biology - topic 2: scaling up

What is diffusion?

The net movement of particles from an area of high concentration to an area of low concentration.

What is an example of diffusion in living organisms?

• Gas exchange in the lungs

• Water and nutrient uptake in plants

What is osmosis?

The spontaneous movement of water molecules across a semipermeable membrane from a region of high water potential to a region of low water potential.

What does isotonic, hypotonic, and hypertonic mean?

• Isotonic: The concentration of the sugar in the external solution is equal to the internal.

• Hypotonic: The concentration of the sugar in the external solution is lower than the internal. Water will move into the cell and the cell will swell (become turgid).

• Hypertonic: The concentration of the sugar in the external solution is higher than the internal. Water will move out of the cell and the cell will shrink.

What is an example of osmosis in living organisms?

• Plant root water uptake

• Cell hydration

What is active transport, and what does it require?

The movement of particles from an area of low concentration to high concentration (i.e. against the concentration gradient). This requires energy from respiration, since molecules move against their concentration gradient.

What is an example of active transport in living organisms?

• Mineral absorption in plants

• Glucose absorption in animals

How many chromosomes do most human cells have?

23 pairs of chromosomes.

What is mitosis?

When one cell divides into two identical daughter cells (cell division).

What is the cell cycle?

The series of steps that take place as the cell grows and divides (undergoes mitosis).

What are the steps of the cell cycle?

(Interphase)

1. Gap 1: Metabolic changes prepare the cell for division — growth.

2. Synthesis: DNA synthesis duplicates each of the chromosomes.

3. Gap 2: Metabolic changes assemble the materials necessary and grows more.

(Mitosis)

4. Mitosis: The cell divides.

What are the stages of mitosis (incl. cytokinesis) and what happens?

Prophase: Occupies over half of mitosis — The DNA and their copies condense, and the membrane disappears.

Metaphase: Chromosomes and their copies line up in the middle of the cell.

Anaphase: Chromosomes and their copies are pulled to different sides of the cell.

Telophase: New membranes form around the chromosomes at either end of the cell.

Cytokinesis: The cell membrane pinches in and eventually divides the cell into two daughter cells.

Why is mitosis vital in asexual reproduction?

Asexual reproduction only involves one parent, therefore it produces it’s offspring by replicating it’s own cells (mitosis).

What are specialised cells?

Cells that have developed unique structures and functions to perform a specific task.

What are stem cells?

Cells that have the ability to differentiate (the process of a cell becoming specialised) their whole lives. They are important in development, growth, and repair.

What is an example of a specialised cell in our body?

• Sperm cells

• Red blood cells

• Nerve cells

• Muscle cells

What is an example of a specialised cell in plants?

• Xylem cells.

• Phloem cells.

• Root hair cells.

What are the three types of stem cells?

• Embryonic stem cells.

• Adult stem cells.

• Meristems.

The circulatory system carries ___ and ___ to every cell in the body.

Oxygen and nutrients.

What is blood?

A tissue that contains red blood cells, white blood cells, and plasma.

What do we mean when we say humans have a double circulatory system?

Our circulatory system has two loops: one passes around the lungs and the other around the body.

Name the three components of the human circulatory system.

Heart, blood, and blood vessels.

What is an advantage of having a double circulatory system?

Blood pressure can be restored at the heart and re-circulated at the correct pressure, meaning blood flows more quickly around the body.

What is the heart?

The organ that pumps blood around the body.

What are the four chambers of the heart and their functions?

• Right atrium: Receives deoxygenated blood.

• Right ventricle: Pumps deoxygenated blood to the lung.

• Left atrium: Receives oxygenated blood.

• Left ventricle: Pumps oxygenated blood to the rest of the body.

What is the process inside the heart?

1. Blood flows into the right/left atrium.

2. The atria contract, forcing the blood into the ventricles.

3. The ventricles contract also, pushing the blood in the right ventricle into pulmonary artery to be taken to the lungs, and the blood in the left ventricle into the aorta to be sent around the body.

4. Valves close to make sure the blood doesn’t flow backwards.

What are the three blood vessels and what do they do?

• Arteries carry blood away from the heart.

• Veins carry blood towards the heart. The tube is wide enough to allow the low pressured blood to flow through.

• Capillaries are tiny blood vessels that responsible for exchanging gases, nutrients, and waste products between the body’s cells and blood.

What is the structure of red blood cells?

• Contain haemoglobin.

• Biconcave to maximise surface area for oxygen to be absorbed.

• No nucleus to create space for haemoglobin.

• Flexible so they can fit through very narrow blood vessels.

What is plasma?

Plasma is the liquid that carries the components of blood, such as blood cells, water, amino acids, and urea.

What is transpiration?

The physiological loss of water in the form of water vapour, mainly from the stomata in leaves.

What is the xylem?

A vascular tissue that transports water throughout a plant's body.

What is the phloem?

The vascular tissue in charge of transport and distribution of the organic nutrients.

As water molecules are _____ to each other, when some molecules leave the plant the rest are ____ __ through the ____. This creates a ______ ____ through the plant.

As water molecules are attracted to each other, when some molecules leave the plant the rest are pulled up through the xylem. This creates a transpiration stream through the plant.

Why does water travel up the xylem?

To replace any water lost at the leaves due to transpiration.

What do guard cells do, and how are they adapted to this?

They open and close the stomata (which opens so transpiration can occur) so gas can be exchanged.

They have adapted since they are kidney shaped, enabling them to bend and curve when turgid (swollen).

What four factors can affect water uptake?

• Increase in light intensity.

• Increase in temperature.

• Increase in air movement.

• Increase in humidity.

What apparatus can be sed to investigate water uptake?

A potometer.

How does a potometer work?

A potometer is a piece of capillary tubing with a plant has been connected. The water uptake is measured by recording the time taken for a bubble in the tube to move a set distance. It is set up underwater to remove air bubbles in the xylem, so the system is air-tight, apart from one singular bubble of air. An environmental condition is usually altered for each experiment.

What is translocation?

The process of transporting sucrose around the plant.