Studying cells Flashcards

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1
Q

What is the structure of nucleus in eukaryotic cells? (3)

A

Largest organelle in the cell
Double membrane called the nuclear membrane/envelope
Nuclear pores which allows the passage of molecules such as mRNA, in and out of the nucleus

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2
Q

What is the function of nucleus in eukaryotic cells? (4)

A

Contains DNA
The nucleolus is responsible for making ribosomal RNA and ribosomes
Ribosomal proteins are synthesised within the nucleus but assembles outside the nucleus
Contains chromatic (DNA coiled around proteins called histones)

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3
Q

What is the structure of mitochondria in eukaryotic cells? (3)

A

Have a double membrane
Inner membrane is highly folded to form cristae to increase surface area for attachment of ATP synthase enzymes
Within the inner membrane, the matrix contains proteins, lipids, mitochondrial DNA and ribosomes

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4
Q

What is the structure and function of rough endoplasmic reticulum in eukaryotic cells? (4)

A

Made from highly folded membranes with 80s ribosomes embedded
Membrane is folded into flattened sacks called cisternae
RER is joined to the nucleus (easier for mRNA to get there to make proteins)
RER synthesises and transports proteins throughout the cell

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5
Q

What is the function of smooth endoplasmic reticulum in eukaryotic cells? (1)

A

Recombines glycerol and fatty acid to make triglycerides

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6
Q

What is the structure and function of ribosomes in eukaryotic cells? (3)

A

Made up of 2 rRNA protein subunits
Two subunits of a ribosomes are made of a combination of long strands of rRNA, dotted with ribosomal proteins
Site of protein synthesis

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7
Q

What is the structure and function of Golgi apparatus in eukaryotic cells? (2)

A

Composed of flattened sacs made of membranes
Sacs are fluid filled and pinch off smaller sacs (called vesicles) at their ends

Sorts, modifies and packages molecules, such as proteins and triglycerides into vesicles

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8
Q

What is the structure of lysosomes in eukaryotic cells? (2)

A

Bound by a single membrane and have no internal structure

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9
Q

What is the function of lysosomes in eukaryotic cells? (2)

A

Used to hydrolyse damaged and worn-out organelles
Contain hydrolytic enzymes which are lysozymes in an acid solution, which must be kept separate from the rest of cell contents prevent them from digesting organelles

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10
Q

What is the structure and function of cell surface membrane in eukaryotic cells? (2)

A

Made up of phospholipids, specific transport proteins and carbohydrates arranged into a fluid mosaic model

Controls the passage of molecules in and out of the cell

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11
Q

What is the function of microvilli in eukaryotic cells? (3)

A

Finger like projections of the cell membrane which greatly increases the surface area of the cell surface membrane, this speeds up absorption of digested food.
Found on epithelial cells in the small intestines

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12
Q

What is the function of centrioles in eukaryotic cells? (2)

A

In mitosis, they form a network of spindle fibres across the cell onto which chromosomes attach
These fibres pull the chromosomes/chromatids apart during mitosis

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13
Q

Describe the structure of viruses (4)

A

Contain DNA or RNA
Surrounded by capsid (protein coat)
Has attachment proteins which enable it to bind to host cells
Has enzymes that it uses to replicate its genetic information and insert it into the host cell DNA

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14
Q

Name 2 structures found within a eukaryotic cell that cannot be identified using an optical microscope (2)

A

Mitochondria
Ribosome
Endoplasmic reticulum
Lysosome
Cell surface membrane

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15
Q

Describe the principles and the limitations of using a transmission electron microscope to investigate cell structure (5)

A

PRINCIPLES:
Electrons pass through very thin specimen
Denser parts absorb more electrons
So denser parts appear darker
Electrons have short wavelength so give a high resolution
LIMITATIONS:
Cannot look at living material/must be in a vacuum
Specimen must be very thin
Artefacts present
Complex staining method/long preparation time

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16
Q

Name 2 structures found within a eukaryotic cell that can be identified using a transmission electron microscope (2)

A

Mitochondria
Ribosome
Endoplasmic reticulum
Lysosome
Cell surface membrane

17
Q

How does SEM work (2)

A

Electrons bounce off the surface
Produces a 3D image

18
Q

Describe the structure of a chloroplast (5)

A

Granum - a stack of thylakoid membranes
Thylakoid membrane - contains chlorophyll for photosynthesis
Stroma - fluid filled part, some of the photosynthetic reactions occur here
Starch grains - the energy storage molecule in plants
DNA and ribosomes - chloroplasts have their own DNA and 70s ribosomes to make enzymes needed for photosynthesis

19
Q

What is the function of the chloroplast (3)

A

Absorbs light energy and converts it to chemical energy
The chemical energy is used to make carbohydrates from CO2 and H2O
These can then be used for respiration or to make other organic molecules in the cell, which will enable the plant to grow

20
Q

What is the cell wall in plants made of? (1)

A

Cellulose

21
Q

What is the cell wall in fungi made of? (1)

A

Chitin

22
Q

What is the cell wall in bacteria made of? (1)

A

Peptidoglycan/murein

23
Q

What is the plasmodesmata? (1)

A

Gaps in the cell walls that connect cell cytoplasm’s together, to allow the easy movement of water soluble molecules

24
Q

Describe the structure of a prokaryotic cell (7)

A

DNA is circular and not associated with histones
Contains no membrane bound organelles
DNA is free in cytoplasm
Contains smaller ribosomes (70s)
Some have capsule, flagella, plasmids
Has mesosomes for ATP synthesis
Has cell wall made of murein

25
Q

Explain why the magnification of the light microscope is limited (1)

A

By using more lenses, a light microscope can magnify by a larger amount, but the problem is at these higher magnifications the microscope loses resolution

26
Q

What does resolution mean (1)

A

The ability to distinguish 2 objects that are close together.

27
Q

How does light affect resolution? (2)

A

The resolution of the light microscope is limited by the wavelength of light
The shorter the wavelength of the light / electrons, the better the resolution

28
Q

Describe how the student could have used an eyepiece graticule to determine the mean diameter of stomata (3)

A

Measure each stomata using an eye piece graticule
Calibrate the eyepiece graticule against a stage micrometer
Take at least 5 measurements and calculate a mean (more measurements are more accurate)

29
Q

Why can electron microscopes be used to see smaller organelles? (2)

A

Electrons have small wavelength
Higher resolution

30
Q

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope (4)

A

Add a drop of water to the microscope slide
Get a thin section of plant tissue and float on the drop of water
Stain with iodine in potassium iodide
Lower the cover slip using a mounted needle to avoid air bubbles