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Biology Y12 > Cell Structure > Flashcards

Cell Structure Flashcards

(61 cards)

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1
Q

Structure of the nucleus

A

Nuclear envelope

Nuclear pores

Nucleoplasm

Chromosomes

Nucleolus

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2
Q

Nuclear envelope

A

Double membrane that controls the entry and exit of materials

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3
Q

Nuclear pores

A

Allow the passage of large molecules e.g. mRNA out of the nucleus

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4
Q

Nucleoplasm

A

Jelly-like material that makes up the bulk of the nucleus

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5
Q

Chromosomes

A

Consist of protein-bound, linear DNA

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6
Q

Nucleolus

A

Small spherical region within the nucleoplasm

Manufactures rRNA and assembles ribosomes

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7
Q

3 functions of the nucleus

A

Act as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis

Retain the genetic material of the cell in the form of DNA and chromosomes

Manufacture rRNA and ribosomes

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8
Q

Structure of the mitochondria

A

Bound by a double membrane
• Outer membrane controls the entry/exit of substances
• Inner membrane is folded inwards, forming cristae

Inbetween the cristae is the matrix

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9
Q

Cristae

A

Extensions of the inner membrane

Provide a large SA for the attachment of enzymes & other proteins in respiration

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10
Q

Matrix

A

Contains proteins, lipids, ribosomes and DNA that allows the mitochondria to control the production of their own proteins

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11
Q

Function of the mitochondria

A

Site of aerobic respiration producing ATP

Therefore, the number of mitochondria in a cell varies with metabolic activity

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12
Q

Main features of a chloroplast

A

Chloroplast envelope: Highly selective double membrane

Grana: Stacks of thylakoids (provides a large SA for the attachment of chlorophyll and enzymes)

Stroma: Fluid filled matrix containing enzymes & starch grains

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13
Q
A
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14
Q

Where does the light dependent reaction take place in the chloroplast

A

Grana / Granum

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15
Q

Where does the light independent reaction take place in the chloroplast

A

Stroma

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16
Q

Ribosomes

A

Non-membranous structure

Found free in the cytoplasm / associated with RER

Site of protein synthesis

Made from rRNA & protein

80s - found in eukaryotic cells
70s - found in prokaryotic cells, mitochondria & chloroplasts smaller

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17
Q

Cell walls

A

Algae cell walls are made of cellulose & glycoproteins

Fungal cell walls are made of chitin, glycoproteins and glycan

Plant cell walls consist of micro fibrils of cellulose, embedded in a matrix

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18
Q

Functions of the cellulose cell wall

A

To provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water

To give mechanical strength

Allow water to pass through it

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19
Q

Vacuoles

A

Fluid filled sac

Single membrane around it called a tonoplast

Plant vacuole contains mineral salts, sugars, amino acids, wastes, pigments

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20
Q

3 functions of the vacuole

A
  1. Support plants by making cells turgid
  2. The sugars & amino acids may act as a temporary food source
  3. The pigments may colour petals to attract pollinating insects
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21
Q

2 functions of the rough endoplasmic reticulum

A

• Provide a large SA for the synthesis of proteins

• Provide a pathway for the transport of materials, especially proteins, throughout the cell

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22
Q

2 functions of the smooth endoplasmic reticulum

A

• Synthesise, store and transport lipids

• Synthesise, store and transport carbohydrates

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23
Q

5 functions of the golgi apparatus

A
  1. Add carbohydrates to proteins to form glycoproteins
  2. Produce secretory enzymes, such as those secreted by the pancreas
  3. Secrete carbohydrates, such as those used in making cell walls in plants
  4. Transport, modify and store lipids
  5. Form lysosomes
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24
Q

What are lysosomes?

A

Vesicles that contain digestive enzymes

They are made in the golgi complex

They isolate these enzymes from the rest of the cell and prevent them from acting upon other chemicals & organelles within the cell

