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AQA GCSE Biology > Cell Biology > Flashcards

Cell Biology Flashcards

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1
Q

What are the two types of Cells?

A
  • Prokaryotic cells

- Eukaryotic cells

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2
Q

What subcellular structures do most animal cells have?

A
  • Nucleus
  • Cytoplasm
  • Cell Membrane
  • Mitochondria
  • Ribosomes
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3
Q

What is the Nucleus?

A

The nucleus is the part of a cell which contains genetic material that controls the activities of the cell.

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4
Q

What is the Cytoplasm?

A

The cytoplasm is a gel-like substance where most of the chemical reactions happen in a cell. It contains enzymes that control those chemical reactions.

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5
Q

What is the Cell Membrane?

A

The cell membrane holds the cell together and controls what goes in and out of the cell.

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6
Q

What is the Mitochondria?

A

The mitochondria is where most the reactions for aerobic respiration take place. Respiration transfers energy that a cell needs to work.

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7
Q

What are Ribosomes?

A

Ribosomes are where proteins are made in the cell. Protein Synthesis.

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8
Q

What extra subcellular structures do plant cells have?

A
  • Cell Wall
  • Permanent Vacuole
  • Chloroplasts
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9
Q

What is the Cell Wall?

A

The cell wall is made of cellulose. It supports the cell and strengthens it.

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10
Q

What is a permanent vacuole?

A

A permanent vacuole is an organelle which contains sap for a plant which is a weak solution of sugar and salts.

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11
Q

What are Chloroplasts?

A

Chloroplasts are where photosynthesis occurs to make food for the plant. Chloroplasts contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.

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12
Q

What subcellular structures does a prokaryote have?

A
  • single circular strand of DNA
  • cell membrane
  • cytoplasm
  • cell wall
  • ribosomes
  • plasmids (small rings of DNA)
  • often have a flagellum
  • slime capsule
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13
Q

What are light microscopes?

A

Microscopes that use light and lenses to form an image of a specimen and magnify it.

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14
Q

What are electron microscopes?

A

Microscopes use electrons instead of light to form an image and magnify it. The have a higher magnification than light microscopes and a higher resolution

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15
Q

What is the formula for calculating the magnification of an image?

A

magnification = image size/real size

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16
Q

How do you prepare a slide?

A

1) Add a drop of water to the middle of a clean slide
2) Place specimen in the centre of the slide
3) Add a stain to the specimen so the objects in the cell are highlighted with colour
4) Place a cover slip over specimen

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17
Q

What are the parts of a light microscope and what do they do?

A
  • Eyepiece (used to look through at the formed image)
  • Objective lenses (lenses that magnify the specimen with different amounts of magnification)
  • Coarse Adjustent Knob (Used to lower and raise the stage)
  • Stage (A platform on which the slide goes on)
  • Fine adjustment knob (Used to focus the image)
  • Light (used to form an image of the specimen)
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18
Q

What is differentiation?

A

Differentiation is the process in which a cell changes to become specialised for its job. The cell develops different subcellular structures to turn into different types of cells so they can carry out specific functions.

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19
Q

When does differentiation occur?

A

Most differentiation occurs as an organism develops. In many animal cells, the ability to differentiate is lost at an early stage after they become specialised. However, lots of plants cells don’t lose this ability.

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20
Q

What cells differentiate in mature animals?

A

Mainly those used for repairing and replacing cells, such as skin and blood cells.

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21
Q

What are cells that don’t differentiate called?

A

Stem Cells

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22
Q

How are sperm cells specialised for reproduction?

A
  • It has a long tail and streamlined head to help it swim to the egg
  • There are lots of mitochondria in the cell to provide the energy needed
  • It carries enzymes in its head (acrosome) to digest through the the egg cell membrane
  • Their job is to get the male DNA to the female DNA
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23
Q

How are nerve cells specialised for rapid signalling?

A
  • The cells are long (the axon specifically) to cover more distance
  • They have branched connections at their nerve endings to connect to other nerve cells and form a network throughout the body
  • Dendrites on the cell can connect to other nerve cells
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24
Q

How are muscle cells specialised for contraction?

