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B2 Flashcards

1
Q

Describe the process of DNA replication

A

DNA molecule unzips —> forms 2 strands
DNA bases on each strand are exposed
Free nucleotides in nucleus line up against strands - follows complementary base pairing
This forms DNA base pairs
Once complete there are 2 identical molecules of DNA

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2
Q

Define mitosis

A

A special type of nuclear division

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3
Q

What are the stages of mitosis?

A

Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

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4
Q

What happens in interphase?

A

Each chromosome replicates so it contains 2 identical chromatids
Interphase=Introduction

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5
Q

What happens in prophase?

A

Chromosomes become visible by shortening and thickening
Prophase=Present

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6
Q

What happens in metaphase?

A

Chromosomes line up along centre of parent cell - moved by spindle fibres
Metaphase=Middle

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7
Q

What happens in anaphase?

A

The 2 chromatids in each chromosome are pulled apart by spindle fibres to opposite poles of cell
Anaphase=Apart

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8
Q

What happens in telophase?

A

There are now two nuclei
Telophase=Two

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9
Q

What happens in cytokinesis?

A

Cell splits to produce 2 daughter cells, each containing the same chromosomes
Cytokinesis=Cut

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10
Q

What is a specialised cell

A

A type of cell that performs a unique and special function

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11
Q

What are 3 examples of specialised cells?

A

3 from:
Sperm cell
Fat cell
Red blood cell
Ciliated cells
Palisade cells

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12
Q

What is cell differentiation?

A

The process by which cells become specialized to perform specific functions in an organism

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13
Q

What is a multicellular organism?

A

An organism with more than one cell

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14
Q

What is a stem cell?

A

An undifferentiated cell
Divides by mitosis forming cells which can differentiate into any type of specialised cell

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15
Q

What does the body use stem cells for?

A

Development
Growth
Repair

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16
Q

What are embryonic stem cells

A

Stem cells derived from 5-7 day old blastocysts
They’re totipotent - capable of generating any cell in the body

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17
Q

What are adult stem cells

A

Found in various body tissues eg brain, bone marrow, skin, liver
Able to develop into some types of cell but not as many as embryonic

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18
Q

Once an animal is fully grown, many adult cells…

A

Remain in a non-dividing state for years

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19
Q

What are meristems (plant stem cells)

A

Regions of the plant that continue to grow throughout their lives - root tips + shoot tips

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20
Q

How do meristems look different to normal plant cells

A

Smaller
Have thin walls
Small vacuoles
No chloroplasts

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21
Q

Why do people object to using stem cells

A

Adult stem cells - people object for religious reasons + benefits may not be very great
Embryonic - embryo can’t consent + it’s a waste of a potential life

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22
Q

What is diffusion

A

The net movement of particles from an area of high concentration to an area of low concentration

