Cell Structure

Question 1

Eukaryotic

Definition

Answer 1

A cell which has a nucleus.

Eukaryotic cells also have other structures in the cytoplasm which have membranes around them

Question 2

Cell membrane

Definition

Answer 2

• surrounds the cell
• selectively permeable membrane controlling the entry and exit of materials

Question 3

Cytoplasm

Definition

Answer 3

• the thick substance inside a cell
• composed of water, salts, and proteins.
• it includes everything enclosed by the cell membrane except the nucleus

Question 4

Compound microscope

Definition

Answer 4

A microscope in which the lens is close to the sample being magnified

Question 5

Depth of field

Definition

Answer 5

The distance between the nearest and furthest objects in focus

Question 6

Haploid def

Answer 6

A sex cell (gamete) that contains one set of chromosomes

Question 7

Light microscope def

Answer 7

Device that uses visible light an a series of lenses to produce an enlarged image of an object

Question 8

Magnification def

Answer 8

The amount that an image of something is scaled up when veiwed through a microscope

Question 9

Mitochondria def

Answer 9

Structures in the cytoplasm of all cells where aerobic respiration takes place (singular is mitochdrion)

Question 10

Prokaryotic def

Answer 10

Description of a cell which doesn’t have a nucleus; the DNA is free in the cytoplasm

Question 11

Ribosome def

Answer 11

The site of protein synthesis In a plant cell

Question 12

Tissue def

Answer 12

A group of similar cells that carry out the same function e.g. muscle

Question 13

Vacuole def

Answer 13

In a plant cell A space within the cytoplasm of plant cells that contains cell sap

Question 14

Animal cells

Answer 14

Animals are made up of cells. These cells are eukaryotic. This means they have a nucleus and other structures which are surrounded by membranes.

Question 15

what animal cells look like under a light microscope and a electron microscope.

Answer 15

Mitochondria (singular: mitochondrion) are visible with a light microscope but can’t be seen in detail. Ribosomes are only visible with an electron microscope.

Question 16

Do animal and plant cells consist of different types of cells or not. why?

Answer 16

Most cells are specialised and are adapted for their function. Animals and plants therefore consist of many different types of cell working together.

Question 17

plant cells

Answer 17

Plants are made up of cells. These cells are eukaryotic. This means they have a nucleus and other structures which are surrounded by membranes.

Question 18

chloroplast def

Answer 18

Organelle that contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. Contains the enzymes needed for photosynthesis.

Question 19

Do animal cells have vacuoles?

Answer 19

yes. Animal cells may also have vacuoles, but these are small and temporary. if it says ‘permanent vacuole’ it means a plant vacuole.

Question 20

bacteria cells

Answer 20

Bacteria are all single-celled. The cells are all prokaryotic. This means they do not have a nucleus or any other structures which are surrounded by membranes. Larger bacterial cells may be visible using a light microscope, however an electron microscope would be needed to see the details of the cell organelles.

Question 21

Chromosomal DNA in a bacteria cell

Answer 21

The DNA of bacterial cells is found loose in the cytoplasm. It is called chromosomal DNA and is not contained within a nucleus.

Question 22

Plasmid DNA in a bacteria cell

Answer 22

Bacteria also have small, closed-circles of DNA called plasmids present in their cytoplasm. Unlike the chromosomal DNA, plasmid DNA can move from one bacterium to another giving variation.

Question 23

Flagella DNA in a bacteria cell

Answer 23

Bacteria can have one or more flagella (singular: flagellum). These can rotate or move in a whip-like motion to move the bacterium.

Question 24

Cell wall in a bacteria cell

Answer 24

Plant and bacterial cell walls provide structure and protection. Only plant cell walls are made from cellulose.

Question 25

How do bacteria cells make more of themselves

Answer 25

Bacteria are amongst the simplest of organisms. Their cells do not divide by mitosis. Instead they copy themselves by binary fission. The process is similar, but we use a different name for it because prokaryotic bacteria are very different from other eukaryotic plant and animal cells.

Question 26

Difference between Eukaryotic cell (plant and animal cell) and Prokaryotic cell (bacterial cell) Size

Answer 26

Eukaryotic cell (plant and animal cell): Most are 5 μm – 100 μm Prokaryotic cell (bacterial cell): Most are 0.2 μm – 2.0 μm

Question 27

Difference between Eukaryotic cell (plant and animal cell) and Prokaryotic cell (bacterial cell) Outer layers of cell

Answer 27

Eukaryotic cell (plant and animal cell): Cell membrane. Surrounded by cell wall in plants and fungi. Prokaryotic cell (bacterial cell): Cell membrane. Surrounded by cell wall.

