Unit C

Module 5 ~ Lesson 1

Read

Read pages 154 and 155 of the textbook. In particular, review the labelled diagrams of cells so that you have a better idea of where photosynthesis and cellular respiration take place.
Read pages 162 to 164 in your textbook.

Cell Organelles

In Science 10, you studied cell theory, cell structure, and cell function. In this lesson, you will build on those basics toward a greater understanding of cellular respiration and photosynthesis. Photosynthesis occurs in the chloroplast.

Can you identify the mitochondrion and the chloroplast in this plant cell? Chloroplasts and mitochondria have unique designs that allow them to carry out photosynthesis and cellular respiration. Plant cells have chloroplast and mitochondria, whereas animal cells have only mitochondria.

By LadyofHats [Public domain], via Wikimedia Commons

Cell Transport

Cells must transport molecules produced during photosynthesis and cellular respiration. Cells must also transport the required compounds for these two processes. Note these types of cellular transport which you studied in Science 10:

passive transport: no energy required; molecules move independently of each other down a concentration gradient (high concentration to low concentration)

diffusion: a process in which molecules move from areas of high concentration to low concentration

facilitated diffusion: a process in which larger molecules need the help of proteins in cell walls to move from areas of high concentration to low concentration

osmosis: the diffusion of water across a semipermeable membrane

active transport: a process that requires energy from ATP to move substances against the concentration gradient (from low to high)

endocytosis: a process in which cell membranes engulf a substance and pinch off inside the cell

pinocytosis: a process in which the cell wall engulfs liquids and their solutes and pinches off inside the cell

phagocytosis: a process in which the cell wall engulfs a large particle, such as bacteria or a blood cell, and pinches off inside of the cell

exocytosis: a process in which a vacuole containing substances from inside a cell (cytoplasm) fuses with the cell wall and the contents are released outside of the cell

ATP

Photosynthesis produces the energy-rich chemical compound of glucose. Cellular respiration breaks down energy-rich compounds such as glucose. Breaking down the chemical bonds in glucose generates ATP.

ATP is the energy currency of cells. When cells need energy, they spend ATP. ATP has three phosphate groups. When one high energy phosphate bond is broken, energy is released and the result is ADP. You will learn more about ATP synthesis later on in this module. See figure 5.3 on page 163.

Self-Check

What is the purpose of facilitated diffusion?

Facilitated diffusion moves large molecules down the concentration gradient. These molecules are unable to diffuse across the cell membrane because of their size, so go through special protein channels embedded in the cell membrane.

Where does a cell get energy for active transport?

Cells get energy from ATP (adenosine triphosphate) when phosphate bonds are broken.

What is ATP used for?

The energy stored in ATP is used for active transport, cell division, movement, muscle contraction, and the synthesis of proteins and other molecules.

How does ATP supply energy to the cell?

Stored chemical energy is released when the bond to the third phosphate group breaks. This energy fuels many cellular functions. See figure 5.3 on page 163.