(todo 1.4-6) Cells and Microscopy - Key Concepts

Question 1

What is the difference between prokaryotes and eukaryotes?

Answer 1

Eukaryotes are organisms made up of eukaryotic cells (these contain a nucleus).
Prokaryotes are single prokaryotic cells (these do not contain a nucleus).

Question 2

Which sub-cellular structures are found in most animal cells?

Answer 2

• Nucleus
• Cell membrane
• Mitochondria
• Ribosomes

Question 3

Which sub-cellular structures are found in most plant cells?

Answer 3

• Nucleus
• Cell membrane
• Cell wall
• Chloroplasts
• Mitochondria
• Vacuole
• Ribosomes

Question 4

Which sub-cellular structures are found in most bacteria?

Answer 4

• Chromosomal DNA
• Plasmid DNA
• Cell membrane
• Ribosomes

Question 5

What is the function of the cytoplasm?

Answer 5

It is a jelly-like material that contains dissolved nutrients and salts. It is where many of the cell’s chemical reactions occur.

Question 6

What is the function of the nucleus?

Answer 6

It controls the cell’s activities. It contains the chromosomes, which carry the genetic material.

Question 7

What is the function of the cell membrane?

Answer 7

It is a thin, partially-permeable (only lets certain substances in and out) boundary boundary around the cell’s cytoplasm.

Question 8

What is the function of the mitochondria?

Answer 8

They are dispersed in the cytoplasm. They host aerobic respiration.

Question 9

What is the function of the ribosomes?

Answer 9

They host all protein synthesis.

Question 10

What is the function of the cell wall?

Answer 10

It is a fully-permeable outer layer (in plants made of cellulose) that strengthens the cell.

Question 11

What is the function of chloroplasts?

Answer 11

They contain chlorophyll (a green pigment) which is used to absorb light energy in photosynthesis.

Question 12

What is the function of the vacuole?

Answer 12

It contains cell sap - a liquid which acts as a reservoir of salts, dissolved sugars, mineral ions, etc. It helps to keep the cell rigid by expanding.

Question 13

What is the function of chromosomal DNA?

Answer 13

It contains the bulk of a bacterium’s DNA, loose in the cytoplasm.

Question 14

What is the function of plasmid DNA?

Answer 14

It is present in closed circles of DNA in the cytoplasm, which can move between bacteria.

Question 15

What is the function of flagella?

Answer 15

They can rotate or move in a whip-like motion to move the bacterium.

Question 16

How are sperm cells adapted to their specialised function?

Answer 16

The head contains the genetic material for fertilisation in a haploid nucleus. The acrosome in the head contains enzymes so that a sperm can penetrate an egg. The middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg. The tail enables the sperm to swim.

Question 17

How are egg cells adapted to their specialised function?

Answer 17

The cytoplasm contains nutrients for the growth of the early embryo. The haploid nucleus contains the genetic material for fertilisation. The cell membrane changes after fertilisation by a single sperm so that no more sperm can enter.

Question 18

How are ciliated epithelial cells adapted to their function?

Answer 18

Cilia on the surface beat to move fluids and particles up the trachea.

Question 19

Describe the use of the two main types of microscope.

Answer 19

Light microscopes are used to study living cells and for regular use when relatively low magnification and resolution is enough.
Electron microscopes provide higher magnifications and higher resolution images but cannot be used to view living cells.

Question 20

How does one calculate the magnification of a light microscope?

Answer 20

Magnification of the microscope = magnification of eyepiece * magnification of objective

Question 21

How does one calculate the magnification based on an image of an object?

Answer 21

Magnification = size of image / (real) size of object

Question 22

What is the difference between the two main types of microscope?

Answer 22

Electron microscopes use a beam of electrons, while light microscopes use rays of visible light.

Question 23

Why can electron microscopes not be used to observe living cells?

Answer 23

Electron microscope samples are placed in a vacuum.

Question 24

Compare the two types of electron microscope.

Answer 24

The transmission electron microscope (TEM) is used to examine thin slices or sections of cells or tissues.
The scanning electron microscope (SEM) has a large depth of field so can be used to examine the surface structure of specimens.
The TEM has superior magnification and resolution.