A student prepares a cell homogenate from spinach leaves. She performs a cell fractionation experiment to determine the shortest amount time of centrifugation at 2000xg that will yield the highest percentage of chloroplasts in the pellet fraction. She splits the spinach homogenate into 5 equal parts and centrifuges the parts at 2000xg for 0, 5, 10, 15 or 20 min. She then determines the proportion of chloroplasts in the supernatant and pellet fractions. The controlled variable(s) in the student's experiment is/are:_____.
a. proportion of chloroplasts in each fraction.
b. use of same plant homogenate throughout.
c. time of centrifugation in minutes.
d. g-force of centrifugation.

Answer:

b. use of same plant homogenate throughout.

Explanation:

In an experiment, the controlled variable, also called the CONSTANT is the variable that is kept the same throughout the course of the experiment in order not to influence the result or outcome of the experiment.

In this question, a student performs a cell fractionation experiment to determine the shortest amount time of centrifugation (manipulated variable) at 2000xg that will yield the highest percentage of chloroplasts (responding variable) in the pellet fraction. In this experiment, the variable being controlled is same spinach plant homogenate used throughout.

List 3 ways that microwaves are beneficial to society

In pea plants, height is determined by an allele for tallness (T) that is dominant over an allele for shortness (t). What is the probability that a gamete, selected at random, would carry the short allele (t) in a cross of heterozygous tall pea plants?

A. 1/8
B. 1/4
C. 1/2
D. 3/4

Leona drew a diagram to compare ginkgoes and conifers.



Which characteristic belongs in the area marked X?

are deciduous
produce cones
look like palm trees
are the largest group

When a certain species disappears from the fossil record, what does that indicate?
The species has moved to a different habitat.
A. the species has moves to a different habbitat
B.
None of the above.

C.
The species has gone extinct.

D.
The species has multiplied.

TMV Assembly Each of these statements is an experimental observation concerning the reassembly of tobacco mosaic virus (TMV) virions from TMV RNA and coat protein subunits. In each case, carefully state a reasonable conclusion that can be drawn from the experimental finding.
a. When RNA from a specific strain of TMV is mixed with coat protein from the same strain, infectious virions are formed.
b. When RNA from strain A of TMV is mixed with coat protein from strain B, the reassembled virions are infectious, giving rise to strain A virus particles in the infected tobacco cells.
c. Isolated coat protein monomers can polymerize into a virus-like helix in the absence of RNA.
d. In infected plant cells, the TMV virions that form contain only TMV RNA and never any of the various kinds of cellular RNAs present in the host cell.
e. Regardless of the ratio of RNA to coat protein in the starting mixture, the reassembled virions always contain RNA and coat protein in the ratio of three nucleotides of RNA per coat protein monomer.

We’re you able to place some events within the periodic table with just a single clue

Darwin noticed that animals on the different islands of the Galapagos appeared to be adapted
to what? *
(10 Points)
O A. differences in their food
O B. differences in their predators
O C. differences in their altitude
D. differences in temperature
WILL GIVE BRAINLIST

What are the three stop codons?

How many stops can you potentially make on your trip? Why?

This is the part of a flower that helps attract animals in order to aid in pollination.


It also starts with pe

write a notice of the department of water and sewage​

maslows theory of self actualization

8. Plant cells have some parts that animal cells do not have. Plant cells have __________, __________, __________.
9. Most of the organelles in plant and animal cells are inside the __________
10. _________ cells have a “box” shape,
11. __________ cells are more round
12. The ____________ in plant cells provide an additional layer outside the cell membrane for support the plant.
13. The cell wall separates the inside of the _________ cell from the environment.
14. __________ in plant cells are responsible for performing the process of photosynthesis. If they stop working, photosynthesis will not be taking place in the plant.
15. Plant cells have a ________________ that stores water, nutrients, food and waste products.
16. The________________ are the organelles that makes proteins.
17. Cells move water and materials through the _____________.

