Chapter 4 Cell Structure and Function
- All living things are composed of one or more cells.
- Cells are the basic units of structure and function in an organism.
- Cells come only from the reproduction of existing cells.
- Cells vary in shape, size and internal organization.
- All cells have a specific job to do and look and function the best for that job.
White blood cells Stem cells
Nerve Cells Heart cells
Skin cells Plant cells
- Many cells have a variety of internal structures called organelles or mini organs.
- Most cells are surrounded by a cell membrane.
- Many cells have a large organelle called the nucleus.
- Cells that contain organelles and a nucleus are called eukaryotic cells.
- Cells that DO NOT contain organelles and a nucleus are called prokaryotic cells.
What’s the difference here?
- Let’s compare three items: a eukaryotic cell, a prokaryotic cell and a virus.
- What are the similarities?
- What are the differences?
Prokaryotes Vs. Eukaryotes Vs. Viruses
- No membrane bound nucleus
- Only a few organelles or none at all.
- Has a capsule surrounding it
- Only plants have cell wall
- Has a lipid bi-layer membrane surrounding it.
- Specialized by thousands of different sizes and shapes.
- Cannot reproduce on its own
- Generally not considered alive by most standards
Parts of the Eukaryotic Cell
- Endoplasmic reticulum (rough and smooth)
Plant Cells Vs. Animal Cells
- Contain chloroplasts for photosynthesis
- Have a cell wall to maintain structure and rigidity
- Usually do not contain lysosomes and peroxisomes
- Cells are square and rigid or geometric shaped
- Have one large central vacuole
- Contain lysosomes and peroxisomes
- Contain cilia and/or flagella
- Cells are fluid and flexible, many shapes
Parts of Eukaryotic Cell You are required to know the parts, what they look like and their function for the test!
- The cell membrane is selectively permeable which means some substances can cross and others cannot cross.
- Cell membranes are made of primarily lipids and proteins.
- Cell membranes are made of a lipid bi-layer.
- A cell membrane is called a fluid mosaic because it behaves more like a liquid than a solid.
- It is flexible and provides an effective barrier and transport function.
- This lies between the cell membrane inside of the cell.
- It is a fluid that all the organelles float in.
- It is sometimes called the cytosol.
- Mitochondria are the powerhouses of the cell.
- Mitochondria create ATP for the cell to use as energy.
- One cell many have thousands of mitochondria depending on its function.
- Mitochondria have two membranes and have their own DNA which only comes from the mother.
- Ribosomes are the most numerous of the cell’s organelles.
- Ribosomes are made of proteins and RNA.
- Ribosomes are responsible for creating proteins.
- Ribosomes are found free in the cytoplasm and also attached to the rough ER. (endoplasmic reticulum)
- The ER comes in two varieties, the rough ER and the smooth ER.
- The rough ER contains ribosomes and makes proteins.
- The smooth ER does not contain ribosomes and makes lipids such as steroids.
- The rough and smooth ER are sometimes attach to each other.
- Both ER are involved in cell product transport of proteins and lipids.
- The golgi is the processing, packaging and transport system.
- It is a system of membranes that work closely with the ER.
- The golgi modifies the products for transport throughout the cell.
- Lysosomes contain enzymes that help digest proteins, carbohydrates, lipids, DNA and RNA.
- These enzymes can also digest old organelles, viruses and bacteria.
- Lysosomes are rare in plant cells.
- Cytoskeleton’s are made of two parts: the microtubules and the microfilaments.
- The microtubules assist in cell division by moving the cells apart.
- Microfilaments are made of protein and help with muscle contractions.
- Both help support the cell and give structure but do allow for movement.
Cilia and Flagella
- Some cells have flagella. They usually only have one.
- Many cells have cilia which can number in the thousands.
- A flagella is like a whip.
- Cilia are like tiny paddles.
- Cilia and flagella are made of microtubules.
- The nucleus is surrounded by a membrane called the nuclear envelope.
- The nucleus contains all the DNA for the cell.
- It directs all the activities of the cell.
- The nuclear envelope contains pores so that RNA can pass into the cytoplasm during protein synthesis.
- The nucleolus is found inside the nucleus.
- It is responsible for making the ribosomes.
- There is usually only one.
- Found in plant cells and bacteria only.
- Not found in animal cells.
- Helps maintain structure and protection.
- Does contain small pores to move water and oxygen and carbon dioxide in and out.
- These are fluid filled and store many different things such as water, waste, enzymes and poisons.
- In plants vacuoles take up 90% of the space.
- Vacuoles are small in animal cells.
- This also called a plastid.
- Chloroplasts have their own membrane and their own DNA.
- Chloroplasts are found only in plant cells and some protists. (little animals)
- Chloroplasts do photosynthesis and contain chlorophyll which make them green.
- Photosynthesis creates sugar from sunlight for the plant to use.