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Biology GCSE OCR Gateway A > B2 - Scaling up > Flashcards

B2 - Scaling up Flashcards

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1
Q

What is diffusion and some examples?

A

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient. Examples include glucose and oxygen diffusing into cells that need them. The lung is also an example of oxygen and Co2 diffusing

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2
Q

What is osmosis?

A

Osmosis is the net movement of water particles from an area of high water potential to low water potential across a semi-permeable membrane down a concentration gradient

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3
Q

How does osmosis occur in plant cells?

A
  • When the surroundings have a higher water potential, water diffuses into the cell via osmosis, the pressure(turgor pressure) in the cell increases, the cell becomes firm or turgid
  • When the surroundings have a lower water potential, water diffuses out of the cell via osmosis, the turgor pressure falls, the cell becomes flaccid
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4
Q

How does osmosis occur in animal cells?

A
  • When surroundings have a higher water potential, water diffuses into the cell via osmosis, the cell swells and may burst, this is called lysis
  • When the surroundings have a lower water potential, water diffuses out of the cell via osmosis, the cell becomes crenated
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5
Q

What is active transport?

A

Active transport allows cells to move substances from an area of low concentration to high concentration, against a concentration gradient therefore energy must be used

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6
Q

What are the 3 key features of active transport?

A
  • Particles are transported against a concentration gradient
  • ATP is required which comes from respiration
  • The process makes use of carrier proteins in the cell membrane
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7
Q

What are carrier proteins?

A
  • Special proteins that span the width of a cell membrane
  • A particular molecule that the cell required binds to a specific carrier protein
  • Energy is transferred from an energy store so the protein is able to change shape or rotate
  • The carrier protein transports the molecule into the cell
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8
Q

Examples of active transport:

A
  • During digestion glucose is actively transported into the blood stream through the villi
  • Plants use active transport to take in minerals from the soil
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9
Q

What is mitosis?

A

Mitosis is the process by which body cells divide(growth, repair). Each cell divides to produce two identical daughter cells which are genetically identical to the parent cell(clones)

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10
Q

What are the 4 stages of the cell cycle?

A

DNA replication, movement of chromosomes, cytokinesis and growth of the daughter cell

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11
Q

How is DNA replicated for mitosis?

A
  • The DNA molecule unzips forming two separate strands
  • The DNA bases on each strand are exposed
  • Free nucleotides in the nucleus line up against each of the strands following the rule of complementary base pairing(A-T, C-G)
  • This forms DNA base pairs
  • When the whole strand is complete there are two identical molecules of DNA
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12
Q

How do the chromosomes move in mitosis?

A
  • The chromosomes line up across the centre of the cell
  • The two identical copies of each chromosome, formed when the DNA replicated, separate and move to opposite ends of the cell
  • Each end contains a full set of chromosomes
  • Two nuclei then form
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13
Q

What is cytokinesis?

A

After the movement of chromosomes the cell membrane pinches inwards to separate and enclose the two nuclei. Then pinches off to form two genetically identical daughter cells

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14
Q

What does it mean when a cell differentiates?

A

It becomes specialised to perform a particular job

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15
Q

Describe the function of a sperm cell and how it is specialised?

A

A sperm cell is specialised to transfer genetic material from the male to the ovum

  • flagellum - allows the sperm cell to move towards the ovum
  • lots of mitochondria - respiration which transfers energy happens in the mitochondria and is needed so the sperm can move
  • acrosome - stores digestive enzymes which are needed to break down the outer layers of the ovum
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16
Q

Describe the function of a fat cell and how it is specialised?

A

A fat cell is specialised to store fat which can be used as energy to keep the animal warm, and to help it survive when food is short
- has a small cytoplasm surrounding a large fat store which can expand up to 1000 times its original size

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17
Q

Describe the function of a red blood cell and how it is specialised?

A

Red blood cells are specialised to transport oxygen around the body

  • biconcave discs - increases surface area to volume ratio increasing the rate of diffusion for oxygen to diffuse in and carbon dioxide or diffuse out of cells
  • packed full of haemoglobin which binds to oxygen
  • no nucleus so there is more space to contain haemoglobin molecules
18
Q

Describe the function of a palisade cell and how it is specialised?

A

Palisade cells are specialised for carrying out photosynthesis

  • found near the surface of the leaf
  • packed full of chloroplasts
  • regular shape to allow close packing within the leaf to maximise the absorption of sunlight
19
Q

What is a stem cell and what is it used for?

A

A stem cell is an undifferentiated cell, they divide by mitosis forming cells which then differentiate and become specialised. They are used by the body during development, growth and repair

20
Q

What are the two main types of stem cells in animals and where are they found?

A
  • Embryonic stem cells are found in animals and can differentiate into any cell type
  • Adult stem cells are found in various body tissues such as brain, liver, bone marrow and skin and can differentiate into some types of cell but not as many as embryonic
21
Q

Where are stem cells found in plants?

A
  • Stem cells are found in the meristems of plants
  • Meristems are the areas of a plant that continue to grow such as root tips, shoot tips
  • The stem cells have thin walls, small vacuoles and no chloroplasts
22
Q

Why do multi-cellular organisms need exchange surfaces unlike uni-cellular organisms?

A

Smaller organisms have a higher SA:V ratio so nutrients can diffuse straight into them fast enough to be able to sustain life. However in multi-cellular organisms there is a lower SA:V ratio, diffusion over this distance cannot happen fast enough to meet all the cells demands so they need exchange surfaces

23
Q

What are exchange surfaces?

