Biology B1 - B3

Question 1

Where is genetic material found in Eukaryotic and Prokaryotic cells?

Answer 1

Eukaryotes - Nucleus

Prokaryotes - Cytoplasm

Question 2

Formula for magnification

Answer 2

magnification = image size / real size

Question 3

What are chromosomes?

Answer 3

Long molecules of coiled up DNA

Question 4

Describe DNA’s structure

Answer 4

• Double Helix (Double stranded)

- Each of the two DNA strands is made up of lots of nucleotides joined together in a long chain.

Question 5

What is the structure of a nucleotide?

Answer 5

Phosphate, Peniose sugar (ribose or deoxyribose) and a base

Question 6

What are the four bases and their pairs?

Answer 6

Adenine, Cytosine, Guanine, Thymine
A-T
C-G

Question 7

What is transcription in terms of protein synthesis?

Answer 7

Transcription is the process of copying DNA. This is done with the help of mRNA, or messenger RNA.
The DNA starts off by unzipping itself. This allows the mRNA to make a copy of the specific gene that is needed. The mRNA copies the complementary base pairs, but instead of A-T, it is A-U (Uracil). T-A still remains. For example, A-T-T-T-C-C is transcribed to be U-A-A-A-G-G
This mRNA is then sent to the ribosomes where it is then translated.

Question 8

What is translation in terms of protein synthesis?

Answer 8

Translation takes the base pairs from the mRNA and splits them up into triplets, or codons. Each of these codons code for a specific Amino Acid.
tRNA, or translator RNA, goes back to the original strand of DNA and takes the second half of the unzipped strand, copying what’s on there and sending it back to the ribosomes. Amino acids are now formed here

Question 9

What are enzymes?

Answer 9

Enzymes are biological catalysts that break that make chemical reactions within the body possible

Question 10

What is the lock and key model?

Answer 10

Within an enzyme, there is an active site which has a shape specific to a certain substrate which it wants to break down. This substrate locks in and is broken down to form products

Question 11

What are the effectors of enzymes

Answer 11

pH and Temperature

Question 12

What is respiration?

Answer 12

The process of transferring energy from the breakdown of glucose. This energy is stored as ATP

Question 13

What is Aerobic respiration?

Answer 13

Respiration when there’s plenty of oxygen

Glucose + oxygen –> carbon dioxide and water

Question 14

What is Anaerobic Respiration?

Answer 14

Respiration without oxygen
In animals, lactic acid is produced (glucose –> lactic acid) whereas in plants, ethanol and carbon dioxide is produced (glucose –> ethanol + carbon dioxide)

Question 15

Describe the steps of mitosis

Answer 15

Mitosis is cell division and here are the steps.

1) The cell has two copies of its DNA all spread out in long strings
2) Before the cell divides, the DNA forms X-Shaped chromosomes. Each “Arm” of a chromosome is an exact copy of the other.
3) The chromosomes then line up at the centre of the cell and the cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cells.
4) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells.
5) The cytoplams divides and you are left with two daughter cells.

Question 16

What is cell differentiation?

Answer 16

Differentiation is the process by which a cell changes to become specialised for its job. In most animal cells, the ability to differentiate is lost at an early stage, but lots of plant cells dont ever lose this ability.

Question 17

What are stem cells?

Answer 17

Stem cells are undifferentiated. Depending on what instructions they’re given, they can divide by mitosis to become new cells.

Question 18

Embryonic stem cells

Answer 18

Embryonic stem cells are found in early human embryos. They have potential to turn into any kind of cell at all. However, there is a lot of ethics behind not being able to use them

Question 19

Adult stem cells

Answer 19

Adult stem cells are only found in places such as bone marrow, but they aren’t as versatile as embryonic stem cells. They can only turn into cells from the tissues they originally came from.

Question 20

Diffusion, Active transport and Osmosis

Answer 20

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. They go down a concentration gradient

Osmosis is the net movement of water molecules from a region of high water potential to low water potential across a partially permeable membrane. They go down a concentration gradient.

Active transport is diffusion, but going against a concentration gradient

Question 21

Transpiration

Answer 21

Transpiration is the movement of food and water through a plant cell.
In phloem tubes, food is transported both up and down the stem to growing and storage tissues. This movement of food substances is known as translocation.

Xylem tubes take water up the plant.
They’re made of dead skin cells and thick side walls made of cellulose to support the plant. They carry water and minerals from the roots up the shoot to the leaves in the transpiration stream.

Transpiration is the loss of water from the plant. Due to the stomata opening and closing, the water that travels up can evaporate and diffuse out the cell.

