Zoology 153 Quiz 2

Solute

Dissolved substance

Flow of Concentration Gradient

High concentration to low concentration

Permeable Membrane

Solute can move across a membrane

Impermeable

Solute cannot move across a membrane (water still can)

Osmosis

Movement of water from an area of low solute concentration to high solute concentration

Contractile Vacuole

Absorbs excess water in the cell and expels it to prevent cells from exploding

Hypertonic RBCs

Surroundings have more solutes than RBC cytoplasm so RBC shrink

Isotonic

Surroundings have solutes comparable to the RBC cytoplasm and RBCs maintain their shape

Hypotonic

Surrounds have fewer solutes than the RBC cytoplasm and the RBCs swell

Cell Wall Function

Provides structural support and protection

Turgor Pressure

Pressure within cell when water moves into the cell through osmosis

Causes plants to wilt

Simple Diffusion

Molecules move directly across the membrane

Facilitated Diffusion

Molecules move from high to low concentration through transporters embedded in the membrane (channels)

Uniport

When the transporter or channel allows movement of one solute

Cotransport

Two solutes move through a single channel

Symport

Two solutes move in the same direction

Antiport

Two solutes move in opposite directions

Primary Active Transport

Cells move substances against their concentration gradient and energy must be expended (ATP)

NA+ / K+ + ATPase is an active transporter / pump that exchanves 3 Na+ for 2 K+ in a four-step process

Secondary (indirect) Active Transport

One solute is moved against its concentration gradient by active transport and a second solute’s movement can be coupled to that of the first by cotransport

Second relies on the active transport of the first

Prokaryotic

“before a nucleus”

Cells (bacteria) that lack a nucleus and typically have little or no internal compartmentalization

Eukaryotic

“true nucleus”

Cells that have a nucleus and internal membrane-bound organelles

Endomembrane System

System of internal membranes that allows specific cellular functions to occur within the localized spaces in the cell

Exocytosis

Fusion of vesicle with the cell’s plasma membrane

Endocytosis

Internalizes materials from the surface to create a new vesicle

Nuclear Envelope

Double membrane that surrounds the nucleus

Regulates traffic in and out of the nucleus

Nuclear Pores

Nuclear envelope is perforated with these large multi-subunit channels that regulate inward and outward movement of solutes and macromolecules

Endoplasmic Reticulum (ER)

Continuous with the nuclear envelope and is a site of lipid and protein synthesis

Rough ER

Studded with ribosomes

Many proteins destined for secretion and transmembrane proteins are synthesized here

Smooth ER

Site of lipid and steroid synthesis

Golgi Apparatus

“stack of pancakes” structure

Modifies proteins and lipids produced in the ER

Sorts proteins and lipids as they move to their final destinations

Synthesize carbohydrates

Golgi Apparatus is made up of

A series of flattened sacs called cisternae

Edges bud off as vesicles carrying proteins or modified sugars to the cell membrane of organelles in the cell

Enzymes within the Golgi Appartus ….

Chemically modify proteins and lipids in a sequence of steps in a different region of the organelle

Lysosomes

Derived from the Golgi apparatus

Degrade damaged or unneeded macromolecules

pH of Lysosomes

Maintain a pH of 4-5

Proton pumps help maintain this low pH

Exocytosis

• Transport (along microtubules) vesicles migrate to the membrane, fuse with it, and release their contents outside the cell

• Production of vesicles, budded from Golgi

• Docking of vesicles with the plasma membrane; fusion of vesicles with the plasma membrane & contents are released; recycling of leftover membrane

Endocytosis

• Macromolecules are taken into the cell in vesicles

• Membrane forms a pocket that deepens and pinches off, forming a vesicle

Receptor-mediated endocytosis

• Vesicle formation is triggered by solute binding to receptors

• Receptor proteins bound to specific solutes are clustered in coated pits that form coated vesicles. The coats are formed by special proteins that aid membrane bending and pinching

• Emptied receptors are recycled to the plasma membrane by the same vesicle

Mitochondria

Extract energy from metabolites

Found in all eukaryotes, double membrane, divide independently and contain their own DNA

Cholorplasts

Harness light energy to create carbon-containing compounds

Found in plants, double membrane, divide independently and contain their own DNA

Endosymbiosis

Biological relationship where one organism lives inside the body or cell of another, usually to the benefit of both

Reason that eukaryotic cells came from prokaryotic cells

Cytosol

The fluid portion of the cytoplasm inside a cellW

Where are mRNAs bound?

