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AS Biology > Topic 2A - Cell Structure and Division > Flashcards

Topic 2A - Cell Structure and Division Flashcards

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1
Q

What organelles would you find in an animal cell?

A
  1. Plasma (cell-membrane) membrane
  2. Rough and smooth endoplasmic reticulum
  3. nucleolus
  4. nucleus
  5. Lysosome
  6. Ribosome
  7. Nuclear envelope
  8. Golgi apparatus
  9. cytoplasm
  10. mitochondria
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2
Q

Which organelles would you find in plant cells?

A

All the same organelles as in plant cells except

  • A cell wall with plasmodesmata (‘channels’ for exchanging substances with adjacent walls)
  • A vacuole (containing cell sap)
  • Chloroplasts
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3
Q

What organelles would you find in algal cells?

A

All the same organelles as plant cells

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4
Q

What organelles would you find in fungal cells?

A

All the same organelles as plant cells EXCEPT

  • their cell walls are made of chitin, not cellulose
  • They dont have chloroplasts (because they dont photosynthesise)
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5
Q

Describe the cell-surface (plasma) membrane and its function.

(DIAGRAM)

A

Description

  • membrane found on surface of animal cells and just inside cell wall of other cells
  • mainly made of lipids and protein]
  • had receptor cells on it

Function

  • regulates movement of substances in and out cells
  • receptor molecules allows cell to respond to chemicals like hormones
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6
Q

Describe the nucleus and its function.

DIAGRAM

A

Description

  • large organelle surrounded by nuclear envelope, containing many pores
  • contains chromosomes made from protein-bound linear DNA
  • Contains nucleolus (nucleoli)

Function

  • controls cell activities (by controlling transcription of DNA)
  • DNA contains instructions to make proteins
  • pores allow substances to move between nucleus and cytoplasm
  • nucleolus makes ribosomes
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7
Q

Describe mitochondria and its function

DIAGRAM

A

Description

  • oval shaped
  • has double membrane - inner one is folded to form structures called cristae
  • inside is matrix, containing enzymes for respiration

Function

  • site of aerobic respiration, where ATP is produced
  • found in large numbers in cells that are very active and require a lot of energy
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8
Q

Describe a chloroplast and its function

DIAGRAM

A

Description

  • small, flattened structure in plant and algal cells
  • surrounded by double-membrane, and has membranes inside called thylakoid membranes. These are stacked up in some parts of chloroplast to form grana. grana are linked together by lamellae - thin, flat pieces of thylakoid membrane.

Function
- site where photosynthesis happens (some parts of process happens in grana and happens in stroma - thick fluid found in chloroplasts)

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9
Q

Describe the golgi apparatus and its function

DIAGRAM

A

Description
- group of fluid-filled, membrane-bound flattened sacs

Function

  • process and packages new lipids and proteins
  • makes lysosomes
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10
Q

Describe golgi vesicles and its function

DIAGRAM

A

Description
- small, fluid-filled sac in cytoplasm, surrounded by membrane and produced by Golgi apparatus

Function
- stores lipids and proteins made by the Golgi apparatus and transports them out of the cell (via the cell-surface membrane)

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11
Q

Describe the lysosome and its function

DIAGRAM

A

Description

  • A round organelle surrounded by a membrane (no clear internal structure)
  • its a type of golgi vesicle
  • Contains digestive enzymes called lysozymes, which are kept separate from the cytoplasm by the surrounding membrane

Functions
- Lysozymes can be used to digest invading cells or to break down worn out components of the cell

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12
Q

Describe ribosomes and its function

DIAGRAM

A

Description

  • Small organelle that floats free in the cytoplasm or is attached to the endoplasmic reticulum
  • made up of proteins and RNA
  • It’s not surrounded by a membrane

Function
- Site where proteins are made

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13
Q

Describe the Rough Endoplasmic Reticulum (RER) and its function

(DIAGRAM)

A

Description

  • system of membranes enclosing a fluid-filled space
  • surface is covered with ribosomes

Function
- folds and processes proteins that have been made at the ribosomes

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14
Q

Describe the Smooth Endoplasmic Reticulum (SER) and its function

(DIAGRAM)

