CELLS
Prokaryotes
Eukaryotes
- One celled organisms
- Few internal structures
- Do not have structures surrounded by membrane
- No nucleus, naked DNA
- Multi-cellular organisms
- Has a nucleus and DNA inside it
- Has structures surrounded by membranes
CHARACTERISTICS OF LIFE
1. Organization of cell
2. Respiration
3. Homeostasis
4. Sensitivity
5. Growth & Development
6. Reproduction
7. Adaptability
8. Excretion
9. Movement
Cell - Smallest unit of life capable of living in a medium free of life.
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**The two main characteristics of life are growth & development and reproduction.
Cell Membrane
- Selectively permeable and fluid like
- Has a lipid bi-layer, proteins and cholesterol
- Cholesterol gives cell membrane added support
- Phospholipids make a bilayer (Phosphate + 2 fatty acids)
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Hydrophobic ends: non-polar, resist water, lipid tail
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Hydrophilic ends: polar, attract water, phosphate head
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Figure 1 Animal Cell Cytoplasm & Cell Membrane
- Cell membrane is not rigid, fluid-like and constantly changing depending on function (fluid like due to hydrophilic ends)
- Selectively permeable due to phospholipid bi-layer
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INTEGRAL PROTEINS INTERACT WITH LIPID BILAYER
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Passive transport pores and channels
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Active transport pumps and carriers
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Membrane-linked enzymes and transducers
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***As the hydrophobic tails do not allow water and dissolved substances to pass through, proteins are present in cell membrane where substances are allowed to pass through. Hence the cell membrane can selectively permit some substances (dissolved in water) to pass through protein 'check-points'.
Cytoplasm & Cytoskeleton
Cytoplasm
- Water based for chemical reactions to take place in
- Helps cook cell from heat energy released during respiration and other chemical reactions
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Cytoskeleton
(All filaments prevent or allow stretching)
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Action Filaments (microfilaments) 5-9 nm diameter with twisted strands.
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Found in muscles. Help contract and relax muscles ​
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Intermediate Filaments 9 nm diameter with 4 strands wrapped around each other. ​
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Makes up bulk of the framework of cells ​
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Microtubules 24 nm diameter that are hollow in nature​
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Transports organelles within cells.​
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Nucleus
- Bi-membrane (two layers) and has pores
- Nucleolus makes ribosomes of the cell. The nucleolus contains protein and RNA.
- DNA present
- Chromatin condenses into chromosomes during replication of cell
- Chromatin stores DNA (Deoxyribonucleic acid)
- Control center of the cell
- Has a nuclear membrane
Figure 2 Nucleus
Cell Wall
- Present in some plants and bacteria
- Made of cellulose in plants
- Made of glycogen based molecules in bacteria
- Supports ans protects the cell
- Completely permeable
Figure 3 Cell Wall in Plant Cell
Endoplasmic Reticulum (ER)
Rough Endoplasmic Reticulum (R.E.R)
- Flattened structure attached with ribosomes (Ribosomes give the R.E.R a rough texture/look
- Joined to the nuclear envelope
- Synthesizes protein and modifies them
Smooth Endoplasmic Reticulum (S.E.R)
- Tubular
- No ribosomes attached
- Synthesizes lipids and steroids (sex hormones)
- Detoxification of harmful material in SER
- Substances synthesized in the E.R (endoplasmic reticulum) are sent to the Golgi apparatus to be chemically modified.
