Chapter 4 BIO1511

Resolution

Resolution

minimum distance two point can be apart and still be distinguished as two separate points

Scanning electron microscopes

beam electrons onto specimen surface

Where is DNA located?

Nucleoid (not segregated) or nucleus (with a nuclear envelope)

Semifluid matrix of organelles and cytosol

Cytoplasm

Prokaryotic cells

*Simplest organisms: have a wall and membrane covering the cytoplasm
*Lack membrane bound nucleus
*Has ribosomes

Bacteria

with peptidoglycan susceptible to antibiotics

In prokaryotic cells where is the DNA located?

DNA is located in the nucleoid

What influences the cell wall shape in prokaryotic cells?

Cytoskeleton

What are BMCs in eukaryotic organelles?

functional but not structural analogs

Prokaryotes possess molecules related to _____ and _____ that influence the shape of the cell wall.

actin and tubulin

How does a flagella help move around?

rotating using the power if proton gradient

What are the properties of BCW?

protects the cell, maintains its shape, and prevent excessive uptake or loss of water

Septate or tight junctions

connect the plasma membranes of adjacent cells in a protective sheet preventing leakage

Communicating junctions

chemical or electrical signal passes directly from one cell to an adjacent on (gap junction, plasmodesmata)

How are eukaryotic cell walls distinct from prokaryotic cell walls?

chemically and structurally

Where are centrioles found?

in most animal cells and most protist

Microtubules organizing centers

can nucleate the assembly of microtubules

Centrosome

the area surrounding the pair of centrioles

Peroxisomes

are small organelles classified as microbodies that bud off the ER

Lysosomes

organelles formed from vesicles budding of the Golgi

Where are proteins and lipids received?

in the cis face

Cell Theory

idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells

Cell Size

most cells are round and small due to reliance on diffusion of substances in and out of the cell

Rate of diffusion is affected by

surface area
concentration gradient
temperature
distance

Which organisms cells have an advantage?

organisms with many small cell has an advantage over organisms with fewer, large cells

What happens as a round cell's size increases?

Its cells volume increases more rapidly than its surface and diffusion slows down

How do some large cells adapt?

by having more then one nucleus (muscle) to help spread information, or being skinny (neurons) to facilitate diffusion

What is the diameter of most cells?

less than 50 micrometers

How far apart do objects need to be apart for the naked eye to resolve them as two objects rather that one?

100 micrometers

Light Microscope

*Use 2 magnifying lenses (compound) with visible light.
*resolve structures that are 200 nm apart.
*limited to resolution using the wavelength of light

Electron microscopes

*Use beam of electrons
*resolve structures that are 0.2 nm apart

Transmission electron microscopes

transmits electrons through the material

Most cells are microscopic except...

vertebrate eggs that can be seen with the naked eye

How thick are cell membranes?

5nm thick

Basic Structural Similarities in all cells

1. Nucleoid
2. Cytoplasm
3. Ribosome
4. Plasma membrane

What synthesizes proteins?

Ribosomes

Phospholipid bilayer withe transport and receptor proteins

plasma membrane

What are the two domains of prokaryotes?

*Archaea and Bacteria

Archaea

With walls made of sugars and proteins

Bacterial microcompartments (BMCs)

Cellular compartments bounded by semipermeable protein shell
*40 to 400 nm in diameter

Functions of BMCs

isolate specific metabolic processes and storage

Cytoskeleton's strength and shape? *prokaryotes

is still determined by the cell wall

What do some prokaryotes have that allows them to move around?

pili (pilus, singular) or flagella (flagellum)

Where is the nucleoid visible in prokaryotic structure?

the nucleoid is visible in dense central region segregated from the cytoplasm

Bacterial cell walls

Composed if peptidoglycan, a sugar polymer (not necessarily glucose) crosslinked by short polypeptides units

What cell walls are different in bacterial cell walls?

cell walls of plants, fungi, and most protist are different

What does the susceptibility of bacteria to antibiotics depend on?

often depends on the structure of their cell walls

What do Archaean cell walls lack?

peptidoglycan

Archean have greater diversity on components. True or false

true

What helps distinguish archaea from bacteria?

membrane lipid structure

What does archaea contain?

saturated hydrocarbons that attach to both ends giving them more thermal protection.

