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Edexcel Biology Gcse > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

Cell membrane

def

A

A selectively permeable membrane surrounding the cell and controlling the entry and exit of materials

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2
Q

Cytoplasm

def

A

The living substance inside a cell (not including the nucleus)

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3
Q

Compound microscope

def

A

A microscope in which the lens in close to the simple being magnified

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4
Q

Depth of field

def

A

The distance between the nearest and farthest objects in focus

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5
Q

Eukaryotic

def

A

Description of a cell which has a nucleus. Eukaryotic cells also have other structures in the cytoplasm which have membranes around them

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6
Q

Haploid

def

A

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

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7
Q

Light microscope

def

A

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

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8
Q

Magnification

def

A

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

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9
Q

Mitochondria

def

A

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

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10
Q

Prokaryotic

def

A

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

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11
Q

Ribosome

def

A

The site of protein synthesis

In a plant cell

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12
Q

Tissue

def

A

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

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13
Q

Vacuole

def

A

In a plant cell

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

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14
Q

Animal cells

A

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

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15
Q

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

A

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

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16
Q

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

A

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

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17
Q

plant cells

A

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

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18
Q

chloroplast

def

A

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

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19
Q

Do animal cells have vacuoles?

A

yes. Animal cells may also have vacuoles, but these are small and temporary.

if it says ‘permanent vacuole’ it means a plant vacuole.

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20
Q

bacteria cells

A

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.

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21
Q

Chromosomal DNA in a bacteria cell

A

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

22
Q

Plasmid DNA in a bacteria cell

A

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.

23
Q

Flagella DNA in a bacteria cell

A

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

24
Q

Cell wall in a bacteria cell

A

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

25
Q

How do bacteria cells make more of themselves

A

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.

26
Q

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

Size

A 
Eukaryotic cell (plant and animal cell):
Most are 5 μm – 100 μm	
Prokaryotic cell (bacterial cell):
Most are 0.2 μm – 2.0 μm
27
Q

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

Outer layers of cell

A 
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.
28
Q

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

cell contents

A 
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.
29
Q

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

Genetic material

A 
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.
30
Q

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

Type of cell divions

A 
Eukaryotic cell (plant and animal cell):
Mitosis	
Prokaryotic cell (bacterial cell):
Binary fission
31
Q

specialised animal cells

A

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.

32
Q

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

A

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.

33
Q

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

A

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.

34
Q

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

A

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

35
Q

How have light microscopes developed?

A

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.

36
Q

Components of light microscopes

A
  • eyepiece
  • objective lenses
  • stage clip
  • condenser
  • mirror
  • coarse focus
  • fine focus
  • arm
  • stage
37
Q

Calculating the magnification of light microscopes

A

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

38
Q

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

A

×400. Because 10 × 40 = 400.

39
Q

Calculating the magnification of an image

A

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:

40
Q

convert 1mm into μm (micrometers)

A

1mm = 1000μm

41
Q

The limits of the light microscope

A

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

42
Q

The electron microscope

A

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).

43
Q

Maths - Quantitative units

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

A

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
44
Q

Standard form is used for:

A

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.

45
Q

Converting between different scientific units.

how many

  • Centimetres
  • Millimetres
  • Micrometres
  • Nanometres

in a metre?

(+ in standard form)

A

-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.

46
Q

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

A

70μm ÷ 7μm = 10

the length of a leaf cell is tens times that of a red blood cell.

47
Q

1 μm = ? nm

A

1 μm = 1000 nm

48
Q

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

A

70μm ÷ 0.5μm = 140

49
Q

Order of magnitude

A

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.

50
Q

What is the calculation for magnification of a light microscope?

A

magnification of eyepiece x magnification of objective

51
Q

What name is given to cells in the trachea?

A

Ciliated cells

52
Q

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

A

Light microscope

Edexcel Biology Gcse (36 decks)

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