Question 28

Difference between Eukaryotic cell (plant and animal cell) and Prokaryotic cell (bacterial cell) cell contents

Answer 28

Eukaryotic cell (plant and animal cell): Cytoplasm. Cell organelles include mitochondria, chloroplasts in plants and ribosomes. Prokaryotic cell (bacterial cell): Cytoplasm. Ribosomes present. There are no mitochondria or chloroplasts.

Question 29

Difference between Eukaryotic cell (plant and animal cell) and Prokaryotic cell (bacterial cell) Genetic material

Answer 29

Eukaryotic cell (plant and animal cell): DNA in a nucleus. Plasmids are found in a few simple eukaryotic organisms. Prokaryotic cell (bacterial cell): DNA is a single molecule, found free in the cytoplasm. Additional DNA is found on one or more rings called plasmids.

Question 30

Difference between Eukaryotic cell (plant and animal cell) and Prokaryotic cell (bacterial cell) Type of cell divions

Answer 30

Eukaryotic cell (plant and animal cell): Mitosis Prokaryotic cell (bacterial cell): Binary fission

Question 31

specialised animal cells

Answer 31

There are many different types of cells in animals. Each type is specialised to do a particular role. These ensure that the organism functions as a whole.

Question 32

How is the specialised animal cell sperm adapted to carry out it’s function?

Answer 32

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. Sperm are the smallest cells in the body and millions of them are made.

Question 33

How is the specialised animal cell the egg cell adapted to carry out it’s function?

Answer 33

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. Eggs are one of the biggest cells in the body and only a few are made.

Question 34

How is the specialised animal cell the ciliated epithelial cell adapted to carry out it’s function?

Answer 34

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

Question 35

How have light microscopes developed?

Answer 35

Glass was developed by the Romans in the first century. Since then, scientists have been trying to magnify objects. No-one knows who first invented the microscope, but there have been key stages in their development: 1590s: Dutch spectacle maker Janssen experimented with putting lenses in tubes. He made the first compound microscope. None of these microscopes have survived, but they are thought to have magnified from ×3 to ×9. Antonie van Leeuwenhoek’s first microscope, 17th centuryAntonie van Leeuwenhoek’s first microscope 1650s: British scientist, Robert Hooke (also famous for his law of elasticity in Physics) observed and drew cells using a compound microscope. Late 1600s: Dutch scientist Antonie van Leeuwenhoek constructed a microscope with a single spherical lens. It magnified up to ×275. The optical quality of lenses increased and the microscopes are similar to the ones we use today. Throughout their development, the magnification of light microscopes has increased, but very high magnifications are not possible. The maximum magnification with a light microscope is around ×1500.

Question 36

Components of light microscopes

Answer 36

-eyepiece -objective lenses -stage clip -condenser -mirror -coarse focus -fine focus -arm -stage

Question 37

Calculating the magnification of light microscopes

Answer 37

The compound microscope uses two lenses to magnify the specimen: the eyepiece and an objective lens. In most microscopes, there is a choice of objectives to use. Magnification can therefore be varied, according to the size of the specimen to be viewed and the level of detail required. The magnification of a lens is shown by a multiplication sign followed by the amount the lens magnifies. So a lens magnifying ten times would be ×10. The total magnification of a microscope is: Magnification of the microscope = magnification of eyepiece × magnification of objective So, if the magnification of an eyepiece is ×10 and the objective is ×4, the magnification of the microscope is: Magnification of eyepiece × magnification of objective = 10 × 4 = 40

Question 38

If the magnification of an eyepiece is ×10 and the objective is ×40, what is the magnification of the microscope?

Answer 38

×400. Because 10 × 40 = 400.

Question 39

Calculating the magnification of an image

Answer 39

Microscopes use lenses to magnify the image of a specimen so that it appears larger. The formula to calculate magnification is: magnification = size of image ÷ real size of object It is important to work in the same units when calculating magnification. Sizes of most cells are given in micrometres, symbol μm. Calculating the magnification, working in micrometres:

Question 40

convert 1mm into μm (micrometers)

