Biology chapter 5

Bioluminescence

energy-converting reactions that produce light by turning chemical energy into visible light

Cell membranes

Composed of a bilayer of phospholipids with embedded and attached proteins in a structure called a fluid mosaic

Phospholipids

unsaturated fatty acids with kinks in their tails that prevent them from packing together too tightly and becoming solid

What do animal cell membranes use cholesterol for?

• stabilize membranes in warm temps

• keep the membrane fluid liquid at cool temps

Functions of membrane proteins (6)

1. Maintain cell shape and coordinate changes inside and outside of the cell

2. Receptors for chemical messengers from other cells

3. Enzymes

4. Cell-cell recognition

5. Intercellular junctions

6. Selective permeability

What do glycoproteins do in the cell membrane?

Perform cell-cell recognition

What do Intercellular junctions do?

Attach adjacent cells together

Selective permeability

Allowing some substances to cross a cell membrane easier than others

Membrane proteins that span the entire membrane

Integral or transmembrane proteins

Membrane proteins that temporarily stick on the sides of the membrane

Peripheral proteins

The formation of phospholipids was a critical step in ______

the evolution of the first cells

Diffusion

The tendency of particles to spread out evenly in an open space

Particles diffuse ___ their ________

down; concentration gradient

Equilibrium

concentration of particles the same throughout

Osmosis

The diffusion of water across a semipermeable membrane

What happens if a water molecule can pass through a semipermeable membrane but the solute cannot?

water crosses the membrane, moving down its own concentration gradient until the solute concentration is equal on both sides

Tonicity

the ability of a solution to cause a cell to gain or lose water

Isotonic solution

Solute concentration the same on both sides

Hypotonic solution

Solute concentration is lower outside the cell

Hypertonic solution

Solute concentration is higher outside the cell

Osmoregulation (like in different -tonic solutions)

The control of water balance

How do hypotonic solutions affect cells?

• Animal cell - Lysed (bad) could burst

• Plant cell - Turgid (normal)

How do isotonic solutions affect cells?

• Animal cell - normal

• Plant cell - Flaccid (not ideal)

How do hypertonic solutions affect cells?

• Animal cell - Shriveled (bad)

• Plant cell - Plasmolyzed (bad)

Hydrophobic substances _____ diffuse across a cell membrane

easily

Polar or charged substances (ions) _____ diffuse across cell membranes

do not easily

Facilitated diffusion

Transportation across the cell membrane that does not require energy and relies on the concentration gradient. Uses transport proteins to move polar or charged substances that cannot easily cross on their own.

2 types of transport proteins

• Channel proteins - work as a hydrophilic tunnel

• Carrier proteins - bind to the passenger, change shape, and release the passenger on the other side

Transport proteins are ___ to the ___ they transport

specific; substrate

Aquaporin

a protein channel that can be used to diffuse water more rapidly than usual

Active transport

Transportation where energy is used to move a solute against its concentration gradient

What happens when phosphate attaches to ADP?

It is phosphorylated and becomes usable ATP energy

Exocytosis

Exports bulky molecules such as proteins or polysaccharides, uses ATP

Endocytosis

Imports substances useful to the livelihood of the cell, uses ATP

Phagocytosis

the engulfment of a particle by wrapping cell membrane around it, forming a vacuole, type of endocytosis

Pinocytosis

the engulfment of a fluid by wrapping cell membrane around it, forming a small vesicle, type of endocytosis

Receptor-mediated endocytosis

uses receptors in a receptor-coated pit to interact with a specific protein, making a vesicle

____ is the capacity to cause change or perform work

Energy

Kinetic energy

energy of motion

Potential energy

stored energy

Heat

aka thermal energy, type of kinetic energy associated with random movement of atoms or molecules

Light

Type of kinetic energy that can be harnessed to power photosynthesis

Chemical energy

the potential energy available to release in a chemical reaction. It is the most important type of energy for living organisms to power the cell

Thermodynamics

the study of energy transformations that occur in a collection of matter

First law of thermodynamics

energy in the universe is constant

Second law of thermodynamics

energy conversions increase the disorder of the universe

Entropy

the measure of disorder or randomness

What happens to stored chemical energy in cellular respiration?

It is converted to a form that the cell can use to perform work

Exergonic reactions

Reactions that release energy in covalent bonds of the reactants. The products have less energy than the reactants. Ex. cellular respiration

Endergonic reactions

Reactions that require an input of energy and yield products rich in potential energy. They begin with reactant molecules with relatively low potential energy but end with products that contain more chemical energy. Ex. photosynthesis

Photosynthesis

An endergonic reaction that uses energy-poor reactants CO2 and water. Energy is absorbed from sunlight and energy-rich sugar molecules are produced

What is a metabolism?

the total of an organism's chemical reactions

Metabolic pathway

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds

Energy coupling

uses the energy released from exergonic reactions to drive essential endergonic reactions, usually using energy stored in ATP molecules

ATP

(adenosine triphosphate) powers nearly all forms of cellular work

ATP consists of…

• the nitrogenous base adenine

• the five-carbon sugar ribose

• three phosphate groups

How does the hydrolysis of ATP work?

It releases energy by transferring its third phosphate from ATP to some other molecule through a process called phosphorylation

After phosphorylation, ATP becomes ____

ADP (adenine diphosphate)

Three main types of cellular work

• Chemical (make proteins and break down carbs)

• Mechanical (using muscles)

• Transport (ex. moving oxygen with blood)

The release of potential energy is _____

not spontaneous

What must be overcome before a chemical reactions can happen?

An energy barrier made of energy called activation energy (E_A)

E_A (activation energy)

The amount of energy needed for a reactant molecule to move “uphill” to a higher energy so the “downhill” part of the reaction can begin

Enzymes

• Biological catalysts that function by lowering the amount of activation energy needed

• Reusable

• Are usually proteins, but can be RNA

• Selective in reactions it catalyzes

Substrate

The specific reactant that an enzyme acts on

Active site

The region of an enzyme that a substrate fits into

Enzyme-substrate complex

The enzyme and substrate after bonding

What is an enzymes optimal temperature?

The temperature that an enzyme produces the highest rate of contact between the reactants and the enzyme’s active site

The optimal pH for most enzymes is ______

near neutrality

Cofactors

Non-protein helpers for enzymes that bind to the active site and function in catalysis. Some are inorganic, like zinc or iron, and some are organic.

Coenzyme

An organic cofactor (ex. vitamins)

Inhibitor

A chemical that interferes with an enzyme’s activity. Important in regulating the cell’s metabolism

Competitive inhibitors

block substrates from entering the active site and reduce an enzyme’s productivity

Noncompetitive inhibitors

bind to the enzyme somewhere other than the active site and change the shape of the active site. Prevents the substrate from binding

Feedback inhibition

The product Acts as an inhibitor of one of the enzymes in the pathway that produced it

An example of enzyme inhibitors that are seen everyday are…

Drugs like ibuprofen, antidepressants, etc.

How can enzyme inhibitors work as pesticides and deadly poisons for chemical warfare?

They can block the ability to make ATP through carbonmonoxide