B2- Scaling up

Question 1

What are the 3 growth stages in the period of cell growth and replications of its contents in cell cycle?

Answer 1

Gap Phase 1
Synthesis
Gap Phase 2

Question 2

What is the stage of cell division in cell cycle?

Answer 2

Mitosis

Question 3

What is the cell cycle?

Answer 3

For growth and repair of cells in the body

GAP PHASE 1: (G1)
Cell grows and new cell structures (ribosomes, mitochondria ect) and proteins are made

SYNTHESIS (S phase)
DNA replication occurs, so that when the cell divides by mitosis each cell will have the identical number of chromosomes

GAP PHASE 2: (G2)
Cell keeps growing and proteins needed for cell division are made

MITOSIS:
The cell divides into two identical cells

• Cycle restarts

Question 4

How does DNA replicate during S phase (synthesis stage)?

Answer 4

1) The enzyme DNA Helicase unwinds DNA strand and they split
2) Free-floating nucleotides in the nucleus pair up with complementary bases on the DNA
3) The new nucleotides join together. So two new identical DNA molecules are formed

Question 5

What is Mitosis?

Answer 5

• When a cell reproduces itself by dividing into two genetically identical cells
• occurs all over the body
• For growth and repair

Question 6

Steps to mitosis:

Answer 6

1) DNA forms x shaped chromosomes.
2) Chromosomes line up at center of the cell and cell fibers pull apart
3) The two ‘arms’ of each chromosomes go to opposite ends of the cell
4) Membranes form around each of the sets of chromosomes forming new nuclei of the two new cells
5) The cytoplasm divides

Question 7

What is cell differentiation and what is the difference in cell differentiation in animal and plant cells?

Answer 7

Cell differentiation: When a cell changes to become a specialised cell with a particular function by switching on and off genes.

-Animal cells: loss ability to differentiate at an early
stage
-Plant cells: most plant cells don’t lose the ability to differentiate

Question 8

Function and adaption of Palisade leaf cells?

Answer 8

F: do most of the photosynthesis in plants

A:

1) Tall shape means they have high surface area for absorbing CO2
2) Thin shape means lots can fit at the top of leaf, nearer to light.

Question 9

Function and adaption of Sperm cells?

Answer 9

F: To get male DNA to the female DNA by penetrating the egg cell

A:

1) Long tails and streamlined heads to help swim
2) Contain lots of mitochondria to provide lots of energy
3) Enzymes in their heads to digest through egg membrane

Question 10

What do specialised cells group to form and so on?

Answer 10

• Group of same specialised cells form tissues
• Different tissues form organs
• Different organs make up organ systems

Question 11

Embryonic stem cells vs Adult stem cells:

Answer 11

EMBRYONIC:
- Found in early human embryos
- Can differentiate into any type of cell
ADULT STEM CELLS:
- Found in certain places like bone marrow
- Are not as versatile as embryonic stem cells as they can only diffrenciate into cells from the tissue the originally came from

Question 12

Plant stem cells:

Answer 12

• Called meristem
• Found in meristem tissues in areas which are growing (like roots and tissues)
• Can differentiate into ANY plant cell as long as the plant is alive

Question 13

What is diffusion?

Answer 13

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

Question 14

How do particles move across a membrane in diffusion, osmosis and active transport?

Answer 14

RANDOMLY

-but is there is more particles of one side there will be a net movement

Question 15

What is Active transport?

Answer 15

The movement of particles across a membrane against the concentration gradient (from an area of low concentration to an area of high concentration) using ATP released in respiration.

Question 16

What is osmosis?

Answer 16

The net movement of water molecules across a semi permeable membrane from an area of high water potential to an area of low water potential.

Question 17

How does water potential tell us about the concentration of a solution.

Answer 17

High water potential = dilute solution

Low water potential = concentrated solution

Question 18

What happens when a plant is watered?

Answer 18

1) Watering a plant increases water potential in the soil
2) Plant draws water from soil via osmosis until they become turgid
3) The contents of the plant cell are pushed against the cell water due to vacuole filled with water - called turgid pressure which supports the plants

Question 19

Potato and osmosis experiment results?

Answer 19

• Potatoes in a higher concentrated solution (lower water potential) lose water and their mass decreases (they begin to shrink)
• Potatoes in a lower concentrated solution (higher water potential) gain water and their mass increases

Question 20

Factors the affect exchange of substances?

Answer 20

1) SURFACE AREA
Rate of diffusion, osmosis and active transport higher in cells with larger surface area to volume ratio
2) TEMPERATURE
Warmer particles have more energy - so they move faster
3) CONCENTRATION GRADIENT
Substances move in and out cells faster the larger the difference in concentration between outside and inside the cells

Question 21

Exchanging of substances in Single-celled organism vs Multicellular organism?

Answer 21

Single-celled: Quick diffusion
-Substances only have to travel short distances
- Have a relatively large surface area to volume ratio
Multicellular: Slow diffusion
- Some cells are deep inside organism - long way from the outside environment
- Have a low surface area to volume ratio

Question 22

How are alveoli adapted to maximise diffusion rate (exchange of substance)?

Answer 22

• An enormous surface area
• Very thin walls
• A moist lining for dissolving gases
• A good blood supply

Question 23

How does the alveoli exchange gases?

