Biology: Diffusion and Concentration Gradients

• Study notes for Biology Exam/Review

Week 5 Chapter 4 (4.1-4.2)

Diffusion Overview

• Diffusion involves the movement of molecules from an area of higher concentration to an area of lower concentration
• Process continues until equilibrium is reached.
• Contains a solute (solid) and a solvent (liquid).
• Molecules never stop moving.
• Vitamins A, K, gases, and water can pass through, O2 and CO2 enter and exit
• Temperature: rate of diffusion increases with temperature
• Pressure affects diffusion

Concentration Gradient

• Movement goes from high to low concentration
• Substances move "down" the concentration gradient

Equilibrium

• Diffusion happens until equilibrium is reached
• Even distribution of molecules with no net movement in any direction after equal distribution

Molecular Size

• Smaller molecules diffuse more quickly than larger molecules
• Small, uncharged molecules can slip between the hydrophilic heads, passing through the hydrophobic tails of the lipid bilayer due to the concentration gradient

Temperature and Diffusion

• Increase in temperature results in faster molecular movement and faster diffusion

Osmosis Overview

• Osmosis is the diffusion of water across a selectively permeable membrane
• Water moves from an area of higher water concentration, to an area of lower concentration, or towards a higher solute concentration
• Osmotic pressure develops in a system due to osmosis

Water Movement

• Water diffuses down its concentration gradient
• Across a selectively permeable membrane water moves toward higher solute concentration

Osmotic Pressure

• Pressure of a system increases to osmosis
• Water diffuses down its concentration gradient, towards a higher solute concentration across a selectively permeable membrane, the greater the potential osmotic pressure

Isotonic Solutions

• Solute concentration is equal inside and outside the cell
• No net water movement occurs in animal or plant cells

Hypotonic Solutions

• Solution has a lower solute concentration than inside the cell, thus water enters the cell potentially causing it to burst (lysis)
• Animal cells gain water, cytolysis occurs, resulting in hemolysis in red blood cells
• Cell gains water and turgor pressure keeps plant erect due to pressure

Hypertonic Solutions

• Solution has a higher solute concentration than inside the cell
• Water leaves the cell, causing it to shrivel (crenation)
• Animal cells lose water; crenation or shriveling occurs and Cell loses water and plasmolysis occurs in plant cells.

Plasma Membrane Structure and Function

Plasma Membrane Overview

• The plasma membrane separates the internal environment of the cell from its external environment
• Regulates the entrance and exit of molecules, only allowing certain molecules to pass to maintain homeostasis

Phospholipid Bilayer

• Acts as a sticky, flexible structure, similar to olive oil
• Has two layers, but not bonded together
• Polar, hydrophilic, and water-loving heads face inside and the outside of the cell
• Nonpolar, hydrophobic, and water-fearing tails face each other in the interior of the membrane
• Cholesterol (steroids) is present within molecules of a phospholipid bilayer to maintain the right consistency, and can stiffen and strengthen the membrane
• Unsaturated fats being not packed together tightly allows fluidity within the membrane
• The membrane is a fluid-mosaic model, formed by a pattern of phospholipids, steroids, and proteins

Membrane Protein Functions

• Transport
• Enzymatic activity
• Signal transduction (receptor cell)
• Cell-to-cell recognition
• Intercellular joining
• Attachment to the cytoskeleton and extracellular matrix

Selective Permeability Overview

• Selective permeability regulates the passage of molecules into and out of the cell
• Selectivity is determined by molecule size, charge, and polarity
• Determines which substances can freely cross the membrane and which need carrier proteins/energy

Molecule Size

Polarity:

• Small, uncharged molecules, like CO2, O2, glycerol, and alcohol, cross freely

Charge:

• Ions and charged molecules cannot freely cross the membrane

Polarity

• Nonpolar molecules cross more readily than polar molecules
• Small, uncharged molecules are able to slip past hydrophobic tails

Charge Requirements

• Requires channel proteins to form a pore, carrier proteins specific to substance, or vesicle formation in endocytosis or exocytosis for charged molecules and ions

Channel Proteins

• Channel proteins allow the passage of solutes through a membrane and allow substances to move across the membrane easily
• Some have a gate that opens upon a signal
• Attached to different sites with proteins but have the same goal to remain cell shape
• Move sugar, amino acids, and charged large molecules
• Aquaporins enable water to cross the membrane and are present in the majority of cells

Receptor Proteins

• Receptors have a shape that allows a specific molecule to bind
• Binding causes the receptor to change shape and initiate a cellular response

