Week 1

Question 1

What are eukaryotic cells?

Answer 1

Eukaryotic cells are complex and include animal and plant cells.
Have a nucleus

Question 2

What is a prokaryotic cell?

Answer 2

Don’t have a nucleus
Smaller than eukaryotic cells
Simpler than eukaryotic cells

Question 3

Name the parts of an animal cell and describe their functions?

Answer 3

Nucleus - contains genetic material that controls the activities of the cell.
Cytoplasm - gel like substance where most of the chemical reactions happen. It contains enzymes to control reactions.
Cell membrane - holds the cell together and controls what goes in and out.
Mitochondria - site of respiration
Ribosome - protein synthesis

Question 4

Name the parts of a plant cell and describe their functions?

Answer 4

Cell wall - made from cellulose, supports the cell and strengthens it.
Vacuole - Contains cell cap, weak solution of sugar and salts.
Chloroplasts - site of photosynthesis, contains green substance called chlorophyll.

Question 5

Features of electron microscopes?

Answer 5

• Expensive to buy and use
• High resolution
• Microscope is larger
• Specimens must be dead
• Images have depth and appear 3D
• Can magnify more than light microscopes

Question 6

Name the parts of a bacterial cell and describe their functions?

Answer 6

Cell membrane
Cell wall
Cytoplasm
Bacteria don’t have chloroplasts or mitochondria
Bacterial cells don’t have a nucleus - they have a single strand of DNA in the cytoplasm
They may also contain one or ore small rings of DNA called plasmids.

Question 7

Features of light microscopes?

Answer 7

• Can magnify x 1000
• Cheaper to buy and use
• Lower resolution
• microscope is smaller
• Specimens can be dead or alive
• Image appears flat (2D)

Question 8

What is the equation for magnification?

Answer 8

Magnification = image size/real size

(The size and the real size should have the same units, if they don’t then you should convert them). MIR

Question 9

Name the parts of a microscope?

Answer 9

• Eyepiece
• Coarse adjustment knob (for fast/rough adjustment)
• Fine adjustment knob (for precise adjustment)
• High and low power objective lenses
• Stage
• Light

Question 10

What is differentiation?

Answer 10

• Cells changing to become specialized for their job. Sub cellular structures are created to help the cell with its job. Cells that are undifferentiated are called stem cells.

Question 11

Give examples of Specialized cells and how they are specialized?

Answer 11

Sperm cells

• Long tail and streamlined head to swim
• Lots of mitochondria to provide the energy needed
• Has enzymes on its head to digest through the egg cell membrane

Question 12

Give examples of Specialized cells and how they are specialized?

Answer 12

Nerve cells

- Long to carry electrical signals

Question 13

Give examples of Specialized cells and how they are specialized?

Answer 13

Muscle cell

• Long so they have more space to contract
• Contain lots of mitochondria to generate the energy needed for contraction

Question 14

Give examples of Specialized cells and how they are specialized?

Answer 14

Root hair cells

- Big surface area

Question 15

Give examples of Specialized cells and how they are specialized?

Answer 15

Phloem and Xylem cells

- Xylem is hollow and phloem has very little sub cellular structures so stuff can flow through them

Question 16

What is Binary fission?

Answer 16

Prokaryotic cells can replicate by binary fission.

Question 17

What is the function of stem cells in embryos?

Answer 17

In a human embryo, stem cells multiply and differentiate to form the different types of cell in the human body.

Question 18

What is the function of stem cells in plants?

Answer 18

Meristem tissue in plants can differentiate into any type of plant cell.

Question 19

How could stem cells be used in medical treatment?

Answer 19

Treatment with stem cells may be able to help conditions such as diabetes (to create insulin) and paralysis (nerve cells for people paralyzed by spine injury)

Question 20

What is therapeutic cloning?

Answer 20

In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.

Question 21

Give 2 disadvantages of using stem cells in medical treatment.

