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Cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define the term 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 and archaea

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2
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 of substances

Involved in cell signalling/cell recognition

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3
Q

Explain the role of cholesterol, glycoproteins and glycolipids in the cell surface membrane

A

Cholesterol: steroid molecule connects phospholipids and reduces fluidity

Glycoproteins: cell signalling, den recognition (antigens) and binding cells together
Glycolipids: cell signalling and cell recognition

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4
Q

Describe the structure of the nucleus

A

Surround by nuclear envelope, a Semi-permeable double membrane

Nucleus press allows substances to enter and exit

Dense nucleolus made of RNA and proteins assembles ribosomes

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5
Q

Describe the function of the nucleus

A

Contains DNA copied around chromatin into chromosomes

Controls cellular processes gene expression determines specialisation and sit of mRNA transcription

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6
Q

Describe the structure of a mitochondrion

A

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

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

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7
Q

Describe the structure of a chloroplast

A

-Vesicular plastic with double membrane
-thylakoids: flattened discs stacked
-grana: contains photosystems with chlorophyll stacks of thylakoids
-stoma: fluid filled matrix
-intergranal lamellae: tubes attaching thylakoids in adjacent grana

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8
Q

State the function of the 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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9
Q

Describe the structure and function of the Golgi apparatus

A

Planar stack of membrane-bound, flattened sacs cis face aligns with rER

Molecules are processed in cisternae vesicles bud of trans face via exocytosis:

Modified and packaged proteins for export
Synthesises glycoproteins

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10
Q

Describe the structure and function of a lysosome

A

Sac surrounded by single membrane embedded H+ pump maintains acidic conditions contains digestive hydrolase enzymes glycoproteins coat protects cell interior

Digests contents of phagocytosis
Exocytosis of digestive enzymes

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11
Q

Describe the structure and function of a ribosome

A

Formed of protein and rRNA free in cytoplasm or attached to ER

Site of protein synthesis via translation:
Large subunit: joins amino acids
Small subunit: contains mRNA binding site

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12
Q

Describe the structure and function of the endoplasmic reticulum ER

A

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

Rough ER: many ribosomes attached for protein systhesis and transport
Smooth ER: lipid synthesis

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13
Q

Describe the structure of the cell wall

A

Bacteria: made of polysaccharide murein

Plants: made of cellulose microfibrils
Plasmodesmata allow molecules to pass between cells, middle lamella acts as boundary between adjacent cell walls

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14
Q

State the functions of the cell wall

A

-Mechanical strength and support
-Physical barrier against pathogens
- part of apoplast pathway (plants) to enable easy diffusion of water

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15
Q

Describe the structure and function of the cell vacuole in plants

A

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

-Controls turgor pressure
-Absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm

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16
Q

Explain some common cell adaptions

A

-folded membrane or microvilli increases surface area
-many mitochondria = large amounts of ATP for active transport
-walls one cell thick to reduce distance of diffusion pathway

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17
Q

State the role of plasmids in prokaryotes

A

-small rings of DNA that carries non-essential genes
-can be exchanged between bacterial cells via conjugation

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18
Q

State the role of flagella in prokaryotes

A

Rotating tail propels the (usually unicellular) organism

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19
Q

State the role is the capsule in prokaryotes

A

Polysaccharide layer:
-prevents desiccation
-acts as food reserve
-provides mechanical protection against phagocytosis and external chemicals
-sticks cells together

20
Q

Compare eukaryotic and prokaryotic cells

A

Both have:
-ribosomes
-cytoplasm
-cell membrane

21
Q

Contrast eukaryotic and prokaryotic cells

A

Prokaryotic:
-Small and unicellular
-no nucleus
-70s ribosomes
-asexual reproduction (binary fission)
-murein cell walls
-circular DNA
-has plasmids and capsule and flagella

Eukaryotic:
-larger and multicellular
-has a nucleus
-linear chromosomes
-80s ribosomes
-sexual reproduction (meiosis/mitosis)
-cellulose cell wall (plants)/chitin (fungi)
-no capsule, plasmid or flagella

