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Biology GCSE > Cell Biology > Flashcards

Cell Biology Flashcards

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1
Q

What is a cell?

A

A cell is the smallest unit of life that can live on its own. Cells make up all living organisms and their tissues.

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2
Q

What are the differences between eukaryotic and prokaryotic cells?

A

Eukaryotic cells are much larger than prokaryotic cells.
Eukaryotic cells contain membrane-bound organelles, while prokaryotic cells do not.
Eukaryotic cells keep their DNA in the form of chromosomes within a nucleus, whilst prokaryotic cells have their DNA loose in the cell.

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3
Q

For animal, plant, and bacterial cells, state whether they are either eukaryotic or prokaryotic.

A

Animal and plant cells are eukaryotic.

Bacterial cells are prokaryotic.

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4
Q

Name 5 sub-cellular structures (organelles) that are found in both animal and plant cells.

A

Cell membrane
Ribosomes
Nucleus
Mitochondria
Cytoplasm

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5
Q

What is the cell membrane and what is its role?

A

The cell membrane is a protective barrier around the outside of the cell.

It controls which substances can pass in and out of the cell.

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6
Q

What is the cytoplasm and what is its role?

A

The cytoplasm is a jelly-like liquid that fills the cell.

It allows substances to dissolve, and chemical reactions to take place.

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7
Q

What is the role of the nucleus?

A

It contains the genetic material (DNA) of the cell, and so controls what the cell does.

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8
Q

What is the role of the mitochondria?

A

They carry out aerobic respiration, so provide energy (in the form of ATP) for the cell to use in chemical reactions.

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9
Q

What is the role of the ribosomes?

A

They are the site of protein synthesis (where proteins are made).

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10
Q

Name 3 sub-cellular structures (organelles) that are found in plant cells but not in animal cells.

A

Chloroplast
Permanent vacuole
Cell wall

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11
Q

In plants, what is the cell wall made of?

A

Cellulose

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12
Q

What is the role of the plant cell wall?

A

It provides strength and structure to the plant cell, preventing it from bursting or shrinking when water enters/leaves the cell via osmosis.

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13
Q

What does the permanent vacuole contain?

A

Cell sap (a solution of sugars, salts, and amino acids).

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14
Q

What is the role of the permanent vacuole?

A

It supports the cell, maintaining its turgidity (shape).

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15
Q

What is the role of chloroplasts?

A

Chloroplasts are the site of photosynthesis, so make glucose for the cell.

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16
Q

What is chlorophyll?

A

A green pigment within chloroplasts that absorbs sunlight for photosynthesis.

It is chlorophyll that makes plants green.

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17
Q

Name 7 sub-cellular structures (organelles) that are found in bacterial cells.

A

Cell wall
Cell membrane
Cytoplasm
Flagellum (only some bacteria)
Ribosome
Plasmid
Circular strand of DNA

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18
Q

What are plasmids, and what are their role?

A

Plasmids are small, circular loops of DNA that are separate to the main DNA.

They contain ‘extra genes’ that are sometimes useful to the bacteria, such as antibiotic resistance.

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19
Q

What is the prokaryotic cell wall composed of?

A

Peptidoglycan

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20
Q

What is the definition of magnification?

A

How many times larger the image appears, compared to the real object.

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21
Q

What is the role of microscope?

A

A microscope is designed to magnify small objects, so that they appear larger.

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22
Q

Define resolution

A

The smallest distance between two objects that can be distinguished. Basically, how much detail you can see in the image.

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23
Q

How does a light microscope work?

A

Light from a mirror (or light source) passes through the specimen, objective lens, the eyepiece lens, and into your eye.

The two lenses magnify the image and cause the image to be much larger than the real object.

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24
Q

What are the two types of microscope?