Question 22

What effects transpiration?

Answer 22

Light intensity
Temperature
Air movement

Question 23

Describe how information is transmitted in the nervous system

Answer 23

Stimulus - receptor - sensory neurones - CNS - motor neurones - effector - response

The body has lots of sensory receptors, which can detect a change in your environment.
The receptors then sends these nervous impulses along sensory neurones to the CNS
The CNS consists of the brain and spinal cord.
The CNS coordinates the response
This information is then sent to the effector along the motor neurone and this effector then responds accordinglu

Question 24

How does the structure of neurones allow transmitting of electrical impulses?

Answer 24

Electrical impulses are passed along the axon of a neurone.
Neurones have branched endings (dendrites) so they can connect with lots of other neurones.
Some axons are also surrounded by a fatty (myelin) sheath. This acts as an electrical insulator, speeding up the electrical impulse.
Neurones are long, which also speeds up the impulse (one longer neurone is faster than 5 short ones)
The connection between two neurones is called a synapse, or just a tiny gap:
- The electrical impulse triggers the release of transmitter chemicals, which diffuse across the gap
- These chemicals bind to receptor molecules in the membrane of the next neurone, setting off a new electrical impulse

Question 25

Reflex actions:

Answer 25

Reflex actions just skip the CNS all together

Question 26

The eye:

Answer 26

The eye is made up of many things.

1) The cornea refracts light into the eye
2) The iris controls how much light enters the pupil
3) The lens also refracts light, focusing it onto the retina.
4) The ciliary body contains ciliary muscles, which are attack to suspensory ligaments - they work together to alter the shape of the lens
5) The retina is the light sensitive part and it’s covered in rods and cones, which detect light
6) Rods are more sensitive to dim light but cant sense colour
7) Cones are sensitive to different colours but are not so good in dim light
8) The optic nerve carries impulses form the receptor the the brain

Question 27

Focusing on near and distant objects:

Answer 27

The look at distant objects:

1) the ciliary muscle relaxes, which allows the suspensory ligaments to pull tight.
2) This pulls the lens into a less rounded shape so light is refracted less

To look at close objects:

1) The ciliary muscle contracts, which slackens the suspensory ligaments.
2) The lens become a more rounded shape, so light is refracted more

Question 28

Long- or short-sighted:

Answer 28

Long sighted:

1) The eyeball is too short or the lens doesn’t bend light enough
2) Use convex lens to correct this

Short sighted:

1) The eyeball is too long or the lens bends light too much
2) Use concave lens to correct this

Question 29

The main parts of the brain (GCSE level) :

Answer 29

1) Cerebrum - Responsible for things like consciousness, intelligence, memory and language
2) Hypothalamus - Involved in maintain body temperature at the normal level. Also produces hormones that control the pituitary gland
3) Pituitary - A gland that produces many important hormones
4) Medulla - Controls unconscious activities
5) Cerebellum - responsible for muscle coordination

Question 30

What are hormones?

Answer 30

Hormones are chemicals produced in various glands called endocrine glands, which make up the endocrine system
They are released directly to the blood

Question 31

Adrenaline:

Answer 31

Adrenaline is a hormone released by the adrenal glands. It prepares the body for flight or fight. It does this by activating processes that increase the supply of oxygen and glucose in cells. For example:

Adrenaline binds to specific receptors in the heart. This causes heart muscles to contract more frequently and with more force, increasing blood pressure. This increases blood flow to the muscle, so the cells will receive more oxygen and glucose to respire.

Something similar happens in the liver with glucose

Question 32

Thyroxine and negative feedback:

Answer 32

Thyroxine regulates metabolism. It is released by the thyroid gland and controls the speed at which chemical reactions in the body occur. Thyroxine is released in response to thyroid stimulating hormone (TSH) which is released by the pituitary gland.

A negative feedback systems keeps the amount of thyroxine in the blood at the right level - when the level is higher than normal, then TSH is inhibited. If there is too little, then TSH is released again.

Question 33

What do each of the hormones in Menstrual Cycle do?

Answer 33

FSH - Causes an egg to mature in one of the ovaries. Stimulates the ovaries to produce oestrogen

Oestrogen - Causes the lining of the uterus to thicken and grow. Stimulates the production of LH and inhibits FSH

LH - Stimulates the release of an egg at day 14 (ovulation). Indirectly stimulates progesterone production

Progesterone - Maintains the lining of the uterus. When it falls and the oestrogen level is low then the lining breaks down

Question 34

Homeostasis

Answer 34

Homeostasis is maintaining a constant internal environment

Body temperature is controlled by the hypothalamus

When you’re too hot, erector muscles relax, so hairs lie flat. Lots of sweat is produced and blood vessels close to the surface of the skin dilate (vasodilation), allowing more blood to flow near the surface so it can transfer more energy to your surroundings.

