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Biology > Cell Structure > Flashcards

Cell Structure Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define the terms eukaryotic and prokaryotic cell

A

Eukaryotic: DNA is contained in a nucleus, contains membrane bound specialised organelles

Prokaryotic: DNA is free in cytoplasm, no organelles e.g bacteria

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2
Q

State the relationship between a system and specialised cells

A

Specialised cells - tissues that perform specific functions - organs made of several tissue types - organ systems

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3
Q

Describe the structure and function of the cell surface membrane

A

‘Fluid mosaic’ phospholipid bilayer with extrinsic and intrinsic proteins embedded

Isolates cytoplasm from extracellular environment

Selectively permeable to regulate transport substances

Involved in cell signalling/ cell recognition

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4
Q

Explain the role of cholesterol in the cell surface membrane

A

A steroid molecule connects phospholipids and reduces fluidity

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5
Q

Explain the role of glycoproteins in the cell surface membrane

A

Involved in cell signalling, cell recognition and binding of cells together

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6
Q

Explain the role of glycolipids in the cell surface membrane

A

Involved in cell signalling and cell recognition

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7
Q

Describe the structure of the nucleus

A

Surrounded by the nuclear envelope, a semi permeable double membrane

Nuclear pores allow substances to enter/exit

Dense nucleolus made of RNA and proteins assembles ribosomes

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8
Q

Describe the function of the nucleus

A

Contains DNA coiled around chromatin into chromosomes

Controls cellular processes: gene expression determines specialisation and site of mRNA transcription, mitosis, semiconservative replication

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9
Q

Describe the structure of mitochondria

A

Surrounded by double membrane folded inner membrane forms cristae: site of electron transport chain

Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins

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10
Q

Describe the structure of chloroplast

A

Vesicular plastid with double membrane

Thylakoids: flattened discs stack to form grana; contain photosystems with chlorophyll

Intergranal lamellae: tubes atach thylakoids in adjacent grana

Stroma: fluid-filled matrix

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11
Q

State the function of mitochondria and chloroplasts

A

Mitochondria: site of aerobic respiration to produce ATP

Chloroplasts: site of photosynthesis to convert solar energy to chemical energy

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12
Q

Describe the structure and function of the Golgi apparatus

A

Stack of membrane bound, flattened sacs aligned with the rough endoplasmic reticulum

Molecules are processed in cisternae vesicles

Modifies and packages proteins for export

Synthesises glycoproteins

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13
Q

Describe the structure and function of a lysosome

A

Sac surrounded by a single membrane embedded H+ pump maintains acidic conditions, contains digestive hydrolase enzymes

Digests contents of phagosome

Exocytosis of digestive enzymes

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14
Q

Describe the structure and function of a ribosome

A

Formed of protein and rRNA free in the cytoplasm or attached to endoplasmic reticulum

Site of protein synthesis via translation:

Large subunit: joins amino acids
Small subunits: contains mRNA binding site

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15
Q

Describe the structure and function of the endoplasmic reticulum

A

Cristernae: network of tubules and flattened sacs extends from cell membrane through cytoplasm and connects to nuclear envelope

Rough ER: many ribosomes attached for protein synthesis and transport

Smooth ER: lipid synthesis

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16
Q

Describe the structure of the cell wall

A

Bacteria: made of the polysaccharide murein

Plants: made of cellulose microfibrils, plasmodesmata allow molecules to pass between cells

17
Q

State the functions of the cell wall

A

Provide strength and support

Physical barrier against pathogens

Part of the apoplast pathway to enable easy diffusion of water

18
Q

Describe the structure and function of the cell vacuole in plants

A

Surrounded by a single membrane: tonoplast
Contains cell sap: mineral ions, water, enzymes, soluble pigments

Controls turgor pressure

Absorbs and hydrolyses potentially harmful substances

19
Q

Explain some common cell adaptations

A

Folded membrane or microvilli increase surface area

Many mitochondria = large amounts of ATP for active transport

Walls one cell thick to reduce distance of diffusion pathway

20
Q

State the role of plasmids in prokaryotes

A

Small ring of DNA that carries non essential genes

Can be exchanged between bacterial cells via conjunction

21
Q

State the role of flagella in prokaryotes

A

Rotating tail propels organism

22
Q

State the role of the capsule in prokaryotes

A

Prevents desiccation

Acts as food reserve

Provides mechanical protection against phagocytosis and external chemicals

Sticks cells together

23
Q

Compare eukaryotic and prokaryotic cells

A

Both have:

Cell membrane
Cytoplasm
Ribosomes

24
Q

Contrast eukaryotic and prokaryotic cells

A

Prokaryotic:

Small cells
No membrane bound organelle and no nucleus

Circular DNA

Small ribosomes

Eukaryotic:

Larger cells

Have organelles and a nucleus

Linear DNA

Large ribosomes

25
Q

How do optical microscopes work?

A
  1. Lenses focus rays of light and magnify the view of a thin slice of specimen
  2. Different structures absorb different amounts and wavelengths of light
  3. Reflected light is transmitted to the observer via the objective lens and eye piece
26
Q

Give 2 advantages and disadvantages of using an optical microscope

A

+ Colour image
+ Affordable apparatus

  • 2D image
  • Lower resolution than electron microscopes
27
Q

Describe how a transmission electron microscope works

A
  1. Pass a high energy beam of electrons through thin slice of specimen
  2. More dense structures appear darker since they absorb more electrons
  3. Focus image onto fluorescent screen or photographic plate using magnetic lenses
28
Q

Give 2 advantages and disadvantages of transmission electron microscopes

A

+ High resolution as electrons have a shorter wavelength than light
+ High magnification

  • 2D image
  • No colour image
29
Q

Describe how a scanning electron microscope works

A
  1. Focus a beam of electrons onto a specimens surface using electromagnetic lenses
  2. Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
30
Q

Suggest the advantages and disadvantages of scanning electron microscopes

A

+ 3D image
+ High resolution as electrons have a shorter wavelength than light

  • No colour change
    Only shows outer surface
31
Q

Define magnification and resolution

A

Magnification: factor by which the image is larger than the actual specimen

Resolution: smallest separation distance at which 2 separate structures can be distinguished from one another

32
Q

Outline what happens during cell fractionation and ultracentrifugation

A
  1. Mince and homogenize tissue to break open cells and release organelles
  2. Filter homogenate to remove debris
  3. Perform differential centrifugation:
    a. Spin homogenate in centrifuge
    b. The most dense organelles in the mixture form a pellet
    c. Filter off the supernatant and spin again at a higher speed
33
Q

State the order of sedimentation of organelles during differential centrifugation

A

Most dense -> least dense

Nucleus - mitochondria - lysosomes - RER - plasma membrane - SER - ribosomes

34
Q

Explain why fractionated cells are kept in a cold, buffered, isotonic solution

A

Cold: slow action of hydrolase enzymes

Buffered: maintain constant pH

Isotonic: prevent osmotic lysis/ shrinking of organelles

Biology (20 decks)

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