Unit 2a Cell Structure and Division-Recall Questions

What are the inner folds of mitochondria called?

Cristae

2. What is the function of the Golgi

Apparatus?

To process & package new proteins & lipids; makes lysosomes.

What is the function of a lysosome?

Contain enzymes- lysozymes used to digest broken/invaded cells.

4. What is the function of a ribosome?

Protein synthesis

What is the function of the smooth ER

Synthesises and processes lipids

Describe the function of the nucleolus?

Makes ribosomes

7. What is the function of the nucleus?

Controls the cells activities by controlling the transcription of DNA. Has Nuclear pores to allow substances to move between the nucleus and cytoplasm.

8. What is the function of the lysosome?

Contains digestive enzymes which are used to digest invading cells or break down worn components of the cell

9. What is the function of the SER?

synthesises and processes lipids

10. List the 3 main stages involved in cell

fractionation

Homogenisation, filtration, ultracentrifugation

What is the heaviest organelle?

Nucleus 

What is the lightest organelle?

ribosomes

why does the solution have to be cold

to prevent any unwanted chemical reactions by enzymes

why does the solution have to be isotonic

to prevent organelles shrinking or swelling due to osmosis

what is cell homogenation

the breaking of a cell in order for the different organelles to separate out in a homogeniser

why must the homogenate with filtered

to remove any large cells or large pieces of cell membrane

what are the first three steps at the start of centrifugation

1. the homogenate is spun in a centrifuge

2. organelles fall to the bottom (order depending on density) forming a pellet

3. the supernatant is removed and spun at a higher speed

explain why an ice-cold isotonic buffered solution is used in cell fractionation

Ice- cold: slow enzyme activity, Isotonic: prevent damage to organelles, Buffered: control pH

what is created through mitosis

2 genetically identical daughter cells. they have the same number of chromosomes as the parent cell.

3 stages of cell cycle

Mitosis, Interphase: (G1, Synthesis, G2), Cytokinesis

What is interphase

Growth stages (most of cell cycle) ie G1, synthesis, G2

22. Describe what happens to a cell in

interphase.

DNA unravels & replicates, organelles replicate & ATP increases.

What is cytokinesis

Final stage of mitosis where the 2 joined cells separate into 2 daughter cells.

List stages of mitosis in order

Prophase

Metaphase

Anaphase

Telophase

What is a centromere

The centre point of a chromosome- holds 2 sister chromatids together.

What is a centriole

Bundles of protein, which produce spindle fibres and move to poles of the cell in prophase.

Describe what occurs in prophase

.Nuclear envelope breaks down, centrioles move to either end, chromosomes condense.

List 2 events that happen in Metaphase

Chromosomes lines up on spindle equator, spindle fibres attach to centromeres.

describe what cells would look like when undergoing anaphase

No nuclear envelope, v-shaped chromatids being pulled apart to opposite ends of the cell.

2 events in telophase

Chromatids uncoil & nuclear envelope reforms.

31. If 10 cells out of a total of 100 are in

metaphase of mitosis & one complete

cycle takes 15 hours, how long do the

cells spend in metaphase? Give answer in

minutes.

15 x 60 = 900 , 10/100 x 900 = 90 mins

32. How could you make chromosomes move

apart from each other in a cell?

Add water so that the cell takes up water through osmosis – elongating it and pulling chromosomes apart.

33. What is the mitotic index?

The proportion of cells in a sample undergoing mitosis.

Formula for mitotic index

Mitotic index = number of cells with visible chromosomes / total number of observed cells

what is an eyepiece graticule

a transparent ruler, attached to the eyepiece used to measure actual size of cells

36. Would you expect the mitotic index of

root tip cells to be higher or lower than

cells from a mature leaf?

Higher- root tip divides to extend.

37. Why do prokaryotes undergo Binary

Fission?

Bacteria replicate using binary fission

38. What replicates in Binary fission?

Chromosomal DNA replicates once- plasmids may replicate many times

39. What formula can you use to calculate

the number of bacteria in a population?

Number of bacteria at the start x 2number of divisions E.g Number of bacteria at the beginning = 1 Number of divisions = 18 1 × 218 = 1 × 262,144 = 262,144 bacteria OR - 2.62 × 105 bacteria in standard form

40. The mean division time for a bacterial

population is 30 minutes. Calculate how

many bacteria will be present after eight

hours, when starting with one bacterium.

Show your working

If after every 30 minutes there is one division, then after 60 minutes (one hour) there are two divisions. 8 hours × 2 divisions = 16 divisions in total. Therefore, 1 × 216 = 1 × 65,536, which is 65,536 bacteria, or 6.55 x 104 bacteria in standard form.