Enzymatic Proteins

• Carry out metabolic reactions directly

Carrier Proteins

• Facilitate the passage of a solute by combining with it
• Help it move across the membrane some require energy others do not

Cell recognition proteins

• Glycoproteins which help the body recognize when its being invaded by pathogens

Concentration Gradient Overview

• The concentration gradient refers to the gradual change in concentration of a solute in a solution between two regions
• Molecules move from an area of higher concentration to an area of lower concentration (down the concentration gradient), until equilibrium is reached
• Moving against the gradient requires energy

Down a Concentration Gradient

• Movement from an area of higher concentration to an area of lower concentration
• Occurs naturally through diffusion until equilibrium is reached
• Does not require an input of energy

Up a Concentration Gradient

• Movement from an area of lower concentration to an area of higher concentration
• Requires an input of energy, often in the form of ATP
• Occurs through active transport mechanisms using carrier proteins (pumps)

Energy Requirement

• Movement down a conce4ntration gradient does not require energy
• Movement up the the gradient requires energy (ATP), to move molecules against their concentration gradient
• Water that is polar would not be expected to readily cross the membrane

Membrane Protein Functions

Membrane Proteins Overview

• Membrane proteins interact with or are part of biological membranes
• Crucial for cell survival and communication, including transporting molecules, recognizing other cells, receiving signals, and catalyzing reactions
• Channel proteins and carrier proteins help large molecules, ions, and charged molecules to cross the membrane

Channel Proteins Function

• Involved in the passage of solutes through the membrane directly
• Some have gates that open in response to specific signals
• Forms a pore and examples includes chloride channels

Carrier Proteins Function

• Facilitate solute passage by binding and transporting them across the membrane
• Required for both facilitated and active transport
• Specific, combine with a molecule or ion to be transported
• Change shape to move molecules across membranes for example Vesicle formation in endocytosis or exocytosis.

Na/K Pump Importance

• The Na/K pump is important for nerve and muscle cells
• Moves Na out and K into cells, and the carriers change shape

Transport Mechanism By Carrier Proteins

• Required for facilitated transport and active transport
• Plasma membrane impedes the passage of all but a few substances
• Substances then enter or exit cells due to carrier proteins

Cell Recognition Proteins

• Differ by person
• Important in the immune system and organ transplantation
• Foreign proteins are attacked by white blood cells

Receptor Proteins

• Facilitate cell communication and response to external signals
• Faulty receptors result in diseases like dwarfism.
• Shaped to bind specific molecules

Enzymatic Proteins

• Catalyze specific reactions at the membrane surface like Adenylate cyclase involved in ATP metabolism.

Passage of Molecules into and out of the Cell

• Molecules are moved across the phospholipid bilayer of the plasma membrane

No Energy Required

• Diffusion, toward lower concentration, requires concentration gradient for example, Lipid-soluble molecules and gases
• Facilitated Transport, toward lower concentration, needs the channel or carreir, and concentration gradient for example, Some sugars and some amino acids
• Includes osmosis

Energy Required

• Active Transport, toward higher concentration, requires carrier and energy, example sugars, amino acids, and ions
• Exocytosis, toward outside, needs a vesicle fused with plasma membrane, example Macromolecules
• Endocytosis, toward the inside, requires vestile formation, and Macromolecules

Plasma Membrane Composition

Overview

• The plasma membrane is composed of a phospholipid bilayer with embedded proteins, steroids, and carbohydrates Structure provides selective permeability and allows cell homeostasis
• Allows small,uncharged molecules to freely cross the membrane. It might require carrier p.roteins or energy based on size, nature of molecule, polarity, and charge

Phospholipids

• Forming a bilayer with hydrophilic (polar) heads facing outward and hydrophobic (nonpolar) tails facing inward.
• Provide a basic barrier to water-soluble substances

Steriods

• Cholesterol (in animal cells) act to stiffen and strengthen the membrane
• Help regulate membrane fluidity.

Proteins:

• Integral Proteins are Embedded within the lipid bilayer, act as channel proteins, carry proteins, able to move laterally, and able to span membrane
• Peripheral Proteins: Located on the side of the membrane

Carbohydrates

Attached to lipids (glycolipids) or proteins (glycoproteins; outer surface) on the outer surface of the membrane, and Involved in cell recognition and interaction

Glycolipids

• Lipids with attached chains.
• Found on the surface of the extracellular surface of the plasma membrane,
• Function in cell signaling and recognition.