Answer 40

1mm = 1000μm

Question 41

The limits of the light microscope

Answer 41

The magnification of a microscope is not the only factor that is important when viewing cells. The detail that can be seen, or resolution, is also important. The ability to see greater detail in an image depends on the resolution or resolving power. This is the ability to see two points as two points, rather than merged into one. Think about a digital photo. It can be enlarged, but over a certain size, you won’t be able to see any more detail. The resolution of a light microscope is around 0.2 μm, or 200 nm. This means that it cannot distinguish two points closer than 200 nm. One nm, or nanometre, is one billionth of a metre. This is written as \text{1/1 000 000 000} or in standard form as 1 × 10^−9 m

Question 42

The electron microscope

Answer 42

Electron microscopes use a beam of electrons instead of beams or rays of light. Living cells cannot be observed using an electron microscope because samples are placed in a vacuum. There are two types of electron microscope: -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 TEMs have a maximum magnification of around ×1,000,000, but images can be enlarged beyond that photographically. The limit of resolution of a TEM is now less than 1 nm. The TEM has revealed structures in cells that are not visible with the light microscope. SEMs are often used at lower magnifications (up to ×30,000). The limit of resolution of a SEM is lower than that of a TEM (approximately 50 nm). Electron microscopes use a beam of electrons instead of beams or rays of light. Living cells cannot be observed using an electron microscope because samples are placed in a vacuum. There are two types of electron microscope: 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 TEMs have a maximum magnification of around ×1,000,000, but images can be enlarged beyond that photographically. The limit of resolution of a TEM is now less than 1 nm. The TEM has revealed structures in cells that are not visible with the light microscope. SEMs are often used at lower magnifications (up to ×30,000). The limit of resolution of a SEM is lower than that of a TEM (approximately 50 nm).

Question 43

Maths - Quantitative units When writing and working with very large or very small numbers, we use standard form.

Answer 43

Standard form shows the size of numbers as powers of ten. Standard from numbers are written as: A × 10n where: A is a number greater than 1 but less than 10 and n is the index or power. Four small numbers you need to know: -milli (10^−3) 0.001 -micro (10^−6) 0.000001 -nano (10^−9) 0.000000001 -pico (10^−12) 0.000000000001

Question 44

Standard form is used for:

Answer 44

Large numbers eg. A population of 120,000,000 microorganisms could be written as 1.2 × 108 Small numbers eg. A red blood cell’s diameter of 7 μm or 0.000007 m could be written as 7 × 10−6 m Calculations eg. When multiplying: add powers. When dividing: subtract powers.

Question 45

Converting between different scientific units. how many -Centimetres -Millimetres -Micrometres -Nanometres in a metre? (+ in standard form)

Answer 45

-Centimetres: 100 1x10^-2 -Millimetres: 1000 1x10^-3 -Micrometres: 1 000 000 1x10^-6 -Nanometres: 1 000 000 000 1x10^-9 Centimetres are odd units in they don’t fit the pattern of reducing in size by 1000 each time. There are one thousand micrometres in one millimetre, and one thousand nanometres in one micrometre.

Question 46

compare the size of a red blood cell (7 μm) and a leaf cell (70 μm)

Answer 46

70μm ÷ 7μm = 10 the length of a leaf cell is tens times that of a red blood cell.

Question 47

1 μm = ? nm

Answer 47

1 μm = 1000 nm

Question 48

What is the width of a cheek cell (70 μm) compared to that of a salmonella bacterium (0.5 μm)?

Answer 48

70μm ÷ 0.5μm = 140

Question 49

Order of magnitude

Answer 49

When two numbers are similar, we say they have the same order of magnitude. Differences in size can be described as differences in order of magnitude. The difference is often calculated in factors of 10. If you increase a number by one order of magnitude, you are multiplying the number by 10. For example, we would say that the numbers 200 and 300 are of the same order of magnitude whereas the numbers 200 and 2000 are of different orders of magnitude. 200 and 300 are both in the magnitude of 102 whereas 2000 is in the magnitude of 103. If you decrease a number by one order of magnitude, you are dividing the number by 10, or multiplying by 0.1. For instance, there is a one order of magnitude difference between a person 2 m tall, and an oak tree, 20 m tall. The person’s height = 2 m = 2 × 100 The oak tree’s height = 20 m = 2 × 101 The oak tree is approximately 10 times bigger than the person. We can also say this as there is an order of magnitude between the height of a human being (2 m) and the height of an oak tree (20 m). When comparing orders of magnitude, actual distances can be approximated. It’s the relative difference that is important.

Question 50

What is the calculation for magnification of a light microscope?

Answer 50

magnification of eyepiece x magnification of objective

Question 51

What name is given to cells in the trachea?

Answer 51

Ciliated cells

Question 52

What type of microscope would you use to study living cells?

Answer 52

Light microscope