Biology (9/30)

How is the plasma membrane brought together?

Brought together because of hydrophobic
interactions of the tails

What do we mean when we say the plasma membrane is self-orienting?

-Head groups face water
-Tails face away from water

What do we mean when we say the plasma membrane is self-sealing?

when the membrane is punctured or disrupted, the phospholipids can quickly rearrange themselves to close the gap and restore the membrane's integrity, preventing the cell from bursting and allowing it to survive

What modifies fluidity in the plasma membrane?

cholesterol

What do we mean when we say the plasma membrane is a fluid mosaic?

phospholipids and other elements move independently

What is the cell membrane’s function?

To act as a selective barrier, controlling the movement of substances in and out of the cell while protecting the cell's interior from the external environment

What can get through the cell membrane?

Small, uncharged molecules (oxygen, carbon dioxide, lipid hormones)

What needs help getting through the cell membrane?

Charged and/or larger molecules (glucose, sodium, potassium)

How do membranes create compartments?

forming physical, membrane-bound sacs (organelles) within a cell, which segregates specific biochemical reactions and processes

What does it mean for the cell when the membrane is selectively permeable?

Being innately selectively permeable means most substances do not
simply flow freely in and out of these compartments

Cell membrane transport

how substances get through the membrane

What can get through the cell membrane?

-gases (oxygen, carbon dioxide)

-hydrophobic molecules (benzene)

-small polar molecules (water, ethanol)

What cannot get through the cell membrane (without help)?

-large polar molecules (glucose)

-charged molecules (amino acids, ions)

Diffusion

the natural movement of molecules from an area of high concentration to an area of low concentration

What happens if a solute can get through a cell’s membrane?

it will simply follow its diffusion gradient seeking balance

Passive transport

the movement of substances across a cell membrane from an area of high concentration to an area of low concentration that does not require cellular energy (like ATP)

Facilitated diffusion

a type of passive (energy-independent) transport that moves large, polar, or charged molecules across a cell membrane with the help of transport proteins

**occurs when proteins in membrane form pores, channels or transporters

What are cell membrane channels?

facilitate the rapid, passive movement of specific substances like ions or water across the cell membrane down their electrochemical gradient

*channels are typically regulated and “fit” their targets

What are transporters in the cell membrane?

specialized membrane-spanning proteins that assist in the movement of ions, peptides, small molecules, lipids and macromolecules across a biological membrane

*once the substance(s) to be transported binds the transporter protein, it changes the shape of the transporter to allow it to help the substance get through

Osmosis

the movement of water molecules from an area of high water concentration to an area of low water concentration, across a semipermeable membrane

-in other terms: the diffusion of water across a semipermeable membrane

What plays a big role in osmosis?

solutes (substance dissolved in a solution)

If the solute cannot balance its gradient, what will happen to the water?

the water will move across the membrane (by osmosis) toward the area with the higher solute concentration (lower water concentration)

Why is osmoregulation important?

it is important for the health of our cells

What happens if we don’t maintain osmotic balance?

it can affect (and even kill) animal cells

Hyper

excessive

Iso 

Same

Hypo

under/below

Tonicity

Concentration of solute outside the cell relative to the inside of the cell

Hypertonic solution

force water out of the cell

Isotonic solution

Do not affect the cell

Hypotonic solution

Force water into the cell

What kind of conditions do plants thrive in?

Hypoosmotic conditions

Hypoosmotic

having a lower concentration of dissolved solutes compared to another solution or the inside of a cell

What is a pump?

an apparatus or machine for raising, driving, exhausting, or compressing fluids or gases by means of a piston, plunger, or set of rotating vanes

Why do people need to pump the handle to get water out?

To overcome gravity and atmospheric pressure

Does water flow upwards?

Yes

Fact about pump

Pumping the handle provides the energy required to make the water flow up and out of the pump

Active transport

the movement of substances across a cell membrane from an area of low concentration to high concentration, which is against their concentration gradient, and therefore requires energy (ATP)

**does this by using protein pumps that run utilizing cellular energy

Exo

out of

Endo

Inside/into

What do cells often use to get things in and out of the cell?

