Bk1 Ch3 tour of cell

Question 1

What is the limiting factor that prevents small structures being discriminated using a light microscope?

Answer 1

The wavelength of visible light.

Question 2

What does a scanning electron microscope (SEM)do?

Answer 2

Studies surface of intact cells and tissues

Question 3

What does a transmission electron microscope (TEM) study?

Answer 3

Studies internal organisation of cells by passing beam of electrons through a very thin tissue section allowing analysis of organelles and other components

Question 4

Cell fractionation

Answer 4

Process involving the separation of components of cells by disruption followed by ultracentrifugation.

Question 5

What is a physiological solution

Answer 5

An artificially prepared solution that has pH and salt concentrations that mimic the internal environment of the cell.

Question 6

Endospores

Answer 6

Dormant structures formed within some types of bacteria when growth conditions are unfavourable, which can later germinate and give rise to new individual bacteria

Question 7

Cytoplasmic inclusions

Answer 7

Gas versicles, endospores, glycogen granules

Question 8

Gas versicle

Answer 8

Surrounded by protein shell and have role in buoyancy of some aquatic bacteria

Question 9

Glycogen granules

Answer 9

Glycogen is a polymer of glucose, which some bacteria store as an energy reserve

Question 10

Peptidoglycan

Answer 10

Large polymer consisting of complex arrangement of sugars linked by amino acids including three amino acids are not found naturally in proteins

Question 11

What are the cell walls of a bacteria composed off?

Answer 11

Peptidoglycan

Question 12

What is the difference between the cell walls of gram positive and gram negative bacteria?

Answer 12

The peptidoglycan layer is much thicker in gram-positive bacteria

Question 13

Suggest some Key cellular functions or processes

Answer 13

Synthesis of DNA, lipids, carbohydrates, proteins. Secretion, movement, protection, Cell division.

Question 14

Suggest two functions of the cell surface

Answer 14

Protection, and absorption of nutrients. Secretion of signalling molecules or enzymes, disposal of selling of wastes, gas exchange, cell to cell recognition.

Question 15

One major difference between different eukaryotes is the presence or absence of a cell ball in which eukaryotic kingdom to all cells lack a cell wall?

Answer 15

Animalia

Question 16

Transmembrane proteins

Answer 16

Integral membrane protein which interacts with and spans the hydrophobic core of the lipid bilayer; may be described as single pass or multipass, depending on whether the polypeptide crosses the membrane once or more than once.

Question 17

Peripheral proteins

Answer 17

Membrane proteins that are not associated with the hydrophobic interior of the lipid membrane; instead they either associate with the membrane indirectly via noncovalent interactions with other membrane proteins, or directly via interactions with the hydrophilic head groups of the lipids. The proteins that mediate attachment of integral membrane proteins to the cell cytoskeleton are examples of peripheral proteins.

Question 18

Cytoskeleton in eukaryotic cells

Answer 18

System of specialised protein assemblies in cytosol of eukaryotes

Not fixed – highly dynamic – essential role in transport of organelles and some molecules within cell

Question 19

Cytoskeleton in prokaryotes

Answer 19

Filaments assembled from proteins similar to eukaryotic cells e.g. actin

Prokaryotic cytoskeleton has role in cell division and maintaining cell shape and polarity.

Question 20

How many types of filament does the cytoskeleton have?

Answer 20

Three

Question 21

Microfilaments

Answer 21

Actin filaments

In all eukaryotes

Thinnest – diameter 6 nm thread like appearance under EM

actin in long helical chain mostly in networks or bundles

Prominent in cell cortex and in microvilli of absorptive epithelial cells

Question 22

Microtubules

Answer 22

Tubulin
Alpha and beta form - maintains cell shape. Intracellular movement of organelles. Reorganisation of chromosomes during cell division
Hollow tubes of 13 parallel filament of tubulin assemblies. External diameter 25 nm
Animal cells microtubules radiate from MTOC – centrosome to cortex
Plant cells no centrosome MTOC appears different times to organise
Unstable assembles and disassembles till reaches organelle or capping protein
Determining cell shape.

Question 23

Intermediate filaments

Answer 23

Diameter 8 to 10 mm

Several types protein e.g. keratin

Eight protofilaments round each other like rope

Main role: mechanical strength to cells and tissues.

Question 24

What might happen to the shape of a cell if the capping proteins become confined to one part of the cell cortex?

Answer 24

Microtubules would only become stabilised at that region of the cell periphery so the cell could become polarised; that is, it could acquire an asymmetrical shape.

Question 25

What types of animal cell are inherently asymmetrical in shape?

Answer 25

Neurons and some kinds of epithelial cells are examples of asymmetrical cells.

Question 26

Capping protein

Answer 26

A protein that attaches to and stabilises microtubules and prevents disassembly

Question 27

Centriole

Answer 27

Tubulin structure present in animal cell to make the cytoskeleton

Question 28

Centrosome

Answer 28

Area in animal cell which contains centrioles

Consists of two centrioles at right angles to each other

Question 29

Glycosylation

Answer 29

Addition of sugar residues

Question 30

Glycosylated proteins

Answer 30

Proteins that have had sugar residues added to them

Question 31

Constitutive secretion

Answer 31

Substances constantly deliver to cell membrane and continuously released

Question 32

Regulated secretion

Answer 32

Molecules released at certain times in response to some kind of signal

Question 33

Exocytosis

Answer 33

Vesicle membrane fuses with cell membrane releasing Vesicle contents outside cell

Question 34

Endocytosis

Answer 34

Extracellular materials are ingested by engulfment by extensions of the cell membraneWhich form into Vesicular structures within the cytosol.