When you’re too cold, erector muscle contract. Hairs stand on end to trap an insulating layer of air, which helps keep you work. Sweat production is inhibited and blood vessels constrict (vasoconstriction) so less blood flows, causing less energy to be transferred. You also shiver which requires respiration, keeping your body warm.

Question 35

How does blood get to the body?

Answer 35

Humans have a double circulator system.

In the first one, the heart pumps deoxygenated blood to the gas exchange surfaces in the lungs to take in oxygen. The oxygenated blood then returns to the heart.

In the second one, the heart pumps oxygenated blood around all the other organs of the body. The blood gives up its oxygen at the body cells and deoxygenated blood returns to the heart to be pumped out to the lungs again.

Question 36

The Heart

Answer 36

Blood flows into the two atria from the vena cava and pulmonary vein.

The atria contract, pushing the blood into the ventricles. The left atrium and ventricle deal with oxygenated blood, and the right side deals with deoxygenated blood.

The ventricles contract, forcing the blood into the pulmonary artery (deoxygenated) and the aorta (oxygenated), and out of the heart.

Question 37

Plant Growth Hormones: Auxin

Answer 37

Auxins are plant hormones which control growth at the tips of shoots and roots. They move through the plant in solution
Auxin is produced in the tips and diffuses backwards to stimulate elongation process which occurs in the cells just behind the tips.
Auxin promotes growth in the shoot, but actually inhibits growth in the root.
Auxins are involved in the growth responses of plants to light (phototropism) and gravity (gravitropism)

Question 38

How do shoots change direction to grow with auxin?

Answer 38

Shoots are positively phototropic (grow towards light)

• When a shoot tip is exposed to light, it accumulates more auxin on the side that’s in the shade than the side that’s in the light
• This makes the cells elongate faster on the shaded side, so the shoot bends towards the light

Shoots are negatively gravitropic (grow away from gravity)

• When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side
• This causes the lower side to grow faster, bending the shoot upwards

Question 39

How do roots change direction to grow with auxin?

Answer 39

Roots are positively gravitropic (grows towards gravity)

• A root growing sideways will also have more auxin on it lower side
• But in a root the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards

Roots are negatively phototropic (grow away from light)

• If a root starts being exposed to some light, more auxin accumulates on the more shaded side
• The auxin inhibits cell elongation on the shaded side, so the root bends downwards, back into the ground

Question 40

What can plant hormones be used for?

Answer 40

1) As selective herbicides - Auxin can disrupt normal growth of weeds
2) Growing from cuttings with rooting powder - If rooting powder, which contains auxin, is added, then the cuttings from certain plants can be replicated rapidly
3) Producing seedless fruit - Auxin and Gibberellins can be applied to unpollinated flowers, eliminating the need of a seed
4) Controlling Dormancy - Force plants to grow at different times of the year that they normally wouldn’t

Question 41

How does ADH control water levels?

Answer 41

It is controlled by a negative feedback system.
If the brain detects that there is excess water, then the pituitary gland releases less ADH, causing the kidney to reabsorb less water. This makes the concentration of urea higher.

If the brain detects that there is too little water, more ADH is released, allowing the kidney to reabsorb more water. This makes the concentration of urea lower.

Question 42

The Nephron

Answer 42

bowman’s capsule -> proximal convoluted tubule -> loop of Henle -> second coiled region -> collecting duct ->

Blood enters the kidney under high pressure from renal artery
The increased blood pressure forces small molecules, including water, glucose, salts and urea, out through the capillary wall into the Bowman’s Capsule
- Large molecules such as proteins remain in the bloodstream
Selective reabsorption then takes place. As the filtrate moves through the proximal convoluted tubule (or nephron tubule) all of the glucose is reabsorbed, as well as some of the water and any salts needed by the body
Finally the filtrate travels through the loop of Henle, second coiled region and the collecting ducts, both of which regulate the amount of salt and water in the body by reabsorbing extra water and salt if needed
The waste solution, urine, collects in the collecting duct and travels to the bladder where it is removed from the body

Question 43

The excretory system

Answer 43

Blood containing urea enters the kidney through an artery.

The kidney removes this urea as well as excess ions and excess water

These leave the kidney as urine and this is stored in the bladder

Blood now leaves the kidney through a vein, containing no urea