Membrane vesicles

**these processes are mirrored 

Exocytosis

the process by which cells export substances (like hormones, proteins, or waste) to the outside environment by using a vesicle

Endocytosis

the process by which a cell takes in material from the outside by engulfing it with its cell membrane, forming a membrane-bound vesicle that brings the substance into the cell's interior

*if an immune cell needs to take up invading bacteria, it can use endocytosis

Energy

The capacity to cause change

What are different forms of energy?

-nuclear energy

-electric energy

-magnetic energy

-potential energy

-kinetic energy

-chemical energy

-thermal energy

Law of Conservation of Energy/First Law of Thermodynamics

energy can neither be created nor destroyed, it can only be transformed

Potential energy

the energy an object has because of its location or structure

Examples of potential energy

-snow atop a mountain prone to avalanches

-a diver standing at the edge of a cliff

-your muscles at rest

Kinetic energy

the energy of motion

Examples of kinetic energy

-boulder rolling down a hill

-diver diving off a cliff

-an arrow flying through the air after being shot from a bow

Heat/Thermal Energy

A type of kinetic energy that can be found in atoms and molecules and their random motion

True/False: all energy contains some sort of heat

true

What are characteristics of heat?

-disordered

-chaotic

Entropy

a measure of disorder and randomness in systems

How does entropy increase?

when energy is converted from one form to another

Chemical energy

The energy stored within the bonds of atoms and molecules

-a form of potential energy found in chemical bonds

What are rich in chemical energy?

carbohydrates, fats, and hydrocarbons

Chemical reactions in humans

chemical reactions that breakdown the carbohydrates and fats releases energy harnessed by cells

How do humans replenish energy?

We eat

What is a calorie?

the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius

What nutrients should we limit in our diet?

1. Total fat

2. Cholesterol

3. Sodium

What nutrients do you need?

1. Vitamin A

2. Vitamin C

3. Calcium

4. Iron

Daily value

5% or less is low

20% or more is high

Diseases linked to obesity

-type 2 diabetes

-dyslipidemia

-cancer risk

-mood disorders

-heart disease

-reproductive disorders

-liver disease

-hypertension

Body Mass Index (BMI)

a calculation used to estimate body fat percentage based on height and weight

Causes of weight gain

-food

-life

-physical activity

-emotions

-environment

-thinking

-time

Adenosine Triphosphate (ATP)

an energy-carrying molecule that fuels cellular functions

What does ATP consist of?

1. Nitrogenous base

2. Ribose

3. 3 phosphate groups

How are food calories converted?

one chemical energy to another

How does the ATP cycle work?

1. When ATP releases a phosphate group, energy is released

2. ATP is then converted to ADP

3. The transfer from energy in the mitochondria of your cells (aka energy absorbed from food) recharges the ADP by adding the last phosphate back to the ADP making it ATP

What are the phosphates charges in ATP?

The phosphates in the tail are all negatively charged

What happens when negatively charged molecules get close to one another?

Repel each other

Uses for ATP

1. Movement

2. Transport

3. On/off switch

4. Passing along a signal

What is enzyme in Greek?

in yeast

Enzymes

Act as catalysts in the body (speed up chemical reactions in the body)

*also make life possible

10³-10²0 times faster

Substrate

a foundational material or molecule upon which something else acts, builds, or resides

What enzyme does pineapple contain?

bromelain

-breaks down proteins

What enzyme does papaya contain?

Papain

-breaks down proteins

Enzymes in yeast produce what?

ethanol

How many genes do we approximately have?

20,000

How many of our genes are thought to be encoded for enzyme subunits?

3,000

Our genome is thought to encode for how many different enzymes?

1,000

What are enzymes made up of?

amino acids

-there are some with RNA molecules

How do enzymatic reactions work?

1. The enzyme catalyzes a reaction

2. During the reaction, the substrate fits into the enzyme and transforms at the active site (lock-and-key)

3. The new product(s) release from the enzyme

4. The enzyme is unchanged and waits for the next reaction

Process: substrate → enzyme → product(s)

*the enzyme can modify its shape to make the substrate a better fit

Activation energy

the minimum energy required for a chemical reaction to start, acting as an energy barrier that must be overcome for reactants to form products

What do enzymes do to speed up reactions?

lower the activation energy required for it to happen

Enzymatic inhibitors

a substance that binds to an enzyme, slowing down or stopping its catalytic activity (regulation)