A

They are adapted to maximise the rate of diffusion and increase the SA:V ratio such as alveoli and villi

24
Q

How are alveoli adapted for gaseous exchange?

A
  • very thin alveolus walls decrease the distance increasing the rate of diffusion
  • a spherical shape increases the surface area increasing the rate of diffusion
  • a good blood supply maintains a steep concentration gradient by removing oxygenated blood and bringing in deoxygenated blood(CO2)
  • ventilation (breathing in and out) also maintains a steep concentration gradient
25
Q

What is the circulatory system?

A

A transport system made up of blood vessels and the heart in which blood transports substances that are needed around the body such as glucose and oxygen for respiration and carries away waste products such as CO2

26
Q

Why is it a double circulatory system?

A

This is because blood flows through the heart twice during each circuit of the body

27
Q

How does blood flow around the body?

A
  • The heart pumps oxygenated blood around the body
  • Oxygen and glucose diffuse into cells that need them and CO2 diffuses out of the cells into the blood
  • The deoxygenated blood returns to the heart and is then pumped to the lungs
  • In the lungs CO2 diffuses out of the blood to be removed from the body and oxygen diffuses back in
  • The oxygenated blood returns to the heart and the cycle repeats
28
Q

What are the 3 main types of blood vessels and how are they adapted?

A

Arteries - carry blood away from the heart under high pressure, to withstand this the artery has a thick and muscular wall which can slightly expand. It also has a small lumen.
Veins - return blood to the heart (low pressure), they have valves which stops the blood going the wrong way, a large lumen and fairly thin walls
Capillaries - They link arteries and veins in tissues and organs, they form a network so every cell is close to a capillary. They have semipermeable walls which are one cell thick so substances can easily move through them

29
Q

What is an advantage of having a double circulatory system?

A

As blood flows through the heart twice it is under higher pressure than a single circulatory system, this higher pressure means that materials are transported much quicker around the body which is essential for larger organisms

30
Q

What’s the heart made up of?

A

It’s made up of cardiac muscle, which doesn’t need to receive an impulse from your brain to contact. The heart contains 4 chambers separated by valves:

  • 2 smaller chambers at the top are atria
  • 2 larger chambers at the bottom are ventricles
31
Q

How does blood flow through the heart?

A

Deoxygenated blood enters the right atrium through the vena cava and is then pumped into the right ventricle. It is then pumped through the pulmonary artery to the lungs to collect oxygen. The blood then returns to the heart via the pulmonary vein into the left atrium. It’s then pumped into the left ventricle(thicker than the right as the blood needs to be pumped at a higher pressure around the body). From here or is pumped at a higher pressure around the body via the aorta

32
Q

What are 4 components that make up blood?

A

Red blood cells - biconcave cells with no nucleus that carry haemoglobin, carry oxygen and fit through the lumen of the capillary one cell at a time
White blood cells - large cells that contain a nucleus, fight disease by making antibodies or by changing shape to engulf microorganisms
Plasma - a straw-coloured liquid (90% water)that is used to transport many dissolved things such as waste products, hormones and glucose
Platelets - tiny structures that help the blood to clot

33
Q

What are the two transport systems for a plant?

A
  • Xylem transports water and mineral ions from the roots to the rest of the plant. Water diffuses into the roots via osmosis and the mineral ions are taken in using active transport.
  • Phloem transports sugars and dissolved food molecules from the leaves to all other areas of the plants(this is called translocation)
    These two tissues form a structure that is known as a vascular bundle which transports and supports a plant
34
Q

What is the structure of the xylem?

A
  • made from dead xylem cells
  • no cell walls in between
  • one way flow of mineral ions and water
  • thick walls stuffed with lignin
35
Q

What is the structure of the phloem?

A
  • made of living phloem cells
  • permeable sieve plates are formed at the ends
  • two way flow of dissolved sugars
36
Q

What is translocation?

A

When soluble sugar molecules are transported around the plant from being produced in the leaves

37
Q

How do the vascular bundles provide support to the plant?

A
  • In a leaf it forms a network that supports the softer leaf tissue
  • In the stem they are located around the outer edge which provides it with resistance
  • In the roots they are found in the centre enabling the root to act as an anchor
38
Q

What is transpiration?

A

The loss of water vapour from a plants leaves

39
Q

How is water lost from a plants leaves?

A

While the stomata are open, water evaporates from cells inside the leaf into the leaf’s air spaces. This means there is a concentration gradient between the surroundings air and the air inside the leaf. Water vapour then diffuses out the leaf(high concentration) into the surrounding air(low concentration).

40
Q

What is the transpiration stream?

A

The constant flow of water from the roots, through the xylem and out of the leaves.

41
Q

How do the stomata open and close?

A
  • When there is plenty of light and water the guard cells take up water by osmosis, this makes them turgid, which opens the stomata
  • When the conditions for photosynthesis are not good, guard cells lose water and become floppy and close, which closes the stomata
42
Q

Which factors affect the rate of transpiration?

A

You can use a potometer to measure how quickly a plant shoot takes up water

  • Light intensity - higher the light intensity the more stomata are open increasing the rate of transpiration until a certain point when all the stomata are open
  • Temperature - higher the temperature the faster water evaporates from the leaf’s cells, diffusion of water vapour becomes faster, increasing the rate of transpiration
  • Air movement - The faster the wind speed the faster water molecules are moved away from the leaf, increasing the concentration gradient, increasing the rate of transpiration
  • Humidity - The higher then humidity, the lower the concentration gradient which means the diffusion of water vapour is slower which lowers the rate of transpiration

Biology GCSE OCR Gateway A (6 decks)

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