biology1[cell photo synthesis respiration]

BBA2106: Basics in Natural Science (FBA) Lecture

CELLS, PHOTOSYNTHESIS & RESPIRATION

Cells

The cell is one of the most basic units of life. There are millions of different types of cells. There are cells that are organisms onto themselves, such as microscopic amoeba and bacteria cells. And there are cells that only function when part of a larger organism, such as the cells that make up your body.

The cell is the smallest unit of life in our body. In the body, there are brain cells, skin cells, liver cells, stomach cells, and the list goes on. All of these cells have unique functions and features. And all have some recognizable similarities.

Below is a labeled diagram of a cell to help you identify some of these structures.

Plasma membrane: All cells have a 'skin', called the plasma membrane, protecting it from the outside environment. The cell membrane regulates the movement of water, nutrients and wastes into and out of the cell. All the working parts of the cell are inside of the cell membrane. They are:

Cells, Photosynthesis & Respiration (Updated on May 15, 2011)


Nucleus: Nucleus is present at the center of the cell. It contains the cell's DNA (the genetic code that coordinates protein synthesis). The transcription phase of protein synthesis takes places in the cell nucleus.

Ribosome: One important cellular organelle is the ribosome. It participates in protein synthesis. After transcription phase is complete, RNA leaves the nucleus and travels to the cell's ribosome, where translation occurs.

Mitochondrion: Another important cellular organelle is the mitochondrion. Mitochondria are often referred to as the power plants of the cell because many of the reactions that produce energy take place in mitochondria.

Lysosome: Lysosomes are organelles that contain enzymes that aid in the digestion of nutrient molecules and other materials.

Plant Cell and Animal Cell

While both plant and animal cells contain the structures discussed above, there are some differences between them. Plant cells have some additional specialized structures.

Many animals have skeletons to give their body structure and support. Plants do not have a skeleton for support and yet plants don't just flop over in a big spongy mess. This is because of a unique cellular structure called the cell wall. The cell wall is a rigid structure outside of the cell membrane composed mainly of the polysaccharide cellulose.

In addition, plant cells contain an organelle called the chloroplast. The chloroplast allows plants to harvest energy from sunlight. Specialized pigments in the chloroplast (including the common green pigment chlorophyll) absorb sunlight and use this energy to complete the chemical reaction:

6 CO2 + 6 H2O + energy (from sunlight) C6H12O6 + 6 O2

Carbon dioxide + Water Glucose + Oxygen

In this way, plant cells manufacture glucose and other carbohydrates that they can store for later use.



Table-1: Some differences between animal cell and plant cell.

Organonelles Animal Cell Plant CellShape Round (irregular shape) Rectangular (fixed shape)Plasma membrane

only cell membrane cell wall and a cell membrane

Cell wall Absent PresentVacuole One or more small vacuoles (much

smaller than plant cells).One, large central vacuole taking up 90% of cell volume.

Plastids Absent PresentLysosomes Lysosomes occur in cytoplasm. Lysosomes usually not evident.Chloroplast Animal cells don't have chloroplasts Plant cells have chloroplasts because they

make their own food

Energy and Cell

All living organisms require energy to conduct the many functions necessary to sustain life. The source of this energy for cells is the chemical bonds of food molecules that are collected from the sun by plants. Cells can be thought of as chemical factories that conduct a variety of chemical reactions.

Photosynthesis and RespirationThe process of converting sunlight energy to chemical-bond energy by the chloroplasts as sugar molecules is photosynthesis. It is one of the major biochemical processes through which plants produce food molecules such as carbohydrates for themselves as well as for all the other organisms on earth. On the other hand respiration, a second major biochemical process made by mitochondria, during which cells release the chemical-bond energy from food and supply to the cells into usable forms.

This cycle of photosynthesis and respiration maintains the balance of carbon dioxide and oxygen on earth.


C6H12O6 6O2 6CO2 6H2O 36ATP

glucose oxygen carbondioxide

water energy

Aerobic cellular respiration


Table-2: Differences between photosynthesis and respiration at a glance.

Photosynthesis RespirationOccurs in the presence of light (and chlorophyll in plant cells).

Occurs at all times in cells.

Requires energy (light) to make sugar (glucose). Releases energy from sugar.Complex substances (sugar) are formed from simpler ones (carbon dioxide and water).

Complex substances (sugar) are broken down into simpler ones (carbon dioxide and water).

Carbon dioxide and water are the raw materials. Carbon dioxide and water are the waste products.Oxygen is given out. Oxygen is taken in.

Questions:

1. What is cell? Name different important parts of a cell. 2. Draw the picture an animal cell and label different parts in it..3. What are the differences between plant cell and animal cell?4. Describe the functions of chloroplast, cell wall, ribosome, mitochondrion etc.5. Draw the picture of a plant cell and label different parts in it.6. Discuss the importance of photosynthesis and respiration.7. What are photosynthesis and respiration? 8. Write the difference between photosynthesis and respiration at a glance.


biology1[cell photo synthesis respiration]

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