The cell Flashcards
The cell is:
The cell is the smallest functioning unit of life capable of maintaining homeostasis - the ability of an
organism to maintain internal equilibrium by adjusting in physiological processes.
Types of cells
There are two kinds of unicellular organisms:
- Eukaryotes (have a nucleus).
- Prokaryotes (don’t have a nucleus).
Eukaryote cells:
- types of species?
- organells?
- DNA location?
- DNA “structure”?
- plasma membrane?
- Contains cell wall?
- reproduction?
- Unicellular or Multicellular species.
- Has bond organelles.
- Nucleus (membrane bonded).
- Has a linear chromosome (double strand 𝐷𝑁𝐴).
- Has plasma membrane.
- Cell wall only in plants, and sometimes in fungi.
- Reproduce by mitosis and meiosis.
Prokaryote cells:
- types of species?
- organells?
- DNA location?
- DNA “structure”?
- plasma membrane?
- Contains cell wall?
- reproduction?
- Unicellular species only.
- No organelles.
- Nucleoid (not a ring nucleus) .
- Has a single circular 𝐷𝑁𝐴.
- Has plasma membrane.
- Usually, have a cell wall.
- Reproduce by fission or budding.
Plasma Membrane:
The plasma membrane is a biological membrane that separates the inner environment of the cell from the
outside world and is selectively permeable.
The nucleus:
the control center of the cell, containing the 𝐷𝑁𝐴 that is organized in chromosomes.
functions:
1. 𝐷𝑁𝐴 protection.
2. 𝐷𝑁𝐴 synthesis (during replication).
3. 𝑅𝑁𝐴 synthesis– transcription.
Ribosomes :
The ribosomes are responsible for producing proteins according to 𝑚𝑅𝑁𝐴. They are composed of 𝑟𝑅𝑁𝐴 and proteins. Ribosomes can be found floating freely in the cytoplasm or bound to the 𝑅𝐸𝑅.
Endoplasmic Reticulum:
there are two types of ER:
1. Rough endoplasmic reticulum - a network of membranes found in proximity to the nucleus and
has ribosomes bound to it. This is the site of synthesis of proteins that need to be exported from
the cell.
- Smooth endoplasmic reticulum – does not contain ribosomes, and is the site of:
* lipid synthesis
* detoxification
* calcium storage.
Golgi Apparatus
A network of membranes that functions like a mailing system. It is divided by proximity to the nucleus -- Cis – closest to the nucleus. -- Medial. -- Trans – closes to the cell membrane.
**The golgi accepts proteins sent to it from that 𝑅𝐸𝑅, and sends them outside of the cell.
Lysosomes/Vesicles
Lysosomes are the garbage dumps. there are few types of vesicles:
1. Sacs - continuing digestive enzymes and acidic 𝑝𝐻.
- Peroxisomes – contains peroxide (𝐻2𝑂2) and used by the immune system to neutralize and kill
pathogens. - Proteasome – a large protein complex in the cytosol that is responsible for degrading proteins
which have been marked for destruction.
Mitochondria
The powerhouse of the cell. Unique organelle surrounded by two membranes: outer
permeable and inner impermeable. The inner membrane has folds called cristae and the inner environment is called matrix. Inside the matrix, we can find 𝐷𝑁𝐴 and ribosomes that are similar to prokaryotic ones.
Functions:
* Aerobic respiration – generation of 𝐴𝑇𝑃 using 𝑂2.
* Apoptosis - programmed cell death.
The Cytoskeleton:
A network of proteins that gives the cell shape, strength and ability to move. Can be divided into three classes.
Microtubules(The cytoskeleton):
Size of ~25 Nano-meters – hollow structure made out of 𝛼 and 𝛽 tubulin. They can elongate and disassemble by the addition and removal of tubulin dimers. Function:
- Intracellular transportation – movement of different material in the cell.
- Structural basis of the cilia and flagella.
- Formation of mitotic spindle – moves chromosomes during mitosis.
Intermediate filaments(The cytoskeleton):
Size of ~12 Nano-meters – give the cell mechanical strength, and help in cell communication.
Microfilaments(The cytoskeleton):
~7 Nano-meters – composed of two actin (type of protein) subunits. Functions:
- Determine shape of the cell and provide and strengths and support.
- Muscle contraction.
- Cell division – form a ring that divides the cytoplasm in the middle.
