole passes out water so that the cell does not overflow and burst.

What is insulin?

Insulin is a protein hormone which signals body cells to take in glucose/sugar.

What solution does not change the shape of a cell?

Isotonic

What is the importance of insulin?

It helps with the digestion and absorption of carbs into the bloodstream. Carbs are needed because they stick out of the membrane and identify certain chemical signals. For example, carbs in the membrane help disease-fighting cells recognize and attack a potentially harmful cell.

How does glucose enter body cells?

It uses carrier proteins for facilitated diffusion

What property of the membrane allows the vesicle membrane to fuse with the outer cell membrane during exocytosis?

Its liquidness

Structure of a cell membrane

Lipid bilayer of phospholipids and proteins Glycoproteins (proteins with carbohydrate attached) Glycolipid: lipid with carb attached

What is the structure of a phospholipid?

Made up of 2 hydrophobic tails for each hydrophilic head. Structure is flexible and changes shape easily due to fluidity. Structure is strong due to attraction between hydrophobic tails. MAINLY HYDROPHOBIC WHICH IS WHY ALL SUBSTANCES CANNOT PASS THROUGH.

What role do membrane receptor proteins play in determining hormone target specificity?

Membrane receptors have a certain shape and bind to certain hormones (in this case, insulin) to signal the cell to do something (in this case, to take in glucose from bloodstream)

Do membrane proteins move?

Most proteins float around individually in the lipid bilayer because the membrane is a liquid crystal and has fluid behavior. Specifically, this is due to the membrane being in a gel-state. This gel state allows phase behavior which means that the protein is able to move around on the surface.

Can channel proteins concentrate molecules within the cell?

NO - molecules move to different concentrations through channel proteins; they are not concentrated themselves

What type of cellular transport uses energy VS does not need energy?

Needs energy: active transport Does nto need energy: diffusion and facilitated diffusion

What happens when positive ions travel across channel protein?

Negative ins line up inside protein to attract the positive ions

Are macromolecules permeable? Why or why not?

No bc they are too big to fit between phospholipids

Are small ions permeable?

No because they have charges and are hence repelled by -phobic/nonpolar interior.

What is dynamic equilibrium?

No overall change in concentration (equal)

How do the general locations of polar & nonpolar amino acids in the 3-dimensional structure of membrane proteins differ from those in cytoplasmic proteins?

Nonpolar on inside for phospholipids, whereas polar on outside for polar liquids and substances to enter. Cytoplasmic proteins are most likely all nonpolar, or the polar hides in the center, because it is submerged into the nonpolar phospholipids.

Is water permeable?

Not really... it is repelled by -phobic interior

What direction is insulin released?

OUTWARD so that insulin can allow carbs into bloodstream

what is facilitated diffusion?

Passive transport (no energy required). Movement from high to low concentration. Carrier/channel protein required. Large or small and charged molecules can pass through using such proteins.

Compare and contrast the type of molecule each type of transporter may transport across the membrane and be able to explain why.

Passive transport: small molecules, facilitated polar, simple diffusion nonpolar only. Active with a carrier, small and big polar. With vessels, very large proteins.

Animal vs plant cells

Plant cells: membrane shrinks away (wilting) with loss of water. With gain of water, it becomes firm. Strong cell wall prevents them from bursting. Animal cells: Too much water gain (osmosis) (hypotonic) means cell can burst bc animal cells do not have cell wall. Also, lack of osmosis/water means CELL ITSELF will shrivel, not just the membrane.

What happens when negative ions travel across channel protein?

Positive ins line up inside protein to attract the negative ions Similar to how polar acids would be transported and interact with several different polar amino acids inside protein

What is endocytosis?

Process by which the cell takes in materials/nutrients that are too large to pass through membrane. Amoebas use endocytosis to eat, but use exocytosis to excrete waste.

What is polar vs nonpolar in a membrane protein?

Side facing top and bottom are polar bc it attracts polar substances to carry across. On the other hand, right and left sides are nonpolar so they stick-to and are attracted to nonpolar phospholipids of the membrane/phospholipid bilayer.

Why are cells so small?

Smaller cells have more surface area across which to pass oxygen, nutrients and waste materials AND so they can maximize their ratio of surface area to volume. Smaller cells have a higher ratio which allow more molecules and ions move across the cell membrane per unit of cytoplasmic volume. Cells are so small because they need to be able to get the nutrients in and the waste out quickly.

solute vs solvent vs solution

Solute is the thing thats being dissolved, solvent does the dissolving, solution is the mixture of the solute and the solvent

What does solutes suck ACTUALLY mean?

Solutes SUCK AWAY the water from hypotonic substances

How does the membrane's structure relate to its function?

Structure follows function Its function is to maintain homeostasis by keeping certain substances out vs in (selectively permeable) Because its stucture is that it is nonpolar (made mainly of fatty acids which are hydropohobic), it only allows nonpolar substance to diffuse through, mkaing it difficult for other molecules to permeate through the membrane.

