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A-Level Biology > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

Nucleus

A
  • Controls cell functions by controlling DNA transcription
  • Controls for:
    Gene Expression
    Protein Synthesis
    Storing DNA
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2
Q

Nucleolus

A

Site of protein synthesis and ribosome production

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3
Q

Cell Surface Membrane

A

Regulates the movement of substances in and out of the cell

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4
Q

Mitochondria

A
  • Site of aerobic respiration
  • Produces ATP
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5
Q

Chloroplast (Plants and Algae)

A

Provides energy for plants and algae via photosynthesis

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6
Q

Golgi Apparatus

A

Processes and packages proteins and lipids to be transported to the vesicles

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7
Q

Golgi Vesicles

A

Stores and transports lipids and proteins out of the cell via the cell membrane

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8
Q

Lysosomes

A

Contains lysozymes (hydrolytic enzymes) that digest unwanted cell parts and complex biomolecules

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9
Q

Hydrolytic Enzymes

A
  • Break down macromolecules
  • Membrane-bound so they don’t self digest
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10
Q

Ribosomes

A

Synthesise proteins from mRNA during translation

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11
Q

Rough Endoplasmic Reticulum

A
  • Synthesizes glycoproteins
  • Produces 3D structures of proteins
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12
Q

Smooth Endoplasmic Reticulum

A
  • Synthesizes lipids, phospholipids and cholesterol
  • Contains enzymes that detoxify harmful substances
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13
Q

Cell wall (Plants, Algae and Fungi)

A
  • Provides structural support by maintaining cell shape
  • Protects the cell from invading pathogens
  • Made of cellulose in plants and algae
  • Made of chitin in fungi
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14
Q

Cell Vacuole (Plants)

A
  • Maintains osmotic pressure in the cell to stop the plant from wilting
  • Store unwanted chemicals as an emergency food store
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15
Q

4 Main Eukaryotic Kingdoms

A
  • Animals
  • Plants
  • Fungi
  • Protists
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16
Q

Cell Fractionation

A
  • The process where cells are broken up and their organelles are separated out
  • Two stage process (homogenation and ultracentrifugation)
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17
Q

Homogenation

A
  • Tissue is cut up and placed in a cold, buffered, isotonic solution
  • Cells are broken up in a homogeniser (releases the organelles from the cell)
  • The homogenate is filtered to remove any cell membrane
  • Suspension of homogenate is placed in a test tube and centrifuged
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18
Q

Conditions of the Solution for Cell Fractionation

A
  • Cold
  • Isotonic
  • Buffered
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19
Q

Why does the solution have to be cold?

A
  • To reduce enzyme activity
  • Makes sure the organelles aren’t broken down
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20
Q
  • Why does the solution have to be isotonic?
A
  • To prevent water being lost/gained
  • Prevents the organelles from bursting/shrinking
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21
Q

Why does the solution have to be buffered?

A
  • To maintain a constant pH
  • Prevents enzyme activity from being impacted
  • Prevents organelle structure from being altered
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22
Q

Ultracentrifugation

A
  • Suspended homogenate is placed in ultracentrifuge and spun at low speed
  • The densest organelles collect at the bottom where they form sediment
  • The supernatant liquid is then put in another tube where it is spun at higher speeds
  • The next densest organelles collect at the bottom
  • Repeat process
23
Q

Order of Organelle Density

A
  • Nucleus
  • Mitochondria/Chloroplast
  • Endoplasmic Reticulum/Golgi Complex
  • Ribosomes
24
Q

How does the speed of the centrifuge impact fragment size?