Answer 21

The use of stem cells has potential risks such as transfer of viral infection.
Some people have ethical or religious objections.

Question 22

Give 2 uses of plant stem cells.

Answer 22

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
• Rare species can be cloned to protect from extinction.
• Crop plants with special features such as disease
resistance can be cloned to produce large numbers of
identical plants for farmers.

Question 23

What is diffusion?

Answer 23

• It is the movement of particles form a high concentration to a low concentration
• It an happen in solutions and gases

Question 24

What things affect the rate of diffusion?

Answer 24

• Temperature - the higher the temperature the faster diffusion happens this is because the particles have more energy to move around
• If the concentration gradient is higher (the difference in concentration) the faster the diffusion rate.

Question 25

Where is diffusion used in the human body?

Answer 25

- In animal cells - cell membranes allow small particles like water, glucose and amino acids to diffuse through them but they don't let larger particles such as proteins through. The larger the cell membranes surface area, the faster the rate of diffusion.

Question 26

What is osmosis?

Answer 26

Osmosis is the movement of water particles across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration

Question 27

What is the practical for investigating osmosis?

Answer 27

- Get two potato cylinders - Measure their mass - Put one in a beaker with 500 ml of pure water and the other in a beaker filled with 500 ml of concentrated sugar solution (1mol/dm^3) - Leave them in there for 24 hours and then dry the outside and measure their mass again. - If they have increased in mass then water has entered if they have decreased in mass then water has left the potato cylinder - Independent - concentration of sugar solution - Dependent - mass of cylinder - Control - volume of solution, temperature, time, type of sugar

Question 28

What is active transport?

Answer 28

The movement of substances from a low concentration to a high concentration against a concentration gradient. Active transport needs energy from respiration.

Question 29

How do root hair cells use active transport?

Answer 29

A plant root is covered in root hair cells. They absorb water and mineral ions from the soil. (Water is taken into root hair cells by osmosis).

Question 30

How do humans use active transport?

Answer 30

Glucose and nutrients actively get transported into the blood.

Question 31

Give examples of exchanging substances?

Answer 31

- Oxygen and carbon dioxide are transferred between cells and the environment - Urea diffuses from cells into the blood plasma for removal from the body. - The ease of exchanging substances is governed by the surface area to volume ratio.

Question 32

How are exchange surfaces adapted?

Answer 32

- They have a thin membrane, so substances only have a short distance to diffuse. - They have a large surface area so lots of substances can diffuse at once. - Have a rich blood supply

Question 33

How are alveoli adapted for their function?

Answer 33

- Large surface area - Rich blood supply - Thin walls - Moist lining for dissolving gases

Question 34

How are villi adapted for their function?

Answer 34

- Rich blood supply - Large surface area - Thin walls

Question 35

How is the leaves of a plant an exchange surface?

Answer 35

- CO2 diffuses into leaves, then diffuses into cells where photosynthesis happens. - The underneath of the leaves are covered in holes called stomata, which the CO2 diffuses through - The oxygen (produced during photosynthesis) and water diffuse out of the stomata. - The size of the stomata are controlled by guard cells. These close the stomata if a lot of water is being lost, without guard cells the plant would wilt. - The flat shape of leaves gives it a large surface area - The air space inside the leaf increase the surface area so that carbon dioxide can get into the cell.

Question 36

How do fish use exchange surfaces?

Answer 36

- The gill are the gas exchange surface in fish - Th water enters the fish through the mouth and passes through the gills. - As this happens the oxygen in the water diffuses into the blood in the gills and CO2 diffuses from the blood into the water. - Each gill is made of lots of plates called gill filaments, which give a big surface area. - The filaments are covered in tiny structures called lamellae which increase the surface area even more. - Lamellae have lost of blood capillaries to speed up diffusion - Also have a thin surface so its easier for diffusion. - Blood flows through the lamellae in one direction and water flows in the other. This maintains a large concentration gradient between the water and the blood.