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A Level Biology Paper 1 > Section 2 - Chapter 3 : Cell Structure > Flashcards

Section 2 - Chapter 3 : Cell Structure Flashcards

Cover Chapter 3 from Kerboodle Textbook

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1
Q

Name the 10 structures found in an animal cell:

A
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosome
  • Smooth Endoplasmic Reticulum (RER)
  • Lysosomes
  • Cell surface membrane
  • Golgi Vesicles
  • Golgi apparatus
  • Smooth Endoplasmic Reticulum
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2
Q

Name the structures of a plant cell:

A
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3
Q

What are the 2 main types of cells

A
  • Eukaryotic Cells
  • Prokaryotic Cells
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4
Q

What are the differences between Eukaryotic Cells and Prokaryotic Cells

A
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5
Q

What is the structure and function of the cell-surface membrane

A
  • Found on surface of animal cells and inside cell walls of other cells
  • Mainly made of lipids and proteins
  • Regulates movement of substances into and out of the cell. Has receptors that respond to hormones.
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6
Q

What is the structure and function of the nucleus?

A
  • Produces mRNA and tRNA and hence proteinsynthesis. Controls cell activities
  • Retain genetic material in the form of DNA and chromosomes
  • Manufacture ribsomal RNA and ribosomes
    • The structure inside the nucleus
      • Nuclear Envelope
      • Nuclear Pores
      • Nucleolus
      • Nucleoplasm
      • Chromosomes - Protein bound linear DNA
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7
Q

What is the structure and function of the Nuclear Envelope

A
  • Is a double membrane that surrounds the nucleus
  • Its outer membrane is continuous with endoplasmic reticulum
  • This controls the entry and exit of materials in and out
  • Also contains reactions taking place within it
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8
Q

What is the structure and function of the Nuclear Pores

A
  • Allows the passage of large molecules (mRNA) out of the nucleus
  • About 40-100nm in diameter
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9
Q

What is the function of the Nucleoplasm?

A
  • Is the granular /jelly like material that makes the bulk of the nucleus
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10
Q

What is chromatin?

A
  • Uncondensed complex of DNA/ Proteins
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11
Q

What is the structure and function of the Nucleolus?

A
  • A small spherical region within the nucleoplasm
    • It manufacture ribosomal RNA and assembles ribosomes
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12
Q

What is the structure of the mitochondrion?

A
  • Rod shaped and 1-10µm in length
  • The organelle has a double membrane - controls the entry and exit of material.
  • The inner membrane is folded to form cristae
    • Cristae provide a large surface area (for attachment of enzymes and proteins in respiration)
  • Central part is the matrix
    • Contains proteins/lipids/ribosomes - allows mitochondria to control production of own protein
    • Enzymes in respiration are found in matrix
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13
Q

What is the function of the mitochondrion?

A
  • Site of aerobic respiration and produces energy carrier molecule ATP from respiratory substances like glucose
  • No of mitochondria is dependant on the cell function. Lots in muscle/epithelial cells
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14
Q

What is the structure of the Chloroplasts?

A
  • A small flattened structure
  • Surrounded by double membrane - highly selective
  • The grana are 100 disc like structures called thylakoids
    • Within thylakoids is the photosynthetic pigment chlorophyll
  • Grana are linked together by lamellae - thin flat pieces of thylakoid membrane
  • The stroma - fluid filled matrix
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15
Q

How are is the adaption suited to its function of chloroplasts?

A
  • Chloroplasts are adapted to harvesting sunlight and carrying out photosynthesis in these ways:
    • The granal membranes provide a large surface area for the attachment of chlorophyll, enzymes and electron carriers to carry out first stage
    • The stroma possesses all the enzymes needed to make sugars in the 2nd stage
    • Chloroplasts contain DNA and ribosomes so they can manufacture their own proteins for photosynthesis
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16
Q

What is the structure of the Golgi Apparatus

A
  • Similar to SER in structure (it is more compact)
  • A group of fluid-filled membrane bound flattened sacs with small rounded hollow structures called vesicles at the edges of sacs.
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17
Q

What is the function of Golgi Apparatus?

A
  • Recieves proteins from RER, lipids from SER
  • Modifies them by adding a non-protein component (carbohydrates added to proteins = glycoproteins)
  • Labels them so they go to right destination
  • Once processed the product is packaged into a vesicle and pinches off the cisternae and transported
  • Packaged vesicles then make their way to fuse with cell membrane and release their contents to the outside.
    • Produce secretory enzymes, secrete carbohydrates, transport modify and transport lipids, form lysosomes.
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18
Q

What is the structure and function of golgi vesicles

A
  • Structure: Small fluid filled sac in the cytoplasm surrounded by a membrane and produced by golgi apparatus
  • Function: Stores lipids and proteins made by Golgi Apparatus and transports them
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19
Q

What is the structure of the lysosomes?

