Cell Biology

Question 1

What is a Eukaryotic Cell?

Answer 1

Complex cells and include all animal and plant cells

Question 2

What is a Prokaryotic Cell?

Answer 2

Smaller and simpler cells, e.g. Bacteria

Question 3

Subcellular Structure of an Animal Cell

Answer 3

Nucleus
Cytoplasm
Cell Membrane
Mitochondria
Ribosomes

Question 4

Subcellular Structure of a Plant Cell

Answer 4

Nucleus
Cytoplasm
Cell Membrane
Mitochondria
Ribosomes
Cell Wall
Permanent Vacuole
Chloroplasts

Question 5

What is the Nucleus?

Answer 5

contains the genetic material for the cell that controls the activities of the cell

Question 6

What is the Cytoplasm?

Answer 6

gel-like substance where most of the chemical reactions happen - contains enzymes which control these reactions

Question 7

What is the Cell Membrane?

Answer 7

holds the cell together and controls what goes in and out

Question 8

What is Mitochondria?

Answer 8

where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs

Question 9

What are Ribosomes?

Answer 9

where proteins are made in the cell

Question 10

What is a Cell Wall?

Answer 10

made of cellulose
supports the cell and strengthens it

Question 11

What is a Permanent Vacuole?

Answer 11

contains cell sap, a weak solution of sugar and salts

Question 12

What are Chloroplasts?

Answer 12

where photosynthesis occurs, which makes food for the plant, they contain chlorophyll which absorbs light needed for photosynthesis

Question 13

What do Bacteria Cells contain?

Answer 13

Cell Membrane
Cell Wall
Cytoplasm
Singular Strand of DNA - instead of a nucleus - floats freely
Plasmids - small rings of DNA

Question 14

What are Light Microscopes?

Answer 14

Use light and lenses to form an image of a specimen.
Allow us to see individual cells and large subcellular structures

Question 15

What is an Electron Microscope?

Answer 15

Use electrons instead of light to form an image.
Much higher magnification and resolution.

Question 16

Magnification Formula

Answer 16

Magnification = Imagine Size/Real Size

Question 17

How to prepare a slide?

Answer 17

1) Add a drop of water to the middle of a clean slide
2) Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissues from the bottom of one of the layers
3) Using the tweezers, place the epidermal tissue into the water on the slide
4) Add a drop of iodine solution - used to highlight objects in the cell
5) Place a cover slip on top.

Question 18

How do you use a Light Microscope to look at your slide?

Answer 18

1) Clip the slide you’ve prepared onto the stage
2) Select the lowest-powered objective lens
3) Use the coarse adjustment knob to move the stage up to just below the objective lens
4) Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
5) Adjust the focus with the fine adjustment knob, until you get a clear imagine of what’s on the slide
6) If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus

Question 19

What is Cell Differentiation?

Answer 19

• Differentiation is when a cell changes to become specialised for its job
• Cells change and develop different subcellular structures, turning into different types of cells, allows them to carry out specific functions
• Differentiation usually occurs as a cell develops, in animal cells this ability i lost at an early stay after they become specialised, however many plants cells do not lose this ability
• Differentiation in mature animals mainly used for repairing and replacing cells, i.e. skin or blood
• Some cells are undifferentiated cells, such as stem cells

Question 20

How are sperm cells specialised for reproduction?

Answer 20

• Function of sperm is to get the male DNA to the female DNA
• A long tail and a streamlined head to help it swim
• Lots of mitochondria to provide the energy needed
• Carries enzymes in its head to digest through the egg cell membrane

Question 21

How are Nerve Cells specialised for Rapid Signaling?

Answer 21

• Function from Nerve Cells is to carry electrical signals from one part of the body to another
• Cells are long (cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body

Question 22

How are Muscle Cells specialised for Contraction?

Answer 22

• Function is to contract quickly
• Cells are long (space to contract) and contain lots of mitochondria to generate the energy needed for contraction

Question 23

How are Root Hair Cells specialised for absorbing Water and Minerals?