22
Q

Why are viruses referred to as particles and not cells

A

Acellular and non living: no cytoplasm, cannot self reproduce and no metabolism

23
Q

Why are viruses referred to as particles and not cells

A

Acellular and non living: no cytoplasm, cannot self reproduce and no metabolism

24
Q

Describe the structure of a viral particle

A

-Linear genetic material (DNA or RNA) and viral enzymes
-surrounded by capsid (protein coat made of capsomeres)
-no cytoplasm

25
Q

Describe the structure of an enveloped virus

A

-Simple virus surrounded by matrix protein
-matrix protein surrounded by envelope derived from cell membrane of host cell
-attachment proteins on surface

26
Q

State the role of the capsid on viral particles

A

-protects nucleic acid from degradation by restriction endonucleases
-surface sites enable viral particle to bind to and enter host cell or inject their genetic material

27
Q

State the role of attachment proteins on viral particles

A

Enables viral particle to bind to complementary sites on host cell: entry via endosymbiosis

28
Q

Describe how 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 objective lens and eyepiece

29
Q

Outline how a student could prepare a temporary mount of tissue for an optical microscope

A

1.obtain thin section of tissue
2.place plant tissue in drop of water
3.stain tissue on a slide to make structure visible
4.add coverslip using mounted needle at 45 degrees to avoid trapping air bubbles

30
Q

Suggest the advantages she limitations of using an optical microscope

A

Positive
Coloured image
Can show living structure
Affordable apparatus

Negative
2D image
Lower resolution than electron microscopes= cannot see ultrastructure

31
Q

Describe how a transmission electron microscope (TEM) works

A

1.pass a high energy beam of electrons through thin slice of specimen
2.more dense structures appear darker since absorb more electrons
3.focus image onto fluorescent screen or photographic plate using magnetic lenses

32
Q

Suggest the advantages and limitations of using a TEM

A

advantages:
-Elections have shorter wavelength then light so high resolution so ultrastructure visible
- high magnification

Limitations
-2D image
-requires a vacuum
-no colour

33
Q

Describe how a scanning electron microscope (SEM) 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

34
Q

Suggest the advantages and limitations of using a SEM

A

Advantages:
-3D image
-Electrons have shorter wavelength then light so higher resolutions

Limitations
-requires to use a vacuum
-no colour image
-only shows outer surface

35
Q

Define magnification and resolution

A

Magnification- factor by which the image is larger then the actual specimen

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

36
Q

Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure

A
  1. Place micrometer on stage to calibrate eyepiece graticule
  2. Line up scales in graticule and micrometer and count how many graticule divisions are in 100ųm
  3. Length of 1 divisions
  4. Used calibrated values to calculate actual length of structures
37
Q

Start an equation to calculate the actual size of a structure from microscopy

A

Actual size = image size/ magnification

38
Q

Outline what gains during cell fractionation and ultracentrifugation

A
  1. Mince and homogenise tissue breaks open cells and releases organelles
  2. Filter homogenate to remove debris
    3.perform differential centrifugation
    A. Spin homogenate in centrifuge
    B. Most dense organelles form a pellet
    C. Filter out supernatant and spin again at a higher speed
39
Q

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

A

Cold-slows action of hydrolase enzymes

Buffered-maintains constant pH

Isotonic- prevents osmotic lysis/ shrinking of organells

40
Q

State what the cell cycle is and outline its stages

A

Cycle of division with immediate growth periods

1.interphase
2.mitosis or meosis
3.cytokinesis

41
Q

Explain why the cell cycle does not occur in some cells

A

After differentiation some cells no longer have the ability to divide

42
Q

What is the difference between the cell cycle and mitosis

A

Cell cycle includes growth periods between divisions, mitosis is only 10% of the cycle and refer to the nuclear division

43
Q

Outline what happens in interphase

A

G1. Cell synthesises protein for replication
S.DNA replicates- 2 sister chromatids instead of one
G2. Organelles divide

44
Q

State the purpose of mitosis

A

Produces two identical daughter cells for:
-Growth
-Cell/ tissue replacement and repair
-Asexual reproduction

45
Q

Name the stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

Biology (8 decks)

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