A
  • Vesicles surrounded by a single membrane which come from the golgi. Type of golgi vesicle.
  • Contain enzymes
    • Proteases and Lipases (50 enzymes in 1 lysosome)
    • Lysozymes - hydrolyse cell walls of bacteria
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20
Q

What is the function of the lysosomes?

A
  • Contain digestive enzymes called lysozymes which hydrolyse materials ingested by phagocytotic cells (WBC or bacteria)
  • Release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell
  • Digest worn out organelles so useful chemicals made from can be re-used
  • Completely breakdown cells after they have died (autolysis)

Commonly found in secretory cells (epithelial and phagocytotic cells)

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21
Q

What is the structure of Ribosomes?

A
  • Very small organelles in the cytoplasm or bound to RER. Not membrane bound
  • Consists of 2 subunits - one large and one small each consist of ribosomal RNA and protein
  • Found as 2 types:
    • 80S - eukaryotic cells (25nm diameter)
    • 70S - prokaryotic cells
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22
Q

What is the function of Ribosomes?

A
  • Site of proteinsynthesis which acts as an assembly line to use mRNA to assemble proteins
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23
Q

What is the structure of the 2 types of endoplasmic reticulum

A
  • Rough endoplamic reticulum (RER)
    • Usually continuous with nuclear membrane
    • Folded membranes (lamellae) form flattened sacs (cisternae)
    • Studded with ribosomes
  • Smooth Endoplasmic Reticulum (SER)
    • Folded membrane (lamellae) that form a more tubular appearance (cisternae)
    • Not studded with ribosomes
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24
Q

What is the function of the Endoplamic Reticulums

A
  • Rough Endoplamic Reticulum (RER)
    • Provide a large surface area for the synthesis of proteins and glycoproteins
    • Provides a pathway for transport of materials (proteins) throughout the cell.
  • Smooth Endoplasmic Reticulum (SER)
    • Synthesise, store and transport lipids
    • Synthesise, store and transport carbohydrates
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25
Q

What is the structure of the Cell Wall in a plant cell?

A
  • Cell wall consists of microfibrils of the polysaccharide cellulose, embedded in a matrix
  • Cellulose microfibrils provide strength to the cell wall
  • There is a thin layer called middle lamella, which marks the boundary between adjacent cell walls and cements adjacent cells together
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26
Q

What are the functions of the cell wall?

A
  • To provide mechanical strength in order to prevent cell from bursting under pressure due to the osmotic entry of water (water intake)
  • To give mechanical strength to the plant as a whole
  • To allow water to pass along it and contributes to movement of water through the plant
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27
Q

What do the cell walls of fungi contain?

What do the cell walls of algae contain?

A
  • Fungi: Nitrogen- containing polysaccharide called chitin (polysaccharide called glycan and glycoproteins)
  • Algae : Made of either cellulose or glycoproteins or a mixture of both
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28
Q

What is the structure of the Vacuole?

A
  • A fluid-filled sac bounded by a single membrane (tonoplast)
  • A plant vacuole contains a weak solution of mineral salts, sugars, amino acids. (cell sap)
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29
Q

What is the function of the Vacuole?

A
  • Maintains pressure and makes plant cell turgid; adds to support
  • The sugars and amino acids may act as a temporary food store
  • The pigments may colour petals to attract pollinating insects
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30
Q

What is differentiation

A
  • As the embryo develops, some cells differentiate fully into specialised cells
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31
Q

What are the adaptation for Epithelial cells, Red Blood cells and Sperm cells

A
  • Epithelial cells
    • Villi - large surface area
    • Villi have microvilli - large surface area for absorbtion
    • Lots of mitochondria - Provide energy for transport of digested food
  • Red Blood Cells
    • Adapted to carry oxygen - no nucleus to make more room for more haemoglobin.
  • Sperm Cells
    • Lot of mitochondria - large amounts of energy to get to egg.
32
Q

What is a tissue

What are organs

What is an organ system

A
  • A collection of similar cells that perform a specific function
  • Is a combination of tissues that are co-ordinated to perform a variety of functions although have a major function
  • Organs work together as a single unit known as an organ system
33
Q