Answer 23

• On the surface of plant roots which grow into long “hairs” that stick out into the soil
• Gives the plant a big surface area for absorbing water an mineral ions from the soil

Question 24

How are Phloem and Xylem cells specialised for Transporting Substances?

Answer 24

• Both are tubes
• Both transport substances such as food and water around plants
• To form the tubes, the cells are long and joined end to end
• Xylem are hollow in the centre
• Phloem have very few subcellular structures, so stuff can flow through them

Question 25

Genetic Information

Answer 25

- Body cells normally have two copies of each chromosome - one from the organisms 'mother', and one from its 'father' - 23 pairs of chromosomes in a human cell

Question 26

The Cell Cycle

Answer 26

1) Body cells in multicellular organisms divide to produce new cells as part of a series of stages 2) The stage of the cell cycle when the cell divides is called mitosis 3) Multicellular organisms use mitosis to grow or replace cells that have been damaged 4) The end of the cell cycle results in two new cells identical to the original cell, with the same number of chromosomes 5) The two main stages of the cell cycle are: Growth & DNA Replication and Mitosis

Question 27

Growth and DNA Replication

Answer 27

1) In a cell that's not dividing, the DNA is a spread out in long strings 2) Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes 3) Duplicates it's DNA - one copy for each new cell. DNA is copied and forms X-Shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other

Question 28

What is Mitosis?

Answer 28

Once the contents and DNA have been copied, the cell is ready for mitosis:- 4) The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell 5) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided 6) Lastly, the cytoplasm and cell membranes divide - Cell produced two daughter cells, same DNA, identical, identical to parent cell

Question 29

What is Binary Fission of Prokaryotic Cells?

Answer 29

- In binary fission, the cell split into two 1) The Circular DNA and plasmid(s) replicate 2) The cell gets bigger and the circular DNA strands move to opposite 'poles' (ends) of the cell 3) The cytoplasm begins to divide and new cell walls begin to form 4) The cytoplasm divides and two daughter cells are produced. Each daughter cell has one cop of the circular DNA, but can have a variable number of copies of the plasmid(s)

Question 30

Binary Fission in Prokaryotic Cells

Answer 30

- In binary fission, the cell splits into two 1) The circular DNA and plasmid(s) replicate 2) The cell gets bigger and the circular DNA strands move to opposite 'poles' (ends) of the cell 3) The cytoplasm begins to divide and new cell walls begin to form 4) The cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of the plasmid(s)

Question 31

A bacterial cell has a mean division time of 30 minutes. How many cells will it have produced after 2.5 hours?

Answer 31

2.5 hours * 60 = 150 minutes 150 minutes/30 minutes = 5 divisions 2 to the power of 5 = 2*2*2*2*2 = 32cells Each cell divides to produce 2 cells, so the number of cells increases by a power of 2 for each division

Question 32

Practical - Culturing Microorganisms Effect of Antibiotics on Bacterial Growth

Answer 32

1) Place paper discs soaked in different types of antibiotics on the agar plate that has an even covering of bacteria 2) Antibiotic-resistant bacteria will continue to grow, but non-resistant strains will die. The clear area where bacteria has died is called the inhibition zone 3) Use an unsoaked paper disc as a control and soak it in sterile water 4) Leave the plate for 48 hours a 25 degrees Celsius 5) The more effective the antibiotic is against the bacteria, the larger the inhibition

Question 33

Practical - Culturing Microorganisms How to prevent contamination

Answer 33

1) The Petri dishes and culture medium must be sterilised before use, to kill any unwanted microorganisms that may be present 2) If an inoculating loop is used to transfer the bacteria to the culture medium, it should be sterilised first by passing it through a hot flame 3) After transferring the bacteria, the lid of the Petri dish should be lighter taped on - to stop microorganisms from the air getting in 4) The Petri dish should be stored upside down - to stop drops of condensation falling onto the agar surface

Question 34

Practical - Culturing Microorganisms Calculating the Sizes of the Inhibition Zones