BIOL1190: LAB 2 - Mitosis and Movement Across Cell Membrane

what are somatic cells?

reproduce for the purpose of growth, replacement, and repair

what is the cell reproduction regulated by?

a series of event known as the cell cycle

what stages are the cell cycle divided into?

- interphase

- cell division

what is interphase?

the time during which the cell grows in size, carries out its normal metabolic activities and prepares for cell division

what is cell division (mitosis)?

the series of events that lead to the production of two identical cells often referred to as "daughter cells" from an original "parent cell"

what are the three phases interphase is divided into?

- G1 (1st Gap Phase)

- S phase (Synthesis)

- G2 (2nd Gap Phase)

what occurs during G1 phase?

- the cell grows and conducts normal cellular functions

- the cell also prepares for cell division by duplicating most of the organelles and other cytoplasmic material

what occurs during S phase?

DNA is replicated

what occurs during G2 phase?

- enzymes and other proteins that will aid in mitosis are produced

- centriole replication is completed

what are stem cells?

cells that continuously divide, giving rise to new cells

what do the frequency of cells dividing vary on?

depending on the type of tissue

what is the G0 phase?

a non-dividing stage.

- neurons and muscles enter this stage, if these cells die, they can never be replaced

what does somatic cell division in eukaryotes consists of?

a series of events called mitosis (M phase) and cytokinesis

what is mitosis?

the division of the nuclear material (DNA/chromosomes)

what is cytokinesis?

the division of the cytoplasm and organelles between two daughter cells

what phases is mitosis subdivided into?

- prophase

- metaphase

- anaphase

- telophase

what occurs during prophase?

- chromatin fibres condense into visible chromosomes

- the nucleolus disappears

- the nuclear envelope breaks down

- the centrioles are pushed to opposite poles by lengthening microtubules

- spindle fibres form and asters are visible around the centrioles

what occurs during metaphase?

- chromosomes lined up at the metaphase plate

- aster visible

what occurs during anaphase?

- the centromeres split and the chromatids separate and move towards opposite poles

- the chromatids are now called chromosomes and appear v-shaped

what occurs during telophase?

- chromosomes are at the poles and begin to uncoil into chromatin

- the nuclear envelope reforms around the chromatin

- the nucleoli reappear

- the spindle breaks down

what occurs during cytokinesis?

- begins in late anaphase, with a slight indent in the plasma membrane called the cleavage furrow

- as the microfilaments contract, the plasma membrane is pulled inward, completing the division of the cell into two separate daughter cells

what happens when cytokinesis finishes?

interphase begins

what happens by the end of cytokinesis?

- each daughter cell is identically identical to the parent cell, and has half the cytoplasm of the mother cell

- the daughter cells grow and carry out their metabolic processes until it is their turn to divide

what do human somatic cells have?

23 pairs of chromosomes

- one chromosome of each pair is inherited from each of the parents via the egg and the sperm

what do each pair of chromosomes contain?

similar genes

- genes are segments of DNA that code for an individual's inherited traits

what is the role of microtubules in cell division?

prophase: begins forming the mitotic spindle

metaphase: attach to kinetochores (central protein structure of centrosome)

anaphase: they shorten, pulling sister chromatids to opposite poles

what is one possible reason that chromatin fibres condense before dividing?

makes them easier to move without breaking

what is a blastula?

an embryonic stage of development that occurs shortly after fertilization, when the embry is undergoing rapid cell division

what do cells import?

a variety of substances such as nutrients, hormones, and oxygen from the extracellular fluid

what do cells export?

wastes and cellular products from the cytosol to the extracellular fluid

what is the plasma membrane?

selectively permeable

what does selectively permeable mean?

it can regulate the passage of materials into and out of the cell

what does transport across membrane occur by?

either pasive or active processes

what do all molecules have?

kinetic energy that causes them to be in constant motion

what is Brownian motion?

molecules in gases and liquids are constantly colliding with adjacent molecules, ricocheting off one another and changing direction with each collision, which can be seen in movement of small particles suspended in water

what do collisions between molecules cause and what is it called?

causes molecules to spread out and eventually reach an equal distribution in a container, which is called equilibrium

what happens once equilibrium has been reached?

the molecules will continue to move spontaneously, but with no net directional change

what do passive processes rely on?

Brownian motion, and do not require energy consumption by the cell

what do passive process move?

molecules along their concentration gradient

what do passive processes include?

- filtration

- diffusion

- osmosis

what do active processes require?

require the use of energy (in the form of adenosine triphosphate (ATP))

what do active processes include?

