CELLS
- Cells are the smallest units of life, but are capable of surviving in mediums free of life.
- There are 2 main types of cells:
- Prokaryotic (Before Nucleus): In unicellular organisms. They have no membrane-bound organelles.
- Eukaryotic (True Nucleus): In multicellular bodies. They have complex organelles and are located in plants, animals
Functions of a cell include:
- Containing DNA
- Sensitivity
- Nutrition
- Making enzymes /proteins
- A cell contains organ elles, mini-organs that carry out these functions.
How a cell compares to a factor:
- Nucleus – Head office
- DNA – Manager
- Proteins – Product
- Smooth Endoplasmic Reticulum + Ribosomes – Machinery
- Cytoplasm – Free space
- Vacuole-Storage Room
- Cell membrane – Guards
- Mitochondria – Power House
- The cell membrane is a sheet like protective surface. It is selectively permeable, and lets only some particles pass through. It is made of a phospho-lipid bilayer.
- Ribosomes are small globular structures that produce proteins. Ribosomes are made in the Nucleolus. There are two types of Ribosome es free and membrane-bound ribosomes. Free ribosomes roam around freely in the cytoplasm. They synthesize proteins for the use of the cell, while the other type, membrane – bound (attached to Rough Endoplasmic Reticulum) synthesize them for external use.
- The Nucleus is the Head office of the cell. It contains the DNA. The Nucleus have 5 components:
- The Nucleolus makes Ribosomes. The Chromatin contains DNA, and it condenses to form Chromosomes
- The Cytoplasm is the jelly-like substance inside a cell that counts as free space.
- The Rough Endoplasmic Reticulum (RER) is right outside the -Nucleus. It is a flattened structure, and is joint to the Nucleus Envelope. It synthesizes and modifies proteins (polypeptides) – It has ribosomes attached to it, giving it a “rough” appearance.
- The Smooth Endoplasmic Reticulum (SER) synthesizes lipids and removes harmful! substances. This process is known as detoxification. The SER also creates vesicles.
- The Golgi Apparatus (also called Golgi Body) is a flattened disk-like structure. It has the same membrane as the Cell Membrane. It processes and packages proteins in vesicles. Vesicles are thus mo diffed with in. Then, they (the vesides) merge with the Cell Membrane. The flattened shape of the Golgi Body gives a higher surface Area: volume Ratio.
- Mitochondria is the “power house of the cell. They carry out cellular Respiration. They have their own ONA. Th of create ATP (Adenine Triphosphate), which helps create and send energy whee ATP is a currency. They have 2 membranes, so enzymes are attached to them?
- The chloroplast is the other organelle with a double membrane. It contains a pigment called Chlorophyll, which gives the chloroplast its green colour and helps in photosynthesis (which is why chloroplasts are only present in plants and algae).
- Vacuoles are large fluid filled spaces enclosed by membranes. Plants have any large, central vacuole, while animals have several temporary and small vacuoles. Their membranes are called tonoplasts. It is permeable to water. vacuoles contain salt and glucose.
- Centrioles are small, round structures that help in coll division. They are only present in animal cells. They appear in pairs. In any cell, there is only one pair of centrioles. They have a copy of the DNA and are protenin nature.
- The Cell Wall is an external layer only present in planks. It is made up of cellulose. It has a rigid structure and is completely permeable. It provides support and prevents bursting. It can withstand water pressure.
- Lysosomes are Digestive Plants for proteins, fats and carbs. They transport undigested material to the cell membrane for its removal. The cell can break down if the Lysosome explodes.
- Differences between plant and animal cells:
Organelles figures:
(1). CELL MEMBRANE (Phospho -Lipid Bilayer)
(2) CELL WALL
(3) NUCLEUS
(4) ENDOPLASMIC RETICULUM
(5) RIBOSOMES
(6) MITOCHONDRIA
(7)GOLGI APPARATUS
(8) LYSOSOMES
(a) CHLOROPLASTS
- Some cells are specialized. They are modified and have particular structures and functions. They are formed through a process called “Cell Differentiation”.
- Classic examples of specialized cells are Red Blood cells (RBCS). They transport oxygen throughout the body and remove Carbon Dioxide. It needs storage, which is why they have no nucleus. It needs to store haemoglobin (a metalloprotein). They are created in the bone marrow. At the time of creation, they have a nucleus, but they remove it for Increased storage. They have a biconcave shape to increase the surface Area to volume patio.
- Stem cells are cells that have not yet differentiated. They are raw cells, and can order for the growth of the Liver, Heat, Kidney etc. Although the Heart, Liver etc. are organs, stem cell’s can order for their growth because:
(1) CELLS
(2) TISSUES
(3) ORGANS
(4) ORGAN SYSTEMS
(5) ORGANISMS
- Histology is the study of tissues. There are 4 types of tissues:
(1) Ephithelial-Coversurfaces
(2) connective -support, Transport, Storage
(3) Muscles – contract
(4) Nevral-Cary Signals
- Antagonistic muscles are pairs of muscles working in opposite directions.