cell structure

Question 1

what is the function of mitochondria

Answer 1

1. the production of ATP, through respiration

2. regulating cellular metabolism

Question 2

explain the structure of mitochondria

Answer 2

1. double membrane, rod shaped organelle
2. size range of 0.5-1 micrometre
3. made up of inner membrane, outer membrane and a matrix
4. membranes are both made out of proteins and phospholipid layers, separated by an intermembrane space
5. the inner membrane has many folds, forming a cristae, and increasing surface area
6. mitochondrial matrix is a fluid that contains enzymes and proteins

Question 3

what is the function of Golgi apparatus

Answer 3

1. modification and sorting of lipids and proteins

2. produces secretory vesicles to eject modified molecules from the cell

Question 4

explain the structure of Golgi apparatus

Answer 4

1. Membrane bound organelle
2. Made up of 5-8 folds called Cisternae
3. Cisternae contain specific enzymes so there are five functional regions which modify proteins

Question 5

what is the function of the nucleus

Answer 5

1. Controls and regulates the activities of the cells

2. Carries the genes

Question 6

explain the structure of the nucleus

Answer 6

1. chromatin and nucleolus surrounded by a nuclear envelope with nuclear pores
2. nuclear pores regulate the movement of molecules from the nucleus to the cytoplasm

Question 7

what is the function of chloroplasts

Answer 7

1. synthesise food by the process of photosynthesis

2. chloroplasts contain chlorophyll which traps solar energy

Question 8

explain the structure of chloroplasts

Answer 8

1. double membrane organelle that contains grana and stroma
2. grana are made up of stacks of thylakoids, thylakoids contain chloroplasts
3. stroma is the homogenous matrix and is similar to cytoplasm, it contains enzymes, DNA and ribosomes

Question 9

what is the function of lysosomes

Answer 9

1. The key function of lysosomes is digestion and removal of waste

Question 10

explain the structure of lysosomes

Answer 10

1. membrane bound organelles with a singular membrane

2. they typically range in size from 0.1 μm to 0.6 μm

Question 11

what is the function of ribosomes

Answer 11

1. assembles amino acids to form proteins (protein synthesis)

Question 12

explain the structure of ribosomes

Answer 12

1. ribosomes range in size eg, prokaryotes, 70s & eukaryotes, 80s
2. ribosomes have two sub-units both contain protein and ribonucleic acid
3. smaller sub-unit, where the mRNA is bound and decoded
4. larger sub-unit, where amino acid is added

Question 13

what is the function of smooth endo-plasmic reticulum

Answer 13

1. responsible for the synthesis of essential lipids
2. responsible for the production and secretion of steroid hormones
3. transports the products of RER to other organelles, mostly golgi

Question 14

explain the structure of smooth endo-plasmic reticulum

Answer 14

1. A series of flattened sacs that are not associated with ribosomes

Question 15

what is the function of a cell wall

Answer 15

1. the cell wall separates the interior contents of the cell from the exterior environment

Question 16

explain the structure of a cell wall

Answer 16

1. made of chitin in fungi

2. made of cellulose in plants

Question 17

what is the function of a cell vacuole

Answer 17

1. storage of food and other nutrients needed by the cell to survive

Question 18

explain the structure of a cell vacuole

Answer 18

1. surrounded by a membrane called a tonoplast

2. contains cell sap

Question 19

what is the function of rough endo-plasmic reticulum

Answer 19

1. responsible for protein synthesis

Question 20

explain the structure of rough endo-plasmic reticulum

Answer 20

1. a series of flattened sac with associated ribosomes

Question 21

Define cell fractionation

Answer 21

The process where cells are broken up and different organelles are separated

Question 22

What must happen before cell fractionation can begin

Answer 22

The tissue is placed in a cold isotonic buffered solution

Question 23

Explain each why, before cell fractionation, the tissue is placed in a cold isotonic buffered solution

Answer 23

Cold- Reduces enzyme activity that may break down the organelles

Isotonic- has the same water potential as the tissue so it prevents the organelles from bursting due to osmosis

Buffered- to prevent damage to enzymes, buffers maintains a constant PH

Question 24

What are the steps of cell fractionation

Answer 24

1. Tissue is placed in cold isotonic buffered solution
2. homogenisation
3. Homogenate is filtered to remove and complete cells
4. centrifugation