Reverse faults are the result of tension.
True or false?

For a trait that is located on the X chromosome, who is more likely to have
a recessive phenotype? Hint: Think about the number of X chromosomes
that a male and female have and think about how someone would express
a recessive phenotype.
Select one:
O a. no difference in the odds
O b. a male
Oc: a female

A Phylum is a more broad taxonomic category than an order.
O True
O False

Question 10
6.7 pts
Which of the following most likely happens in the cells of a person running a
marathon?
The respiration rate increases to produce more ATP.
The cell division rate increases to produce more muscle fibers
The photosynthesis rate increases to produce more sugars
The replication rate increases to produce more DNA

5.Write observation and conclusion of each of the following activities​

please help me im timed and will give brainiest:(​

Which of the following rows in the table best compares the function of a plant's xylem and phloem? I Need help ASAP!

Row 1

Xylem

- transports glucose absorbed by the roots to the rest of the plant


- alive at maturity

Phloem

- transports water and nutrients produced by photosynthesis in the leaves to the rest of the plant


- dead at maturity


Row 2

Xylem

- transports glucose produced by photosynthesis in the leaves to the rest of the plant


- dead at maturity

Phloem

- transports water and nutrients absorbed by the roots to the rest of the plant


- alive at maturity


Row 3

Xylem

- transports water and nutrients absorbed by the roots to the rest of the plant


- dead at maturity

Phloem

- transports glucose made during photosynthesis in the leaves to the rest of the plant


- alive at maturity


Row 4

Xylem

- transports water and nutrients produced by photosynthesis in the leaves to the rest of the plant


- alive at maturity

Phloem

- transports glucose absorbed by the roots to the rest of the plant


- dead at maturity

What are some common properties that most terriers share?

The ability to taste the chemical PTC is determined by a single gene in humans with the ability to taste given by the dominant allele T and the inability to taste by the recessive allele t. Suppose two heterozygous tasters (Tt) have a large family. What is the likelihood that their first child will be a taster

What is one of the causes of mechanical weathering? A acid rain B oxidation C animal actions D carbon dioxide​

Which statement correctly describes an interaction between organelles in the model?
A
Letter U and letter S control the collection and release of waste from the cell.
В.
Letter T and letter R store the genetic material necessary for replication of the cell.
ОООО
C
Letter Q and letter S are responsible for creating and delivering nutrients throughout the cell.
D
Letter U and letter R are involved with the processes of transcription and translation for the cell.

Select the correct answer.
Why will a decrease in pH of the stomach affect protein digestion?
OA. Decrease in pH of the stomach will distort the structure of peptides in food, which affects the action of the enzyme pepsin.
O B. Decrease in pH of the stomach will distort the active site of the enzyme pepsin, which affects its
action.
O C. Decrease in DH of the stomach will distort the active site of the enzyme lipase, which affects protein digestion. Yes

please help I don't understand ​

why are plastids called kitchen of the cell​

18. Marlon took the microscope and observed a sliced plant leat. He switched it into 100% magnification and saw
a green pigment. In which part of the plant cellis it found?
a nucleus b. mitochondrion G chloroplast d. lysosome​

How can a hunter help wildlife conservation efforts? A, By making sure to always obey the rules of firearm safety By making sure to always obey the rules of firearm safety B, By always bagging under the daily limit By always bagging under the daily limit C, By donating to conservation organizations, or helping to build habitats for local wildlife By donating to conservation organizations, or helping to build habitats for local wildlife D, By always bagging over the daily limit By always bagging over the daily limit

The island spotted skunk and the island fox are both predators of the island
deer mouse (the prey). How could these two predators establish different
niches and still prey upon island deer mice? *

A. the island spotted skunk hunts at different times than the island fox
B. the island spotted skunk hunts in the same area as the island fox
C. the island fox eats only cherries instead of deer mice
D. the island deer mice swim to a different island to avoid predators