A
  • Slower speeds = larger fragments
  • Faster speeds = smaller pellets
25
Q

Magnification

A

The number of times an image is enlarged compared with the real size of the object

26
Q

Magnification Equation

A

Size of image/Size of actual object

27
Q

Resolution

A

The minimum distance two objects can be apart in order for them to appear as separate items

28
Q

Optical (Light) Microscope

A
  • Used for specimens above 200nm
  • Specimens can be alive or dead
  • Wavelength of light is longer than electron wavelength so resolution is lower
  • Produces coloured images
  • Used to look at whole cells, small organisms and tissues
29
Q

Electron Microscope

A
  • Used for specimens above 0.5nm
  • Shorter wavelength so higher resolution
  • Electrons are absorbed or deflected by molecules in the air
  • Vacuum is needed so can’t be used to observe living organisms
  • TEMs and SEMs
30
Q

Transmission Electron Microscope (TEM)

A
  • Beam of electrons passes through
    a thin part of the specimen
  • Parts of the specimen absorb the electrons and make the specimen appear dark
  • Parts of the specimen transmit electrons and make the specimen appear light
  • Resolving power of 0.1nm
31
Q

Limitations of TEMs

A
  • Black and white image due to absorbed (dark parts) and transmitted (light parts) electrons
  • Specimen has to be extremely thin
  • Image may contain artefacts
32
Q

Scanning Electron Microscope (SEM)

A
  • Beam of electrons passes across the surface of the specimen and scatter along the surface
  • The pattern of scattering builds up a 3D image of the specimen
  • Resolving power of 20nm (lower than TEMs)
33
Q

Limitations of SEMs

A
  • Black and white image due to absorbed (dark parts) and transmitted (light parts) electrons
  • Image may contain artefacts
  • However the specimen doesn’t have to be thin as electrons don’t penetrate the specimen
34
Q

Artefacts

A

Damage caused in specimen preparation and can be confused with structures within the specimen

35
Q

Cell Differentiation

A
  • The process where cells become differentiated
  • Cells acquire different sub-cellular structures and change shape
36
Q

Sperm Cell

A
  • Flagellum allows cell to swim through the uterus and fallopian tube to reach the egg
  • Streamline head (same reason as flagellum)
  • Lots of mitochondria provide energy for movement
  • Digestive enzyme in the head to infiltrate egg cell
37
Q

White Blood Cells

A
  • ## High amount of lysosomes to break down invading pathogens
38
Q

Mitosis

A
  • A form of cell division that produces genetically identical cells
  • 4 stages: Prophase, Metaphase, Anaphase, Telophase
39
Q

Interphase

A
  • G1: Cell carries out metabolic functions, Proteins that cell organelles are synthesized from are produced
  • S: Synthesis, DNA replicates, 2 sister chromatids form from each chromosome
  • G2: Mitochondria divides and cell continues to grow
40
Q

Prophase

A
  • Chromosomes condense and become visible when stained
  • Nuclear envelope disintegrates
  • Nucleolus disappears
41
Q

Metaphase

A
  • Spindles form
  • Chromosomes line up on the equator
  • Pairs of chromatids attach to spindles by centromeres
42
Q

Anaphase

A

Spindle fibres contract and pull chromatids by centromeres to opposite poles

43
Q

Telophase

A
  • Chromatids reach poles
  • Nuclear Envelope reforms
  • Nucleolus reappears
  • Spindles disintegrate
  • Chromosomes uncoil and become long and thin
44
Q

Cytokinesis

A
  • Replicated organelles move to opposite poles
  • Cytoplasm divides
  • 2 new daughter formed
45
Q

Prokaryote Structural Differences

A
  • Between 10-100 times smaller than eukaryotes
  • No membrane-bound organelles
  • Smaller ribosomes
  • No nucleus
  • Cell wall is made of murein instead of cellulose
46
Q

Plasma Membrane

A

Regulates the movement of substances in and out of the cell (same as eukaryotes)

47
Q

Mesosomes

A

In-foldings of the cell membrane that increase surface area for attachment of enzymes involved in respiration

48
Q

Slime Capsule

A
  • Slimy layer that prevents the cell from desiccation (drying out)
  • Protects the cell against the action of a host’s digestive enzymes
49
Q

Pili

A

Hair-like structures which
attach to other bacterial cells

50
Q

Flagellum

A
  • Tail like structure
    which rotates to move the cell
51
Q

Plasmids

A

Circular DNA

52
Q

Virus

A
  • Non cellular and border between living and non-living
  • Smaller than prokaryotes
  • Have nucleic acid and a capsid (protein coat)
  • Some have a lipid envelope with attachment proteins on it
  • All viruses are parasitic
53
Q
A

A-Level Biology (8 decks)

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