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Biology 3.2 > Cell structure > Flashcards

Cell structure Flashcards

1
Q

Define eukaryotic cells

A

Have a distinct nucleus and membrane bound organelles

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2
Q

What is the structure of the cell surface membrane

A
  • 7nm thick
  • Plasma membrane
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3
Q

What is the function of the cell surface membrane

A
  • Partially permeable membrane which controls exchange between the cells and its environment
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4
Q

What is the structure of the nucleus

A
  • Surrounded by 2 membrane known as the nuclear envelope
  • The envelope has small holes or pores-nuclear pores about 40-100nm across
  • The nucleus contains linear DNA, chromosomes which are usually in a loosely coiled state known as chromatin. The nucleus contains a darker staining area, the nucleolus
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5
Q

What is the function of the nucleus

A
  • It controls the cell activities
  • Contains genetic material as DNA and chromosomes
  • Produces mRNA and tRNA
  • The nucleolus manufactures ribosomal RNA and ribosomes
  • Nuclear pores allow mRNA and ribosomes to leave the nucleus and nutrients and hormones to enter the nucleus
  • The nuclear envelope controls entry and exit of materials, and contains the reactions in it
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6
Q

What is the structure of the mitochondria

A
  • This organelle is surrounded by 2 membranes called the envelope
  • 1-10um in length
  • The inner membrane is folded to form projections called cristae ( larger surface area) which project into the interior solution, the matrix
  • The matrix contains proteins, lipids, ribosomes and DNA so they can produce their own proteins
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7
Q

What is the function of the mitochondria

A
  • The later stages of aerobic respiration
  • They make ATP
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8
Q

What is the structure of the endoplasmic reticulum

A
  • Extensive system of membranes, continuous with the nuclear membrane
  • Forms a system of flattened sacs called cisternae
  • Ribosomes can be attached to the membrane ( rough endoplasmic reticulum)
  • No ribosomes ( smooth endoplasmic reticulum)
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9
Q

What is the function of the endoplasmic reticulum

A

Rough endoplasmic reticulum=
-Provides a large surface area for the synthesis of proteins and glycoproteins, and then transports these proteins through the cell.
- Makes the golgi apparatus
Smooth endoplasmic reticulum=
- Synthesises, stores and transports lipids and carbohydrates

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10
Q

What is the structure of ribosomes

A
  • Can be found free in the cytoplasm or attached to endoplasmic reticulum
  • made by RNA and protein
  • Found in two sizes : 80s in eukaryotic cells and 70s in prokaryotic cells
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11
Q

What is the function of ribosomes

A
  • site of protein synthesis
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12
Q

What is the structure of golgi apparatus

A
  • Stack of flattened sacs called cisternae
  • formed from vesicles which bud off the rough endoplasmic reticulum
  • broken down at the other end to form golgi vesicles
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13
Q

What is the function of golgi apparatus

A
  • Molecules, particularly proteins and lipids are collected, processed and sorted into golgi vesicles for transport
  • Transport, modify and store lipids
  • Makes lysosomes
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14
Q

What is the structure of lysosomes

A
  • Have a single membrane
  • Size up to 1.0 um
  • Contain hydrolytic enzymes ( proteases, lipases, and lysozymes
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15
Q

What is the function of lysosomes

A
  • Digest old cell organelles and cells after they have died
  • Hydrolyse material ingested by phagocytic cells ( white blood cells digest bacteria)
  • Release enzymes to the outside of the cells
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16
Q

What is the structure of the cell wall

A
  • Plant cells are surrounded by a relatively rigid cell wall made of polysaccharides such as cellulose embedded in a matrix
  • The middle lamella is a thin layer marking the boundary between adjacent cell walls and cements cells together
  • Algae cell walls are made up of cellulose or glycoproteins or a mixture. In fungi they are made out of chitin
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17
Q

What is the function of the cell wall

A
  • Provides mechanical strength to the cell and the plant as a whole and prevents the cell from bursting when water enters by osmosis
  • Allows water to pass along it contributing to movement of water through the plant
  • Freely permeable
18
Q

What is the structure of the large central vacuole

A
  • Surrounded by a membrane called a tonoplast
  • Vacuole is fluid filled
  • Contains mineral salts, sugars and amino acids ( temporary food store) oxygen, carbon dioxide, pigments ( to colour petals)
19
Q