A

Light microscopes
Electron microscopes

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25
What is the magnifying power of a light microscope?
X2000
26
Give 3 advantages of light microscopes (compared to electron microscopes).
Cheaper Easier to use. Smaller so easy to transport. Colour images Samples can be alive
27
Explain the main disadvantage of light microscopes (as compared to electron microscopes).
Light microscopes rely on light, whereas electron microscopes rely on electrons. Light has a much longer wavelength than electrons, which means that light microscopes have a lower resolution than electron microscopes. This in turn means that light microscopes have a lower maximum magnification, and so can’t see many details within cells, such as the details of sub-cellular structures.
28
What is the magnifying power of an electron microscope?
X2000000
29
What is the main advantage of electron microscopes (compared to light microscopes)?
Electron microscopes have a greater resolution and magnification. This means they can be used to see details within sub-cellular structures.
30
Why do electron microscopes have a greater magnification and resolution than light microscopes?
They use a beam of electrons rather than light waves, and the electrons have a shorter wavelength than light waves.
31
Give 5 disadvantages of electron microscopes (compared to light microscopes).
Expensive. Difficult to use, and require specialist training. Large, so difficult to transport. Images generated are in black and white. Can only view dead specimens.
32
What is the equation for magnification?
Magnification= image size/object size
33
34
Give 3 reasons why multicellular organisms require a continuous supply of new cells.
Growth (we need more cells as we grow). Development (we need new cell types as we develop new tissues). Repair (we need to replace the cells we lose each day).
35
What is the cell cycle?
The cell cycle is the series of steps that take place as a cell grows and then divides.
36
Where in the body does mitosis take place?
Everywhere
37
How many cells does mitosis produce?
Mitosis produces 2 cells. 1 cell divides into 2 cells.
38
What do we call the cells produced by mitosis?
Daughter cells
39
Are the cells produced by mitosis genetically identical or unique?
Genetically identical
40
How many divisions are there when a cell divides by mitosis?
1
41
How many pairs of chromosomes do most human cells have?
23 pairs of chromosomes.
42
What are the steps of mitosis and cytokinesis?
DNA condenses to form chromosomes. Chromosomes line up along the centre (equator) of the cell. Cell fibres pull the two arms of each chromosome to opposite sides (poles) of the cell. Cytokinesis - the entire cell divides to form two identical daughter cells.
43
Which type of organism(s) divide via binary fission?
Bacteria
44
What is binary fission?
The process by which bacteria divide and reproduce.
45
Is binary fission an example of sexual or asexual reproduction?
Asexual
46
Which two things must a bacterial cell do before it can divide?
Grow. Replicate its genetic material.
47
Describe the steps of binary fission.
The bacteria grows and reproduces its genetic material (this happens before binary fission, but is often on the mark scheme for exam questions like this). The two circular strands of DNA move to opposite sides of the cell. A new cell wall forms down the middle of the cell. The two halves pull apart to form two cells.
48
During binary fission, is the genetic material split equally between the two new cells?
Yes and no. Each cell will always receive one copy of the circular strand of DNA, however, the plasmids are randomly arranged, so there are often more plasmids in one cell that the other.
49
In binary fission, what is the mean division time?
The mean (average) time it takes for a bacterial cell to divide.
50
Which three conditions do bacteria require for fast growth?
Warmth. Moisture. Plenty of nutrients.
51
What is differentiation in cells?
The process by which a cell changes to become specialised for its job
52
What happens during differentiation?
Cells develop different sub cellular structures and turn into different types of cells, allowing them to carry out different functions
53
When do most animal cells use their ability to differentiate?
At an early stage, after they become specialised
54
When do most plant cells lose their ability to differentiate?
They dont
55
What are cells that differentiate in mature animals used for?
Repairing and replacing cells
56
What are undifferentiated cells called?
Stem cells
57
What is the function of sperm?
To get the male DNA to the female DNA
58
What adaptations do sperm cells have and how does it help?
Long tail and streamlined head- helps it swim to the egg Lots of mitochondria- to provide the energy needed Enzymes in head- digest through the egg cell membrane
59
What is the function of nerve cells?
Carry electrical signals from one side of the body to the other
60
What are the adaptations of nerve cells and how do they help?
Long-cover more distance Branched connections- connect other nerve cells and form connections throughout the body
61
What is the function of a muscle cell?
To contract quickly
62
What are the adaptations of muscle cells?
Long- so they have space to contract Lots of mitochondria- generate energy needed for contraction
63
What is the function of a root hair cell?
Absorbing water and mineral ions from soil
64
What are the adaptations of a root hair cell?
Long and stick out into soil- gives the plant a big surface area for absorbing mineral ions
65
What is the function of phloem and xylem cells?
Transporting substances such as food and water around plants
66
How do xylem and phloem cells form xylem and phloem tubes?
Cells are long and joined end to end
67
How are xylem and phloem cells/tubes adapted?
Xylem cells are hollow in the centre and phloem cells have very few sub cellular structures- so things can flow right through them
68
Where can stem cells be found?
Early human embryos Bone marrow
69
Why are embryonic stem cells exciting to doctors/medical researchers?
They have the potential to turn into any kind of cell at all
70
How do bone marrow stem cells differ from embryonic ones?
They do not have the ability to turn into any type of cell at all— only certain ones like red blood cells
71
How are stem cells used in a lab?
They can be grown in a lab to produce clones and made to differentiate into specialised cells to be used in medicine or research
72
How does medicine already use adult stem cells to cure disease?
Stem cells transferred form the bone marrow of a healthy person can replace faulty blood cells in a sick person
73
How are embryonic stem cells used in medicine?
To replace faulty cells You could make insulin-producing cells to cure diabetes Or nerve cells for people paralysed by spinal injuries
74
What is therapeutic cloning?
An embryo could be made to have the same genetic information as the patient So stem cells form it will contain the same genes So they wouldn’t be rejected by the patients body
75
What are the risks of using stem cells in medicine?
Stem cells grown in a lab may become contaminated with a virus and passed on to the patient and make them sicker.
76
Why are some people against stem cells to research?
Human embryos shouldn’t be used for experiments since each one is a potential human life
77
What do people that support stem cells to research think?
Curing patients that already exist and who are suffering is more important than the rights of the embryos They argue that embryos used are usually unwanted ones from fertility clinics which would otherwise be destroyed
78
What do campaigners for the rights of embryos think scientists should do?
They should focus on finding and developing other sources of stem cells without having to use embryos
79
In some countries, stem cell research is banned. What about the UK?
It is allowed but has to follow strict guidelines
80
Where are stem cells found in plants?
The meristems
81
When can meristem tissues differentiate and into what cells?
Throughout the plants entire life Any type of plant cell
82
What can plant stem cells be used for?
To create clones of whole plants quickly and cheaply And to grow more plants of rare species to prevent them from being wiped out Grow crops of identical plants that have desired features for farmers (e.g. disease resistance)
83

Biology GCSE (2 decks)

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