Cytosol by ribosomes

Translation

Making of proteins which begins in the cytosol

Sorting Sequence

Specific amino acids incorporated into the polypeptide dictate where it will be transported

Proteins destined for the ________ system are made in the ____

Endomembrane system; rough ER

Squirted into the lumen (center) of the ER

Some are completely released, other remain inserted into a piece of the ER membrane

Proteins that are completely released will …

Remain in the aqueous medium inside a vesicle; typically screted

Proteins that remain inserted into a piece of the ER membrane will …

Be inserted into a membrane (like the plasma membrane)

ER-Targeting Signal Sequences

• Specific N-terminal signal sequence with attached ribosome bind to the ER

• Signal sequence is bound by the signal recognition particle (SRP)

• When SRP binds, translation pauses until the SRP binds the SRP receptor on the ER

• Translation begins again

• SRP will disassociate from the polypeptide

  • Polypeptide will be fed into the ER lumen

Hight temperature on membranes

Causes greater molecular motion of the bilayer which can increase permeability to solutes and can eventually destabilize the bilayer

Low temperature on membranes

Causes excessive membrane rigidity and impedes proper membrane transport

Homeoviscous Adaptation

Altering lipid composition to adjust membrane viscocity

Extremophiles

Organisms that have more drastic adaptations (more disulfide bonds, other modifications, etc.)

Cytoskeleton

Provides internal structural support

Enables transport within the cell via motor proteins

Formed from long chains of protein subunits joined together

3 Main Polymers of Cytoskeleton

1. Microfilament; from actin monomers

2. Intermediate filament; from protein subunits

3. Microtubule; from tubulin dimers

Centrosome

Central organizing center where a microtubule has their minus end

Why are Microtubules Important

Important for chromosome segregation during cell division

Allow vesicle transport

Formation of Cilia and flagela

Where does growth occur in a microtubule and microfilament

Growth occurs more quickly at the plus ends while minus ends are less dynamic

What causes a bend in a microtubule

Dyneins are positions to slide adjacent microtubules which are locked togther into an integrated network; this uses energy (ATP)

Kinesin Function

Moves cargo toward the plus end of MTs; requires energy (ATP)

Dynein Function

Moves cargo toward the minus end of MTs; requires energy (ATP)

What are cells organized into?

Tissues

Extracellular Matrix

Associated with sheets of cells

Lies outside of cells

Cell-cell Adhesion

Cells stick togetherC

Cell-ECM Adhesion

Cells need to stick to ECM

Cadherins

Cadherins are cell adhesion proteins that help connect one cell to another cell. They bind to cadherins on neighboring cells and are connected to the cytoskeleton inside the cell.

Integrins

Integrins are cell adhesion proteins that attach to the ECM and connect to the cytoskeleton inside the cell.

Junctions

Adhesion molecules assemble in sheets of cells (epithelia)

Tight Junctions

Permeability barrier, sealing the sheet so solute movement is restricted

Adherens Junctions

Contain cadherins and confer adhesion

Desmosomes

Connect to intermediate filaments to form mechanically strong “spot welds” between cells

Gap Junctions

Allow passage of small molecules between cells

Cisternae

A series of flattened sacs of Golgi

Metabolism

Building and breakdown of carbon sources to harness or release energy

Anabolism

Building of molecules from smaller units, requiring an input of energy (ATP)

Catabolism

Breakdown of molecules into smaller units, producing energy (ATP)

First Law of Thermodynamics

Energy cannot be created or destroyed; it can only be transformed

Potential Energy

Stored energy

Chemical Energy

Considered a form of potential energy

As energy in the cell is transformed …

The energy available to do work in the cell decreases

Entropy (S)

Measure of disorder; cells do work to combat increases in entropy

Gibbs Free Energy

Measure of the energy available to do work

Allows us to predict whether a reaction is favored

G = H - TS

Exergonic

DG is negative and the reaction is favored

Products store less free energy than the reactants and it is spontaneous

Liberate energy

Endergonic

DG is positive and the reaction is not favored

Products store more free energy than the reaction and it is non-spontaneous

Require energy input

Is glucose oxidation exergonic or endergonic?

Exergonic!

How to make an endergonic reaction favorable?

Couple it with an exergonic one like the synthesis of glutamine!

Phosphorylated Intermediate

The P from ATP gets moved around when you couple a reaction to ATP

Minority Shareholder of ATP

GTP

Minority Shareholder of NADH

FADH2

Intermediate Energy

Allows ATP to drive reactions but also be readily replenished

Reduced

Molecules acquire electrons

Oxidized

Molecules lose electrons

Important electron carriers in cellular respiration

NAD+ and FAD

What helps a reaction proceed

Enzymes!

What do enzymes do?

Lower the activation energy; delta G is the same

Enzymes often require a ….

Cofactor: metol ion, etc.

Enzyme process

1. Enzyme binds to substrate

2. Complicated interaction occurs between the reactants and the enzyme

3. Substrate is converted to products

4. Products are released

5. the same enzyme is ready to undergo another round

Active Site

Formed within the function protein, depends on tertiary structure

Helps stabilize the transition state

Hexokinase

Enzyme that catalyzes the first step in glycolysis

Induced Fit

Enzyme’s shape changes to fit substrate more tightly

Competitive Inhibition

A substance binds to the active site and blocks it from substrate