What tissues is the stomach made of

A
  • Muscle - to churn and mix the stomach contents
  • Epithelium - it lines the stomach wall to protect and produce secretions. Consists of sheets of cells.
  • Connective - To hold other tissues
34
Q

What tissues make a leaf (organ)

A
  • Palisade Mesophyll - made of leaf palisade cells that carry out photosynthesis
  • Spongy Mesophyll - Adapted for gaseous diffusion
  • Epidermis - To protect leaf + allow gaseous diffusion
  • Phloem - To transport organic materials away from the leaf
  • Xylem - To transport water and ions into the leaf + give meachanical support
35
Q

Name some examples of Organ Systems in the human body

A
  • Digestive System :
    • Digests and processes food
    • Made of oesophagus, salivary glands, stomach, duodenum, ileum, pancreas and liver
  • Respiratory System:
    • Used for breathing and gas exchange
    • Made of trachea, bronchi, lungs
  • Circulatory System:
    • Pumps and circulates blood
    • Made of heart, arteries, and veins
36
Q

What are the structures present in a Prokaryotic (Bacterial)Cell

A
  • Cell Wall (made of murein):
    • Physical barrier that excludes certain substances + protects mechanical damage/osmotic lysis
  • Capsule:
    • Protects bacterium from other cells + helps bacteria to stick together for further protection
  • Cell Surface Membrane + 70s ribosomes:
    • Acts as a permeable layer/ controls entry + exit of chemicals
  • Circular DNA:
    • Possesses genetic material for replication of cells
  • Plasmid:
    • Possesses genes to aid in survival in adverse conditions
37
Q

What is the cell division in Prokaryotic Cells

A
  • Binary Fission
    • The circular DNA molecule replicates and both copies attach to the cell membrane
    • The plasmids also replicate
    • The cell membrane begins to grow between the 2 DNA molecules and begins to pinch inwards, dividing cytoplasm into 2
    • The new cell wall forms between the 2 molecules of DNA, dividing the original cell into 2 identical daughter cells, each with a single copy of circular DNA and some plasmids (variable)
38
Q

What are viruses

A
  • Are acellular, non-living particles.
  • Smaller than bacteria (20-300nm)
  • Contain nucleic acids such as DNA or RNA as genetic material but can only multiply inside living host cells
39
Q

What is the structure of a virus

A
  • Nucleic acid is enclosed within a protein coat called a capsid
  • Some viruses are surrounded by a lipid envelope
  • The lipid enevelope (if not present), the capsid has attachment proteins to allow the virus to identify and attach to a host cell
  • Are accellular, non-living and smaller than bacteria
40
Q

What happens in the Replication of Viruses

A
  • As viruses are non-living they cant undergo cell division.
  • Instead they replicate by attaching to their host cell with the attachment proteins on their surface to the complementary receptor proteins.
  • Inject their nucleic acid into the host cell.
  • The genetic information on the injected viral nucleic acid then provides the ‘instructions’ for the host cell. and Genetic materials and proteins are replicated.
  • This produces viral components which are the assmebled into new viruses
41
Q

What is magnification

A
  • The degree to which the size of the image is larger than the object itself
  • Usually expressed numerically x40, x100
42
Q

How do you calculate Magnification:

A
  • Magnification = image size / actual size
43
Q

What is resolution?

A
  • The degree to which it is possible to distinguish between 2 objects that are close together
44
Q

How do you convert between metres, cm, mm, um, nm

A

Metres→multiply by 100 = cm

Cm→multiply by 10 = mm

mm→ multiply by 1000 = um

um→multiply by 1000 = nm

45
Q

How do you calibrate an eyepiece graticule

A
  • To calibrate an eypiece graticule you first need to use a special microscope slide called a stage micrometer.
    • This slide has a scale etched onto it
  1. Place the stage micrometer onto the microscope stage
  2. Line up the divisions on the eyepiece graticule with those of the micrometer
  3. Work out the length of 1 eyepiece graticule (glass disc with scale etched on it) in micrometers
  4. Repeat for each of the objective lenses on the microspe
46
Q

How do you use the eyepiece graticule to measure the length of the object

A
  1. Place the slide onto the microscope stage
  2. Measure the length of the specimen of 1 cell in eyepiece graticule
  3. Calculate the length in micrometers by multiplying length in the eye piece graticule by the callibration value for 1 unit
47
Q

What are the 3 types of microscopes

A
  • Optical (light) microscopes
  • Transmission Electron Microscopes
  • Scanning Electron Microscopes
48
Q