Answer 23

1) Deoxygenated blood passing next to the alveoli has a higher concentration of CO2 and low concentration of O2
2) The alveoli has a higher concentration of O2 and low CO2 concentration
3) Carbon dioxide from the blood diffuses to the alveoli to be breathed out
4) Oxygen from the alveoli diffused into the blood

Question 24

What is the Villi and how is it adapted for exchanging substances?

Answer 24

1) In the small intestine there are millions of villi where dissolved food molecules are absorbed out the digestive system and into the blood

• High surface area
• A single layer of surface cells
• A very good blood supply to assist quick absorption

Question 25

How are leaves adapted for gas exchanging?

Answer 25

1) Leaves are broad, for high surface area for diffusion 2) Thin, gases only have to travel a short distance 3) Air spaces in the leaves let CO2 and O2 move easily between cells 4) The lower surface have stomata which let CO2 and O2 diffuse in and out

Question 26

How does roots absorb water and mineral ions ?

Answer 26

They have root hair cells - increases surface area for absorbing water and mineral ions - > Water: drawn in from osmosis - > Mineral ions: drawn in via active transport (there is more mineral ions in the roots than the soil)

Question 27

What are the advantages of the double circulatory system?

Answer 27

- Returning blood to the heart after picked up oxygen at the lungs means it can be pumped around body at high pressure - Therefore, rate of blood flow faster supplying body cells with oxygen faster - Mammals require lots of oxygen for body temperature maintenance

Question 28

Direction of blood flow in the body?

Answer 28

Vena cava - Right atrium - Right Ventricle - through the tricuspid value in Pulmonary artery - to the lungs - Pulmonary vein - Left atrium - Left ventricle - Aorta - rest of the body

Question 29

Three types of blood vessels and their functions?

Answer 29

Arteries: Carries blood away from the heart Capillaries: involved in the exchange of materials Vein: Carries blood into the heart

Question 30

Arteries properties:

Answer 30

1) Carries blood at high pressure so strong elastic walls 2) Thick walls compare to the lumen 3) Arteries branch into arterioles

Question 31

Capillaries properties:

Answer 31

1) Arterioles branch into capillaries 2) Have permeable walls so diffusion can occur 3) Walls are one cell thick, increasing the rate of diffusion (decreases distance) 4) Very small lumen 5) Branch into venules

Question 32

Vein properties:

Answer 32

1) Venules join up to form veins 2) Blood flows at lower pressures so walls not as thick 3) Bigger lumen 4) Valves to prevent backflow of blood at the low pressure

Question 33

What is the 3 layers in blood from heaviest to lightest?

Answer 33

HEAVIEST 1)Red blood cells: packed with haemoglobin 2) White blood cells and platelet layer 3) Plasma containing... - Urea - Carbon dioxide - Ions - Glucose - Hormones - Amino acids - Antibodies

Question 34

What is haemoglobin?

Answer 34

A protein that undergoes a reversible reaction with oxygen to form oxyhaemoglobin which breaks down to supply body cells with oxygen for respiration.

Question 35

Red blood cell adaptions?

Answer 35

1) Biconcave disc shape: give a high surface area to volume ratio for maximizing diffusion 2) No nucleus: frees up space for as much haemoglobin 3) Small and flexible to fit in tight spaces like capillaries

Question 36

What is the Phloem tubes in plants?

Answer 36

- Transport food substances both up and down the stem called translocation - Made of columns of living cells called sieve tubes - Sieve tubes have no nucleus so they need companion cells to survive

Question 37

What is the xylem tubes in Plants?

Answer 37

- Transports water and minerals up from the roots to shoots in transpiration - Made of dead cells strengthened with lignin

Question 38

What is transpiration?

Answer 38

- Is the loss of water caused by evaporation and diffusion of water from a plant's surface. - The evaporation and diffusion creates water shortage so more water is draw up through xylem vessels to replace it

Question 39

Benefits of transpiration in a plant:

Answer 39

1) Constant stream of water keeps plant cool 2) Constant supply of water for photosynthesis 3) Creates turgor pressure giving plant support to stop it wilting 4) Minerals needed by plant are drawn up with the water

Question 40

Factors affecting transpiration rate?

Answer 40

LIGHT INTENSITY: Brighter light, high rate of transpiration As photosynthesis increases so stomata opens and water can escape TEMPERATURE: Warmer it is, the higher transpiration rate Warm water particles have higher energy to evaporate out the stomata AIR MOVEMENT: Lots of wind movement, higher rate if transpiration High wind movement, water molecules are swept away and concentration gradient becomes larger. Faster osmosis

Question 41

How are plants adapted to balance water loss with water uptake?

Answer 41

1) Waxy cuticle on upper epidermis making upper surface waterproof 2) More stomata on lower surface of leaves where it is darker and cooler slowing diffusion of water out of leaves 3) Plants in hot climates have smaller and fewer stomata

Question 42

What is the stomata?

Answer 42

1) Open and closed automatically as guard become turgid or flaccid to let gases in and out for photosynthesis 2) Sensitive to light: Guard cells turgid in the light and stomata opens Guard cells flaccid in the dark and stomata closes