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Biology OCR GCSE > B2.1 Supplying The Cell > Flashcards

B2.1 Supplying The Cell Flashcards

1
Q

Diffusion

A

Passive net overall movement of particles from a region of high concentration to a region of low concentration down a concentration gradient

Transports Carbon dioxide, oxygen, water, food substances, wastes: urea

No energy needed

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2
Q

Particles move ……. and …….. by diffusion

A

Particles move constantly and randomly by diffusion

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3
Q

Key gas we need to diffuse from our lungs to our blood stream

A

Oxygen

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4
Q

Key nutrient diffused from our blood stream to muscle cells

A

Glucose

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5
Q

Factors affecting diffusion

A

Surface area

Temperature

Concentration gradient

Distance

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6
Q

Key adaptations of the body to facillitate diffusion

A

Alveoli
Very thin - small distance to diffuse over
Covered by a network of fine capillaries - diffuse straight into bloodstream, maintains concentration gradient
Moist - allows gases to dissolve
Large combined surface area

Small intestines
Villi - increases surface area, therefore increases volume of nutrients that can be absorbed
Good blood supply – substances diffuse straight into the bloodstream, maintains concentration gradient

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7
Q

Role diffusion plays in nerve impulses

A

Diffusion allows a nerve impulse to travel between two neurones at a synapse
Neurotransmitter molecules diffuse from vesicles towards the neurotransmitter receptors, moving from an area of high concentration to low concentration

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8
Q

How the placental organ is adapted to maximise diffusion

A

A large surface area between it and the uterus wall
Villi (finger like projections that extend into the uterus wall), which further increase the surface area of the placenta
A rich supply of maternal blood vessels

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8
Q

Role diffusion plays in enabling photosynthesis

A

Carbon dioxide diffuses in through stomata
Oxygen and water diffuse out of stomata
During photosynthesis, level of CO2 is low inside leaf, creating a big concentration gradient so CO2 diffuses into the cell

Time of day affects the state of stomata
At night, they close because, in the absence of sunlight, carbon dioxide is not required for photosynthesis
At this time only objective is preventing water loss

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9
Q

Osmosis

A

Special type of diffusion
Diffusion of water molecules across a partially (selectively) permeable membrane from an area of high water concentration to an area of lower water concentration down a concentration gradient

Transports ONLY WATER
No ATP energy needed

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10
Q

Hypertonic

A

Fluid has a higher osmotic pressure (lower water potential) than a particular fluid, typically a body fluid or intracellular fluid

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11
Q

Hypotonic

A

Fluid has a lower osmotic pressure (higher water potential) than a particular fluid, typically a body fluid or intracellular fluid

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12
Q

Turgid

A

When water enters the cell by osmosis and fills the vacuole
This pushes against the cell wall, making the cell turgid

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13
Q

Flaccid

A

When water moves out of the cell by osmosis
Vacuole shrinks and cell becomes flaccid

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14
Q

Plasmolysis and crenation

A

Plasmolysis happens if too much water leaves a PLANT cell, and cytoplasm moves away from cell wall
Crenation is same as above but for animal cells

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15
Q

Isotonic solution

A

Has same osmolarity, or solute concentration, as another solution

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16
Q

Lysis

A

When an ANIMAL cell is placed in a hypotonic solution,
causing too much water to enter cell by osmosis and the cell to swell and burst

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17
Q

Crenation

A

When an animal cell is placed in a hypertonic solution,
causing too much water to leave the cell by osmosis making the cell shrink and shrivel

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18
Q

Osmosis takes place over a…

A

Selectively/semi-permeable membrane

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19
Q

Active transport

A

Transport of particles from an area of low concentration to an area of high concentration,
against a concentration gradient
ATP energy needed

Examples:
Transports mineral ions into plant roots
Glucose from the gut into intestinal cells, from where it moves into the blood

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20
Q

Carrier proteins

A

Protiens embembedded within the cell surface membrane
They bind with useful molecules and then use ATP to rotate or change shape to transport the molecule into the cell
Allow transport of useful molecules against a concentration gradient

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21
Q

Example of active transport in plants

A

Root hair cells - Transport of mineral ions from low concentration in soil to higher concentration in root hair cell

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22
Q

2 examples of active transport in animals

A

Nerve cells - active transport used to pump sodium & potassium ions required to create nerve impulses
Digestion - active transport used to transport the final products of digestion into the bloodstream through villi

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23
Q

Why do cells that carry out active transport contain a lot of mitochondria

A

Mitochondira produce energy and energy is required for active transport to take place

