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Ocr Gcse Biology > B2 > Flashcards

B2 Flashcards

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1
Q

How do particles in a gas or solution behave?

A
  • They are constantly moving, movement can be random so particles can move in all directions
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2
Q

What is the defenition for diffusion?

A

Diffusio in the net movement of particles from an area of high concentration to an area of low concentration. Moving down a conc gradient

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3
Q

When does diffusion continue until?

A
  • Concentration gradient is zero, conc of particles same everywhere
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4
Q

Is energy transferred during diffusion?

A
  • No its a passive process as it is the ordinary motion of particles
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5
Q

Where does diffusion occur in the body?

A
  • Glucose and blood for respiration is transported by blood and diffuses into cells
  • Some chemical reaction waste products are toxic, eg, CO2, it diffuses out respiring cells
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6
Q

What are 3 factors affecting rate of diffusion?

A
  • Distance
  • Conc gradient
  • Surface area
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7
Q

How does distance affect rate of diffusion?

A

To increase rate of diffusion
- Decrease distance particles need to move, less time shorter distance. E.g Capillaries 1 cell thick increases rate of diffusion gasses in and out blood

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8
Q

How does conc graident affect rate of diffusion?

A
  • Steeper conc gradient, greter net movement of particles. E.g. Plants use CO2 in photosynthesis, CO2 conc in plants drop increasig rate ofdiffusion CO2 into cells
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9
Q

How does surface are affect rate of diffusion?

A
  • Allows more space for diffusion, more patricles move in a period of time. E.g. Small intestine wall folde to increase surface area in cnotact with blood, increasing rate of diffusion of molecules
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10
Q

What is defenition of Osmosis?

A

Osmosis is net movement of water particles across a semi permeable memebrane from an are of high water potential to low water potential

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11
Q

How does water potential work?

A
  • Pure water highest water potential, all molecules free to move
  • Conc solution, lower water potential
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12
Q

What is a semi/partially permeable membrane?

A
  • Memebrane with small holes, only tiny molecules like water can pass through
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13
Q

Do water particles move both ways in osmosis?

A
  • Yes, as water molecules move randomly all the time

BUT net movement high water potential to low water potential

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14
Q

What happens to a plant cell if surroundings are more or less concentrated than cell contents?

A
  • Surroundings lower water potential, cell loses water by osmosis - turgor pressure falls, cells becomes flaccid - after cell wall colapses Cell is known as plasmolyed cell
  • Surroundings higher water potenial, cell takes water by Osmsis, turgor pressure increases, cell becomes firm and rigid
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15
Q

What happens to an animal cell if surroundings are more or less concentrated than cell contents?

A
  • Surroundings lower water potential, cell loses water by osmosis, becomes crenated(crinkles)
  • Surroundings higher water potential, cell takes up water, swells and may burst, lysis
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16
Q

Why is watering a plant extremly important (in terms of osmosis)?

A
  • Watering plant increases water potential of soil around it - plant cells draw in water by osmosis til they’re turgid - contents of cell push cell wall,turgor pressure, this supports plant
  • If no water in soil, cells become flaccid, plant starts to droop - but not comlete;y
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17
Q

Whats defenition of active transport?

A

Active transport is the movement of particles across a membrane against a concentration gradient using ATP released during respiration

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18
Q

What are 3 key features of active transport?

A
  • Particles transported agaisnt a conc gradietn
  • ATP is required - that comes from respiration
  • Process makes use of carrier proteins in cell memebrane
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19
Q

Why do cells that carry out a lot of active transport have high amounts of mitochondira?

A
  • So they can respire rapidly producing large amounts of ATP, rate at which actove transport occurs depends on rate of respiration to produce ATP
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20
Q

What are carrier proteins?

A
  • Special proteins that span the width of a memebrane
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21
Q

How do carrier protiens work in active transport?

A
  • Particular molecule cell requires binds to sppecific carrier protein
  • Energy transferred from energy to store to protein so it can chage shape or rotate
  • Carrier protein transports molecule to cell
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22
Q

How is active transport used during digestion?

