Human Anatomy and Physiology 1 Week 1 Part 2
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2.1 Identify the structure and function of the cell and its organelles
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2.2 Describe the structure and capabilities of the cell membrane
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Cells (-cyte)
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Smallest unit of life
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The structural units of nearly all living things
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Comes in a variety of shapes and sizes - their anatomy 'complements' their physiology
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Most cells have 3 main parts: Nucleus, cytoplasm, plasma (cell) membrane
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Nucleus - Control centre
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Cytoplasm - jelly-like substance that acts as support. Contains H2O (cytosol) & Organelles ('little organs')
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Plasma (cell) membrane - Outer 'coat'
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Found inside the cell
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They are structures designed to carry out specific functions
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For example:
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Ribosomes - float free or attached to rough ER, makes proteins
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Mitochondria
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Endoplasmic reticulum (ER) - 2 types (rough & smooth)
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Golgi apparatus
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Lysosomes
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Cytoskeleton
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Almost every cell has one
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Cytoplasm inside the nucleus is called nucleoplasm
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Nucleus contains the genetic material (DNA) seen as strings called chromatin
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Nucleus is surrounded by a double membrane containing pores - sometimes called the nuclear envelope
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Function
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Directs the activity of the cell i.e.:
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Cell division
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Makes ribosomes required by a cell, most ribosomes migrate into the cytoplasm where protein synthesis occurs
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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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Sausage shaped organelle with a double layered membrane
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'Powerhouse of the cell' as it converts food into energy (uses O2 to break down food)
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Some power escapes as heat but the rest is used to form ATP molecules
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ATP is vital for cell function
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All living cells require ATP for its activities
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Network of channels transporting substances around the cell
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Two types: Rough and smooth
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Rough ER
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Smooth ER
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Called rough as it has ribosomes on its surface (and inside)
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No role in protein synthesis
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Proteins made here are dispatched to other ares of the cell in vesicles
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Assists with cholesterol & lipd metabolism
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Detoxifies drugs and pesticides
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Flexible barrier surrounding the cell
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Every cell has a plasma membrane
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Seperates the intra-cellular environment (inside) from the extra-cellular environment (outside)
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Made up of four main components: Bi-layer of phospholipids, Proteins, Cholesterol, Carbohydrates - Glycolipids & Glycoproteins
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It's ability to regulate entry & exit of substances makes it 'selectively permeable'
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Phospholipids arrange themselves so their hydrophilic end is outwards & their hydrophobic end is inwards, creating an oily film
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Plasma (cell) membrane proteins:
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Proteins found in the plasma membrane do most of the specialised functions
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They act as:
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Receptors - for messenger molecules like neurotransmitters & hormones
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Channels - act as gates allowing water & other substances through
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Carriers - pumping things in and out of the cell
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Membranous bags containing powerful digestive enzymes
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Demolition site of the cell
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Digests worn out materials for the cell - Focus on bacteria, viruses & toxins
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Dense support scaffold of filaments & cylinders for transport & shape
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E.g., actin & myosin in muscles
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Stack of flattened membrane sacs with many vesicles
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Collects proteins from the rough ER
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Modifies and repackages proteins
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Sorts and redirects proteins
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End product is transported around the cell in vesicles to three different destinations:
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Become part of the cell
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Are secreted from the cell
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Ramain inside the cell
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