What is the function of the large central vacuole

A
  • Tonoplasts controls the exchange of materials between the vacuole and the cytoplasm
  • Make cells turgid to support herbaceous plants
20
Q

What is the structure of the chloroplasts

A
  • Surrounded by 2 layers of membrane- envelope
  • Around 2-10um long
  • Stroma a jelly like substance inside
  • There are membranes forming flattened sacs called thylakoid membranes
  • Stacks of thylakoid membranes= grana
  • Small starch grains and lipid droplets are present in the stroma
21
Q

What is the function of the chloroplasts

A
  • Photosynthesis
22
Q

Describe the division of labour

A

1) DNA in the nucleus contains instructions to make proteins
2) Protein synthesised on ribosomes
3) Proteins transported through rough endoplasmic reticulum
4) Protein molecules are pinched off in vesicles and are transported towards the golgi apparatus
5) Vesicles fuses with golgi apparatus
6) Golgi apparatus process and packages protein molecules ready for release
7) Packaged protein molecules are pinched off in vesicles from the golgi apparatus and are transported towards the plasma membrane
8) Vesicle fuses with plasma membrane
9) Protein leaves the cell by exocytosis

23
Q

Define cell

A

The basic unit of living things

24
Q

Define tissues

A

A group of similar or different cells working together for a specific function

25
Define organ
Different tissues work together for a specific function
26
Define organ system
Different organs working together to support the whole system
27
Define organism
Different systems working together to support the whole organism
28
What structures are always present in prokaryotic cells
- Cell surface membrane - Circular DNA - Ribosomes (smaller) - Cell wall made up of murein ( a glycoprotein) 10-80nm thick
29
What additional structures can prokaryotic cells have
- Pili ( for attachment to other cell surfaces, involved in sexual reproduction) - Plasmids ( small circular piece of DNA) - Capsule ( A mucilaginous layer of slime) - Mesosome ( Infolding of the plasma membrane, may have enzymes on for processes such as respiration) - Infolding of plasma membrane ( may form a photosynthetic membrane, or carry out nitrogen fixation) - Flagellum ( used for locomotion)
30
Describe a virus
- Have no cellular structure ( they are acellular) - They are non- living - They can only reproduce when inside other cells ( host cells) - 50 times smaller than bacteria ( 20nm to 300nm )
31
Describe the structure of a virus
- Nucleic acids such as DNA and RNA as genetic material - The capsid is a protein coat that encloses the nucleic acid - Some viruses have a lipid envelope - The lipid envelope, or if this is not present, the capsid, have attachment proteins which are essential to allow the virus to identify and attach to host cell
32
How do you prepare a slide ( light microscope)
- Add a drop of water to (glass) slide - Obtain thin section and place on slide - Stain with iodine in potassium iodine - Lower cover slip using mounted needle - Press cover slip down firmly so cells don't overlap to allow light to pass through
33
Describe an electron microscope
- Electrons have a smaller wavelength than light. Electrons= 1nm. Light= 400nm - Electrons can pass between two objects that are extremely close together - Electron microscope can distinguish two extremely close objects - The maximum resolving power is 0.1- 0.2 nm
34
Describe a TEM ( transmission electron microscope)
-Can see internal structures of the cell - Image is 2D - Resolution = 0.1nm
35
Describe a SEM ( scanning electron microscope)
- Electron beam is directed on to the surface of the sample - Image is 3D - Resolution = 20nm
36
What are the principles and limitations of the electron microscope
- Use electrons to pass through specimen - Greater resolution - Smaller organelles visible - Dead specimen - No colour - Thinner specimen
37
What are the principles and limitations of the light microscope
- Uses light to pass through specimen - Lower resolution - Larger organelles visible - Living specimen/ view living processes - Coloured - Thicker specimen
38
Define artefact
Structures that look different then should due to damage caused by slide preparation
39
Describe the process of separating cell components
1) Cell homogination to break up cells 2) Filter to remove debris 3) Use isotonic solution to prevent damage to organelles 4) Keep cold to prevent damage to organelles by enzymes 5) Use buffer to prevent enzyme denaturation 6) Centrifuge at low speed to separate nuclei and cell fragments 7) Pour off liquid and re-spin at higher speeds to get mitochondria 8) Repeat
40
Why is cell fractionation carried out
To study structure and function of organelles in the cell

Biology 3.2 (4 decks)

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