BIOL 102 Lecture 6: Chapter 6:7 Membrane Structure and Function

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6. Membrane Structure and Function 30/09/2016

Microscopy is used to look at cellular structure. An electron microspore as a much great power

so as to look and cellular organisms.

- Magnification is the ratio between the size of an image produced by a microscope and its

actual size.

- Resolution (clarity) is the ability to observe two adjacent objects as distinct from one

another.

- Contrasts Is the ability to distinguish different structures and can be enhance using dyes.

Light microscope

- Uses light for illumination

- Resolution 0.2 um

Electron microscope (SEM, TEM)

- Uses an electron beam (short wavelength)

- Resolution 2 nm

- Requires coating with heavy metal

Physical and Biological Principles that influence cell structure

- All life can be placed into two categories

o Prokaryotes (bacteria, archaea)

o Eukaryotes

- Cell structures as key organizing features

o The cell membrane is the border between cell exterior and its interior

o The interior of the cell is called cytoplasm

o All cells export macromolecules from their cytoplasm to outside the cell to form

a potetie ati o the eteio side of the ell’s eae.

o Cytoplasm is an aqueous environment further organized into specific

compartments by internal membranes or complex protein assemblages.

- Creating and maintaining cell structure requires

o Matter, energy, organization, and information

Structure + function example: membrane lipids in archaea vs bacteria (+ eukaryotes)

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Typical bacterial cell

Plasma membrane – barrier

Cytoplasm – contained inside plasma membrane (cytosol as fluid surrounding all organelles)

Nucleoid – region where genetic material found (may also be extra-chromosomal DNA)

Ribosomes – involved in protein synthesis

Eukaryotic cells

- DNA housed inside nucleus

- Compartmentalization

Organelle – membrane-bounded compartment

with its own unique structure and function

Shape, size, and organization of cells vary

considerably across species and even among

different cell types of the same species.

Eukaryotic cell has internal membranes that

partition the cell. Plant and animal cells have

most of the same organelles.

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The proteome determines the characteristics of

a cell

Proteome controlled by genome

Identical DNA in different cells but different

proteomes – proteome is dynamic.

The proteome of a cell determines its structure

and function

Gene regulation, amount and type of protein, and

potei odifiatio a ifluee a ell’s

proteome

Proteomes in live cells are different from the

proteomes of neurons, skin cells, etc.

Cytosol

- Surrounds organelles but inside the plasma membrane

- Cytoplasm includes everything inside the plasma membrane

o Cytosol = the milieu surrounding organelles

Metabolism

- Cytosol is central coordinating region for many metabolic activities of eukaryotic cells

- Catabolism – breakdown of a molecule into smaller components

- Anabolism – synthesis of cellular molecules and macromolecules

Translation

- Process of polypeptide synthesis

- Information within a gene is ultimately translated into the sequence of amino acids in a

polypeptide.

- Ribosome- site of synthesis

- Transfer RNA (tRNA) – brings amino acids

- Messenger RNA (mRNA) – information to make a polypeptide

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Document Summary

Microscopy is used to look at cellular structure. An electron microspore as a much great power so as to look and cellular organisms. Magnification is the ratio between the size of an image produced by a microscope and its actual size. Resolution (clarity) is the ability to observe two adjacent objects as distinct from one another. Contrasts is the ability to distinguish different structures and can be enhance using dyes. Physical and biological principles that influence cell structure. All life can be placed into two categories: prokaryotes (bacteria, archaea, eukaryotes. Creating and maintaining cell structure requires: matter, energy, organization, and information. Structure + function example: membrane lipids in archaea vs bacteria (+ eukaryotes) Cytoplasm contained inside plasma membrane (cytosol as fluid surrounding all organelles) Nucleoid region where genetic material found (may also be extra-chromosomal dna) Organelle membrane-bounded compartment with its own unique structure and function.

