Microbiology Review Unit 1

Cell size is not limited by its surface-to-volume ratio

False

Smaller cells have a \_____ amount of surface area compared to the volume

larger

An increase in surface are allows for \_____ nutrients to pass into the cell and \____ wastes to exit the cell (same word)

more

The plasma membrane is also called the...

cell membrane

The plasma membrane is a \_____ bilayer that surrounds cells

phospholipid

The plasma membrane surrounds the whole cell

True

Phospholipids are \_______ molecules

amphipathic

The hydrophobic region faces __

in

The hydrophilic region faces \________

out

Membranes contain what two macromolecules?

proteins and lipids

The plasma also contains what other macromolecule, used for structural support?

carbohydrates

Three functions of the cell membrane:

cell signaling, membrane transport, cell adhesion

How does the structure of the membrane relate to its function as a selectively permeable barrier for the cell?

the semipermeability of the phospholipid bilayer allows ions and molecules to enter/exit the cell

Are the heads of phospholipids polar or nonpolar?

polar

Are the tails of phospholipids polar or nonpolar?

nonpolar

What is diffusion?

the movement of particles from high to low concentration

What are the two types of passive transport?

simple diffusion and facilitated diffusion

Passive transport requires energy to go down/with a gradient

False

What is simple diffusion?

substance moves across a membrane without any transport proteins

What is facilitated diffusion?

solute can move through a membrane with the help of a transport protein

What is active transport?

movement of substances from low to high concentration with the help of a membrane protein and ATP

Does active transport need energy to move a substance across the membrane?

Yes

What type of molecules diffuse through membranes?

Gases, water molecules, lipids, lipid soluble molecules, and small non-charged molecules

High permeability occurs with liquids and small uncharged molecules

False

Moderate permeability occurs with water and urea

True

Low permeability occurs with nonpolar organic molecules

False

Very low permeability occurs with ions, charged polar molecules, and large molecules

True

Cells maintain \_____ across membranes

gradients

What gradients do cells have to maintain?

transmembrane and electrochemical gradient

What is osmosis?

the diffusion of water molecules from a high to low water concentration

Explain isotonic solutions

equal solute concentration on both sides of membrane

Explain hypertonic solutions

solute concentration is higher on one side of the membrane

Explain hypotonic solutions

solute concentration is lower on one side of the membrane

Normally, body fluids are \______ to cells

isotonic

Cells do not change size in isotonic solutions

True

Hypotonic solutions can cause cells to...

swell and burst (lysis)

Hypertonic solutions can cause cells to...

shrink (crenation)

\______ pressure drives osmosis

osmotic

Only one molecule can move at a time with transport proteins

False

Protein transporters are very specific and can move certain molecules

True

Most channels are \____

gated

What are gated channels?

they open for the diffusion of solutes and close to prohibit diffusion

Active transport moves molecules with the concentration gradient

False

What are the two types of active transport?

primary and secondary

How does primary active transport work?

directly uses energy with a pump to transport solute

How does secondary active transport work?

uses a (different) pre-existing gradient to drive transport

How does a sodium-potassium pump work?

pumps Na out and K in

Does a sodium-potassium pump flow against or with the concentration gradient?

against

Is there more sodium in or outside of the cell?

outside

Is there more potassium in or outside of the cell?

inside

Purpose of sodium-potassium pumps

helps maintain ion gradients

Cells use \____ transport to move large molecules across the membrane

bulk

What is endocytosis?

the transporting of molecules or cells into the cell by engulfing it with the cell membrane

What are the three types of endocytosis?

phagocytosis, pinocytosis, receptor-mediated endocytosis

What is phagocytosis?

ingestion of bacteria by white blood cells

What is pinocytosis?

ingestion of fluid with small particles

What is receptor-mediated endocytosis?

particles first bind to receptors in the plasma membrane to initiate endocytosis

What is exocytosis?

the transporting of molecules outside the cell via the fusion of a vesicle with the plasma membrane

Why is exocytosis important?

allows cells to recycle membranes and receptors

All integral membrane proteins can move

False

Membranes have the same composition of lipids, proteins, and carbohydrates

False

Membrane proteins can rotate and move laterally in the plane of a membrane at a faster rate than lipids

False

The optimal level of fluidity for the cell membrane is essential for....

cell function growth and division

What happens in the nucleus?

genetic material is organized and expressed

What is a nuclear pore?

a passageway for molecules into and out of the nucleus

What does a nucleus contain?

chromatin (a complex of DNA, histones, and other proteins)

What makes the nucleus delimited?

nuclear envelope

What happens in the nucleolus?

ribosome subunit assembly

The nucleolus is enclosed by a membrane

False

What is the nucleolus?

dense area within the nucleus

What is the end product of the synthesis that occurs in the nucleolus?

ribosomes

What is the nuclear envelope?

double membrane that encloses nucleus

What is the function of free ribosomes?

synthesize nonsecretory and nonmembrane proteins

What is the function of membrane-bound ribosomes?

secrete or insert proteins into the ER membrane, becoming integral proteins

The endomembrane system includes what structures?

nuclear envelope, ER, golgi apparatus, lysosomes. membrane-bound vesicles (endosomes)

What does the endomembrane system do?

divides the cell into functional compartments and organizes the transport of substances throughout the cell

What is the golgi apparatus?

flattened stacks that process, package, and deliver proteins and lipids from the ER

What is the function of the golgi apparatus?

site of modification, sorting, and secretion of lipids and proteins

What do lysosomes do?

break down macromolecules

What do endosomes do?

use endocytosis for the uptake of extracellular material

What enzyme do lysosomes contain that help them to break down macromolecules?

hydrolytic enzymes

Lysosomes fuse with endosomes and digest contents

True

What is the function of the endoplasmic reticulum?

Modifies, packages, and transports proteins

What is the function of the Rough ER?

protein sorting and secretion, attachment of carbohydrates to lipids and proteins

What happens in the smooth ER?

drug and alcohol detoxification, lipid synthesis, calcium storage, metabolism

Where do lysosomes originate?

rough ER

Where do peroxisomes originate?

smooth ER

What makes up cytoskeleton?

microtubules, microfilaments, intermediate filaments

Microtubules are composed of...

polymers of tubulin

What is the largest component of the cytoskeleton?

microtubules

Microtubules help...

maintain cell shape

Microtubules act as \____ that help the organelles move

tracks

During cell division, microtubules form the...

spindle apparatus

Microfilaments are made of the protein called...

actin

The smallest component of the cytoskeleton are the...

microfilaments

What do microfilaments do?

produce movements of cell edges and move contents of cell interior

Intermediate filaments are composed of various proteins like...

keratin, desmin, lamin

Intermediate filaments provide \_____ but do not produce \___ (two words)

structure; movements

Intermediate filaments form the network of the nuclear lamina

True

What are peroxisomes?

eukaryotic organelles that contain catalyse to break down hydrogen peroxide