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24
Mitosis
Nuclear cell division that is used by cells for growth, repair, and healing and asexual reproduction Stage within cell cycle
25
Cell cycle
Process of cell growth and division for growth and repair of body cells Has three main stages interphase, mitosis, cytokinesis Results in 2 identical daughter cells
26
Why interphase is important
Stage of growth (G1) and replication (S) Before a cell can divide it needs to grow and duplicate all of its cellular contents
26
Homologous chromosomes
Pair of chromosomes, one from the mother, and one from the father, which are very similar to one another and have the same size and shape Most importantly, they carry the same type of genetic information: they have the same genes in the same locations
27
Diploid and haploid
Diploid = full set of chromosomes, 23 pairs/46 strands in humans Haploid = half of the full set of chromosomes, 23 strands in humans
28
Name given to 2 identical copies of each chromosome
Sister chromatids
29
Name of attatchment between sister chromatids
Centromere
30
Name given to the way in which DNA replicates
Semi-conservative
31
Semi-conservative replication
After replication each strand has one original strand, and one new ‘complementary’ strand
32
Key stages in DNA replication
Double helix untwists Hydrogen bonds between bases broken, DNA ‘unzips’ Bases exposed on each of two strands Free nucleotides form hydrogen bonds with the exposed base (A-T, C-G) Covalent bonds form between nucleotides to form ‘backbone’
33
What happens during cell cycle after DNA replication but before mitosis
Replicated DNA is checked for errors and corrections made to avoid mutations being passed on to new cells
34
What happens in each key stage of mitosis
Prophase - Chromosomes align in the middle of the cell Metaphase - Spindle fibres pull the arms of each chromosome to opposite ends of the cell Anaphase - Membranes form around each of the sets of chromosomes - these become the nuclei of the two new cells – the nucleus has divided Telophase - Cytoplasm and cell membrane divide to produce two identical daughter cells, each containing the same chromosomes
35
Cytokinesis
Formation of 2 new nuclear membrane, and pinching in of the cell membrane to separate and enclose the 2 new nuclei, to separate the 2 new cells
36
Why chromosome number must stay the same when cells divide by mitosis
To ensure the cells produced are normal body cells, identical to their parent cell
37
When do the sister chromatids condense
During prophase, sister chromatids condense to form x-shaped chromosomes linked by a centromere
38
Longest stage of the cell cycle called
Interphase
39
During what stage does the G1, S, and G2 phases happen
Interphase
40
Where in a plant does mitosis take place
Tips of roots and shoots Meristems
41
How mitosis can be easily observed in a school laboratory
Be preparing a root squash Method of preparing root tip meristem cells to observe them using a light microscope at different stages of the cell cycle
42
Differentiation
Process by which stem cells become specialised into different types of cells. They become more suited for a specific role
43
What is produced once a sperm cell enters an egg cell
Zygote
44
By what process does a zygote divide
Mitosis
45
The zygote is composed of what type of cells
Stem cells
46
When does a zygote become an embryo
3-5 days after fertilisation
47
How the cells of a zygote differ from an organisms somatic cells
They are unspecialised and can therefore differentiate into any type of specialised cell
48
Where stem cells are found in animals
Embryos - Embryonic stem cells Brain, bone marrow, skin, liver Adult stem cells N.B Multipluripotent stem cells have also now been isolated in the umbilical cord
49
Where stem cells are found in plants
The meristems - unspecialised cells found in the root tips, shoot tips and in rings around the stem
50
How do the cells in the meristem differ from normal plant cells
Differentiated plant cells cannot divide as they have thick & rigid cell walls Meristem cells are much smaller, have thin walls, small vacuoles and no chloroplasts
51
State a key difference between specialised plant and animal cells
Once differentiated animal cells can only divide to produce that specialised cells Plant cells however, under the right conditions, can become unspecialised and then re-specialise in order to adapt to their environment
52
Types of specialised cells that a stem cell could differentiate into
Animal Gamete e.g sperm cell, ovum Muscle cell Adipocyte cell Osteoblast Blood cell e.g erythrocyte, neutrophils Nerve cell Cilliate epithelial cell Goblet cell Plant Palisade cells Root hair cell Guard cell
53
How is a red blood cell specialised for its role
Biconcave discs - increases surface area and allows for the rapid diffusion of oxygen Haemoglobin - binds to and releases oxygen No nucleus - more room for oxygen transport
54
How is sperm cell is specialised to transfer genetic material
Flagellum - movement Mitochondria - provide energy for movement Acrosome - contains digestive enzymes to allow breakdown the outer membrane of ovum
55
How an adipocyte specialised for its role
Can expand to 1000 times original size Small layer of cytoplasm Contains a fat reservoir
56
What is the function of a goblet cell
Produces mucus to trap dust mucus and bacteria which the cillia then waft back up the throat to be swallowed
57
How palisade cells are adapted for their function
Regularly shaped - can be closely packed cells that form a continuous layer at top of leaf Large surface area - able to absorb more light for photosynthesis Packed with chloroplasts - for photosynthesis
58
How are root hair cells adapted for their function
Surround the stoma and regulate the rate of transpiration and CO2 uptake Inner wall thicker causing the ‘bean-like’ shape and gap when turgid Open to allow exchange Close to prevent exchange
59
What type of cells can adult stem cells differenetiate into
Only into cells from the type of tissue where they are found
60
Why are adult stem cells not as useful for medical research
They only differentiate into a narrow range of cell types: Only used for replacing damaged cells
61
What are embryonic stem cells and why are they more useful to stem cell research
Cells taken from 3-5 day old zygotes: Can specialise into any type of specialised cells Potential to cure and treat disease
62
Why are embryonic stem cells controversial
Embryos are killed to obtain the cells
63
What are induced-pluripotent stem cells and how may they be useful
Adult somatic cells altered to have properties of embryonic stem cells May allow use of reprogrammed cells instead of embryonic stem cells Solution to immune system rejection of ‘foreign’ stem cells
64
Exchange surfaces
Thin membrane reduces the diffusion distance Large surface area allows a greater amount of substance to diffuse at the same time Exchange surfaces: Surfaces that are adapted to maximise the efficiency of gas and solute (a substance dissolved in a liquid) exchange Blood vessels: In animals, for substances that are exchanged through blood, exchange surfaces are densely packed with these to replenish the blood supply Ventilation: This process helps to maintain a high concentration gradient and increase the rate of exchange when a gas is exchanged
65
Examples of specialised exchange surfaces
Lungs Roots Leaves Gills Small intestine

Biology OCR GCSE (16 decks)

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