A
  • Cells are long so they have space to contract
  • They contain lots of mitochondria to generate the energy needed for contraction
  • Store glycogen which is a store of glucose which can be broken down in respiration
  • They have special proteins that slide over each other which allow them to contract
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25
Q

How are root hair cells specialised for absorbing water and minerals?

A

-Grow into long “hairs” that stick out into the soil. This gives the roots a large surface area for absorbing
water and minerals from the soil
-Lots of mitochondria as energy is needed for mineral uptake (active transport)

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26
Q

How are Phyloem cells specialised for transporting sucrose and amino acids?

A
  • Form Phloem tubes
  • To form the tubes, the cells are long and joined end to end
  • Phloem cell walls break down to form sieve plates so food can move up and down easily
  • Phloem cells have very few sub-cellular structures so that substances can flow through them easily
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27
Q

What does a nucleus contain and how?

A

The nucleus contains your genetic material in the form of chromosomes.

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28
Q

What are chromosomes?

A

Chromosomes are coiled up lengths of DNA molecules. Each chromosome carries a large number of genes.

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29
Q

How many copies of chromosomes do we have?

A

Body cells usually have two copies of each chromosome-one from the organism’s “mother” and one from its “father”

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30
Q

What is the cell cycle?

A

Where body cells in multicellular organisms divide to produce new cells

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31
Q

What is mitosis used for?

A

Multicellular organisms use mitosis to grow or replace cells that have been damaged.

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32
Q

What is the result of the cell cycle?

A

The cell cycle results in two new cells identical to the original cell with the same number of chromosomes.

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33
Q

What are the two main stages in the cell cycle?

A
  • Growth and DNA Replication

- Mitosis

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34
Q

What happens the Growth and Replication stage in the cell cycle?

A

1) The DNA is spread out in long strings
2) The cell has to grows and increases the amount of subcellular structures such as mitochondria and ribosomes
3) The cell then duplicates its DNA so there is one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each “arm” of the chromosome is an exact duplicate of the other.

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35
Q

What is the Mitosis stage of the cell cycle?

A

4) The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite “poles” (ends) of the cell.
5) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells-the nucleus has divided
6) The cytoplasm and cell membrane divide

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36
Q

How do Prokaryotic cells replicate?

A

Using binary fission

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37
Q

What is the binary fission process?

A

1) The circular DNA and plasmid(s) replicate
2) The cell gets bigger and the circular DNA strands move to opposite poles (ends) of the cell
3) The cytoplasm begins to divide and the new cell walls begin to form
4) The cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of plasmids

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38
Q

How can bacteria divide quickly?

A

When given the correct nutrients and an optimal temperature

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39
Q

What is an inoculating loop used for when culturing micro organisms on a culture medium?

A

Inoculating loops are wire loops that can be used to transfer microorganisms to the culture medium

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40
Q

What can be used instead of an inoculating loop?

A

A sterile dripping pipette and spreader for a more even cover of bacteria

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41
Q

What do culture mediums contain?

A

They contain the carbohydrates, minerals, proteins and vitamins, bacteria and other microorganisms need to grow on them

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42
Q

Name two examples of culture mediums:

A
  • Nutrient broth solution

- Solid agar jelly

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43
Q

How do you make an agar plate?

A

Pour hot sterlie agar jelly into a sterile Petri dish

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44
Q

How can you test the action of antibiotics or antiseptics on a culture of bacteria?

A

Place paper discs soaked in different types or concentrations of antibiotics/septics on an agar plate that has an even covering of bacteria

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45
Q

How will the bacteria react to antibiotics or antiseptics on an agar plate?

A

Antibiotic resistant bacteria will continue to grow but non-resistant strains will die. A clear area will be left where the bacteria has died

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46
Q

What is the area where the bacteria has died called?

A

The inhibition zone

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47
Q

What is the control in the agar experiment ?