A

Description
- similar to RER, but with no ribosomes

Function
- synthesises and processes lipids

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15
Q

Describe the Cell Wall and its function

DIAGRAM

A

Description

  • rigid structure surrounding cells in plants, algae and fungi
  • made mainly of carbohydrate cellulose, but in fungi, its made of chitin

Function
- Supports cell and prevents them from changing shape

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16
Q

Describe the Cell Vacuole and its function

DIAGRAM

A

Description

  • membrane-bound organelle found in cytoplasm of plant cells
  • contains cell-sap - a weak solution of sugar and salts
  • The surrounding membrane is called the tonoplast

Function

  • helps maintain pressure inside cell and keep cell rigid to stop plants wilting
  • involved in the isolation of unwanted chemicals inside the cell
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17
Q

Why do cells become specialised in multicellular eukaryotic organisms?

A

So that they can carry out specific functions

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18
Q

What helps a specialised cell carry out its specific function?

A

The cells structure (its shape and the organelles it contains)

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19
Q

What is a tissue and what makes up a tissue?

A

A tissue is a group of specialised cells working together to perform a particular function

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20
Q

What makes up an:

1) organ?
2) organ system?

A

Organ = different tissues working together

Organ system = different organs

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21
Q

Describe how one cell like an epithelial cell can link to an organ system in the end

A 
Tissue = epithelial tissue
Organ (stomach) = epithelial tissue, muscular tissue and glandular tissue working together
Organ system (digestive system) = Made up of all organs involved in digestion and absorption of food
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22
Q

Define magnification.

A

Magnification is how much bigger the image is than the specimen

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23
Q

How do you calculate magnification?

A

Mag = image/actual

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24
Q

Define resolution.

A

how well a microscope distinguishes between two points that are close together (how detailed an image is)

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25
Q

If the resolution of an image isn’t great, will increasing the magnification help?

A

No

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26
Q

How do optical microscopes work and what are their max resolutions and magnifications?

A
  1. They use light to form an image
  2. max resolution: 0.2 micrometers (so you cant view organelles smaller than 0.2 micrometers e.g. ribosomes, lysosomes and endoplasmic reticulum but you might be able to just about see mitochondria and a nucleus)
  3. max useful mag: x1500
  4. They CAN view living cells.
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27
Q

How do electron microscopes work and what are their max resolution and magnifications?

A
  1. They use electrons to form an image
  2. They have a higher resolution than optical so they give a more detailed image (and can show more organelles)
  3. Max resolution: 0.0002 micrometers
  4. Max useful magnification: x 1,500,000
  5. They CANNOT view living cells. .
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28
Q

Name the two types of electron microscopes

A
  1. Transmission electron microscopes (TEM)

2. Scanning electron microscopes (SEM)

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29
Q

How do TEM’s work and evaluate their uses.

A
  1. They use electromagnets to focus a beam of electrons, which is then transmitted through the specimen
  2. Denser parts of the specimen absorb more electrons, which make them look darker on the image you end up with

They’re good as they give high resolution images (due to electron’s short wavelength’s), so you can see the internal structure of organelles like chloroplasts BUT they can only be used on thin specimens

30
Q

How do SEM’s work and evaluate their uses.

A
  1. SEM’s scan a beam of electrons across the specimen. This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
  2. The final images show the surface of the specimen and they can be 3D

They’re good as they can be used on thick specimens BUT they give lower resolution images than TEM’s

31
Q

Describe how to view specimens under an optical microscope.

A
  1. Pipette a drop of water onto slide (clear glass/plastic). Use tweezers to place thin section of specimen onto of water drop
  2. Add a drop of stain to highlight objects in cell
  3. Add a cover slip by standing the slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. (try not to get air bubbles under there)
32
Q

What are the 3 main steps of cell fractionation?

A
  1. Homogenisation (breaking up the cell)
  2. Filtration (getting rid of the big bits)
  3. Ultracentrifugation (separating the organelles)
33
Q

Describe the homogenisation process

A
  1. Cell may be vibrated/grinded in a blender to break up the plasma membrane and release the organelles into solution.
  2. Solution should be ice-cold to reduce activity of enzymes that break down organelles
  3. Solution should be isotonic - have same conc. of chemicals as cells being broken down to prevent damage to organelles by osmosis
  4. A buffer solution should be added to maintain pH
34
Q

Describe the filtration process.

