Cell Types

Question 1

Cells
All living organisms are made up of cells. Cells are the basic unit of living organisms. They provide structure and carry out certain functions. There are two different types of cell:

Answer 1

Eukaryotic cells
Eukaryotic cells are found in plants, animals, fungi and protists (single-celled organisms that don’t fit other categories). They are 10-100 micrometers in size.
A eukaryote is an organism made up of eukaryotic cells.

Prokaryotic cells
They are 0.1 - 5.0 micrometers in size.
A prokaryote is an organism made up of prokaryotic cells.
Bacteria are prokaryotes.

Question 2

Prokaryotic Cells
The key features of prokaryotic cells are:

Answer 2

Lack of nucleus
Prokaryotic cells do not have a nucleus (where DNA is stored).
Instead, their genetic material is stored in a single DNA loop in the cytoplasm (watery jelly that fills the cell).

Plasmids
Prokaryotic cells may have one or more small rings of DNA, which are called plasmids.
These plasmids can replicate (have copies made) and move between cells so that genetic information can be shared.

Mitochondria and chloroplasts
Prokaryotic cells do not contain mitochondria (where respiration takes place) or chloroplasts (where photosynthesis takes place).

Question 3

Which sub-cellular structures (structures inside the cell) can be found in Prokaryotic cells?

Answer 3

Cell membrane, plasmids and single DNA loop

Question 4

All eukaryotic cells contain a cell membrane, cytoplasm and a nucleus. _________cells do not have a nucleus. Instead, their genetic material is stored in a single ____ loop in the cytoplasm.

Answer 4

1. Prokaryotic 2. DNA

Question 5

Animal Cell
Sub-cellular structures are things found in a cell. An animal cell contains the following sub-cellular structures:

Answer 5

Cell membrane
The cell membrane separates the interior (inside) of the cell from the environment outside.
It is selectively permeable (it can control substances moving in and out of the cell).

Nucleus
The nucleus contains chromosomes (which contain the cell’s genetic material).

Ribosomes
Ribosomes are responsible for synthesising (making) proteins.

Mitochondria
Mitochondria is where aerobic respiration takes place.
Aerobic respiration is a process which uses glucose and oxygen to release energy.

Cytoplasm
Cytoplasm is a jelly-like fluid that fills the cell.
It is where most of the cell’s chemical reactions take place

Common types of animal cells
Skin Cells
Muscle Cells
Blood Cells
Nerve Cells
Fat Cells

Question 7

Which of the following is a type of animal cell? Nerve cell, phloem cell, root cell, guard cell

Answer 7

Nerve cell

Question 8

A typical animal cell contains:

Answer 8

Mitochondria: Aerobic respiration takes place in this part of the cell. Aerobic respiration is a process which uses glucose and oxygen to release energy.

Cytoplasm: A jelly-like fluid that fills the cell. It is where most of the cell’s chemical reactions take place.

Ribosomes: Responsible for synthesising (making) proteins.

Cell membrane: Separates the interior of the cell from the environment outside. It is selectively permeable (it can control substances moving in and out of the cell).

Nucleus: Contains chromosomes (which contain the cell’s genetic material).

Question 9

Plant cells
In addition to the sub-cellular structures found in an animal cell, a typical plant cell also has:

Answer 9

Permanent vacuole
A permanent vacuole is a fluid-filled sac that stores water.
It is enclosed in a membrane (a wall that substances can pass through).
It can make up as much as 90% of a plant cell’s volume.

Chloroplasts
Chloroplasts contain chlorophyll, which is needed for the process of photosynthesis.

Cell wall
The cell wall surrounds the cell and is made of cellulose.
The cell wall increases the structural strength of the cell.

Question 10

Bacterial Cells
Bacterial cells are examples of prokaryotic cells. The sub-cellular structures found inside them include:

Answer 10

Flagella
Some bacteria have flagella
These are whip-like structures used for movement

Cell wall and cell membrane
Bacterial cells contain a cell membrane and a cell wall, which provides structure.

Ribosomes
Ribosomes are responsible for making proteins.

Cytoplasm
Cytoplasm is a jelly-like fluid that fills the cell.
It is where most of the cell’s chemical reactions take place.

Plasmids
Plasmids are small rings of DNA.

Question 11

Flagella

Answer 11

Flagella
Bacterial cells are examples of prokaryotic cells. The sub-cellular structures found inside some bacteria include flagella which are whip like structures used for movement.

Question 12

Sperm cell definition

Answer 12

Sperm Cell
Sperm cells are specialised (can perform a specific function). Sperm cells are specialised to fertilise egg cells. To do this, they need to travel long distances relatively to their size. They then break through to the egg cell and fertilise it (combine the sperm DNA with the egg DNA).

Question 13

Acrosome definition

Answer 13

The acrosome at the tip of the head contains an enzyme needed to penetrate (break into) an egg cell.

Question 14

Head

Answer 14

The ‘head’ contains the sperm cell’s nucleus. The nucleus carries one half of an organism’s genetic material.
This combines with the egg cell’s half of genetic material to fertilise the egg cell.

Question 15

Tail

Answer 15

The ‘tail’ is used for the cell’s motion. This allows sperm cells to travel towards the egg cell.

Question 16

Middle section

Answer 16

The middle section is filled with mitochondria to provide the sperm with the energy it needs to travel a long distance to reach the egg cell.

