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HRAY SCIENCE GCSE > BIO - CELLS > Flashcards

BIO - CELLS Flashcards

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1
Q

How many types of cells are there and what are they called?

A

There are two different types of cells and they are called ‘Eukaryotic’ and ‘Prokaryotic’ cells.

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2
Q

Where are eukaryotic cells found in?

A

They are found in plants, animals, fungi and protists.

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3
Q

What is a eukaryote?

A

A eukaryote is an organism made up of eukaryotic cells.

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4
Q

Where are prokaryotic cells found in?

A

They are found in bacteria.

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5
Q

What are the key features of prokaryotic cells?

A
  • They have plasmids
  • They do not contain mitochondria or chloroplasts
  • They do not have a nucleus - they have a single DNA loop in the cytoplasm
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6
Q

What are the different types of units used for distance?

A 
1 kilometre (km) = 1000 metres
1 metre (m) = 100 centimetres
1 centimetre (cm) = 10 millimetres
1 millimetre (mm) = 100 micrometres 
1 micrometre (µm) = 1000 nanometres (nm)
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7
Q

What are sub-cellular structures?

A

Sub-cellular structures are things found in a cell.

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8
Q

What sub-cellular structures are found in an animal cell?

A
  • Cell membrane
  • Nucleus
  • Ribosomes
  • Mitochondria
  • Cytoplasm
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9
Q

What is the cell membrane?

A

The cell membrane separates the inside of the cell from the outside. It controls substances moving in and out of the cell (selectively permeable).

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10
Q

What is the nucleus?

A

The nucleus is the control centre of the cell. It contains chromosomes (which contain the cell’s genetic material).

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11
Q

What are the ribosomes?

A

The ribosomes are responsible for making (synthesising) proteins.

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12
Q

What is the mitochondria?

A

The mitochondria are the ‘powerhouses’ of the cell. Aerobic respiration takes place in the mitochondria meaning energy is released in the mitochondria.

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13
Q

What is cytoplasm?

A

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

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14
Q

What sub-cellular structures are found in a plant cell?

A

In addition with the sub-cellular structures in an animal cell, a plant cell contains:

  • Permanent vacuole
  • Chloroplasts
  • Cell wall
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15
Q

What is the permanent vacuole?

A

The permanent vacuole is a fluid-filled sac that stores water. It is enclosed in a membrane (a wall that substances can pass through).

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16
Q

What are the chloroplasts?

A

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

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17
Q

What is the cell wall?

A

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

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18
Q

How do plant cells differentiate?

A

Plant cells can differentiate throughout their lives. Plants are always able to create new tissues.

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19
Q

How do animal cells differentiate?

A

Most animal cells differentiate early on in their development. In mature animals, cells mostly divide to replace cells and repair tissues that are already present. New tissues are rarely created by cell differentiation.

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20
Q

What sub-cellular structures are found inside bacterial cells?

A
  • Flagella
  • Plasmids
  • Cell wall
  • Cell membrane
  • Cytoplasm
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21
Q

What is the flagella?

A

The flagella are whip-like structures used for movement.

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22
Q

What are plasmids?

A

Plasmids are just small rings of DNA.

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23
Q

What is cell differentiation?

A

Cell differentiation is the process where a cell develops new sub-cellular structures to let it perform a specific function. This makes the cell specialised.

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24
Q

What happens in embryonic cell differentiation?

A

Cell differentiation happens during an organism’s development. Organisms start as one cell. These cells divide to form embryos that differentiate to produce cells that can perform all of the body’s functions.

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25
Q

What is the function of the sperm cell?

A

Sperm cells are functioned to fertilise egg cells.

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26
Q

How do sperm cells carry out their job?

A

Sperm cells travel long distances. When they get to the egg cell, they break through the egg cell and fertilise it.

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27
Q

How does the middle section of sperm cell work?

A

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.

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28
Q

How does the head of the sperm cell work?

A

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.

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29
Q

How does the tail of the sperm cell work?

A

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

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30
Q

How do sperm cells move their tails to get to the egg?

A

The sperm cells spin their tails in a corkscrew motion to move themselves towards the egg.

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31
Q

What happens when the sperm cell reaches the egg cell?

A

The sperm cell fuses with the egg, sharing its genetic information to make a complete genome (all the DNA needed to make a whole organism).

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32
Q

What is the function of the nerve cell?

A

The function of the nerve cell is to transmit electrical messages around the body.

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33
Q

What is another word for a nerve cell?

A

Another word for a nerve cell is a neurone.

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34
Q

How does the axon of a nerve cell work?

A

The axon is the part of the cell that electrical signals travel along. Nerve cells have a long axon, which increases the distance that electrical signals can travel.

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35
Q

How does the myelin sheath of a nerve cell work?

A

A sheath made of material called myelin surrounds the nerve cell. This stops the electrical nerve signals from leaking out of the nerve cell. This increases the speed of transmission (travel) of electrical signals.

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36
Q

What do the dendrites of a nerve cell work?

