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Gcse Biology > B2.1 - supplying the cell > Flashcards

B2.1 - supplying the cell Flashcards

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1
Q

Is diffusion a passive/active process

A

= Passive process, no energy is transferred

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2
Q

Factors to increase rate of diffusion:

A
  • decrease distance the particles need to move
  • increase concentration gradient
  • increase surface area
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3
Q

Describe how diffusion links to cells:

A

Diffusion is one process by which particles enter/leave cells
- pass through cell membrane from region of high conc to region of low conc

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4
Q

Describe examples of diffusion into cells

A

All cells need glucose & oxygen for respiration

  • Blood transports these around your body
  • Then substances diffuse into cells that need them
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5
Q

Why might diffusion occur out of cells? Describe an example of diffusion out of cells:

A

Some chemical reactions that happen inside cells make waste products, can be toxic
- CO2 is poisonous at high levels, diffuses out of respiring cells

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6
Q

Osmosis:

A

= diffusion of water molecules across a selectively permeable membrane (into/out of cells)

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7
Q

Water potential:

A

= conc of free water molecules

(when solute dissolves in water, water molecules cluster around solute molecules, leaves fewer water molecules free to diffuse to other areas)

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8
Q

What has the highest water potential?

A

= pure water

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9
Q

What is the relationship between concentration and water potential?

A

More concentrated solution = lower water potential

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10
Q

Explain osmosis in terms of water potential:

A

= movement of water molecules from a high water potential to a low water potential

Greater difference in water potential = greater rate of osmosis

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11
Q

Osmosis in PLANT cells:

A
  • surrounding solution less concentrated (higher water potential)
    = takes up water by osmosis, turgor pressure (pressure in cell) increases, becomes firms/turgid
  • surrounding solution more concentrated (lower water potential)
    = loses water by osmosis, turgor pressure falls, becomes flaccid(soft), eventually cell contents collapse away from cell wall = plasmolysed cell
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12
Q

Osmosis in ANIMAL cells:

A
  • surrounding solution less concentrated (higher water potential)
    = takes up water by osmosis, swells/may burst = lysis
  • surrounding solution more concentrated (lower water potential)
    = loses water by osmosis, becomes crenated(crinkles)
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13
Q

Active transport:

A

= allows cells to move substances from an area of low conc to an area of high conc, against concentration gradient (energy must be transferred from energy store)

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14
Q

3 key features of active transport:

A
  • particles are transported (pumped) against a concentration gradient
  • ATP required (from respiration)
  • process makes use of carrier proteins in cell membrane
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15
Q

What do cells that carry out lots of active transport contain and why?

A

= lots of mitochondria

- can respire rapidly to produce large quantities of ATP

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16
Q

What does the rate of active transport depend on?

A

= rate of respiration to produce required ATP

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17
Q

Carrier proteins:

A

= special proteins that span width of cell membrane,

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18
Q

Describe how carrier proteins carry out active transport:

A
  • particular molecules cell requires binds to specific carrier protein
  • energy transferred from ATP to protein so it can change shape/rotate
  • carrier protein transport molecule into cell
  • rotates back again (using more energy/ATP)
19
Q

Example of active transport in digestion:

A
  • in small intestine, carbohydrates broken down into glucose
  • glucose is actively transported into bloodstream through the villi
  • blood takes glucose to wherever it’s needed in body
20
Q

Example of active transport in nerve cells:

A
  • carrier protein actively pumps sodium ions out of cell as potassium ions pumped back in
  • sodium potassium pump plays important role in creating nerve impulses
21
Q

Examples of active transport in plants:

A
  • to take minerals in from soil
  • plants need nitrate ions to make proteins for growth
  • normally lower conc in soil water surrounding roots than in plant
  • plant root hair cells use active transport to move nitrate ions across cell membrane into root cell
22
Q

Mitosis

A

= process by which body cells divide

To replace worn out cells, repair damaged tissue, enable organism to increase in size

23
Q

What does each cell divide into?

