Cell Structure & Microscopy

Question 1

What is a eukaryote?

Answer 1

An organism whose cells have genetic material enclosed in a nucleus.

Question 2

Give two examples of eukaryotic cells?

Answer 2

Animal cells and plant cells.

Question 3

Where is the cytoplasm found in eukaryotic cells?

Answer 3

It is enclosed in a cell membrane.

Question 4

What is a prokaryote?

Answer 4

A single-celled organism whose cells do not have a nucleus.

Question 5

Give an example of a prokaryotic cell?

Answer 5

A bacterial cell.

Question 6

Where is the DNA found in prokaryotic cells?

Answer 6

Floating freely in the cytoplasm.

Question 7

What are plasmids?

Answer 7

Extra pieces of smaller circular DNA found in bacterial cells.

Question 8

What surrounds the cytoplasm in a bacterial cell?

Answer 8

A cell membrane.

Question 9

What is found outside the cell membrane in bacterial cells?

Answer 9

A cell wall.

Question 10

How do prokaryotic cells compare in size to eukaryotic cells?

Answer 10

They are much smaller.

Question 11

What is the size range of animal and plant cells?

Answer 11

Between 0.1 mm and 0.01 mm.

Question 12

What is the average size of a bacterial cell?

Answer 12

Approximately 0.001 mm.

Question 13

Why do cells have different shapes and features?

Answer 13

To carry out different functions in the body.

Question 14

How are sperm cells adapted for movement?

Answer 14

They are long and thin with a flagellum and many mitochondria.

Question 15

What does the flagellum do in a sperm cell?

Answer 15

It helps the sperm swim to the egg.

Question 16

Why do sperm cells have lots of mitochondria?

Answer 16

To provide energy for movement.

Question 17

What do dendrites in nerve cells do?

Answer 17

They form connections with other cells.

Question 18

What surrounds a nerve cell and why?

Answer 18

A fatty sheath that insulates the cell and speeds up nerve impulses.

Question 19

Why do muscle cells contain many mitochondria?

Answer 19

To provide energy for muscle contraction.

Question 20

How are root hair cells adapted for absorption?

Answer 20

They are long and thin to provide a large surface area.

Question 21

What is the function of xylem vessels?

Answer 21

To transport water through a plant.

Question 22

Why do xylem vessels have no cell walls at their ends?

Answer 22

To form a continuous tube for water flow.

Question 23

What does lignin do in xylem cell walls?

Answer 23

It gives strength to the xylem vessel.

Question 24

What is the function of phloem vessels?

Answer 24

To transport sugars through a plant.

Question 25

What are sieve plates in phloem vessels?

Answer 25

End structures with pores that allow sugars to move between cells.

Question 26

Why do phloem cells contain few organelles?

Answer 26

To provide more space for sugar transport.

Question 27

What are unspecialised cells called?

Answer 27

Stem cells.

Question 28

What is the role of stem cells?

Answer 28

To differentiate into any type of cell.

Question 29

Where are many stem cells found in early development?

Answer 29

In the developing embryo.

Question 30

What do embryonic stem cells become?

Answer 30

All the cells of the human body including heart

Question 31

When do animal cells usually differentiate?

Answer 31

At a very early stage in development.

Question 32

What happens to cell differentiation after the body is fully formed?

Answer 32

It mostly stops.

Question 33

Where are some stem cells still found in the human body?

Answer 33

In the bone marrow.

Question 34

What is the main role of stem cells in adults?

Answer 34

To repair and replace damaged cells.

Question 35

How does cell differentiation in plants compare to animals?

Answer 35

Plant cells can differentiate throughout their life.

Question 36

What happens to a cell as it differentiates?

Answer 36

It gains or loses features to suit its function.

Question 37

What happens to a red blood cell as it differentiates?

Answer 37

It produces haemoglobin and loses its nucleus.

Question 38

Why does a red blood cell lose its nucleus?

Answer 38

To provide more space for oxygen transport.

Question 39

What type of microscope is commonly used in schools?

Answer 39

A light microscope.

Question 40

How does a light microscope work?

Answer 40

It uses light to magnify objects.

Question 41

What is the maximum magnification of a light microscope?

Answer 41

Around 1,500.

Question 42

Why can't light microscopes show small organelles like ribosomes?

Answer 42

Because they have low resolution.

Question 43

What are light microscopes typically used for?

Answer 43

Visualising whole cells or tissues.

Question 44

What type of microscope is used to see organelles in detail?

Answer 44

An electron microscope.

Question 45

How do electron microscopes compare in magnification to light microscopes?

Answer 45

They have a much higher magnification.

Question 46

What is the magnification range of an electron microscope?

Answer 46

Between 500,000x and 1,000,000x.

Question 47

Why do scientists use electron microscopes?

Answer 47

To study cells and organelles in finer detail.

Question 48

How has electron microscopy helped scientists?

Answer 48

It has improved our understanding of cell structures.

Question 49

How do bacteria reproduce?

Answer 49

By a process called binary fission.

Question 50

What type of reproduction is binary fission?

Answer 50

Asexual reproduction.

Question 51

What happens during binary fission?

Answer 51

The bacterial DNA is duplicated and the cell divides into two by cytokinesis.

Question 52

How quickly can bacteria divide?

Answer 52

Once every 20 minutes.

Question 53

What conditions are needed for rapid bacterial reproduction?

Answer 53

Plenty of nutrients and an optimum temperature.

Question 54

Where are bacteria grown in the lab?

Answer 54

In a nutrient broth solution.

Question 55

What does nutrient broth contain for bacterial growth?

Answer 55

Glucose, amino acids & oxygen

Question 56

What is agar?

Answer 56

A jelly-like substance used to grow bacteria.

Question 57

What does agar contain to support bacterial growth?

Answer 57

Glucose and amino acids.

Question 58

How are bacteria transferred to an agar plate?

Answer 58

From a nutrient broth and placed at a suitable temperature.

Question 59

What appears on the agar plate after a few days?

Answer 59

Colonies of bacteria.

Question 60

What is a bacterial colony?

Answer 60

A visible mass of bacteria.

Question 61

What shape are bacterial colonies usually?

Answer 61

Spherical.

Question 62

How do you calculate the area of a bacterial colony?

Answer 62

Using the formula πr².

Question 63

Why must bacterial experiments avoid contamination?

Answer 63

To prevent other microorganisms from growing on the agar plate.

Question 64

What is used to clean the work area in aseptic technique?

Answer 64

Disinfectant.

Question 65

How are Petri dishes and culture media sterilised?

Answer 65

Before use to kill any unwanted microorganisms.

Question 66

How is the inoculating loop sterilised?

Answer 66

By passing it through a Bunsen flame.

Question 67

Why is the lid of the Petri dish sealed with tape?

Answer 67

To stop bacteria from the air entering the dish.

Question 68

Why are agar plates incubated at 25°C in schools?

Answer 68

To reduce the risk of growing harmful human pathogens.

Question 69

Why is 37°C avoided when growing bacteria in schools?

Answer 69

Because it is body temperature and may grow dangerous microbes.

Question 70

How can we calculate the number of bacteria after a certain time?

Answer 70

By knowing the division time and using the population formula.

Question 71

If bacteria divide every 20 minutes, how many divisions occur in 2 hours?

Answer 71

6

Question 72

Why does the bacterial population grow exponentially?

Answer 72

Because the number of bacteria doubles every division.