A

The paper disc that has only been soaked in sterile water so that you can see the paper is correct and the difference antibiotics makes

48
Q

How should a petri dish be stored? Why?

A

Upside down to prevent drips of condensation falling on the agar. The lid of the Petri dish should be lightly taped on to stop microorganisms from the air getting in

49
Q

What are stem cells?

A

Stem cells are undifferentiated cells. They can divide to produce lots more undifferentiated cells.

50
Q

What is useful about stem cells?

A

They can turn into different types of cell depending on their instructions

51
Q

Where are stem cells found?

A

They are found in early human embryos. Adults have stem cells but they are only in certain places like bone marrow and can only turn into certain cells not any like in an embryo.

52
Q

How can stem cells be used by scientists and doctors?

A

The can be grown in a lab to produce clones (genetically identical cells) and made to differentiate into specialised cells for medicine or research.

53
Q

How can stem cells from a healthy adult’s bone marrow help?

A

The can be placed in a patient who needs faulty blood cells replaced.

54
Q

What are two ways embryonic stem cells can be specialised to help people?

A

They could be made into insulin producing cells for people with diabetes or nerve cells for patients with paralysed spinal injuries.

55
Q

What is therapeutic cloning and how is it useful?

A

When an embryo is made to have the same genetic information as a patient. This means the stem cells contain the same genes as the patient so will not be rejected by the body.

56
Q

What are dangers with using stem cells for medicinal purposes?

A

Stem cells grown in a lab could become contaminated with a virus and would be passed on to a patient which could make them sicker

57
Q

Where are stem cells found in plants?

A

The meristems

58
Q

How are stem cells from meristems used?

A

The are cloned to produce identical copies of whole plants quickly and cheaply. This can grow more plants of rare species or grow crops of identical plants that have desired features

59
Q

What is diffusion?

A

Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration

60
Q

In what states can diffusion occur?

A

Liquids and gases

61
Q

How is the rate of diffusion increased?

A
  • with a bigger concentration gradient
  • in a higher temperature
  • with a larger surface area to volume ratio
62
Q

How do small molecules pass through a cell?

A

They diffuse through the cell membrane

63
Q

How is the rate of diffusion through a cell membrane increased?

A

The larger the surface area of a membrane the faster the diffusion rate (more particles can pass through at once)

64
Q

What is osmosis?

A

The net movement of water from an area of higher water concentration to an area of lower water concentration through a partially permeable membrane. It is also the net movement of water from an area of low solute concentration to an area of high solute concentration.

65
Q

What happens to the side of the membrane with fewer water molecules during osmosis?

A

There is a steady net flow of water into the region with fewer water molecules. The water tries to “even up” the concentration of water molecules either side of the membrane

66
Q

What is osmosis a type of?

A

Diffusion

67
Q

How can osmosis be shown through an experiment?

A

1) Cut up potatoes into identical cylinders
2) Get some identical beakers and put different concentrations of sugar solution and water in them
3) measure the mass of the cylinders and put one in each beaker and leave for 24 hours
4) take out the cylinders and dry them
5) weigh them

68
Q

What are the different variables in the osmosis experiment?

A
  • Dependent = Chip mass
  • Independent = Concentration of sugar solution and water
  • Control variables = volume of solution, temperature, time, type of sugar used etc.
69
Q

What is active transport?

A

The process in which substances are absorbed against the concentration gradient (e.g. smaller concentration to larger concentration). It requires energy and is therefore active

70
Q

Name two places where active transport takes place:

A
  • Root hair cells (allows plant to absorb minerals from a very dilute concentration in the soil against the concentration gradient in the root hair cell)
  • The Gut (sometimes there is a lower concentration of nutrients in the gut than there is in the blood but the nutrients still need to get into the blood to be transported around the body)
71
Q

What do we need to know when working out how easily stuff moves between an organism and its environment?

A

The surface area to volume ratio (SA:V)

72
Q

What is good about diffusion in single-celled organisms?