A
  • each cell divides to produce two identical daughter cells = clones
  • increases number of cells in multicellular organism
24
Q

What is the cell cycle, name the 4 stages:

A

= process of cell growth & division (cell cycle = daughter cells continue)

  • DNA replication
  • movement of chromosomes
  • cytokinesis
  • growth of daughter cell
25
Q

DNA replication:

A
  • DNA molecules unzips forming 2 separate strands
  • DNA bases on each strand are exposed
  • free nucleotides in nucleus line up against each of the strands following rule of complementary base pairing (A-T, C-G)
  • forms DNA base pairs
  • when whole strand complete, there are 2 identical molecules of DNA
  • DNA molecules zip back up
26
Q

Movement of chromosomes:

A
  • chromosomes line up across centre of cell
  • the 2 identical copies of each chromosome separate & move to opposite ends of cell
  • each end now contains full set of identical chromosomes
  • 2 new nuclei then form
27
Q

Cytokinesis:

A
  • cell membrane pinches inwards to separate & enclose the 2 new nuclei
  • pinches off to split original cell into 2 new, genetically identical daughter cells
28
Q

Example of where mitosis occurs rapidly:

A
  • humans constantly lose cells from surface of skin
  • mitosis occurs constantly to replace these cells

(Approx 300 million body cells die & are replaces evert minute)

29
Q

Cell differentiation:

A

= cells becomes specialised to perform a particular job, during the development of a multicellular organism

30
Q

Examples of cells that become so specialised they can only perform one function in the body:

A
  • sperm cell
  • fat cell
  • red blood cell
  • ciliated cell
  • palisade cell
31
Q

Sperm cell differentiation & adaptations:

A

= specialised to transfer to genetic material from male to ovum(egg)

  • flagellum, propels sperm to ovum
  • lots of mitchondria, respiration reactions transfer energy from chemical stores to move flagellum
  • acrosome, stores digestive enzymes which break down outer layers of ovum to allow sperm to transfer its genetic material
32
Q

Fat cell differentiation & adaptations:

A

= specialised to store fat

  • small layer of cytoplasm surrounding a fat reservoir, so can expand up to 1000 its original size as they fill with fat
33
Q

Red blood cell differentiation & adaptations:

A

= specialised to transport oxygen around body

  • biconcave discs, biconcave shape = increases surface area to volume ration, increases diffusion of oxygen into cell, carbon dioxide out of cell
  • packed full of haemoglobin, protein bings to oxygen to form oxyhaemoglobin(bright red)
  • no uncles, more space for haemoglobin molecules
34
Q

Ciliated cells differentiation & adaptations:

A

= specialised to sweep mucus, produced by goblet cells, away from lungs to back of throat, mucus then swallowed, bacteria killed in stomach

  • cilia (tiny hairs) on top of cell sweeps mucus
35
Q

Palisade cells differentiation & adaptations:

A

= specialised for carrying out photosynthesis

  • found near surface of leaf, closer to sunlight
  • packed full of chloroplast, absorbs more sunlight & converts to more energy
  • regular shape, to allow close packing within leaf, maximising absorption of sunlight
36
Q

Stem cells:

A

= undifferentiated cells

Can develop into any type of specialised cells, form all types of tissues/organs (divide by mitosis, forming cells which develop into specialised cells)

37
Q

Embryonic stem cells:

A
  • found in embryos
  • divide by mitosis to produce all cells needed to make an organism
  • have the ability to differentiate into all cell types
38
Q

Adult stem cells:

A
  • found in various body tissues (brain, bone marrow, skin, liver)
  • ability to differentiate into some different types for cell, but not all
39
Q

What do blood stem cells (in bone marrow) differentiate into:

A
  • red blood cells
  • white blood cells
  • platelets
40
Q

What are the main purpose of adult stem cells:

A

= act as a repair mechanism for the Boyd

  • once animal fully grown, adult stem cells remain in non-dividing state for years
  • if activated by disease/tissue injury, cells start to divide
  • generates many cells, can be used to repair damage
41
Q

Where are stem cells found in plants, why?

A

= meristems (shoot/root tips)

= particular part of plant that continues to grow throughout their life

42
Q

How are stem cells in plants different to normal plant cells:

A
  • very thin walls
  • small vacuoles
  • no chloroplasts
43
Q

why can’t differentiated plant cells divide?

A

= cell walls are thick & rigid

Gcse Biology (15 decks)

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