A
  • In small intestine, carbs broken down to glucose
  • Glucose actively transported into bloodstream through villi
  • Blood takes glucose to where it is needed in body
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23
Q

How is active transport used in nerve cells?

A
  • Carrier protein pumps sodium ions out cell, same time potassium ions pumped back in
  • Sodium potassium pump plays big role in creating nerve impulses
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24
Q

How is active transport used in plants?

A

To take minerals from soil

  • Plants need nitrate ions forgrowth, soil water usually has lower conc of nitrate ions compared to plant
  • Root hair cels use active transport to move the ions across cell membrane into root cell
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25
Q

Why does mitosis occur?

A
  • To replace worn out cells, to repair damaged tissue and to enable the organism to increase in size
26
Q

What is mitosis?

A
  • Process by which cellsdivide, each cell divides to produce 2 indentical daughter cells - that are genetically identical to parent cell, they’re clones
  • Mitosis increases number of cellsin a multi cellular organism
27
Q

What are the 4 stages of the cell cycle

A
  • DNA replication
  • Movement of chromosomes
  • Cytokinesis
  • Growth of daughter cell
28
Q

Explain how DNA is replicated in DNA replication?

A
  • DNA molecule unzips to 2 strands
  • DNA bases in each strand exposed
  • Free nucleotides in nucleus line up to each strand, following complementary base pairing
  • Forms DNA base pairs
  • When strand comlete 2 identical molecules DNA formed
29
Q

How do chromosomes move in 2nd stage of mitosis?

A
  • Chromosomes line up across centre of cell
  • 2 identical copies each chromosome formed when DNA replicated, seperates and moves to opposite ends of cell
  • Each end contains full set of identical chromosomes
  • 2 new nuclei form
30
Q

What happens when a cell beocmes specialised?

A
  • its structure chnges so its better adapted to perform its function
  • makes organism more efficient as life roceses carried out more effectively
31
Q

What is differentiation?

A
  • Proccess by which cells changes to become speciaised for its job
32
Q

How are sperm cells specialised?

A

Sperm cellsare specialised to transfer gentetic material to ovum. Adaptations include:

  • Flagellum - Whips side to side propelling sperm 2 ovum
  • Lots of mitochondria - Respiration occurs in mitochondria, respiration transfers energy from chem store so flagelum can move
  • Acrosome - Stores digestvie enzymes that break vum wall, so sperm can incorporategenetic material
33
Q

Why is the cell cycle a cycle?

A
  • Following growth of daughter cell, the daughter cells will begin replicating their DNA and the cell cycle will continue
34
Q

How are fat cells specialised?

A
  • Small layer of cytoplasm currouning fat resevoir

- They can expand to 1000 times original size to store fat

35
Q

How are red blood cells specialised?

A
  • Bioconcave discs, pushed on each side mkaing bioconcave shape, increasing sa:vol, increasing rate of diffusion of oxygen into and CO2 out cell
  • Full of haeoglobin, protin binds to form oxyhaemoglobin - red
  • No nucleus, space for more haemoglobin
36
Q

How are cilliated cells specialised?

A
  • Located in airways, in between these are goblet cells, that porduce mucus - trapping dirt and bacteria
  • Cillia on topof cell sweep mucus to backof throat where swallowed
37
Q

How are palisade cells specialised?

A
  • Specialised for carrying out photosynthesis
  • Near surface of leaf, full of chloroplasts
  • Regular shapeallow close packing within leaf, maximising sunlight absorption
38
Q

What are stem cells and what do they do?

A
  • Stem cells are undifferentiated cells, that depending on intructions they are given - they can divide by mitosis to become newcells that can differentiate becomin specialised
39
Q

What are stem cellsused forin the body?

A
  • Used during development growth and repair
40
Q

What is special about embroynic stem cells?

A
  • They can divide by mitosis to produce all cells needed to makean organism - have ability to differentiate into all cell types
41
Q

Where are adultstemm cells found?

A
  • In various body tissues, brain, bone, marrow, skin, liver
42
Q

What can adult stem cells specialise into?