Related Questions

What electron or light microscopy technique would you use toobserve the following?

a) the fine detail of the outer surface of hair cells in theinner ear.

b) the interior and exterior of surfaces of the plasma membraneto support the Fluid-Mosaic Model of membrane structure.

c) very thin cross sections made in Epon in order to visualizethe fine structure of cellular organelles and cell architecture inthe cell interior.

d) particulate matter (like large multisubunit enzyme complexesor viruses) so as to exhibit the subunit structure. Negativestaining.

e) specifically localize a molecule like tubulin in a cell usinga light microscope.

f) the highly organized structure at the molecular level of thespindle of a dividing cell using the lightmicroscope.

g) technique using lasers to optically section large specimens;the images may be computer-enhanced.

h) living cells without killing them by adding stain.

i) a three-dimensional view (almost bas-relief view)of chromosomes in a dividing cell.

j) living cells with high resolution and with extraordinarycontrast at extremely low light levels to keep the cells aliveduring the observation.

k) viewing poorly stained specimens by focusing light on thespecimen alone; the specimen stands out brightly against a darkerbackground

ceruleanfox955

__________ are fairly small organelles that provide a safe place within the cell to carry out certain biochemical reactions that generate harmful, highly reactive oxygen species. These chemicals are both generated and broken down in the same location.

Lysosomes

Endosomes

Peroxisomes

Nucleosomes

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies?

rapid rate of reproduction

all of the above

ability to grow under controlled conditions

amenability to genetic manipulation

By definition, prokaryotic cells do not possess __________.

ribosomes.

a nucleus.

membrane bilayers.

replication machinery.

Cell biologists employ targeted fluorescent dyes or modified fluorescent proteins in both standard fluorescence microscopy and confocal microscopy to observe specific details in the cell. Even though fluorescence permits better visualization, the resolving power is essentially the same as that of a standard light microscope because the resolving power of a microscope is limited by the __________ of light.

intensity

absorption

wavelength

filtering

Choose the phrase that best completes this sentence: Microtubules ____________ and are required to pull duplicated chromosomes to opposite poles of dividing cells.

generate contractile forces

can rapidly reorganize

are found in especially large numbers in muscle cells

are intermediate in thickness

Despite the differences between eukaryotic and prokaryotic cells, prokaryotes have proteins that are distantly related to eukaryotic actin filaments and microtubules. What is likely to be the most ancient function of the cytoskeleton?

cell division

cell motility

vesicle transport

membrane support

DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA?

It contains thymine.

It has 5'-to-3' directionality.

It is single-stranded.

It contains uracil.

Double covalent bonds are both shorter and stronger than single covalent bonds, but they also limit the geometry of the molecule because they ____________________.

prevent additional bonds from being formed with the bonded atoms.

limit the rotation of the bonded atoms.

create a new arrangement of electron shells.

change the reactivity of the bonded atoms.

Drosophila melanogaster is a/an __________. This type of animal is the most abundant of all animal species, making it an appropriate choice as an experimental model.

mammal

amphibian

bird

insect

10.

If the isotope 32S has 16 protons and 16 neutrons, how many protons, neutrons, and electrons will the isotope 35S have, respectively?

16, 19, 17

16, 19, 15

16, 19, 16

16, 20, 15

11.

Living systems are incredibly diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Despite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit?

cell

organelle

protein

DNA

12.

Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable?

the concentration of each molecule

the size of each molecule

surface complementarity between molecules

the rate of synthesis

13.

Many of the mechanisms that cells use for maintenance and reproduction were first studied at the molecular level in bacteria. Which bacterial species had a central role in advancing the field of molecular biology?

E. coli

S. pombe

C. elegans

D. melanogaster

14.

Many types of cells have stores of lipids in their cytoplasm, usually seen as fat droplets. What is the lipid most commonly found in these droplets?

cholesterol

isoprene

triacylglycerol

palmitic acid

15.

Mitochondria contain their own genome, are able to duplicate, and actually divide on a different time line from the rest of the cell. Nevertheless, mitochondria cannot function for long when isolated from the cell because they are __________________.

anaerobes.

viruses.

parasites.

endosymbionts.

16.

Mitochondria perform cellular respiration, a process that uses oxygen, generates carbon dioxide, and produces chemical energy for the cell. Which answer below indicates a correct pairing of material âburnedâ and the form of energy produced during cellular respiration?

17.

Polar covalent bonds are formed when the electrons in the bond are not shared equally between the two nuclei. Which one of these molecules contains polar bonds?

BIOL 102 Lecture 6: Chapter 6:7 Membrane Structure and Function

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