Question 17

Features and adaptations of sperm cells

Answer 17

Sperm cell
Head
Acrosome
Contains enzymes for penetrating egg
Nucleus
Carries 1/2 of organism’s genetic material
Middle section
Filled with mitochondria
Gives energy for swimming
Tail
Motion (swimming to egg)

Question 18

Sperm Cells
Sperm cells are highly specialised to travel to and then fertilise an egg.

Answer 18

Tail movement
Sperm spin their tails in a corkscrew motion to move themselves towards their target - the egg.

Question 19

Sperm cells are specialized to

Answer 19

Sperm Cell

Sperm cells are specialised to enable them to fertilise egg cells. To do this they need to travel long distances - relative to their size - to reach the egg, then break through to the egg and fertilise it (combine the sperm DNA with the egg DNA).

Question 20

Digestive enzymes are found in many places in organisms

Answer 20

including the stomach, the saliva and the acrosomes on the heads of sperm cells.

Question 21

Egg Cell

Answer 21

The egg cell is fertilised by a sperm cell to become a zygote (which grows into an embryo). An egg cell is much larger than a sperm cell and it is specialised to support the zygote as it grows.

Question 22

Cytoplasm in zygote

Answer 22

The cell is large and contains lots of cytoplasm, which is packed full of nutrients that the zygote will need to grow.

Question 23

Haploid nucleus

Answer 23

Haploid nucleus
The nucleus contains half the genetic information needed for the new zygote.
The sperm cell provides the other half.

Question 24

Cell membrane

Answer 24

The cell membrane is adapted to change structure once the egg is fertilised so that no more sperm can get into the egg cell.

Question 25

What do sperm and egg cells have in common?

Answer 25

Haploid nucleus

Question 26

Ciliated Epithelia

Answer 26

Ciliated Epithelial cells line the airways. Their function is to waft mucus (which traps harmful microorganisms) to the back of the throat to be swallowed.

Question 27

Mitochondria in Ciliated Epithelia

Answer 27

Moving the cilia needs energy (from respiration), so these cells contain many mitochondria.

Question 28

Cilia

Answer 28

The cells have hair-like structures on them called cilia, which can be moved in unison (all together).

Question 29

Cilia Ciliated Epithelial cells waft mucus

Answer 29

(which traps harmful microorganisms) to the back of the throat to be swallowed.

Question 30

Magnification and Resolution When using microscopes, two variables matter the most: magnification and resolution.

Answer 30

Magnification Magnification tells us how many times larger an image seen through a microscope is compared to the real object. Resolution Resolution is the ability to distinguish between (tell apart) two or more objects that are close together.

Question 31

Which of these objects are only visible through light microscopes? Ribosomes, xylem, cell membrane, leaves, hair, skin

Answer 31

Ribosomes, xylem, cell membrane

Question 32

Magnification The magnification of a microscope is the size of the image seen with the microscope divided by the size of the real object. It is how much bigger the object under the microscope appears. Example: A cell has a diameter of 0.001cm. An image of that cell seen through the microscope has a diameter of 5 cm.

Answer 32

The magnification is 5 cm/0.001 cm = x5000

Question 33

Equation for magnification

Answer 33

Magnification= size of the image/side of the real object

Question 34

When calculating magnifications, ensure that all measurements have the same units. For example, both measurements could be in

Answer 34

cm

Question 35

An object that is 5mm (1mm = 0.001m) long looks 10cm long underneath a microscope. What is the magnification of this microscope? (4 marks)

Answer 35

Remember the equation for magnification Magnification = magnified size of object ÷ real size of object Remember to convert one of the lengths to the unit the other length is in 10cm = 100mm Substitute into the equation. Remember that magnification has no unit! Magnification = 100mm ÷ 5mm = × 20

Question 36

Describe the developments in microscopy

Answer 36

Developments in Microscopy Developments in microscopy (use of the microscope) have allowed us to see smaller details inside cells. This has improved our understanding of cell functions.

Question 37

Light microscope

Answer 37

A light microscope passes light through a specimen, and creates a magnified image using lenses. The first light microscope was made using two lenses in the late 16th century. It had a resolution better than the human eye itself.

Question 38

Discoveries using light microscopes

Answer 38

Light microscopes allowed bacteria to be seen for the first time. They also allowed us to see plant cells and animal cells as separate objects. However, we still could not tell lots of sub-cellular (within the cell) structures apart.

Question 39

Electron microscope

Answer 39

The electron microscope was first used in 1933. Electron microscopes work in a similar way to light microscopes. However, electrons are passed through the specimen instead of light. They can now resolve distances of 1nm (better resolution) with magnifications of ×500,000.

Question 40

Discoveries using electron microscopes

Answer 40

The high level of detail of electron microscopes allowed scientists to see sub-cellular structures more clearly. They also allowed scientists to study how structures such as mitochondria, chloroplasts and ribosomes function.

Question 41

Name some sub-cellular structures found in plant cells, but not animal cells:

Answer 41

chloroplasts permanent vacuole cell wall

Question 42

Light Microscope Experiment

Answer 42

-Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide. -Add a few drops of a suitable stain/dye (e.g. iodine). -Place a coverslip on top of the tissue and place the slide onto the microscope stage. -Use the objective lens with the lowest magnification, and focus on the sample. -Increase the magnification and refocus to see different features of the cell.

Question 43

When using a light microscope, use the _____ power objective lens, and focus on the sample. Increase the power and refocus.

Answer 43

Lowest

Question 44

What is the name of the lens with the lowest magnification that we use to initially focus on a sample?

Answer 44

Objective

Question 45

When using a light microscope a _____ is used to give contrast to the features of the cells, to make them visible.

Answer 45

Stain