A
  • Only certain ones from the tissue they originally came form
43
Q

What happens to adult stem cells when an animal is fully grown?

A
  • Remain in non dvodding state for years

- If activated by disease, tissue injury they can start to divide and regenerate

44
Q

What are the cells that divide by mtosis in plants called?

A
  • Meristems, found in growing parts ofplant, roots and shoots
45
Q

Why can differentited plant cells not divide?

A
  • Their cell walls are too thick
46
Q

What type of cells do meristems produce?

A
  • Unspecialised stem cells able to specialise onto any plant cell, but can onoly do this when plant is alive
47
Q

Why is SA: VOL ration important?

A
  • Small organism have large sa: v, nutrients can diffuese directly into organism to live as diffusion distances are small
  • Larger organism, smaller sa:v, most multicellular rgasnism can’t rely on smple diffusion tolive, diffusion over great distance isn’t fast enough tomeet standaards
48
Q

How are alveoli specialised to maximise diffusion of CO2 and O2?

A

They have:

  • Enourmous surface area, lots of ubstance can move at once
  • Vey thinwalls, short distance to travel
  • Goodblood supply, maintains concentraiton gradient by removing 02and bringing in CO2
49
Q

How is absorption from digested food in small intestine to blood maximised? (diffusion rate)

A
  • They contain villi
  • Villi increase SA, s dissolved food molecules absorbed much quicker
  • Vili specialised, single layer of surface cells, very good blood supplyto assist quick absorption
50
Q

Why is crculatory system known as a closed system?

A
  • Blood remains within the structures
51
Q

What happens in the doubecirculatory system?

A
  • Deoxyganated blood first umped from heart to lungs, to take in O2, oxygenated blood returs to heart
  • 2nd, Heart pumps oxygenated blood to all other organs of body, bloodgives oxygen at cells, deox bloodreturnto heart to repeat
52
Q

Pros of double circulatory system?

A
  • returning blood to heart once ixygenated allows pumping of high pressure
  • increases rate of blood flowin tissues, more oxygen delivered to cells
53
Q

Why do ateries have a thick outer arteial wall?

A
  • To widthstand high pressurewaves caused from bloood leaving heart at high pressure
  • Wall expands with each contraction, then snaps back pushing blood forward
54
Q

What is blood made upof?

A
  • Red blood cell, fit through luen of capillary 1at a time
  • White blood cells, contain nucleus, fight disease making anti bodies or changing shape
  • PLasma, many materialstransported in, amiino acids, glucose, hormones, antibodies
  • Platelelts, tiny structures that help bloodclot
55
Q

What transport systems do plants have?

A
  • Plants have 2 seperate types of transport vessels - xylem and phloem, for transporting things around
  • Both types of vessels goto every part of plant but are completely seperate
56
Q

What do xylem tissue transport and how do they get the materials?

A
  • trasports water and miner ions from roots to stem leaves and flowers in transpiration stream
  • Water diffuses to roots by osmosis, mineral ions taken up by active transpot
57
Q

What do phloem tissues transport and how do they get thematerials?

A
  • Transport dissolved sugars made in photosynthesis and other soluble food molecules from leaves to all areas of plant
  • This is translocation
58
Q

What is the vascular bundle?

A
  • Structure formed by phloemand xylem tissue
59
Q

What is the structure of the xylem?

A
  • Made of dead cells, joined with no end walls between and lumen down middle
  • Thick side walls made of cellulose - strong and stiff, giving plant support - cell walls also stregthened by lignin
60
Q

What is the structure of phloem?

A
  • Columns of living cells, ‘sieve tube elements’, with seive plates - allowing sugars to flow through
  • Sieve tubes can’t survive on their own, have no nucleus, rely on companion cell, carrying out living functiosn
61
Q

How do vascular bundles provide support?

A
  • In leaf, form network supporingsifter leaftissue
  • in stem, located outer edgegiving resistance to bendign in breeze
  • in root, found in centre, root canact as anchor - rootcan bend and plant moves in wind

Ocr Gcse Biology (4 decks)

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