A

The dendrites are the branches of a nerve cell. Several dendrites spread outwards from the cell body to transfer electrical messages (impulses) to other nerve cells.

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37
Q

What are synapses?

A

Synapses are the gaps between neurones.

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38
Q

What is the function of a muscle cell?

A

The function of the muscle cells is to move and contract.

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39
Q

What do the protein fibres inside the muscle cell do?

A

The protein fibres can contract, allowing the muscle to move.

40
Q

How do muscle cells generate energy?

A

Muscle cells contain lots of mitochondria generating lots of energy for motion.

41
Q

What is the function of a root hair cell?

A

The function of a root hair cell is to absorb minerals and water for the plant.

42
Q

What do the long projections of root hair cells do?

A

The long projections increase the surface area which increases the amount of water and minerals absorbed.

43
Q

Why do root hair cells not contain chloroplasts?

A

Root hair cells are located underground. This means that they do not contain chloroplasts as there is no light for photosynthesis.

44
Q

What is the function of a xylem cell?

A

The function of a xylem cell is to transport water up the stem of a plant and into the leaves.

45
Q

Why do the xylem cells have no end walls?

A

Xylem vessels are made up of a series of connected dead xylem cells. The end walls of the dead cells are broken to allow water to move through.

46
Q

What does the lignin do in xylem cells?

A

Lignin is a substance that strengthens the cell walls of xylem cells.

47
Q

What is the function of a phloem cell?

A

The function of a phloem cell is to transport food products to parts of the plant where they are needed.

48
Q

What are phloem vessels made up of?

A

Phloem vessels are made up of columns of living cells.

49
Q

What do the small holes of phloem cells do?

A

The end walls of phloem cells contain small holes to allow food products to move up and down through the phloem vessels throughout the plant.

50
Q

What is magnification?

A

Magnification tells us how many times larger an image seen through a microscope is compared to the real object.

51
Q

What is resolution?

A

Resolution is the ability to distinguish between (tell apart) two or more objects that are close together.

52
Q

What is the equation for magnification?

A

Magnification = image size / real size

53
Q

How does a light microscope work?

A

A light microscope passes light through a specimen, and creates a magnified image using lenses.

54
Q

How does an electron microscope work?

A

An electron microscope passes electrons through a specimen. They have a much higher resolution and magnification. They let us see sub-cellular structures within cells.

55
Q

Explain thoroughly the light microscope experiment?

A
  • 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.
56
Q

What are chromosomes?

A

Chromosomes are made of molecules of DNA and are found in the nucleus of cells. Each chromosome carries a large number of genes. In body cells, they are usually found in pairs.

57
Q

What is the cell cycle?

A

The cell cycle is the series of events involved in cell growth and cell division.

58
Q

What is the first stage of the cell cycle?

A

The first stage is the initial growth stage. Extra ribosomes, mitochondria and other sub-cellular structures are produced. The cell’s chromosomes are replicated (copied) so that there are two sets of the cell’s chromosomes.

59
Q

What is the second stage of the cell cycle?

A

The second stage is mitosis. The two sets of chromosomes are pulled to opposite ends of the cell. Then, the nucleus divides in two.

60
Q

What is the third and final stage of the cell cycle?

A

The third stage is when the cell divides. Two identical cells are created by the division of the cytoplasm and cell membranes.

61
Q

What does mitosis ensure?

A

Mitosis ensures that the two daughter cells both have the same chromosomes as each other and the parent cell. Identical cells being produced is very important - it could grow and repair tissues and asexual reproduction.

62
Q

What are stem cells?

A

Stem cells are undifferentiated cells that have not been specialised yet to perform a specific function.

63
Q

What can stem cells do?

A

Stem cells can create more stem cells. They can also differentiate to perform another function.

64
Q

Where are stem cells found in?

A

Stem cells are found in plant meristems, bone marrow and embryos.

65
Q

What are plant stem cells?

A

Plant stem cells are found in the meristem tissue. Plant stem cells can differentiate into all types of plant cell throughout the life of the plant. This allows plants to grow for their whole lives.

66
Q

What are human adult stem cells?

A

Human adult stem cells are found in bone marrow, but they can be also found in other tissues and organs. Adult stem cells differentiate into fewer cell types than stem cells in embryos. They are used to replace dying cells and damaged tissues.

67
Q

What are embryonic stem cells?

A

Embryonic stem cells can differentiate into most cell types, to produce all of the cell types that will make up the organism.

68
Q

What can stem cells be used for?

A

Stem cells can be used for medical, scientific and commercial purposes.

69
Q

How are stem cells used for treating patients?

A

Stem cells are able to replace damaged cells in the body. They can replace the damaged cells that cause diseases.

70
Q

How are plant stem cells used?

A

Plant stem cells can be used to quickly and cheaply produce cloned plants. This could help to protect rare plant species from extinction and create large populations of plants with special features.

71
Q

What is therapeutic cloning?

