Biology Lesson # 2 Animal & Plant Cells

The Cell Cytology – the branch of biology that studies cells. It is made possible by the microscope. Robert Hooke first used the word “cell” in 1663. He was examining cork under a microscope, and thought that cork had many compartments or “cells” throughout its entirety. He originally thought that cells were for the passages of fluids, but we now know today that many other things occur within cells. Anton van Leeuwenhoek studied simple living organisms, and thought them to be little living molecules, called “animalcules”

Cell Theory 1. All living things are composed of cells. 2. The cell is a functional unit of life – our basic building blocks. 3. All cells come from pre-existing cells. Our bodies are made up of between 10 – 100 trillion cells.

Cell Processes Each cell contains smaller parts called organelles, which have special functions that maintain all the life processes of the cell, including: Intake of nutrients Movement Growth Response to stimuli Exchange of gases Waste removal Reproduction

Cell Membrane Diffusion Video A protective barrier around the cell made of a double layer of lipids (fat-like molecule that does not dissolve in water). The membrane allows different substances to move in and out of the cell, which is called diffusion. *More below*

Cytoplasm A jelly-like substance that fills the cell and surrounds the organelles. It contains the nutrients required by the cell to carry on its life processes. All organelles are suspended in the cytoplasm, and they are able to move around within it when needed.

Nucleus The control centre of the cell. It controls all the activities in the cell, including growth and reproduction. The nucleus is surrounded by the nuclear envelope, which allows pores to transport materials in and out of the nucleus itself. The most dense area of the nucleus is called the nucleolus. The nucleus contains the cell’s DNA (deoxyribonucleic acid), which is bound to proteins called chromatin. DNA contains the coded information for making proteins and other molecules.

Centrioles Only found in animal cells. Structures responsible for cell division.

Vesicles & Vacuoles Membrane-bound organelles that store nutrients, wastes, and other substances used in the cell. When the vesicle stores water, it is specifically called a vacuole. The vacuole in a plant cell is much larger than in an animal cell.

Mitochondria The powerhouse of the cell – this is where chemical reactions occur to convert chemical energy in sugar into energy that the cell can use.

Lysosomes Small organelles that are filled with enzymes (proteins that speed up chemical reactions) where digestion takes place. They also break down invading bacteria and damaged cell organelles – the clean-up system in the cell.

Ribosomes Small organelles where proteins are assembled. They can be free in the cell, or attached to the endoplasmic reticulum.

Endoplasmic Reticulum A series of interconnected small tubes that carry materials throughout the cell Rough ER is associated with making proteins, and have ribosomes attached to it. Smooth ER is associated with the production of fats and oils.

Golgi Apparatus Receives proteins from the ER, and modifies, sorts, and packages them for delivery throughout the cell or even outside the cell.

Cytoskeleton Internal network of fibres, made of proteins, which helps maintain the cell’s shape.

Cell Wall Only found in plant cells. A rigid frame around the cell that provides strength, protection, and support.

Chloroplasts Only found in plant cells. Contain a green substance called chlorophyll, which uses energy from the sun to convert carbon dioxide and water into sugar and oxygen in a process called photosynthesis. Chloroplasts are made up of little sacs called thylakoids, surrounded by a fluid called stroma. A stack of thylakoids is called a granum. They are “solar collectors” for photosynthesis to produce carbohydrates, which are used for plant growth.

Diffusion Diffusion is the movement of molecules from an area of high concentration to an area of low concentration until the 'mixture' is even: this is known as equilibrium. Diffusion is faster in gases (like oxygen) than in liquids (like water), because particles in gases move faster than particles in liquids.

Diffusion (continued) The amount of diffusion depends on the concentration of the particles on both sides of the cell membrane. For example, if there is not enough oxygen in a cell, then oxygen will diffuse from outside the cell through the cell membrane and inside where it is needed. Another example – if there is too much carbon dioxide inside the cell, then it will diffuse from inside the cell through the cell membrane and inside where it can be removed by the body. The cell membrane is semi-permeable, meaning that it is not completely solid, and so gases and liquids are able to pass through the small holes. Solid objects, however, cannot.

Osmosis When water is the particle that diffusing through a semi-permeable membrane, it is specifically called osmosis.

Cell Videos Crash Course – Animal Cells