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Biology > Cell structure > Flashcards

Cell structure Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe the function and structure of the cell-surface membrane

A

function is to regulate movement of substances into and out of cell

  • a bilayer of lipids (phospholipid)
  • large surface area
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2
Q

describe the function and structure of the nucleus

A

function is to control reactions within the cell

  • has a double membrane
  • contains genetic material
  • has pores so substances can move in and out
  • nucleolus which manufactures rRNA and assembles ribosomes
  • nucleoplasm - jelly-like material
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3
Q

describe the function and structure of the mitochondrion

A

function is to release energy during aerobic respiration

  • has a double membrane
  • has a folded inner membrane
  • folds are called cristae
  • inner fluid is called matrix
  • high surface area for more efficient respiration
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4
Q

describe the function and structure of the chloroplast

A

function is to absorb light energy during photosynthesis

  • has a double membrane
  • folded inner membrane
  • folds are called thylakoid
  • chlorophyll within thylakoid
  • liquid is called stroma
  • high surface area for more efficient photosynthesis
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5
Q

describe the function and structure of the Golgi apparatus

A

function is to process and package polypeptides for exocytosis

  • a stack of fluid-filled membrane-bound sacs
  • have a high surface area
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6
Q

describe the function and structure of the lysosomes

A

function is to hydrolyse unwanted material using hydrolytic enzymes

  • a vesicle containing enzymes
  • lots in one cell for faster breakdown
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7
Q

describe the function and structure of the ribosomes

A

function is for protein synthesis during translation

  • made up of 2 sub-units
  • consist of proteins and rRNA
  • no membrane so sub-units can move
  • 80s in plant cells and 70s in prokaryotic cells
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8
Q

describe the function and structure of the RER

A

function is to transport polypeptides

  • a fluid-filled membrane
  • covered in ribosomes
  • large surface area
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9
Q

describe the function and structure of the SER

A

function is to process and synthesise lipids

  • fluid-filled membranes
  • large surface area
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10
Q

describe the function and structure of the cell wall

A

function is to support and maintain shape of cell

  • made from cellulose - condensation of beta glucose molecules form fibrils - fibrils joined by hydrogen bonds which collectively provide strength
  • found on the surface of plant, algal and fungal cells
  • arrangement of fibres gives strength
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11
Q

describe the function and structure of the cell vacuole

A

function is to maintain the shape and pressure of the cell, and to move chemicals

  • membrane-bound (tonoplast)
  • within the cytoplasm
  • contains cell sap
  • membrane separates sap from cytoplasm
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12
Q

describe how a lysosome can break down eg. proteins

A
  • the lysosome will fuse with the faulty protein and the phospholipid biolayers will join together to become 1
  • the hydrolytic enzymes within the lysosome are released which will break down the protein into amino acids
  • exocytosis then occurs (when the waste molecules leave the cell)
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13
Q

name the structures found within prokaryotic cells

A
  • cell wall made from murein
  • cell membrane
  • slime capsule (for protection)
  • DNA loop
  • ribosomes (70s)
  • flagellum for mobility
  • plasmid which can transfer DNA to other cells
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14
Q

describe how light microscopes work

A
  • light from a mirror is reflected up through the object into the objective lens
  • the image produced is magnified by the eyepiece lens
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15
Q

describe how an SEM microscope works

A
  • a beam of electrons is produced at the top of the microscope by an electron gun
  • the electron beam follows a vertical path through the microscope held within a vacuum
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16
Q

describe how a TEM microscope works

A
  • electrons are emitted which travel through a vacuum
  • electromagnetic lenses are used to focus the electrons into a thin beam which is directed into the object
17
Q

why can electron microscopes give a higher resolution?

A

electrons have a shorter wavelength than visible light so produce higher resolution images

18
Q

what are the advantages and disadvantages of light microscopes?

A

advantages:
- cheap to purchase and operate
- simple and easy sample preparation

disadvantages:
- low magnification
- lower resolution than electron microscopes

19
Q

what are the advantages and disadvantages of SEM microscopes?

A

advantages:
- higher magnification and resolution than light microscopes
- can look at 3D structures

disadvantages:
- very expensive
- cannot look at live specimens
- produces only black and white images
- lower resolution than TEM’s

20
Q

what are the advantages and disadvantages of TEM microscopes?

A

advantages:
- high magnification and resolution
- can see internal structures

disadvantages:
- very expensive
- cannot look at live specimens
- produces only black and white images
- can only be used with very thin objects

21
Q

what are artefacts in microscopy and give some examples

A

they are things that can be seen under the microscope which are not meant to be there

eg. foreign bodies such as eyelashes, clumps of stain/dye

22
Q

what is the formula for magnification

A

magnification = image size divided by actual size

23
Q

how do you convert from nm to mm

A

divide by 1,000,000

24
Q

how do you convert from micrometers to mm

A

divide by 1000

25
Q

what is cell fractionation?

A

the process of separating different organelles of a cell, so they can be studied in detail

26
Q

what are the steps involved in cell fractionation and give reasons

A
  • tissue is cut up and kept in a cold (to stop enzymes breaking down cells), isotonic (to stop osmosis), buffered solution (to stop a pH change).
  • cut-up tissues are further broken up in a homogeniser to make the tissue as small as possible and to break open the cells to release organelles
  • mixture is filtered to remove cell debris
  • homogenised tissue is spun in an ultracentrifuge at a low speed to force the heaviest organelles to sink to the bottom, to form a pellet
  • the supernatant is transferred to another tube and spun at a different speed to form pellets of different organelles

Biology (25 decks)

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