Honors Bio - The Working Cell: TEST

What is the purpose of the cell membrane and what is it’s function?

1. Site of many enzyme driven chemical reactions and metabolic pathways

2. Separates the cell from its outside environment

What are the two important aspects of the cell membrane?

1. Selectively permeable membrane

2. Phospholipid bilayer

What is the semi permeable/selectively permeable membrane?

Limits what enters/exits the cell based on:

1. Size —> if molecule is small enough to squeeze through it, it can pass

2. electrochemical charge —> ± can’t pass through, but neutral charged molecule can

3. polarity —> if it’s polar, it’s impermeable. if it’s nonpolar, it’s permeable

What is the phospholipid bilayer?

A structural component of the cell membrane that consists of:

• a circular phosphate head —> polar, hydrophillic

• fatty acid tails (saturated and unsaturated) —> hydrophobic

Polar region is descirbed as HYDROPHILLIC

Nonpolar region is described as HYDROPHOBIC

What is in the intracellular environment?

• Cytosol —> mostly H2O cytoplasm

What’s in the extracellular environment?

• Plasma (surrounds blood)

• Interstitial fluid (surrounds organs)

• Mostly H20 —> dissolves well, makes aqueous solutions

Extracellular environment is constantly changing

What is fluid mosaic model? (the fluid part)

1. The cell membrane is not rigid (like a water bed —> groups of phospholipids/proteins don’t stay in place)

2. Phospholipids and proteins drift laterally throughout the membrane —> will float in one direction and previous place will get filled immediately

3. Cholesterol: anchors phospholipids together, part of what adds to fluidity as it holds phospholipids together, and acts as spacers to increase fluidity

What is the fluid mosaic model? (the mosaic part)

Many different components acting towards the same goal —> membrane acts like a mosaic

What are the components of the plasma membrane?

2 diff. varieties of protein

1. Peripheral protein: gives structure & support, anchors the phospholipids together, an attachment site for the cytoskeleton (since it’s in INTRACELLULAR area, this makes it important)

2. Integral/transmembrane proteins (can be referred to as “integrins”): “trans” means it CROSSES the membrane

   a. transport channels

   b. enzymes for metabolic pathways

   c. signal transduction

Transmembrane proteins are responsible for what?

Responsible for the TRANSPORT of things

—> transports molecules that are too large, electromagnetically charged (±), and polar

Transmembrane proteins have what that will allow for the transport of larger molecules?

Channel proteins: open, will allow certain things to pass through. Each channel has a different responsibility

1. Ion channels: transports ions (Na+, Cl-, K+) —> “sodium gated channels”

2. Carrier proteins: moves things too large, charged, and/or polar

This is facilitated diffusion

What is enzymatic activity?

Responsible for the chemical reactions of metabolism (cellular respiration, photosynthesis) —> providing energy to the cell

• will be found on proteins embedded in phospholipids

What is the signal transduction pathway?

A series of processes by which a cell responds to external signals (like hormones, nutrients, or other molecules).

• These signals are received by receptors on the cell's surface, and then they are passed along through a chain of molecular events inside the cell

• This leads to a specific cellular response, such as gene expression, metabolism changes, or cell division.

**Example of how person goes to the door, mom answers, tells dad to get friend, tells sister to get friend and friend responds

What is the result of the signal transduction pathway?

Results in a change in cellular function

• Leaving cells on that aren’t required at the moment is a waste of energy —> body only turns on cells when we need it through signal transduction

• Change of control and gene expression —> when there’s a demand for a certain protein, the cell turns on to create it. When there isn’t a demand for that certain type of protein, it turns off to save energy

What do hormones do?

When you grow

• Growth happens by causing one cell to reproduce over and over again

• Growth is the reproduction of cells/increase in the number of cells

What is cyclin?

Causes cells to reproduce

What is a receptor protein?

A molecule on the surface of a cell that helps it respond to signals from the environment, like hormones or other chemicals.

• Gene responsible for building receptor

• Mutating the DNA changes the shape of protein/receptor

What is cancer?

Refers to any disease related to the uncontrolled growth of cells caused by a genetic mutation affecting the receptor portion of a protein that controls the cell cycle

• The specific gene when mutated that results in cancer are called oncogenes (onco means “related to the cancer state”

What causes these mutations that affected the receptor portion of a protein that controls the cell cycle which can result in cancer?

They’re caused by chemical or physical environmental factors that are called mutagens

• Mutagens affect the DNA and impacts the protein which causes it to continue to send signals to keep making cells

• Carcinogen is a mutagen that impacts oncogenes

What happens to the receptor protein when a mutation occurs (aka cancer happening)?

Outside force causing receptor to be mutated (ex: carcinogens like cigarettes, too much sun exposure, etc)

• When a mutation occurs in a receptor protein, it can cause the receptor to become activated even when it shouldn’t be.