Glycoproteins

• Proteins with attached chains.
• Found on the extracellular surface of the plasma membrane,
• Function in cell signaling and recognition.
• Roles in cell recognition and in signalling

Solutions and Tonicity

Overview

• Tonicity refers to the relative solute concentrations of two solutions (inside and outside the cell) separated by a semipermeable membrane

Isotonic

• Solute concentration is equal inside and outside the cell
• No net movement of water. animal and plant cells volume stay neutral

Hypotonic

• lower solute concentration than inside the cell
• Water moves into the cell. this can cause Cytolisis of cell

-Hypertonic

• higher solute concentration than inside the cell
• Water move outs of the cell causing it to shrivel

Membrane Response Animal Cells:

• Isotonic: normal cell shape
• Hypotonic: Water influx, cell swelling and potential lysis
• Hypertonic: water efflux, cell shriveling

Plant Cells:

• Isotonic: no net water movement, cell is flaccid
• Hypotonic is turgid
• Hypertonic: plasmolysis occurs as the cytoplasm pulls away from the cell wall.

Transport mechanism Overview

• Transport molecules across cell membranes essential
• Mechanisms include passive processes like facilitated transport, which doesn't require energy, and active processes like active and bulk transport, which need energy from ATP

Facilitated Transport

• The passage of molecules such as glucose or amino acids and transports watersoluble molecules down their concentration gradients
• Requires carrier proteins that go under shape conformational changes by reversibe combinations
• Used for molecules like glucose and amino acids that are not lipid soluble and does not require ATP

Active Transport

• Transports molecules through pumps against their concentration gradient and cell
• Needs ATP
• Accumulates molecules

Bulk Transport

• Transports macromolecules via vesicle formation
• Requires energy to forms vesicles from its membrane
• Can occur through exocytosis (exit cell) and endocytosis (enter into cell).

Exocytosis

• Type of bulk transport where macromolecules exit via vesicles
• Cells of organs specialize for export and production

Endocytosis

• Type of bulk transport, macromolecules eneter cell
• Part of which envelops the substance forming intracellular vesicle

Pinocytosis

• Form of endocytosis (liquids and small particles) where cell digests material

Phagocytosis

• Form of endocytosis (food) molecules, large particles, consume whole and food such bacteria amoeba

Receptor-Mediated Endocytosis

• Another form of endocytosis where molecules bind to cell surface triggering formation

*Week 6 chapter 17.1-17.2

• Synaptic Integration
• A collection of signals, neurons stimilated

-Excitatory signals

• Causes polarision and a new a action potential

-Inhibitory signals

• Effect on axon and inhibits from triggering potentials

Synaptic integration

• The excitatory and inhibitory signal
• Deetermines future actions

Nervous Tissue

• Sensory reception in our tissue
• Envirmonmental reception

Nervous system

• Brain and spinal cord
• CNS is found in the Spinal cord

Neuron and neuroglia

• Nuron is a the transmitter
• Neuroglia is the in extrecellular

Nueron types

• 3 systems send information
• Sensors in the body

Interneurons

• Brain to spinal cord
• Transmmited through central messages

-Motors NUerons:

• From NS effector
• Effectors and Synaptic axon

Transmission of

• Nuerons use impluse through infomratoin in the cel

##RESTING POTENTIAL IMPUlse

• No condiction

#Sodim Potsssium pump The in and out transfer of K

-Resting potential

• Separation of changes

Sodium Pump

• Activating ions across the axis Ions distribution
• High amounts of Sodium inside outside and posssium axis side

Membrane premeable

• Memrbane is pereeabel K potessoum diffuser

Nervous System

• CNS brain annd cord
• Resoponsbile for desison making
• Spinal cord connect brain and Pns system

-2 types of nervous cell

matter cells

• Grey matte Nymellinate spinal and cord

WHITE MATTER CELLS

• Mileynated Axon cord and tracts

PERIPHERAL SYSTEMS

• Sensory and motos system messaged through CNS glandss

Schwannin cell

• Nueron
• The forms Sheeths

-NODEs AND Ranvier

• Gaps in myelin sheathh
• Mypelin sheath and importqant for regenration

##NUERON STRUCTRURE

• Cell body: Contains the nucleus and other organelles to integrate its signal from from the the external envrimeont
• AXON: Condcuts inpulws from the

Cell Body:

• Contains Nucleus and other organelle
• Integrates their signals

DEndridtesss

• EXxtenisons signelas through cells

AXon:

• Conducts nerve impusles

Mylon sheets

• Fatty insulation

ACtion poteinntal

• Change in polatiry which can Axom memerbraness and cahnnel ACtion begins after srimus