- active transport (primary and secondary)

- vesicular transport

what happens in active transport?

water-soluble subtances are moved against their concentration gradient

what is vesicular transport used for?

to move molecules too large to pass through membrane channels

what do ink particles look like under the microscope (Brownian motion)?

the ink looks like they're vibrating and are changing direction often due to collision with one another

what is diffusion?

the movement of molecules from an area of higher concentration to an area of lower concentration

what is the driving force behind diffusion?

kinetic energy

what are examples of simple diffusion in living system?

- movement of oxygen from lungs into the pulmonary capillaries

- movement of urea into the collecting ducts in the kidneys

where can diffusion of molecules occur in?

through solids, liquids, gasses, and across cell membranes

what example in lab is used to demonstrate simple diffusion?

diffusion of dyes through agar

what variables can affect diffusion?

- temperature

- concentration gradient

- size of the molecule

- distance

what is osmosis?

refers to a type of simple diffusion where water moves through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration

how else can osmosis be explained as?

the net movement of water through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration

when does osmosis occur?

when the membrane is permeable to water but not to other substances

what is a solute?

any substance that dissolves in another, forming a solution

what is a solvent?

the substance the solute dissolves in

what does a hypertonic solution mean?

solutions outside of the cell has a higher solute concentration relative to the inside of the cell

what does a hypotonic solution mean?

solutions outside of the cell has a lower solute concentration relative to the inside of the cell

what does an isotonic solution mean?

two solutions with equal solute concentration

what is used in the lab to demonstrate osmosis?

the osmometre

how was the osmometre set up?

using a thistle tube, dialysis membrane, and coloured 80% sucrose solution, suspended in a beaker of water

what happened in the osmometre demonstration?

the net movement of water by osmosis from an area of low solute concentration in the beaker to an area of high solute concentration in the tube through a selectively permeable membrane

why did osmosis occur in the osmometre demosntration?

the dialysis membrane has very small holes, and sucrose is a very large molecule that cannot fit through the holes, but water is much smaller and passes freely

what are red blood cells permeable to?

water and relatively impermeable salt

what happens when a RBC is placed in an isotonic solution?

the cell remains the same size and shape

what happens when a RBC is placed in a hypotonic solution?

water enters the cell, eventually causing it to burst, a process known as hemolysis

what happens when a RBC is placed in a hypertonic solution?

water will leave the cytosol and enter the solution outside the cell. the cell crenates and appears shrivelled with spiked edges

which solution in the osmosis in RBC test was isotonic to the RBC?

0.9% NaCl

which solution in the osmosis in RBC test was hypertonic to the RBC and what did it cause?

- 3% NaCl

- caused the RBC to crenate

which solution in the osmosis in RBC test was hypotonic to the RBC and what did it cause?

- distilled water

- caused the RBC to hemolyze

what is used in the lab to demonstrate osmosis and diffusion across a selectively permeable membrane?

the experiment in which the dialysis bag which contained glucose, sodium chloride, and starch, was suspended in water

what is a positive control?

shows what a positive effect looks like

what is a negative control?

shows what a negative effect looks like

what does iodine test for?

the presence of starch

what does silver nitrate test for?

the presence of chloride ions

what is used to test for glucose?

a glucose test strip

what is the positive and negative result for starch when it reacts with iodine?

- positive: colour turns blue/black

- negative: colour turns yellow

what is the positive and negative result for chloride ions when it reacts with chloride ions ( from NaCl)?

- positive: solution is cloudy white

- negative: solution is clear

what does a positive and negative result show for a glucose strip?

- positive: any yellow-green or brown colouring

- negative: light blue

what happened to the dialysis bag after it sat for an hour?

it gained weight

why did the dialysis bag gain weight?

water moved into the bag by osmosis

what happened to the chloride ions in the dialysis bag experiment?

it moved out by diffusion as it's a smaller molecule

what happened to the glucose in the dialysis bag experiment?

it moved out by diffusion as it's a smaller molecule

what happened to starch in the dialysis bag experiment?

none as it's too big to move out of the bag

what happened to iodine in the dialysis bag experiment?

it moved into the bag by diffusion as it's a smaller molecule

what was the final result for the dialysis bag experiment?

iodine diffused across a selectively permeable membrane from an area of high concentration of iodine outside the bag, to an area of low concentration of iodine inside the bag. the diffusion of iodine into the bag caused the bag to turn blue-black as the starch reacted with iodine