A

Therapeutic cloning is a process that produces an embryo that has the same genome (DNA needed to make an organism) as the patient. Stem cells taken from this embryo will have the same DNA as the patient. This means that the patient’s body will not reject the stem cells or body cells made from the embryo’s stem cells. This is ideal for use in stem cell medical treatments.

72
Q

What are disadvantages of stem cells?

A

Stem cells transplantation could transfer viral infections. There are also lots of ethical beliefs that are against stem cells use.

73
Q

What are the main ethical beliefs against use of stem cells?

A

People believe that life begins at conception, meaning that the embryo is alive. This means that people view the use of embryonic stem cells as killing an embryo.

74
Q

What is diffusion?

A

Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration. It describes the movement of particles in liquids and gases. The particles all move randomly. Substances can move in and out of cells across cell membranes via diffusion.

75
Q

What are the factors that affect diffusion?

A
  • The concentration gradient
  • The temperature
  • Membrane surface area
76
Q

How does the concentration gradient affect diffusion?

A

The concentration gradient is the difference in concentration between two areas. The bigger the difference in concentration between two areas, the greater the concentration gradient and faster the rate of diffusion.

77
Q

How does temperature affect diffusion?

A

The higher the temperature, the faster the rate of diffusion.

78
Q

How does the membrane surface area affect diffusion?

A

The larger the surface area of the membrane that a substance is diffusing through, the faster the rate of diffusion.

79
Q

What is the difference in SA:Volume ratios for smaller and larger organisms and how does if affect diffusion for the different size organisms?

A

Small organisms have a higher ratio than larger organisms. This means diffusion can happen through a large area in small organisms. This makes diffusion useful for transporting molecules through a small organism. However, large organisms need a transport system with specialised surfaces to exchange molecules because their cells are too far from the external environment.

80
Q

What are exchange surfaces?

A

Exchange surfaces are surfaces that are adapted to maximise the efficiency of gas and solute (a substance dissolved in a liquid) exchange across them.

81
Q

What are the adaptations of exchange surfaces?

A
  • Thin membrane - reduces the diffusion distance
  • Large surface area - allows more of a substance to diffuse at the same time
  • Blood supply
  • Ventilation - in animals, if a gas in exchanged, the surface is ventilated to maintain a high concentration gradient and increase the rate of exchange
82
Q

What is the blood supply adaptation for exchange surfaces?

A

Where substances are exchanged through blood in animals, exchange surfaces are densely packed with blood vessels - these blood vessels replenish the blood supply to maintain a high concentration gradient by bringing in new blood as diffusion starts to even out the concentrations.

83
Q

How is the small intestine a specialised exchange surface?

A

The small intestine is adapted for exchanging nutrients between digested food in the small intestine and the blood.

84
Q

How are the lungs a specialised exchange surface?

A

The lungs are adapted for exchanging carbon dioxide and oxygen between the blood and the air.

85
Q

How are gills a specialised exchange surface?

A

The gills are adapted for exchanging oxygen that is dissolved in water, with the carbon dioxide in a fish’s bloodstream.

86
Q

How are roots a specialised exchange surface?

A

Roots are adapted for taking up both water and minerals from the soil around them.

87
Q

How are leaves a specialised exchange surface?

A

Leaves are adapted for exchanging carbon dioxide and oxygen between the leaves and the surrounding air.

88
Q

What is osmosis?

A

Osmosis is a special case of diffusion where water moves across a partially permeable membrane from a high water concentration to a low water concentration.

89
Q

What is a synonym for high and low water concentration?

A

High water concentration - dilute solution

Low water concentration - concentrated solution

90
Q

What does a partially permeable membrane do in osmosis?

A

A partially permeable membrane allows water through, but won’t let larger molecules dissolved in water pass through.

91
Q

What is the water movement in osmosis?

A

Water will move to make the concentrations the same on both sides of the membrane. When there are lots of water molecules in a high water conc on one side of a partially permeable membrane, but not many on the other side, water will move from the higher water conc to the lower water conc.

92
Q

What is the net movement of water in osmosis?

A

Water molecules will move through the membrane in both directions, but the overall (net) movement of water will be from a higher water conc to a lower water conc.

93
Q

What is the difference between the independent variable and the dependent variable?

A

Independent variable - variable that YOU control and changed

Dependent variable - variable that is measured as an outcome of the experiment.

94
Q

How does active transport work in animals?

A

Active transport allows sugar molecules, which are needed for cell respiration, to be absorbed into the blood from the gut, even when the sugar concentration of the blood is higher.

95
Q

How does active transport work in plants?

A

Active transport in the root hairs of plants allows plants to absorb mineral ions, which are necessary for healthy growth, even though the concentration of minerals is usually lower in the soil than in the root hair.

96
Q

What is active transport?

A

Active transport is the net movement of particles form an area of lower concentration to an area of higher concentration. Active transport is against the concentration gradient.

97
Q

Is energy needed for the three main forms of transport in cells (diffusion, active transport and osmosis)?

A

Active transport requires energy
Diffusion does not require energy
Osmosis does not require energy
Osmosis and diffusion are examples of passive transport

HRAY SCIENCE GCSE (6 decks)

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