• Makes the receptor think that cyclin (signal for cell prod.) is present

• causes the receptor to continually send signals for cell reproduction, even when it should be shut down

As a result, the cell keeps reproducing, leading to the accumulation of mutations in the DNA, which can contribute to uncontrolled cell growth, such as cancer.

What are antibodies?

The immune system’s memory

• Humans develop antibodies through exposure —> that’s why vaccines tend to work

• Trained to identify the glycolipids and glycoproteins, engulf them and die —> when this happens, there’s a liquid left over called a lymph (dead white blood cells)

• Detects what’s supposed to be in your body and what’s not supposed to be there **doesn’t do the actual “kicking out,” only identifies the foreign invaders

What’s the function of glycolipids and glycoproteins?

Identify a cell so that it can communicate w/ other cells and tell them that they belong in your body (cell to cell communication), important especially w/ the immune system response

What’s the difference between the glycolipids and the glycoprotein?

They differ in where they get attached

• Glycoprotein attaches to the external protein of the transmembrane protein

• Glycolipids are carbohydrate chains attached to the polar heads of the phospholipids

What’s in a vaccine to help prevent you from getting sick?

An reduced/dead version of the virus in the vaccine

• Your body knows that the vaccine shouldn’t be in your body because it doesn’t have YOUR glycolipids and glycoproteins

• When your immune system sees it, it kills the dead version of the virus and holds memory of what it looked like

• You’ll get “sick” after you get a vaccine because you get the symptoms of the sickness, not the actual sickness

Why is it hard to treat cancer w/ a vaccine?

Your cancer cells are your own (looks the same as normal, healthy cells), so immune system isn’t trained to identify cancer cells because they think they’re normal

What other factor does the fluid mosaic have?

Also has carbohydrates —> not only proteins or phospholipids

Why are there so many different blood types?

Each different blood type have very specific glycoproteins and glycolipids

• Identifying markets on the blood is how they communicate

• Blood type O has NO antigens —> that’s why it’s the universal giving blood type

• Blood type AB can receive blood from anyone because it has the type A and type B flags on it

What happens when the wrong type of blood enters your body?

Wrong-flagged blood cells are quickly identified by your body as they don’t have the same glycoproteins and glycolipids as your RBC’s

• Results in a triggered immune response, and immune system will attack the foreign RBCs

If you get the wrong blood type, the wrong blood would trigger the glutination response and now your blood would start to clot

• Now, you can’t transport blood and nutrients which would prevent ATP from occurring —> cells would stop working

What is the transmembrane transport?

Getting nutrients from outside fluid into cells so that the nutrients can be utilized

• Depends on concentration (how much of substance (solute) is found dissolved in solution (solvent))

What are the different concentrations?

• Concentration: based on parts per million (PPM) or parts per thousand (PPT)

• Relative concentration: ratio of concentrations in two separate areas

• Concentration gradient: areas of high concentration and areas of low concentration

  • will occur until concentration is equal

• Equilibrium: equal concentration in two separate areas

  • nature seeks equilibrium —> will move up or down the concentration grade until it’s equal

How does alcohol get to the brain?

Through transmembrane transport (ex: alc. % is 4%)

• When consuming it, it goes to the stomach, then through your intestines

• Normal alc. content in stomach is 0, consuming alc. will turn the % of stomach to however much the alc. % is (4% in this case)

• Next to the stomach are blood vessels and their job is to pick up nutrients (avg. alc. content also 0)

• Area of high concentration and low concentration will cause the concentration gradient, so alc. now begins to diffuse into the blood until equilibrium

• BAC is now 2% —> blood is now flowing through your body, carrying alc. throughout your body

• Blood flows to the brain and flows to the cells of the brain and the gradient is still working —> as blood flows to the brain, the alc. content of your brain goes from 0% to 1%

This example also applies to other foods/beverages (such as caffeine)

What is transport?

Moving molecules across the membrane into the cell

Transport can either be ___ or _____

passive or active

What is passive transport?

1. Doesn’t require ATP (doesn’t requrie an input of energy)

2. Particles move DOWN the concentration gradient (areas of high C to low C)

3. Move TOWARDS equilibrium

4. Usually works for smaller, non-polar products

Will follow natural law, particles will move down/with the concentration gradient

**has to check off all boxes to determine if it’s passive or not

What drives equilibrium from areas of [high] to [low]?

Molecules are bumping into one another

• when it gets too hot for the molecules, it’ll move to area will low conc.

• won’t stay close together all the time

• odds of crashing into another molecule in [high] is higher

Example allows to salt, sugar, protein (and more) molecules

What is active transport?