MEMRANeS

• Cause the reach threshoulds Potietnals

-Depolarix

• Depolsaruxarions- Threshold - open chanel More posotive

Gateed Chanels

• Open durning infuxs

Theroushold:

• If there is action its triggerws Refratory period and its over

Refratory Periodss-

-Soidum, If there is strong an d

CONDUCtionss

• Innonmellinated actions which
• Small setgment at a

Action potenital

• Travels down

Satatoty

• Action potenails that jymm
• GATEDS IOON chanel underneath
• MYLINNN 3 and 6

Chapter Synpatic Tranismssiion

• Neuros communicate other system
• Involvess releaes of neurnot

At synapse

• COntains veseiclaes called axon

-AXOn

• Lies through Cell of musscles -Synaptic Cliiff

-Acerto

• Releaasseds upon
• Neuro transmotter can mimcs Actiocn for nuer Can int

Synaptic Integratiion

• Sing cell resives signals

Exicixtatry system

• The de polatirty

Inhibitory

• A new potenital

##Drugs

• Interfere with

CAPTIONS 6

ENEERGT FORMS

OVERveiw

• 2 PRIMATY forms Potientla KINTEC ewrngy

PTTENTIALL

• Sroed eneegy for capacoty Food

Kintets energysss!

-BAll Roll

CHEMICALS

• Store in them chemical
• CHeamical reactions or metobalisnm

Mechicanla

• Objects and wrokr

COUPOLES REACTISOD

• The energiies that happens in the body

REACTS REACTION

• ATP breakdown which is used up in the enegergt system

Endogermic

• Requries and energiies

REACTA REACTATS

• transferer
• Changin sjaoes

ATP energergises

• ATP provide energt
• Acvhieve

-Atp CHanges

• Hrytolosis alrters the shape of reacnt
• ACbieve though photr

CAPTP compoents

• Anergeeny is stortd Anergry curenciied

ATPS energym

CHEMICAOW

• Enerrghyt sznthesis
• Anbolisnm

TRransport

• ENERGY TOP OUMOP OUMPO

MECHIANCALLSL

• Muslsde constact cia

Enxyymees

Over

• REacion s eptialised

-BUiooo

• Speeed up reascctions No constratints

SUBSTATWE

Limipery

-Meteoblic PATH

• Linked reacrtions
• Eazh reacrtiosn

-Enxrgy activato0

• Exnzynes llower the actio9on

Engrymesss

• Eznxuyes bind susttatr
• Ebnzuymes

ACTITVE SITE

• PAwt of enzume
• The sibsrtate

-ACTITVWE SITES

• Changess shaoed

MMetoaboslummm

• OVER:
• Brejask down annb oilsn

CATA

Crap breakdowwn

REleasea ENErgy

• ANnnnbolizm

Reactionss

• Substatntes enteredr

CONvurtwd

Pr0dcuts

• Chemassi

Exxergoinzc

-Negtive chenge

Endefdrogoniczz

POOSITIE SHIFT

REDDOX REDACVTT

Electrrng

• Reductions and oxizdationssz

OHICADATINOS

• Losss elxtrtinoss
• LOSS H

EREDUCTINSZ

• Giaion elictironsx
• Eample chlroire gaing

TTRANESFER

• Elcttrron transfered Cello

EHYROGEN

• Los and gaion of hts Oxyzxdaut

- Enszyme reagulation

• Cello con trol enzzymticc and respovds

-SUBRSTAE

• Engenxc reations
• INFLUENCES

-TEERMMMPERARUTES

• High temp denateyr
• Ccaustructure

PUH

• Ezxh enxyzme has optal hte

Engyzmee

• Generates ptoducdzing erngess

TACTIVATES

• Inavtve enszyme

Einhbiti0nsh

• OCCOR WHEN SUCSTSATE

FEEDback

• Dinds to entyme d

POISoSNESSS

• ENZME CORTRAORR
• CO ENZXTYMES
• VIATNS chAPTRS>0 7

PPEPAROTS REACTION

• cruical and cell
• Cotymaed

ACEA-2

Pyrouatvde

cell.

• Cortsde

-IMOPUTS

• Pyrout
• ACetys coay and NADH
• 2 TIMES TO gluous ==

Explore the fundamentals of diffusion, focusing on molecular movement from high to low concentration until equilibrium is achieved. Learn about factors influencing diffusion rates, including temperature and molecular size, and how different molecules pass through cell membranes. Understand the role of concentration gradients in substance movement.