A

Gases and dissolved substances can be directly diffused in or out of the cell across the cell membrane. This is because they have a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volume of the cell.

73
Q

What is the problem with multi-cellular organisms and diffusion?

A

Multi-cellular organisms have a smaller surface area compared to their volume. This means not enough substances can diffuse from their outside surface to supply their entire volume.

74
Q

What do multi-cellular organisms need for efficient diffusion?

A

An exchange surface

75
Q

How are exchange surfaces adapted to maximise effectiveness?

A
  • They have a thin membrane, so substances only have a short distance to diffuse
  • They have a large surface area so lots of substance can diffuse at once
  • Exchange surfaces in animals have lots of blood vessels, to get stuff into and out the blood quickly
  • Gas exchange surfaces in animals are often ventilated
76
Q

How are alveoli specialised for the diffusion of oxygen and carbon dioxide in the lungs?

A
  • They have an enormous surface area (about 75m^2 in humans)
  • They have a moist lining for diffusing gases
  • Very thin walls
  • A good blood supply
77
Q

Where is the job of villi?

A

Absorb the digested food and nutrients into the blood using diffusion in the small intestine

78
Q

Why are villi so good at diffusion?

A
  • They have a single layer of surface cells
  • They have a very good blood supply to assist quick absorption
  • Create a large exchange surface in great numbers
79
Q

Where is the exchange surface on a leaf and what parts of the leaf are found there?

A

It is found on the underside of the leaf. It is covered in tiny biddy holes called stomata which are controlled by guard cells. Guard cells close the stomata if the plant is losing water faster than it is being replaced by the roots.

80
Q

What diffuses through the stomata?

A

Carbon dioxide diffuses in.

Oxygen and water vapour diffuse out

81
Q

Why is the leaf’s exchange surface successful?

A
  • The flattened shape of the leaf increases the surface area of the exchange surface
  • The walls of the cells inside the leaf form another exchange surface.
  • The air spaces inside the leaf increase the the area of the surface so there is more chance for carbon dioxide to get into the cells.
82
Q

Where is the gas exchange in a fish?

A

The gills

83
Q

What happens to water in a fish’s gills?

A

Water enters through the fish’s mouth and passes through the gills. The gills allow the oxygen to diffuse from the water into the blood. Carbon dioxide diffuses from the blood into the water

84
Q

What are each gill made up of?

A

Gill filaments. They provide a big surface area for gas exchange.

85
Q

What are gill filaments covered in?

A

They are covered in lots of tiny structures called lamellae which increase the surface area even more

86
Q

What characteristics of lamellae help with diffusion? (expect their large abundance)

A
  • They have lots of blood capillaries to speed up diffusion

- They have a thin surface layer of cells to minimise the distance that the gases have to diffuse

87
Q

Which way does the blood and water flow in lamellae and why?

A

Blood flows one way through the lamellae and water flows in the opposite direction. This maintains a large concentration gradient between the water and the blood. The concentration of the oxygen in the water will always be higher than the that in the blood so as much oxygen as possible diffuses from the water into the blood

88
Q

What happens to a plant cell when water moves in ?

A

The cell swells up and becomes turgid

89
Q

What happens when water moves out of a plant cell?

A

The cell becomes flaccid and plasmolysis occurs

90
Q

What is plasmolysis?

A

When the cell membrane pulls from the cell wall

91
Q

What happens in an animal cell when water moves in?

A

The cell bursts as there is no cell wall. This is known as lysis

92
Q

What happens when water moves out an animal cell?

A

The cell becomes shrivelled

93
Q

What does isotonic mean?

A

Isotonic is a state in osmosis when the concentration of the solution is the same as in the cell

94
Q

What does hypertonic mean?

A

Hypertonic is a state in osmosis where the concentration of the solution is higher than in that of the cell

95
Q

What does hypotonic mean?

A

Hypotonic is a state in osmosis where the concentration of the solution is lower than the concentration in the cell

96
Q

How are red blood cells specialised for carrying oxygen?