1. Does require an input of energy (ATP)

2. Particles move UP or AGAINST the concentration gradient (areas of [low] to [high])

3. Move AWAY from equilibrium

4. For larger or polar particles

Not letting particles go to [low], pushing it back to area w/ [high]

• Trans membrane protein pumps H ions in & out —> if it reaches equilibrium we can NOT make ATP —> results in no cellular work

In what situation would we want an environment AWAY from equilibrium?

Grist Mill example: makes bread in the summer and uses flow of water for energy input (in the summer there isn’t much rain, so water doesn’t flow as much)

• Pumps water from a well for water from a small to a bigger pond

• Pumps water from [low] to [high] elevation

• DO NOT WANT equilibrium b/c then the flow of water would stop

Grist Mill represents the mitochondria and how the mitochondria makes ATP, water represents hydrogen ions

Types of passive transport: what is simple diffusion?

Movement of solute (dissolved particles) from an area of [high] to [low] across a semi permeable membrane

• only applies to things that can squeeze btwn the phospholipid bilayer —> particles must be small, polar, and neutral (ex: CO2 & O2)

• will go from [high] to [low}

Diffusion will happen until equilibrium is reached —> NO NET MOVEMENT

• Dynamic equilibrium: still get movement in and out, movement is just balanced

  • Equal in magnitude, just opposite in direction

Types of passive transport: what is facilitated diffusion?

**facilitate = help

Sometimes particles are too large to pass btwn spaces of membrane, so they need help → this means that their diffusion is facilitated

• Requires protein channels/channel proteins

• Applies especially for charged ions like Na and Cl

• They can’t squeeze into phospholipid bilyar b/c the molecules is either too big, nonpolar, or electromagnetically charged

What are certain types of channel proteins?

1. Aquaporins: channel proteins specifically designed to transport polar H2O molecules across the membrane —> will only open when we need water and aquaporins will ONLY transport water. (only sometimes occurs b/c water is a solvent NOT a solute)

2. Ion channels: transport charged ions across the membrane (ex: electrolytes)

3. Osmosis: Diffusion of only water across a semi-permeable membrane **takes place through aquaporin

Ex: cystic fibrosis is a mutation in one of these channels that mutates these channels so it won’t let certain ions go through

Why can’t a freshwater fish be in salt water and vice versa?

Has to be in freshwater

• Animals want to be at equilibrium (or isotonic) w/ their environment

• Humans feel dry, thirsty, etc after swimming in salt water b/c we are freshwater creatures

• Fish in their own environment helps them maintain homeostasis

• If a freshwater fish jumped into the sea it would die b/c that’s not their environment → fish’s intracellular environment isn’t at equilibrium

• Environment is hypertonic (solute conc. is higher outside cell rather than inside)

• Fish is now hypertonic → water will move against the salt, water will diffuse from fish’s cells to environment (pulling water out = osmosis)

What is an isotonic solution?

Concentrations of solute and water are equal both inside and outside the cell

• Cell is in equilibrium = no net movement

• Often the function of the central vacuole in plants → gives plant cell rigidity

What happens when you dehydrate?

The concentration of salt increases in your plasm which shrivels the cells → creating cremation

• Problematic b/c now RBCs aren’t able to carry oxygen

• An IV will return you back to hydration

What is a hypertonic solution?

The extracellular concentration of solute is greater than the intracellular concentration

• No net movement in solute or water

Ex: when a cell becomes plasmolyzed the cell membrane pulls away from the cell wall in a hypertonic environment

What is a hypotonic solution (hypo = less/lower)?

Concentration of solute is greater in the intracellular environment than the extracellular fluid

• Therefore, water moves IN and solute moves OUT

• Causes cells to swell, become turgid, and explode

• Turgor pressure causes animal cells to burst → NOT plant cells b/c plant cells have the cell walls

• Plant cells want this rather than isotonic

Why don’t plants want an isotonic environment?

Needs as much water movement (in and out) as they can get

• Central vacuole will push out water when it’s full → “turgor pressure”

• Wants lots of turgor pressure so that the P. cells can stack on top of each other

Why do humans drink water?

• To maintain an isotonic environment → osmoregulation

• Humans must respond to stimulus to maintain homeostasis

OPEN ENDED ON TEST (maybe): Why can’t humans drink tons of water and not let it out?

• The rapid intake of large amounts of water dilutes the sodium levels in the blood, which can cause water to move into cells, including brain cells, causing them to swell

• Can lead to water intoxication

• Body is around 60% water, RBCs are 9.91% water (0.9% is salt) → drinking bottle water will fill stomach with pure water (close to distilled water), and this makes the water concentration in your stomach 99.7%

  • RBCs are surrounded by a fluid that is normally isotonic and drinking too much water can change that balance

• The blood becomes hypotonic compared to the cells, which causes water to move into cells (including brain cells). This is why the brain swells in extreme cases of water intoxication