A2.2 Cell Structure

Question 1

State the three parts of cell theory

Answer 1

All living things are composed of cells

The cell is the basic unit of life

Cells come from pre-exisiting cells.

Question 2

Inductive vs. Deductive reasoning

Answer 2

Inductive reasoning: using specific observations to form a general conclusion.

Deductive reasoning: using a general premise to form a specific conclusion.

Question 3

Formula for magnification

Answer 3

Magnification: how much larger an object appears compared to its real size.

Ocular X objective = magnification

Question 4

How to focus the microscope on a sample

Answer 4

While looking at lens, adjust light source. Turn coarse adjustment so stage moves and image comes into broad focus. Then turn fine adjustment for perfect focus.

Question 5

How to make a temporary wet mount and stain a sample

Answer 5

Place sample on slide.
Use a pipette to place a drop of water on sample.
If necessary, a stain can be dropped as well.
Place cover slip over sample.

Question 6

How to measure the field of view diameter of a microscope under low power

Answer 6

Place a ruler under the objective lens of a microscope to measure diameter.

Question 7

How to measure the field of view diameter of a microscope under high power

Answer 7

Must be calculated:

(diameter (LP) x magnification of LP objective) / magnification of HP objective = diameter (HP)

Question 8

Formula for actual size of specimen

Answer 8

Size of image / magnification

Question 9

Define resolution

Answer 9

Smallest interval distinguishable by the microscope (degree of detail visibility in an image)

Question 10

Functionality of light microscope (Function + benefits & drawbacks)

Answer 10

Use multiple lenses to bend light and magnify images.

Benefits:
- easy to use
- less expensive
- can observe both dead and living cells
- cell movement can be studied
- quick specimen prep time

Drawbacks:
- maximum magnification of about 1500X
- low resolving power

Question 11

Functionality of electron microscopes (Function + benefits & drawbacks)

Answer 11

Use beams of electrons focused by electromagnets to magnify and resolve.

Benefits:
- magnification of 100,000X to 300,000X
- high resolving power

Drawbacks:
- expensive to use
- requires cells to be killed
- no movement
- requires a stain to see color
- high voltage electricity required
- specimen prep takes days

Question 12

State a benefit of using fluorescent stains to visualize cell structures

Answer 12

Stains that generate a particularly bright image.

Question 13

Outline the use of immunoflorescence

Answer 13

Technique that uses fluorescently stained antibodies to bind to specific target proteins within a cell, in order to visualize the specific protein.

Question 14

Process of freeze fracture to produce images

Answer 14

Rapid freezing of cells and fracturing them along lines of weakness (slice membranes)

Surfaces are then etched and viewed via electron microscopy.

Question 15

Process of cryogenic electron microscopy to visualize proteins

Answer 15

Solution with protein is frozen and bombarded with a beam of electrons.

A computer analyzes patterns of diffraction off sample to produce an image of the protein structure.

Question 16

Structures common to all cells and their functions

Answer 16

Plasma membrane: separates interior from exterior. Phospholipid bilayer.

Cytoplasm: liquid part of cytoplasm - water and many dissolved solutes. Substances are needed for metabolic processes.

DNA: All living organisms use DNA as genetic material.

Ribosomes: catalyze synthesis of polypeptides during translation

Question 17

Functions of prokaryotic cell components (cell wall, plasma membrane, cytoplasm, 70s ribosome, nucleoid DNA)

Answer 17

Cell wall: Provides shape and allows cell to withstand turgor pressure.

Plasma membrane: regulates what moves in and out of cell.

Cytoplasm: site of metabolic reactions. Contains many dissolved substances required for these reactions.

70s ribosome: build proteins during translation.

Nucleoid DNA: not enclosed by membrane, free in cytoplasm. Not associated with proteins “naked”.

Question 18

Difference between eukaryotic and prokaryotic cells

Answer 18

Prokaryote:
- small
- no membrane bound organelles
- division by binary fission
- DNA in nucleoid
- DNA is circular and naked
- 70s ribosomes
- can have plasmids
- all unicellular

Eukaryote:
- bigger
- membrane bound organelles
- division by binary fission, mitosis or meiosis
- DNA in nucleus
- DNA is linear and associated with histone proteins
- 80s ribosomes
- no plasmids
- unicellular or multicellular

Question 19

Functions of eukaryotic cell components (plasma membrane, cytoplasm, 80s ribosome, nucleus, mitochondria, chloroplast, endoplasmic reticulum, golgi apparatus, vesicles, vacuoles, lysosomes, cytoskeleton of microfilaments and microtubules)

Answer 19

Nucleus: contains DNA and nucleolus (ribosome subunits made). Double membrane with pores to separate transcription and translation.

80s ribosomes: synthesis of polypeptides during translation.

Rough endoplasmic reticulum: series of flattened membranous sacs: transport of polypeptides. Ribosomes bound to it where polypeptide are synthesized and released into RER.

SER: Synthesis of phospholipids and cholesterol for repair and formation of membranes.

Golgi apparatus: modifies polypeptides into functional state.

Vesicles: membrane bound sacs that transport materials within cells.

Lysosomes: small spherical organelles that contain enzymes that digest large molecules for recycle. Also for digesting pathogens.

Mitochondria: production of ATP via aerobic cellular respiration.

Chloroplasts: capture light energy and use it for photosynthesis.

Vacuoles: water storage and maintenance of turgor pressure.

Cytoskeletons: maintain shape of cells.

Question 20

MRS GHENM

Answer 20

Movement, Homeostasis, Sensitivity, Growth, Reproduction, Excretion, Nutrition, Metabolism

Question 21

Features of skeletal muscle fibers that make it atypical

Answer 21

Skeletal muscle fibers result from the fusion of multiple cells. This causes multiple nuclei to be present in a cell.

Question 22

Features of aseptate fungal hyphae that make it atypical

Answer 22

Sometimes not divided into individual cells, so continuous with multiple nuclei.

Question 23

Features of red blood cells that make it atypical

Answer 23

No nucleus or mitochondria.

Question 24

Features of phloem sieve tube elements that make it atypical

Answer 24

No organelles.

Question 25

Explain the origin of mitochondria and chloroplast with reference to endosymbiosis

Answer 25

Endosymbiosis: one cell within the other and interdependence increasing until unit exists as a whole. Evidence: - shape and size of mitochondria and chloroplasts approximately same as prokaryotes. - both have double membrane (membrane of prokaryote + membrane from engulfing) - Both have 70s ribosomes while eukaryotes have 80s - both have naked DNA - both move and reproduce independently of host through binary fission.

Question 26

Benefits of cell specialization in a multicellular organism

Answer 26

More complexity and efficiency.

Question 27

Define Differentiation

Answer 27

Development of specialized structures and functions in cells.