How to measure sizes of objects using a Light Microscope

A
  • Measure the sizes of objects by using an eyepiece graticule
    • This is a glass disc that is placed in the eyepiece and has a scaled etched on it
  • The graticule must first be calibrated for a particular objective lens
49
Q

How do use an Optical Microscope

A
  1. Start by clipping slide prepared onto stage
  2. Select lowest powered objective lens
  3. Use the coarse adjustment knob to bring the stage just below objective lens
  4. Look down eyepiece. Use coarse adjustment to move stage downwards, away from objective lens until image is in focus
  5. Adjust focus with fine adjustment knob until clear image
  6. If you need to see slide with higher magnification swap to higher powered objective lens and refocus
50
Q

Description of an Optical Microscope

A
  • Use light to form an image
  • Focussed by a condenser lens and focussed further by an objective and eye piece lens
  • Have a maximum resolution of about 0.2µm can’t see objects smaller than this
51
Q

What are the advantages of using an Optical Microscope?

A
  • Cheaper
  • Shows in colour
  • No complex staining process required
  • Only living specimens
  • Easy to use
52
Q

What are the disadvantages of using an Optical Microscope

A
  • Larger organelles only
  • Lower resolution and Magnification
  • Longer wavelength therfore a low resolving power
53
Q

Description of a Transmission Electron Microscope

A
  • Use electromagnets to focus a beam of electrons which is transmitted through a thin section of the specimen
  • Denser parts absorb more electrons making it looker darker
54
Q

What are the advantages of using a Transmission Electron Microscope

A
  • Ultrastructure (smaller organelles can be seen)
  • Have a short wavelength (high resolution/resolving power)
55
Q

What are the disadvantages of using a Transmission or Scanning electron microscope

A
  • Vacuum is needed as electrons can be deflected by air molecules
  • Only dead specimens are viewed
  • High energy electrons may destroy the specimen
  • Must be thinner than light preparation (TEM extremely thin)
  • More complex staining process required
  • Black and white image - not coloured
  • The image may contain artefacts - result from preparation (not naturally)
56
Q

Description of a Scanning Electron Microscope

A
  • Direct a beam of electrons across the surface of specimen (from above)
  • The beam is passed back and forth across the specimen in a regular pattern
  • The electrons are scattered - the pattern of the scattering depends on the contours of the surface
  • The images show the surface of the specimen can be 3D
57
Q

What are the advantages of using a Scanning Electron Microscope

A
  • Higher Resolution
  • 3D
  • Doesn’t need to be extremely thin (can be used on thicker specimens)
58
Q

How do you prepare a microscope slide

A
  1. Pipette a small drop of water onto the centre of the slide
  2. Then use tweezers to place a thin section of the specimen on the water drop
  3. Add a drop of stain (highlights objects in the cell)
  4. Finally add coverslip (protects specimen). To do this, stand the slip upright on the slide next to specimen and lower it carefully do avoid air bubbles
59
Q

Why do you use a stain in the mitosis practical

A
  • Staining increases contrast so chromosmes become visible
60
Q

What does the process of Cell Fractionation do and what is typically the heaviest to lightest organelle?

A
  • Is the process where cells are broken up and the different organelles they contain are separated out
  • This is to study the structure and function of organelles - obtain large numbers of isolated organelles
  • Nuclei → Chloroplasts → Mitochondria → Lysosomes → Endoplasmic Reticulum →Ribosomes
61
Q

What are the 2 stages of Cell Fractionation?

A
  • Homogenation
  • Ultracentrifugation
62
Q

What happens before Cell Fractionation can begin

A
  • The tissue is placed in a cold, buffered solution of the same water potential as the tissue. The solution is:
    • Cold - to reduce enzyme activity that might break down the organelles
    • Same water potential as the tissue - prevent organelles bursting or shrinking due to osmotic gain/loss of water
    • Buffered - So pH does not fluctuate. Any change in pH can alter the structure of organelles or functioning of enzymes
63
Q

What is the first stage of Cell Fractionation and what happens

A
  • Homogenation
    • Cells are broken up by a homogeniser (blender).
      • This releases the organelles from the cell
    • The resultant fluid (homogenate) is filtered to remove any complete cells/large pieces of debris
64
Q

What is the 2nd Stage of Cell Fractionation and what happens

A
  • Ultracentrifugation
    • Process where fragments in the filtered homogenate are separated in a machine called a centrifuge.
      • This spins tubes of homogenate at high speeds in order to create centrifugal force

For animal cells:

  • The tube of filtrate is placed in the centrifuge and spun at low speed
    • Heaviest organelles (nuclei) are forced to the bottom of the tube where they form a thick sediment or pellet
  • The fluid at the top (supernatant) is removed and transferred to another tube just leaving the sediment of nuclei.
  • Supernatant is spun in the centrifuge at a faster speed than before
  • The next heaviest oragnelles are forced to the bottom
  • This process is continued so each increase in speed the next heaviest organelles is sedimented and separated
65
Q

What has cell fractionation enabled scientists to do?

