Lab Quiz: Microscopy / Cell Structure

What does Benedict’s Reagent test for?

the presence of monosaccharides and disaccharides (not polysaccharides).

When using Benedicts Reagent, what does green indicate? What about orange-red?

small amount (green); large amount (orange-red)

Which substances showed Monosaccharide/Disaccharide present in the experiment?

glucose solution, apple juice, potato flakes

What is Iodine used to test for?

starch

What color is Iodine? What color does it turn in the presence of starch?

yellow-brown; blue-black

Which substances showed starch present in our experiment?

starch solution and potato flakes

What does Biuret Reagent test for?

peptides and proteins

What color is Biuret Reagent originally?

blue

What color is Biuret Reagent in the presence of peptides?

pink

What color is Biuret Reagent is the presence of proteins?

purple

Which substances showed protein present in our experiment?

albumin, pepsin

What does the sports drink in our experiment include that kept cells from breaking open and releasing their DNA before collection?

Sodium Cloride

What did adding the detergent do in our experiment?

broke down the phospholipid membranes

In our experiment, we needed the DNA to be separated from the other cellular contents but remain in the solution. What did we use to accomplish this?

ethanol

Why was salt added to the detergent-based lysis solution?

DNA is negatively charged, so the addition of a positively charged ion (such as sodium) attracts DNA molecules and keeps them in a solution

Why did we use ethanol to separate the DNA from other cellular contents?

DNA is insoluble (doesn’t mix) in ethanol, and it precipitates out and can be seen.

What is used to adjust the height of the stage on a Microscopy?

The coarse and fine focus knobs

How is total magnification calculated?

objective lens magnification (4x,10x, 40x, or 100x) x ocular lens magnification (10x)

Which knob is used to sharply focus the image?

fine focus knob

How is the contrast of the image improved?

adjusting diaphragm or adjusting the microscopes illumination

Which objective should be in place when preparing a microscope for storage?

lowest-power objective

Compound light microscope

microscope you will use most often; has two sets of lenses: ocular lenses and objective lenses

resolution

the ability of a microscope to distinguish detail

total magnification

how much larger the image appears when viewed through both sets of lenses

field of view

the area of the slide visible through the microscope when you look into the eyepieces

working distance

the distance between the slide on the mechanical stage and the tip of the objective lens you are using

depth of field

the vertical depth of the specimen clearly in focus

cell

smallest unit that can perform the functions of life

cytoskeleton

made up of various types of protein filaments; functions include movement, support and structure

microvilli

increase surface areas of plasma membrane

Structure of plasma membrane

double layer of lipids within which proteins are embedded; externally facing proteins and some lipids have attached sugar groups

Structure of Ribosomes

two subunits: ribosomal RNA and protein; free or attached to rough ER

What does cytoplasm consist of?

cytosol (containing dissolved solutes), inclusions (stored nutrients, pigment granules), and organelles (metabolic machinery of cytoplasm)

Structure of Rough Endoplasmic Reticulum

membrane system of sacs and tubules externally studded with ribosomes

Structure of Smooth Endoplasmic Reticulum

membranous system of sacs and tubules; free of ribosomes

Structure of Golgi Apparatus

a stack of smooth membrane sacs close to the nucleus

Structure of Lysosomes

membranous sacs containing acid hydrolases

Structure of Mitochondria

rodlike, double-membrane structures; inner membrane folded into projections called cristae

Structure of Peroxisomes

membranous sacs of oxidase enzymes

Structure of Microfilaments

fine filaments of the contractile protein actin

Structure of Intermediate Filaments

protein fibers; composition varies

Microtubules

Cylindrical structures made of tubulin proteins

Structure of Centrioles

paired cylindrical bodies, each composed of nine triplets of microtubules

Structure of Nuclear Envelope

double-membrane structure; pierced by the pores; continuous with the cytoplasmic ER

Structure of Nucleoli

Dense spherical (non-membrane-bound) bodies

Structure of Chromatin

granular, threadlike material composed of DNA and histone proteins

Function of plasma membrane

external cell barrier; transport of substances, external proteins act as receptors; cell-to-cell recognition

Function of ribosomes

sites of protein synthesis

Function of Rough ER

ribosomes on the RER make proteins; makes the cell’s membranes

Function of Smooth ER

lipid and steroid hormone synthesis; lipid metabolism; drug detoxification

Function of Golgi Apparatus

packages, modifies, and segregates proteins for secretion from the cell; inclusion in lysosomes, and incorporation into the plasma membrane

Function of lysosomes

sites of intracellular digestion

Function of mitochondria

site of ATP synthesis; powerhouse of the cell

Function of peroxisomes

the enzymes detoxify a number of toxic substances; the most important enzyme, catalase, breaks down hydrogen peroxide

Function of Microfilaments

involved in muscle contraction and other types of intracellular movement; help form the cell’s cytoskeleton

Function of intermediate filaments

stable cytoskeletal elements; resist tension forces acting on the cell

Function of microtubules

support the cell and give it shape; involved in intracellular and cellular movements; form centrioles

Function of centrioles

organize a microtubule network during mitosis to form the spindle and asters; form the bases of cilia and flagella

Function of nucleus

control center of the cell; responsible for transmitting genetic information and providing the instructions for protein synthesis

Function of nuclear envelope

separates the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus

Function of nucleoli

site of ribosome subunit manufacture

Function of chromatin

DNA constitutes the genes