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23
Q

Diffusion happens in what states of matter

A

Liquid and gas because the particles are free to move

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24
Q

What are examples of molecules that can diffuse through a cell membrane

A

Glucose
Amino acids
Water
Oxygen

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25
What are examples of molecules that cannot fit through a cell membrane
Starch Proteins
26
What is active transport
The movement of particles across a membrane against a concentration gradient, using ATP released during respiration
27
How does active transport work in the digestive system
When there’s higher concentration of nutrients in the gut they diffuse into the blood Sometimes there’s lower concentration - active transport allows nutrients to be taken into the blood It requires ATP from respiration
28
What is osmosis
The net movement of water molecules across a partially permeable membrane from a region of high water concentration to low water concentration
29
What is a partially permeable membrane
A membrane which only allows certain molecules through
30
What is water potential
The potential of water molecules to diffuse in or out of a solution
31
If a solution has a high water potential…
There’s a high concentration of water molecules
32
If a solution has a low water potential…
It has a low concentration of water molecules
33
How does watering a plant affect the plant cells
Increases water potential of soil Plant cells draw in water by osmosis until they become turgid Contents of cell push against cell wall - this is called turgor pressure which helps support plant tissues
34
If there’s no water in the soil, how does this affect plant cells
A plant starts to wilt because the cells have become flaccid - start to lose water The plant doesn’t completely lose shape because the inelastic cell wall keeps thing in position
35
How can animal cells be affected by water potential
They can burst if they’re surrounded by a solution with a higher water potential
36
How can you investigate osmosis
1. Prepare sucrose solutions (different concentrations) 2. Measure mass of each piece of food eg potato before putting in solution 3. Place in solution 4. Remove and dry 5. Weigh again and record change in mass
37
In an osmosis investigation, what are the independent, dependent and control variables?
Independent - concentration of sucrose solution Dependent - mass of potato Control - everything else
38
How do you calculate percentage change in mass?
% change = final mass - initial mass / initial mass x100
39
If the % change in mass is positive…
It has gained mass
40
What results would you see from an osmosis investigation
Potato in solutions with higher water potential will have drawn in water by osmosis - mass increase In solutions with lower water potential will have lost water - mass decrease
41
What factors affect rate of diffusion
Surface area to volume ratio Temperature Concentration gradient
42
How does surface area to volume ratio affect rate of diffusion
Rate of diffusion / osmosis / active transport is higher in cells with larger sa:v ratio
43
How does temperature affect rate of diffusion
As particles get warmer they have more kinetic energy so move faster
44
How does concentration gradient affect rate of diffusion
Substances move in and out of cells faster if there’s a big difference between inside and outside of cell
45
Proteins can’t be stored by the body so…
Excess amino acids are converted in the liver into fats and carbohydrates which can be stored
46
Why is diffusion quick in single celled organisms
Substances only travel a short distance Large SA:V ratio
47
Why is diffusion slower in multicellular organisms
Longer distance to travel Lower SA:V ratio
48
Instead of exchanging substances through their outer membrane, multicellular organisms…
Need specialised exchange organs, each with a specialised exchange surface Transport systems to carry materials from exchange organs to body cells and to remove waste
49
How are exchange surfaces adapted to maximise exchange
Thin - short distance to travel Large surface area - lots of substance can move at once Often ventilated
50
How do lungs exchange gases
Contain alveoli These are specialised to maximise diffusion CO2 diffuses out of blood into alveolus O2 diffuses out of alveolus into blood
51
What is the role of the lungs
To transfer oxygen to the blood and remove waste carbon dioxide from it
52
What are alveoli
Millions of small air sacs in the lungs where gas exchange takes place
53
How are alveoli specialised
Large surface area Very thin walls Moist lining for dissolving gases Good blood supply
54
The blood passing next to the alveoli…
Has just return from the body via the heart Contains lots of CO2 and little O2
55
How does the small intestine exchange substances
Dissolved food molecules are absorbed out of digestive system into blood Inside of small intestine covered in tiny projections called villi Increase surface area - food molecules are absorbed more quickly into the blood
56
How are villi adapted
Have single layer of surface cells Have good blood supply to assist quick absorption
57
How are leaves adapted for efficient gas exchange
Leaves are broad - large surface area Thin - gases travel short distance Air spaces inside leaf - lets gases move between cells Stomata - let gases diffuse in and out, + allow water to escape (transpiration)
58
When plants photosynthesise they…
Use CO2 and produce O2
59
When plants respite they
Use up O2 and produce CO2 as a waste product
60
How are root hair cells adapted to exchange substances
Big surface area for absorbing water and mineral ions Usually higher water concentration in soil so water drawn in by osmosis Mineral ions move by active transport
61
The circulatory system is made up of…
Heart, blood vessels and blood
62
How does the double circulatory system work
The heart pumps deoxygenated blood to lungs to take in oxygen, it then returns to heart Then the heart pumps oxygenated blood around the body, the blood gives up its O2 and the deoxygenated blood returns to the heart
63
What are the advantages of a double circulatory system
Returning blood to heart after it’s gained O2 from lungs means it can be pumped around body at higher pressure This increases blood flow to tissues so more O2 can be delivered to cells
64
Why is a double circulatory system important for mammals
Because they use a lot of oxygen maintaining their body temp
65
Why does the heart have valves
To make sure blood flows in right direction
66
When the ventricles contract…
The tricuspid and bicuspid valves close and the semi-lunar valves open. This prevents backflow
67
How does the heart work
1. Blood flows into the 2 atria from the vena cava and pulmonary vein 2. Atria contract, pushing blood into the ventricles 3. Ventricles contract forcing blood into pulmonary artery + aorta - out of heart 4. Blood flows to organs through arteries, returns through veins
68
The heart is made of
Cardiac muscle
69
The cardiac muscle cells contain
Lots of mitochondria to provide cells with ATP
70
What are the three types of blood vessel
Artery Vein Capillary
71
Arteries carry blood ___ from the heart
Away
72
Capillaries are involved in
The exchange of materials at the tissues
73
Veins carry blood ___ the heart
To
74
Describe features of arteries
Strong elastic walls due to high pressure Walls are thick compared to lumen Arteries branch into arterioles
75
Describe features of capillaries
Arterioles branch into capillaries One cell thick wall, carry blood close to cells to exchange substances Permeable walls Small lumen Branch into venules
76
Describe features of veins
Venules join up to form veins Blood is lower pressure so walls less thick than arteries Bigger lumen to help blood flow despite lower pressure Valves to stop backflow
77
How does total cross sectional area of vessels affect blood flow
As total cross sectional area increases, mean velocity of blood decreases
78
Why does blood flow slowly through capillaries
Although they’re tiny, there are so many that the total cross sectional area is huge Blood flows slowly allowing more time for exchange of substances
79
The mean pressure of blood is highest in arteries because
They’re closest to heart but larger total cross sectional area of capillaries causes pressure to fall
80
What is plasma
A pale yellow liquid transporting substances like red blood cells, water, digested food products, CO2, urea etc
81
What is the role of red blood cells
Transport oxygen from lungs to body Small with biconcave shape to give large surface area : volume ratio No nucleus - space for more haemoglobin so they can carry more O2
82
What are phloem tubes for
Transporting food
83
Describe features of phloem
Made of columns of living cells These have perforated end plates to allow substances to flow through Transport food substances (mainly sugars) up and down stem to growing and storage tissues
84
The movement of food substances around a plant is known as
Translocation
85
What do xylem cells do
Take water up the plant
86
Describe features of xylem
Made of dead cells with no end walls between them Thick side walls made of cellulose - strong and stiff to support plant Cell walls also strengthened with lignin Carry water + minerals from roots to leaves in the transpiration stream
87
What is transpiration
The loss of water from a plant
88
Transpiration is caused by
The evaporation and diffusion of water from a plant’s surface
89
Most transpiration happens at
The leaves
90
Why is there a constant transpiration stream through the plant
Evaporation and diffusion creates shortage of water in leaf More water drawn up through xylem vessels to replace it Constant transpiration stream
91
What are benefits of the transpiration stream for the plant
Constant water stream keeps plant cool Constant supply of H2O for photosynthesis Turgor pressure in plant cells - support plant and stop it wilting Minerals needed can be brought in along with water
92
Factors that affect transpiration rate
Light intensity Temperature Air movement
93
How do plants reduce water loss
Waxy cuticle makes upper surface waterproof Stomata are on lower surface of leaf where it’s darker and cooler Plants in hot climates have smaller or fewer stomata

Biology 🧬 (9 decks)

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