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Human Anatomy and Physiology 1 Week 1 Part 2
Objectives
2.1 Identify the structure and function of the cell and its organelles |
2.2 Describe the structure and capabilities of the cell membrane |
General
Cells (-cyte) |
Smallest unit of life |
The structural units of nearly all living things |
Comes in a variety of shapes and sizes - their anatomy 'complements' their physiology |
Most cells have 3 main parts: Nucleus, cytoplasm, plasma (cell) membrane |
Nucleus - Control centre |
Cytoplasm - jelly-like substance that acts as support. Contains H2O (cytosol) & Organelles ('little organs') |
Plasma (cell) membrane - Outer 'coat' |
Structure of a generalised cell
Organelles - 'little organs'
Found inside the cell |
They are structures designed to carry out specific functions |
For example: |
Ribosomes - float free or attached to rough ER, makes proteins |
Mitochondria |
Endoplasmic reticulum (ER) - 2 types (rough & smooth) |
Golgi apparatus |
Lysosomes |
Cytoskeleton |
The Nucleus
Almost every cell has one |
Cytoplasm inside the nucleus is called nucleoplasm |
Nucleus contains the genetic material (DNA) seen as strings called chromatin |
Nucleus is surrounded by a double membrane containing pores - sometimes called the nuclear envelope |
Function |
Directs the activity of the cell i.e.: |
Cell division |
Makes ribosomes required by a cell, most ribosomes migrate into the cytoplasm where protein synthesis occurs |
Nuclear envelope regulates substances in and out of the nucleus through pores; without a nucleus, the cell cannot survive very long |
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Mitochondria
Sausage shaped organelle with a double layered membrane |
'Powerhouse of the cell' as it converts food into energy (uses O2 to break down food) |
Some power escapes as heat but the rest is used to form ATP molecules |
ATP is vital for cell function |
All living cells require ATP for its activities |
Endoplasmic reticulum (ER)
Network of channels transporting substances around the cell |
Two types: Rough and smooth |
Rough ER |
Smooth ER |
Called rough as it has ribosomes on its surface (and inside) |
No role in protein synthesis |
Proteins made here are dispatched to other ares of the cell in vesicles |
Assists with cholesterol & lipd metabolism |
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Detoxifies drugs and pesticides |
Plasma membrane
Flexible barrier surrounding the cell |
Every cell has a plasma membrane |
Seperates the intra-cellular environment (inside) from the extra-cellular environment (outside) |
Made up of four main components: Bi-layer of phospholipids, Proteins, Cholesterol, Carbohydrates - Glycolipids & Glycoproteins |
It's ability to regulate entry & exit of substances makes it 'selectively permeable' |
Phospholipids arrange themselves so their hydrophilic end is outwards & their hydrophobic end is inwards, creating an oily film |
Plasma (cell) membrane proteins: |
Proteins found in the plasma membrane do most of the specialised functions |
They act as: |
Receptors - for messenger molecules like neurotransmitters & hormones |
Channels - act as gates allowing water & other substances through |
Carriers - pumping things in and out of the cell |
Lysosomes
Membranous bags containing powerful digestive enzymes |
Demolition site of the cell |
Digests worn out materials for the cell - Focus on bacteria, viruses & toxins |
Cytoskeleton
Dense support scaffold of filaments & cylinders for transport & shape |
E.g., actin & myosin in muscles |
Golgi apparatus
Stack of flattened membrane sacs with many vesicles |
Collects proteins from the rough ER |
Modifies and repackages proteins |
Sorts and redirects proteins |
End product is transported around the cell in vesicles to three different destinations: |
Become part of the cell |
Are secreted from the cell |
Ramain inside the cell |
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