A
  • Enabled considerable advances in biological knowledge.
  • Allowed a detailed study of the structure and function of the organelles - by showing what isolated components do
66
Q

What are the 2 types of cell division

A
  • Mitosis - produces 2 daughter cells that have the same number of chromosomes as the parent cell and eachother
  • Meiosis - produces 4 daughter cells with half the number of chromosomes of the parent cell
67
Q

What are the stages of the cell cycle

A
  • Interphase - most of its time (cell isnt dividing).
    • Considerable cellular activity - replication of DNA + new organelles synthesised + chromosomes are joined at the centromere and arent visible
  • Mitosis (split into 4 stages)
    • Prophase
    • Metaphase
    • Anaphase
    • Telophase
  • Cytokinesis
68
Q

What happens in Prophase of the cell cycle

A
  • Chromosomes become visible, initially as long, thin threads, which later shorten and thicken
  • Animal cells contain centrioles which move to opposite poles (2 cylindrical organelles).
    • From each centriole spindle fibres develop which span the cell from pole to pole
  • The nucleolus disappears and the nuclear envelope, leaving chromosomes free in the cytoplasm
  • The chromosomes are drawn to the equator of the cell by spindle fibres attached to the centromeres
69
Q

What happens in Metaphase of the Cell cycle

A
  • By metaphase the chromosomes are seen to be made of 2 chromatids. Each chromatid is an identical copy of DNA from the parent cell
  • Chromosomes align across the middle of the cell - spindle fibres attach to the centromeres and help aligning
    • This helps next stage so when chromosmes are separated they have 1 copy of each chromosome
70
Q

What happens in Anaphase part of the cell cycle

A
  • In anaphase, the centromeres divide into 2 and the spindle fibres contract and pull the individual chromatids apart.
  • The chromatids move to the opposite poles of the cell and are referred to as chromosomes
  • The energy for this process is provided by mitochondria
  • If cells are treated with chemicals this destroys spindle fibres and chromosomes remain at the equator
71
Q

What happens in the telophase/cytokinesis stage of the cell cycle

A
  • The chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether leaving widely spread chromatin
  • The spindle fibres disintegrate and nuclear envelope and nucleolus reform.
  • Finally the cytoplasm divides in a process called cytokinesis
72
Q

What is the importance of mitosis and how do you calculate mitotic index

A
  • Growth
  • Repair - damaged so cells have same structure as original
  • Reproduction of single-celled organisms

Mitotic Index = number of cells with visible chromosomes/ total number of cells observed

73
Q

How is the observing mitosis root tip squash practical done

A
  1. Get onion roots - use roots as they have meristem (have a lot of mitosis
  2. Cut some root tips and put into watch glass
  3. Add 2 mol of hydrochloric acid and then add an equal volume of stain (acetic orsein stain)
  4. Heat the mixture (gently) and liquid eveporate use a hot plate for about 5 minutes
  5. Transfer to a clean microscope slide + add 1 drop of aceitic orsein stain
  6. Cover with coverslip
  7. Use tissue to blot dry and add some pressure to make sure it is thin and be able to transmit light
  8. Observe under optical microscope
74
Q

What are the 2 types of tumours

A
  • Benign - grow slowly, less life threatening and more compact
  • Malignant - grow rapidly, less compact, and more life threatening
75
Q

What is the treatment of cancer

A
  • Involves killing dividing cells by blocking a part of the cell cycle
  • Drugs used to treat cancer usually disrupt the cell cycle by
    • Preventing DNA replicating
    • Inhibiting the metaphase stage of mitosis by interfering with the spindle formation
76
Q

What is the problem of using drugs to treat cancer

A
  • They disrupt the cell cycle of normal cells
  • However the drugs are more effective against rapidly dividing cells (cancer cells) .
  • Hair cells are also vulnerable as they divide rapidly

A Level Biology Paper 1 (15 decks)

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