Abundant in secretory cells and white blood cells

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25
4 functions of lysosomes
1. Hydrolyse material injected by phagocytic cells e.g. WBC & bacteria 2. Release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell 3. Digest worn out organelles so that the useful chemicals they are made of can be re-used 4. Completely break down cells after they have died (autolysis)
26
Mesosome of prokaryotic cells
Instead of mitochondria, they are in-folding of the cell membrane that provide a large SA for the attachment of enzymes in respiration
27
Nucleoid of prokaryotic cells
Free DNA that possesses all genetic information for replication
28
Plasmid of prokaryotic cells
Aid survival of bacteria in adverse conditions as it contains resistance genes
29
Cell wall of prokaryotic cells
Made of murein
30
Ribosomes of prokaryotic cells
70s Site of protein synthesis
31
Flagellum of prokaryotic cells
Rotates , allowing the bacterium cell to move
32
Capsule of prokaryotic cells
Slime is a type of protein that stops the cell from drying out , sticks cells together and protects the cell against digestive enzymes
33
Binary fission (asexual division)
1. Circular DNA molecule replicates and both copies attach to the cell membrane 2. The cell membrane begins to grow inbetween the two DNA molecules, pinches inwards, dividing the cytoplasm in 2 3. A new cell wall forms, results in 2 identical daughter cells which are genetically identical to the parent cell
34
Why are viruses described as acellular?
No cell membrane
35
Why are viruses described as non-living?
Have no metabolic reactions
36
Viral replication
1. Attach to host cell with attachment proteins 2. Inject their nucleic acids into the host cell 3. Host cells metabolic processes start producing the viral components 4. These are assembled into new viruses
37
Definition of a tissue
Collection of similar cells that perform a specific function
38
Definition of an organ
A combination of tissues that are coordinated to perform a variety of functions
39
Leaves are an organ made up of these tissues:
Palisade mesophyll: Made of palisade cells that carry out photosynthesis Spongy mesophyll: Adapted for gaseous diffusion Epidermis: Protect the leaf & allow gaseous diffusion Phloem: Transport organic materials away from the leaf Xylem: Transport ions & water into the leaf
40
Interphase
DNA replicates before mitosis, making each chromosome consist of 2 identical sister chromatids connected at the centromere The cell is producing proteins and making spindle fibres
41
Prophase
Chromosomes condense as 2 sister chromatids Centrioles move to opposite poles of the cell Spindle fibres develop Nuclear envelope breaks down Nucleolus disappears
42
Metaphase
Sister chromatids align along equator of cell Each sister chromatid is attached to a protein spindle fibre by its centromere
43
Anaphase
Centromere divides in 2 Allows chromatids to separate Spindle fibres contract -> Pulls chromatids towards poles This requires ATP from mitochondria
44
Telophase
Chromosomes are long and thin Spindle fibres disintegrate Nuclear membranes & nuclelous reform
45
Cytokinesis
Cell division follows nuclear division The parent cell is “pinched” into 2 daughter cells Each daughter cell has the same homologous chromosomes The separation of the cytoplasm occurs by contractile proteins shortening
46
Magnification definition
How much bigger you can make the image
47
Resolution definition
How focused/clear the image is
48
Light microscopes
Specimens must be cut thin so light can pass through it Use a stain to make parts visible Can use living/dead specimens Wave length of visible light= 500-650nm
49
Electron microscopes
Electrons are used instead of light so a greater resolution Electrons have a short wavelength - gives a higher resolving power Electrons are negatively charged so electromagnets can focus them
50
The Transmission Electron Microscope (TEM)
Electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet Beam passes through thin section of the specimen , parts absorb electrons and appear dark , parts allow it to pass through and appear light
51
Main limitations of the TEM
Whole system must be in a vacuum - living specimens cannot be observed Complex “staining” process is required Specimen must be extremely thin Image may contain artefacts 2D image
52
The Scanning Electron Microscope (SEM)
Directs a beam of electrons onto the surface of the specimen from above, rather than penetrating from below Electrons are scattered by the specimen and the pattern depends on the contours of the specimen surface Can create a 3D image
53
Main limitations of the SEM
Whole system must be in a vacuum - living specimens cannot be observed Complex “staining” process is required Image may contain artefacts
54
Formula for total magnification
Magnification of eyepiece lens x magnification of objective lens
55
Formula for size of image
Actual size x total magnification
56
Using a scale bar to find actual size
Image length divided by scale bar length x scale bar value
57
Measuring cells using an eyepiece graticule
Eyepiece graticules have to be calibrated (by using a stage micrometer) before measuring objects as each objective lens will magnify to a different degree Once it has been calibrated at each objective lens, it doesn’t have to be done again
58
How to calibrate an eyepiece graticule?
Stage micrometer is used, usually the scale is 2nm long & its smallest subdivision is 0.01mm When you know what the scale is on the stage micrometer, you can calculate the divisions on an eyepiece graticule at different magnifications
59
Before cell fractionisation:
Cold- Reduce enzyme activity that might break down the organelles Buffered- So the pH does not fluctuate, change in pH could alter the structure of the organelles Isotonic- Same water potential, so prevents organelles shrinking/bursting
60
Cell fractionisation
Parts of cells are homogenised by using either a pestle&mortar, electric blender or electric homogeniser After breaking up, the fluid mixture left is called the homogenate The homogenate is suspended in a buffer solution to keep the pH constant The homogenate is filtered to remove bits of cells that have not been broken properly
61
Ultracentrifugation
Filtrate is put in the centrifuge Larger organelles such as nuclei pellet first If smaller organelles are wanted, the liquid on top of the pellet (the supernatant) has to be spun again Nuclei, chloroplasts Mitochondria, lysosomes Rough RER, ribosomes

Biology Y12 (9 decks)

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