Student Notes: Chapter 2

Chapter 2The Functioning Cell

Cell MembranePermeable Membrane allows all substances to pass.

Impermeable Membrane allows no substances to pass.

Semi-Permeable Membrane allows some substances to pass.

DiffusionDiffusion is a spreading out process where a substance spreads from an area of high concentration to an area of low concentration until a balance is reached.

For example, what happens when a door is opened between a warm room and a cool room? The warm air (high concentration) will spread into the cool air (low concentration) until the rooms are the same temperature (balanced).

A cell acquires the air and other gases it needs by diffusion. Oxygen outside the cell (area of high concentration) goes into the cell (area of low concentration) through its semi-permeable membrane until a balance is reached between the oxygen outside and inside the membrane. This is also how the cell takes on water, although that process is called osmosis.

Diffusion

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Student Notes: Chapter 2

OsmosisOsmosis is the movement of water across a semi-permeable membrane. This is caused by a difference in water concentrations on the two sides of the membrane. Osmosis is a type of diffusion specific to water.

Osmosis

Active TransportNot all the cell’s needs are met by diffusion and osmosis (which happens without energy). Cells require some substances in greater concentration. Glucose particles (food) must move from an area of low concentration (outside the cell) to high concentration (inside the cell).

To do this, cells have Carrier Proteins embedded in the membrane. Each carrier protein uses energy to attract a particular substance, attaches to it, moves it through the membrane, and releases it on the other side. This is called Active Transport. Active transport is the opposite of diffusion and osmosis, which are types of passive transport.

Active Transport

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Student Notes: Chapter 2

Summary of Passive and Active TransportPassive Transport is when material is moved from an area of high concentration to an area of low concentration until a balance is reached. No energy is required to make this happen. Diffusion (in air) and osmosis (in water) are both examples of passive transport.

Active Transport is when material is moved from an area of low concentration to an area of high concentration by using a protein carrier. Energy is required to make this happen. A cell taking in food is an example of active transport.

How a Cell Gets EnergyCellular Respiration is a process by which cells produce energy; specifically, oxygen combines with food particles to produce energy.

Cellular Respiration occurs in all living cells because cells require chemical energy from food (carbohydrates) in order to work. This process happens in the mitochondria of the cell.

Before exercising, eat food rich in carbohydrates (like pasta) because it provides your body with energy.

After exercising, eat food rich in protein (like chicken) because it helps rebuild muscle tissue.

The word equation for cellular respiration:

carbohydrates + oxygen = carbon dioxide + water + energy

The word equation for photosynthesis:

carbon dioxide + water + light energy = carbohydrates + oxygen

How Cells ReproduceRegeneration is the ability to reproduce body parts.

Mitosis, also known as cell division, is the process of genetic material duplicating into identical sets of chromosomes.

Chromosomes are clusters of dark, threadlike objects containing the cell’s genetic material, or DNA, and are only visible when a cell is about to divide.

DNA stands for deoxyribonucleic acid and is the instructions for producing new cells with the same characteristics as the parent cell.

Your skin cells wear out quickly, lasting only days or weeks. However, your nerve cells last a lifetime.

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Student Notes: Chapter 2

Cells and CancerCancer is a disease caused by an uncontrolled division of abnormal cells in a part of the body.

Specifically, it is when chromosomes undergo a change, causing the cell’s nucleus to send out abnormal orders. This causes the cell to go wrong, multiplying uncontrollably, with each new cell containing the same defect. Eventually, a tumour is formed.

The tumour then forms many blood vessels, ensuring it gets the oxygen and nutrients it needs in order to live and grow. However, the tumour only becomes dangerous when the cancerous cells travel through the blood vessels; once this happens, the cancerous cells can invade the body’s organs and create new tumours. This spreading process is called metastasis.

Carcinogens are factors that produce cancer. There are four main carcinogens:

1. Hereditary Abnormalities

2. Exposure to Viruses

-HIV-Hepatitis B, C, D

3. Exposure to Toxic Agents

-chemical products-radiation-sun

4. Unhealthy Behaviour

-alcohol consumption-tobacco smoking-diet rich in fat, low in fruits and vegetables

Treatments for cancer include surgery, radiation, and chemotherapy.

Specialized CellsHumans have about one hundred different types of cells.

Specialized Cells means different cells have different appearances and do different jobs. In other words, they are specialized for particular tasks.

The shape and size of the cell depends on its job. For example, red blood cells are thin disks; this gives them a large surface area to pick up oxygen and carry it to parts of the body.

-End of Test #2-4