A
  1. Homogenised cell solution is filtered through gauze to separate large cell or tissue debris, e.g. connective tissue, from the organelles
  2. Organelles are much smaller than debris, so they pass through the gauze
35
Q

Describe step 1 of the ultracentrifugation process

A
  1. Cell fragments are poured into tube. Tube is put into centrifuge and is spun at low speed
    - heaviest organelles e.g. nucleus, pile up at bottom of tube and form a thick sediment - the pellet. The rest of the organelles stay suspended in the fluid above the sediment - the supernatant
36
Q

Describe step 2 of the ultracentrifugation process

A
  1. Supernatant is drained off, poured into another tube and spun in centrifuge at higher speed
    - Heavier organelles e.g. mitochondra, forim a pellet at the bottom of the tube. Supernatant is drained off and spun at an even higher speed
37
Q

Describe step 3 of the ultracentrifugation process

A
  1. Process is repeated at higher and higher speeds, until all organelles are separated. Each time, the pellet is made up of lighter and lighter organelles
38
Q

Give the order of heaviest to lightest organelles that form the pellet during ultracentrifugation.

A
  1. Nuclei (heaviest)
  2. Mitochondria
  3. lysosomes
  4. Endoplasmic Reticulum
  5. Ribosomes (lightest)
39
Q

Name all the structures in a prokaryotic cell

A
  1. Cytoplasm
  2. Plasma membrane
  3. Cell wall
  4. Flagellum
  5. Plasmids
  6. A capsule
  7. Ribosomes
  8. A long coiled up circular DNA molecule
40
Q

Describe the structure of the cytoplasm in prokaryotic cells.

A

It contains no membrane-bound organelles. It contains ribosomes, but they’re smaller than those in a eukaryotic cell

41
Q

Describe the structure and function of the plasma membrane in prokaryotic cells.

A

Structure: Mainly made up of lipids and proteins

Function: regulates movement of substances in and out of the cell

42
Q

Describe the structure and function of the flagellum in prokaryotic cells.

A

Structure: A long, hair like structure

Function: Rotates to make the cell move

( prokaryotic cells may have one or more flagella)

43
Q

Describe the structure of the DNA in prokaryotic cells.

A

It doesnt have a nucleus. Instead, the DNA floats free in the cytoplasm as one long coiled up circular DNA strand

44
Q

Describe the structure and function of plasmids in prokaryotic cells.

A

Structure: small loops of DNA that arent part of the main DNA strand

Function: Contain genes for things like antibiotic resistance and can be passed between prokaryotes

(- prokaryotic cells may have one or more plasmids)

45
Q

Describe the structure and function of the capsule in prokaryotic cells.

A

Structure: Made up of secreted slime

Function: Helps to protect from attack by cells of the immune system

46
Q

Describe the structure and function of the cell wall in prokaryotic cells.

A

Structure: Made of a polymer called Murein. Murein is a glycoprotein (protein with a carbohydrate attached)

Function: supports the cell and prevents it from changing shape

47
Q

Describe the structure of viruses.

A
  1. Contains a core of genetic material (DNA or RNA) surrounded by a protein coat, called the capsid
  2. Attachment proteins stick out from the edge of the capsid to let the virus cling onto a suitable host cell
48
Q

What makes viruses and bacteria different?

A

Viruses have no plasma membrane, no cytoplasm and no ribosomes

49
Q

How do viruses invade and reproduce? (brief explanation)

A

As they cant undergo cell division (as they’re dead), they inject their DNA or RNA into a host cell - it uses the host cells structures (e.g. enzymes/ribosomes) to replicate the viral particles and to infect other cells

50
Q

How do prokaryotic cells replicate?

