Biology

Question 1

Three parts of the cell theory

Answer 1

1. The cell is the smallest functional unit of life
2. All cells arise from pre-existing cells
3. All living organisms are composed of one or more cells

Question 2

Francesco Redi’s experiment and contribution to the cell theory

Answer 2

Experiment: meat jar

Cell theory: All cells arise from pre-existing cells

Gathered evidence AGAINST spontaneous generation

Question 3

Louis Pasteur’s experiment and contribution to the cell theory

Answer 3

Experiment: s shaped flasks with broth

Cell theory: all cells arise from pre-existing cells

Gathered evidence AGAINST spontaneous generation

Question 4

Robert Hooke’s experiment and contribution to the cell theory

Answer 4

Experiment: discovered cells by looking at the cork layer of a tree

Cell theory: all living organisms are composed of one or more cells and the cell is the smallest functional unit of life

Question 5

Antonie Van Leeuwenhoek’s experiment and contribution to the cell theory

Answer 5

Experiment: discovered “animalcules” (single celled organisms)

Cell theory: all living organisms are composed of one or more cells

Question 6

Matthias Jakob Schleiden and Theodor Schwann’s experiment and contribution to the cell theory

Answer 6

Schleiden studied plant cells; Schwann studied animal cells. Discovered nuclei.

Cell theory: all living organisms are composed of one or more cells

Question 7

Rudolf Virchow’s experiment and contribution to the cell theory

Answer 7

Experiment: observing that bone cells could develop from cartilage cells

Cell theory: cells arise from pre-existing cells

Question 8

Cell membrane function

Answer 8

Holds in fluids, chemicals and structures that the cell needs to survive. Protects the cell from the environment. Semipermeable.

Question 9

Nucleus function

Answer 9

Control centre. Conducts cellular activities.

Question 10

Mitochondria function

Answer 10

Powerhouse of the cell. Creates and supplies ATP/ energy needed for activities within the cell

Question 11

Golgi apparatus function

Answer 11

Post office. Receives and packages things in vesicles to be transported to where they are needed.

Question 12

Vacuole function

Answer 12

Storage for waste, nutrients and water

Question 13

Cell wall function

Answer 13

Supports the shape of the cell and protects it from the outer environment

Question 14

Endoplasmic Reticulum (ER) function - rough & smooth

Answer 14

The ER is a network of folded membranes and tubes connected to the nucleus.

The rough ER is studded with ribosomes. Ribosomes build proteins. These are then packaged into vesicles for transport.

The smooth ER has no ribosomes. It synthesizes lipids and packages large molecules (proteins or lipids) in vesicles. These vesicles are transported to other parts of the cell, usually the cell membrane or the Golgi apparatus.

Question 15

Lysosomes function

Answer 15

Inside, materials are degraded with the help of digestive enzymes - a type of protein.

Question 16

Chloroplasts function

Answer 16

Site of photosynthesis. Contain chlorophyll - the molecule responsible for photosynthesis

Question 17

Xylem function

Answer 17

Xylem: Moves water & minerals from the roots to the leaves of the plant

Question 18

Phloem function

Answer 18

Phloem: Moves the sugars produced in the leaves to other parts of the plant!
• Thicker tubes, located on the bottom of most diagrams

Question 19

Turgor pressure

Answer 19

High turgor pressure: guard cells are filled with water and stomata are open

Low turgor pressure: guard cells are empty and stomata are closed

Question 20

Transpiration

Answer 20

As water vapour exits the leaf, the air inside the leaf gets drier. This causes water to diffuse out of the leaf cells and into the fluid between cells.
• This causes more water to evaporate from the surface of the leaf.
• Cohesive forces between water molecules pull more water up the xylem to replace the water that was evaporated/transpired!

Question 21

Epidermis cells

Answer 21

Protective layer

Question 22

Cuticle

Answer 22

Waxy layer to protect the leaf and keep it from drying out

Question 23

Palisade tissue layer

Answer 23

“Fence” layer. Contains chloroplasts and does photosynthesis

Question 24

Spongy tissue cells

Answer 24

Also contain chloroplasts but are not the main site of photosynthesis. Their structure helps exchange water and gases with the environment.

Question 25

Lower epidermis

Answer 25

Guard cells in the lower epidermis contain stomata. Stomata allow gases in and out of the leaf. CO2 comes into the leaf via the stomata and oxygen exits via the stomata. Water vapour can also diffuse through the leaf via these openings. Most stomata are on the underside of the leaf. Each stomata is flanked by two guard cells that regulate its size.

Question 26

Vascular bundle

Answer 26

Contains xylem: transports water and minerals up the roots to the leaves.

Contains phloem: transports sugars created by the leaves elsewhere in the plant.

Question 27

Gelatine experiment

Answer 27

Peter Boysen-Jensen placed gelatine or mica between the leaf and stem of seedlings.

The seedlings with the gelatine grew towards the light source because the gelatine was permeable to the auxin chemicals; the seedlings with the mica grew up regardless of the light source because the mica was not permeable to the auxins.

Question 28

Agar experiment

Answer 28

Fritz Went:

1) placed agar blocks under the tips of multiple seedlings & chemicals diffused into the agar

2) cut the tips of the seedlings and:
- placed agar directly on the stem: plant grew upward
- placed agar on one side of the stem: plant curved away from the side with the agar block
- placed agar with no hormones on a stem: plant didn’t grow at all.

Went discovered and named AUXINS

Question 29

Gravitropism

Answer 29

The observation that plants grow depending on gravity

Positive gravitropism - roots grow toward gravity

Negative gravitropism - stems grow away from gravity

Question 30

Phototropism

Answer 30

The observation that plants grow in response to light

Question 31

Gas exchange

Answer 31

1) air diffuses through the stomata and into the leaf and circulates in the space between the spongy tissue cells

2) CO2 diffuses from the air into the palisade and spongy tissue cells (which contain chloroplasts)

3) the chloroplasts use this CO2 for photosynthesis which produces oxygen

4) the oxygen diffuses out of the cells, then out of the leaf (via the stomata) and into the atmosphere

Woody plants (trees) use lenticels for gas exchange

Question 32

Describe endocytosis

Answer 32

1) material comes into contact with cell membrane and fuses, which forms a pocket around it

2) the cell membrane folds in and encloses the material

3) the membrane pinches off into a vesicle (for transport) or a vacuole (for storage)

Question 33

Carrier proteins vs channel proteins

Answer 33

Carrier Proteins: Lock & Key model. The large molecule & a molecule of ATP bind to the carrier protein, which changes its shape. This allows the large molecule to enter/exit the cell.

Channel Proteins: Magnetic Key card model. The charge of ions is opposite to that of the channel protein, this creates enough energy to open the channel. Ions then flow into/out of the cell through the channel depending on their concentration

Question 34

3 modes of passive transport

Answer 34

Diffusion: the movement of particles down a concentration gradient (areas of [high] to [low])

Osmosis: Diffusion of water molecules down a concentration gradient (areas of [high] to [low])

Facilitated Diffusion: Movement of large molecules facilitated by transport proteins down a concentration gradient (areas of [high] to [low])