What sis the machinery that replicates DNA more closely related to?

more closely related to eukaryotic systems than to bacterial systems

What is archaea more closely related to?

Eukaryotes on a molecular basis

What are the similarities of animal and plant cells?

They have plasma membranes.
Most of the same organelles.
Possess a cytoskeleton for support and to maintain cellular structure

Animal Cell

no cell wall, no chloroplast, no vacuoles, and no Glyoxysome

Plant Cell

Have cell wall outside plasma membrane, chloroplasts, vacuoles, Glyoxysome

Glyoxysome

for fat to sugar conversion through glyoxylate cycle

Nucleus

repository for genetic information

How many nucleuses do most eukaryotic cells possess?

a single nucleus

Nucleiolus

region where ribosomal RNA synthesis takes place

Nuclear envelope

two phospholipid bilayers (double membrane) that the formation of: nuclear pores- control movement in and out.

What is the outer layer continues with? Nuclear envelope

cytoplasmic endoplasmic reticulum

Where to the two bilayer come together?

at regularly spaced nuclear pores

What does the pore allow?

free diffusion with ions and small molecules while controlling the passage of proteins and RNA-proteins complexes made in the nucleoli

How is DNA divided in eukaryotes?

multiple linear chromosomes

Chromatin

chromosomes plus protein

How do cytoplasmic connections occur?

Through gaps in cells to communicate.

What connects the ER of two cells?

Central tube

Cadherin-mediated junction

the cadherins are anchored by actins in cytoskeleton of two adjacent cells allowing their interaction

Adhesive Junctions

mechanically attaches cytoskeletons of neighboring cells or cells to the ECM (include adherends junctions, desmosomes, hemidesmosomes

Cell-to-Cell Interactions

the surface proteins and other give cells identity

How do proteins give cell identity?

cells make contact, "read" each other, and react

Glycolipids

The most tissue-specific cell surface markers make the blood types (A, B, O) in red cells

MHC proteins

Major histocompatibility complex, are part of the recognition of "self" and "non-self" cells by the immune system

extracellular matrix

Instead of cell, Animal cells secrete a mixture of glycoproteins into the intercellular space.

What is ECM composed of?

collagen, Elastin and proteoglycan

What is ECM sometimes attached to?

The plasma membrane by a glycoprotein named fibronectin

What does fibronectin bind to?

to proteins called integrins

Integrin proteins

attached to microfilaments (Actin) and intermediate filaments of cytoskeleton

What does connectivity allow the ECM to do?

Influence cell behavior such as gene expression and migration patters

What is the most abundant protein in humans?

Collagen (25%)

Where is eukaryotic Cell Walls present?

plants, fungi, and some protists

What are plants and protist cell walls made of?

cellulose

What are fungi walls made of?

chitin and N-acetyl glucosamine

What helps cells move?

actin filaments, microtubules, or both

What do cells use to crawl?

actin microfilaments

What is the eukaryotic flagella and cilia made up of?

9 microtubules pairs surrounding 2 central microtubules

What is more common flagella or cilia?

cilia, they are shorter and more numerous

Cilia

Serve to move over the tissue surface, move air waves, etc.

Centrioles

Barrel-shaped organelles occurring in pairs surrounded by centrosomes

What is the centrioles surrounded by?

The pericentriolar material composed of tubulin.

What is the centrosomes responsible for?

For organizing of microtubules during cell division

Cytoskeleton

is the network of three types of protein fibers that crisscross the cell and help materials within

Actin

2 proteins twisted filaments involved in cellular movements

Microtubules (largest)

dimers of a- and B-tubulin subunits help move cell and materials within

Intermediate filaments (keratin, ect)

the most stable, give most of the support to the cell

Endosymbiosis Theory

Proposes that some present-day eukaryotic organelles evolved by a symbiosis between two free-living cells

Precursor of modern eukaryotes

one cell, a prokaryote, was engulfed by and became part of another cell

What has similarities to prokaryotic cells?

Mitochondria and chloroplast

Chloroplast

Organelles of plants and some other eukaryotes surrounded by two membranes produce sugars using light as a source of energy (translated by ATP) and CO2 as a source of carbon