A
  • Don’t have a nucleus so there is more space to carry oxygen
  • Biconcave shape
  • Contain haemoglobin which binds to oxygen to carry it
97
Q

How are ciliated cells specialised for stopping lung damage?

A
  • Line all the air passages in the lungs and they have tiny hairs called cilia
  • Cilia sweep mucus with trapped dust and bacteria back up the throat
98
Q

What substances do plants uptake?

A

-Minerals and ions

99
Q

What food molecules are absorbed by epithelial cells by active transport?

A

Monosaccharides e.g. amino acids

100
Q

What pressure is osmosis important in maintaining in a plant?

A

Turgor pressure (keeps plant structured and rigid- prevents plasmolysis)

101
Q

Why do Animal cells not require a cell wall like in a plant?

A

Plant cells need a cell wall in order to maintain turgor pressure, provide structure and provide shape. However, in animals, there is a skeletal system which maintains the structure and shape of the animal. It is also a more effective way of organ protection.

102
Q

What is a way (other than with a calculation) to measure the sizes of cells?

A

Use a microscope with an eyepiece graticule and stage micrometer. Once scales are aligned, the reading can be used to calculate the calibration factor for the objective lens in use. The cell can then be measured

103
Q

What is magnification?

A

How much larger an image appears compared to its actual size (an enlargement)

104
Q

What is resolution?

A

The resolving quality of a image (ability to distinguish between two points)

105
Q

Compare the advantages and disadvantages of an electron microscope and a light microscope:

A
  • Better quality images of internal cell structure with electron microscope than light microscope
  • Electron microscopes have a better resolution
  • Electron microscopes have a better magnification
  • Electron microscopes are very expensive compared to light microscopes
  • Electron microscopes are much bigger and not as portable
  • Specialist training is required to use an electron microscope
  • Specimen must be dead for viewing with an electron microscope
  • Specimen must be prepared in a vacuum with an electron microscope
  • Specimen takes longer to prepare and study with an electron microscope
106
Q

How are both human gametes adapted to ensure successful growth and development of an embryo?

A

Both sperm and egg cells are haploid so the fertilised egg will be diploid. Cytoplasm of egg cell is packed with nutrients to supply the fertilised egg with energy and raw materials for growth and development

107
Q

Why does a prokaryote have a slime capsule?

A

For protection

108
Q

Why does a prokaryote often have a flagellum?

A

For movement

109
Q

What do light microscopes allow us to see?

A

Individual cells and large subcellular structures like nuclei.

110
Q

What do electron microscopes allow us to see?

A

Smaller things in detail such as the internal structures of mitochondria and chloroplasts and even let us see ribosomes and plasmids.

111
Q

How are Xylem cells specialised for transporting water and minerals?

A
  • Form tubes
  • To form the tubes, the cells are long and joined end to end
  • When Xylem cells die, they form hollow tubes so substances can pass easily through the tubes
  • Xylem contain lignin in their cell walls which help strengthen them
112
Q

What are the advantages of using cultured meat over farmed meat?

A
  • cultured meat can be mass produced to feed an increasing population
  • disease and antibiotic free meat
  • lower fat
  • less intensive farming
  • more land available for farming crops
  • reduces rate of global warming
113
Q

How does using cultured meat reduce the rate of global warming?

A
  • uses fewer cows
  • less methane
  • less CO2 in the atmosphere because of less deforestation and less plants consumed
114
Q

Organism A has a SA;V of 20:1. Organism B has a SA:V of 4:1. Which organism has the slowest rate of exchange? Why?

A

Organism B has the smallest surface area to volume ratio so the rate of exchange across its surface would be the slowest

115
Q

How does temperature affect the rate at which organisms exchange substances with the environment?

A

A higher temperature would mean a faster rate of exchange because the diffusing particles would have more energy and move around more

116
Q

How does concentrated salt solution kill weeds?

A
  • it causes water to move out the cells in the weeds by osmosis
  • this will kill the weeds because cells need water for chemical reactions to take place e.g. photosynthesis

AQA GCSE Biology (9 decks)

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