- DNA controls cell by making proteins synthesize
Golgi Apparatus
- Flattened disk like structures stacked onto one another
- Chemically modifies substances made by the ER (lipids, steroids, proteins)
- Processes and packages substances in membrane (vesicle) for secretion outside of the cell
Figure 7 Movement of Substances from Golgi Apparatus to outside cell
Figure. 4 Endoplasmic Reticulum
Ribosomes
- Small, globular structures
- Do not have membrane; protein in nature
- Made in nucleolus
* Lying freely - Protein for use inside the cell
*Attached to the ER - Protein for use outside the cell (sent to Golgi Apparatus by ER)
Mitochondria
- Powerhouse of the cell
- Sausage shaped
- Double membrane
- Makes energy for cell
- Cellular respiration takes place in mitochondria
*Contains ATP (Adenosine tri phosphate) ​
Figure 6 Mitochondria
Centrioles
- Small oval structures
- Appear in pairs
- Found near the nucleus
- Helps in cell division
- Found in only animal cells
Vesicles: Lysosomes
- Lysosomes are a type of vesicle which have enzymes inside them and digest harmful material inside a cell
-All membranes inside the cell are similar to allow the easier integration of substances from one organelle to another (as can be seen with the ER and Golgi Apparatus)
Chloroplast
- Double membrane
- Contains chlorophyll (green pigment)
- Chlorophyll is essential for photosynthesis
Vacuole
- A fluid filled space surrounded by membrane (called tonoplast)
- Stores substances for usage later on
Plant: Permanent large vacuole
Animal: Temporary small vacuoles
Figure 7 Chloroplast
Figure 8 Vacuole in a Plant Cell
Difference between Animal and Plant Cell
Plant Cells
- Large Permanent Vacuole
- Cell Wall
- Chloroplast
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Animal Cells
- Multiple small temporary vacuoles
- Centrioles
Figure 8 Difference between animal (left) and plant (right) cell
Specialized Cells
There are 50 - 75 trillion cells present in the body, of which there are 220 types of specialized cells.
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Specialized cells carry out different functions; they have different shapes, sizes, and features according to the function of the cell. Stem cells become into specialized cells through cell differentiation.
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Stem Cells
- Do not have a 'specific' function
- Reproduce quickly and have all organelles
- Become specialized through cell differentiation
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Red Blood Cells (RBCs)
- Contain haemoglobin (contains iron - binds to oxygen)
- Oxygen transported around the body
- No nucleus (more area for haemoglobin)
- Increased surface area to volume ration (SA:V)
- Made in bone marrow
- Cannot divide and replicate once specialized
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Root Hair Cells
- Long and narrow --> SA:V
- Water and minerals obtained through diffusion
- Found only in plants
- Does not contain chlorophyll
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Xylem Vessels
- Long hollow tubes from root to leaves
- Narrow and no cross walls in lumen
- Don't have protoplasm
- Walls thickened with lignin for support
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Nerve Cells
- High Potassium to Calcium Gradient
- Long 'arms' to cover greater distance
- Sends electrical impulses to and from the brain to the body.
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Cilia
- Tiny hair like extensions
- Found in trachea and in ears
- In ear, cilia helps to discern the 'pitch' of sound
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Trachea Cilia
- Helps keep dirt out of lungs
- Secrets mucus
- These extensions use muscles to move dirt away from lungs to the mouth
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Muscle Cells
- Contracts and Expands
- Mitochondria uses ATP (Adenine tri-phosphate) to produce energy when muscles contract
- Too much of chemicals can make muscles forget to relax (resulting in muscle spasms)
Cells
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Tissues (Simple/Complex)
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Organ
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Organ System
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Organism
Stem Cells & Diseases
- Also called pluripotent cells (multiple potential) or germ cells
- Contain organelles and aren't specialized
- Zygote is a stem cell
- Found in umbilical cord, teeth and bone marrow
- Can be used to treat certain diseases
LEUKEMIA
- Uncontrolled growth of blood cells
- All blood must be taken out, chemo and radiation of bone marrow
- New stem cells transplanted in bone marrow
- Very small success rate, painful process
STARGARDTS DISEASE
- Degenerative genetic disease
- Causes eyes to prematurely deteriorate
- Lens loose flexibility, difficulty in focusing
- Stem cells injected in deteriorating cells
MUSCULAR DYSTROPHY
- Muscles loose their ability to move
- Cannot perform their job and die out at a faster rate
- Stem cells injected in dying cells