Question 25

Explain the process of homogenisation

Answer 25

1. Cells are broken up by a homogeniser | 2. This releases the organelles

Question 26

Explain the process of centrifugation

Answer 26

1. Homogenate is spun at a low speed 2. The heavier organelles are pushed to the bottom of the tube due to the force generated 3. The supernatant is then transferred into a new tube, leaving the pellets (of the organelles) in the other test tube 4. The supernatant is then spun again at a higher speed to separate the lighter organelles 5. The process is repeated

Question 27

What is the order of cells separated during centrifugation (remember the acronym)

Answer 27

``` Nucleus Chloroplasts Mitochondria Lysosomes Endo-plasmic Reticulum Ribosomes ```

Question 28

Give one disadvantage and one advantage of an optical light microscope

Answer 28

Disadvantage- 1. Samples must be very thin 2. Resolution is limited to lights wave length 3. 2D image Advantages- 1. Inexpensive 2. Portable 3. sample can be living

Question 29

Give one disadvantage and one advantage of a transmission electron microscope

Answer 29

Disadvantages- 1. Sample must be thin 2. Sample must be dead 3. Must be done in a vacuum 4. Often find artefacts Advantages- 1. High resolution 2. Can see the internal structure 3. Higher magnification

Question 30

Give one disadvantage and one advantage of a scanning electron microscope

Answer 30

Disadvantages- 1. Sample must be dead 2. Must be done in a vacuum 3. Can’t see the internal structure Advantages- 1. Sample can be thick 2. 3D image

Question 31

What is the magnification equation

Answer 31

Image size Magnification= ———————— Actual size

Question 32

How many micrometres in a millimetre How would you change the units from mm-um and um-mm

Answer 32

1000 ``` mm-um= x1000 um-mm= ‘/, 1000 ```

Question 33

Give the 4 stages of the cell cycle

Answer 33

1. G1 2. S 3. G2 4. Mitosis

Question 34

Explain G1, phase of the cell cycle

Answer 34

The cells contents are duplicated

Question 35

Explain G2, phase in the cell cycle

Answer 35

The cell check for errors

Question 36

Explain S, phase in the cell cycle

Answer 36

Chromosomes are duplicated

Question 37

What is the structure of chromosomes at G1

Answer 37

Single chromatid

Question 38

What is the structure of chromosomes at S phase

Answer 38

Sister chromatid joined together at the centromere

Question 39

What part(s) of the cell cycle make up interphase

Answer 39

G1, S, G2

Question 40

What happens during mitosis

Answer 40

The cell divides into two identical daughter cells

Question 41

what are the differences between eukaryotes and prokaryotes

Answer 41

- prokaryotes have no true nucleus while eukaryotes have a distinct nucleus with a nuclear envelope - in prokaryotes DNA is not associated with proteins but in eukaryotes it is associated with histone proteins - prokaryotes some of the DNA is in circular stands (plasmids) whilst in eukaryotes it is linear - prokaryotes have no membrane bound organelles but eukaryotes have membrane bound organelles such as mitochondria - prokaryotes have smaller ribosomes (70S) whilst eukaryotes have larger ribosomes (80S)

Question 42

State and explain the two types of cell division

Answer 42

- Mitosis, produces two daughter cells that have the same number of chromosomes as the parent cell - Meiosis, produces four daughter cells with half the number of chromosomes as the parent cells

Question 43

Explain prophase

Answer 43

- In prophase the chromosomes first become visible - The nuclear envelope disintegrates - the centrioles move to the poles of the cell and form spindle fibres

Question 44

Explain metaphase

Answer 44

- The centromere attaches to the spindle fibres | - They appear to be lined up along the equator of the cell

Question 45

Explain Anaphase

Answer 45

- The centromeres split pulling the chromatids apart - The chromatids are pulled by the spindle fibres to opposite poles - We now refer to the separated chromatids as chromosomes

Question 46

Explain Telophase

Answer 46

- spindle fibres disintegrate - a nuclear envelope forms around the chromosomes - the chromosomes uncoil and form chromatin

Question 47

How does cell division occur in prokaryotes | describe the process

Answer 47

Binary fission - DNA replicates - plasmid replicates - A cell membrane forms between the two DNA molecules - A cell wall forms and separates the two new identical daughter cells