A

By binary fission (cell replicates its genetic material before physically splitting into 2 daughter cells)

51
Q

Describe the process of binary fission

A
  1. The Circular DNA and plasmid(s) replicate. The main DNA loop is replicated ONCE, but plasmids can be replicated many times
  2. The cell gets bigger and the DNA loops move to opposite ‘poles’ (ends) of the cell
  3. The cytoplasm begins to divide (and new cell walls begin to form)
  4. The cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of the plasmid
52
Q

How do attachment proteins relate to viruses?

A
  1. Viruses use their attachment proteins to bind to complementary receptor proteins on the surface of host cells
  2. Different viruses have different attachment proteins and therefore require different receptor proteins on host cells. As a result, some viruses can only infect one type of cells
53
Q

What are the two types of cell division in eukaryotes called?

A

Mitosis and Meiosis

54
Q

Briefly outline what happens in mitosis (in a sentence)

A

A parent cell divides to produce 2 daughter cells which are genetically identical to each other and to the parent cell

55
Q

What is mitosis needed for?

A
  1. The growth of multicellular organism (like us)

2. Repairing damaged tissue

56
Q

Do ALL cells keep their ability to divide?

A

No

57
Q

What does the cell cycle consist of?

A
  1. A period of cell growth and DNA replication - Interphase. Interphase is divided into three separate growth stages (G1, S, G2)
  2. Mitosis happens after that
58
Q

What happens during gap phase 1 (G1)?

A

Cell grows and new organelles and proteins are made

59
Q

What happens during synthesis (S)?

A

Cell replicates its DNA, ready to divide by mitosis.

60
Q

What happens during gap phase 2?

A

Cell keeps growing and proteins needed for cell division are made

61
Q

What are the 4 stages of mitosis? (DIAGRAM ALERT!!!)

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
62
Q

What happens during interphase?

A
  • The cell carries out normal functions, but also prepares to divide
  • The cell’s DNA is unravelled and replicated, to double its genetic content
  • The organelles are also replicated so it has spare ones, and its ATP content is increased (ATP provides energy needed for cell division)
63
Q

What happens during prophase?

A
  • The chromosomes condense, getting shorter and fatter.
  • Tiny bundles of proteins called centrioles start to move to opposite ends of the cell, forming a network of protein fibres across it called the spindle
  • The nuclear envelope (membrane around nucleus breaks down and chromosomes lie free in the cytoplasm
64
Q

What happens during metaphase?

A

The chromosomes (each with 2 chromatids) line up along the middle of the cell and become attached to the spindle by their centromere

65
Q

What happens during anaphase?

A
  • The centromeres divide, separating each pair of sister chromatids
  • The spindles contract, pulling chromatids to opposite poles (ends) of the spindle, centromere first. This makes the chromatids appear V-shaped
66
Q

What happens during telophase?

A
  • The chromatids reach opposite poles on the spindle
  • They uncoil and become long and thing again. They’re now called chromosomes again
  • A nuclear envelope forms around each group of chromosomes, so there are now 2 nuclei
  • The cytoplasm divides (cytokinesis) and there are now 2 daughter cells that are genetically identical to the parent cell and to each other
  • Mitosis ends and new daughter cells starts interphase stage to get ready for next round of mitosis
67
Q

Why do chromosomes already have 2 strands before mitosis begins?

A

Each chromosome had already made an identical copy of itself during interphase

68
Q

Do questions relating to time taken for each stage of mitosis

A

page 33

69
Q

What causes cancer?

A
  1. Mitosis and the cell cycle are controlled by genes
  2. Normally, when cells have divided enough times to make enough new cells, they stop. But if theres a mutation in a gene that controls cell division, the cells can grow out of control
  3. The cell keeps on dividing to make more and more cells, which form a tumour
  4. Cancer is a tumour that invades surrounding tissue
70
Q

What are some cell cycle targets of cancer treatments?

A
  1. G1 (cell growth and protein production) - Some chemical drugs (chemotherapy) prevent the synthesis of enzymes needed for DNA replication. If these arent made, the cell cant enter the S phase, disrupting the cell cycle and forcing the cell to kill itself
  2. S phase (DNA replication) - Radiation and some drugs damage DNA. At several points in cell cycle (including just before and during S phase), DNA in cell is checked for damage. If severe damage is detected, the cell will kill itself - preventing further tumour growth.

AS Biology (12 decks)

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