What are vesicles?

Structure within a cell for the storage and transport of molecules

What is osmosis? How long does osmosis continue?

The diffusion of water across a selectively permeable membrane from high concentration to low concentration until equilibrium is reached (no net movement of water). No protein is required unless it is moving through a membrane, which in this case a carrier protein is required (Aquaporin).

What is the membrane made of? What are its properties?

The membrane is made of phospholipids (fatty acids that bend and form a membrane with the help of polar molecules that bond them together. THERE ARE ALSO SOME GLYCEROL MOLECULES). Fatty acids are nonpolar, hence making the membrane hydrophobic. It is fluid, explaining why molecules can move side to side within the membrane. Also, membrane is selectively permeable, meaning it maintains homeostasis by regulating movement of substances in and out of the cell. MEMBRANE IS A PHOSPOLIPID BILAYER (2 layers of fatty acids/phospholipids) Hydrophobic, non-polar molecules (including oxygen, carbon dioxide and steroids) can diffuse freelythrough the membrane because the phospholipid 'tails' create a hydrophobic core.

What is passive transport?

The movement of substances across the cell membrane without using cellular energy. High concentration to low concentration.

What is selective permeability?

The property of a membrane by which it permits the passage of certain substances but restricts the passage of others.

What is diffusion? What uses diffusion? How do particles act?

The random spreading movement of particles from an area of high concentration to an area of low concentration. NO NRG needed to get fatty acids transported because they are absorbed into the bloodstream (as they are nonpolar). No aid of intermediary protein is used. Gases and dissolved substances use diffusion. EXPERIMENT WITH PLASTIC TUBE IN CUP IS EXAMPLE OF THIS - BE ABLE TO EXPLAIN WHY FOR THE TEST

How does salt dissolve into bloodstream?

They are very small and polar, so they use carrier proteins to pass through the nonpolar membrane, and then use a channel protein into the bloodstream (bc they are past nonpolar membrane and are small enough for channel proteins). This is active transport when passing through the membrane: needs NRG.

What are protein pumps?

Type of membrane protein that requires energy to move molecules across the cellular membrane against a concentration gradient. Carrier proteins only.

What structure do amoebas use for maintaining homeostasis?

Vacuoles. "This organelle is a space within the cytoplasm of the amoeba that fills with fluid as waste. Once full, it ejects its contents out of the cell. This allows the amoeba to maintain the needed internal fluid levels to encourage osmosis of water and oxygen molecules through its membrane. If the amoeba becomes oversaturated with the water, no new molecules will pass through the membrane, essentially killing the amoeba by depriving it of vital substances like oxygen." IF YOU POP VACUOLE, AMOEBA WOULD ALSO OVERFLOW WITH WATER AND HENCE DIE.

How do carbs enter bloodstream?

Very big and polar (since they are made of simple sugars), hence making them too big for channel proteins. They use carrier proteins to pass the membrane and enter the bloodstream. This is active transport: needs NRG.

Explain how insulin actually works.

When the body absorbs carbs into blood glucose, it signals pancreas cells to release insulin by exocytosis. Insulin binds to receptor and triggers removal of glucose from cell wall and the movement of glucose through exocytosis into bloodstream. Insulin then signals the cell to take in glucose from the bloodstream so it can be converted to energy or stored for later usage. INSULIN IS SIMPLY A SIGNAL-ER/HORMONE

Is diffusion spontaneous?

Yes - One solute is independent of the concentration gradients of other solutes and because it involves a passive transport process, which implies that energy is not expended when substances diffuse down their concentration gradient. RANDOM MOVEMENTS OF PARTICLES IS IN THIS

Are gases permeable?

Yes - they are small and nonpolar

Are nonpolar molecules permeable?

Yes if not too large. They are not repelled by -phobic interior, but if too large cannot pass through and would need assisting carrier protein.

What is exocytosis?

a process by which the contents/molecules of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane. Vesicles are involved

How do you find concentration of water or solute in a substance? How do you know whether something will gain the greatst amount of mass?

amount of solute/water DIVIDED BY total amount of substance (solute + water) 1 gram = 1 mL REMEMBER - 0.03 = 3% You know if the solution is hypotonic and the difference between solutes for outside and inside is the largest difference.

What solution causes a cell to shrink?

hypertonic solution

What are membrane receptor proteins?

membrane receptors are specialized protein molecules in themembranes of cells, to which external molecules (hormones, neurotransmitters, drugs) attach, triggering changes in the function of the cell. This process is called transduction: the external signal is transduced into action.

What are motor proteins?

proteins that turn energy into mechanical work? FULLY ANSWER THIS

What is active transport?

the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

What is aquaporin?

water CHANNEL protein in a cell (for osmosis)