Cell Physiology Lecture 1 Flashcards
Cell Surface
the part of the cell that is exposed to the outside world
What three things do all cells have
- A plasma cell membrane which surrounds the cell surface
- Cell organelles which do tasks
- Interior of the cell which consists of the nucleus and the cytoplasm
Cell organelles: membrane-bound or _________________
non-membrane bound
What is the cytoplasm
The region outside the nucleus and is composed of cytosol which is a gel like fluid in which the cell organelles are suspended
The ___________ is the largest organelle in the cell
nucleus
What are the 4 functions of the plasma cell membrane?
- Physical barrier between the Intracellular fluids (ICF) and the extracellular fluids (ECF)
- Cell to cell communication
- Structural Support
- Transport
Plasma Membrane Function:
Physical Barrier between ICF and ECF
-Keeps organelles and proteins inside cell
-Maintains difference in ion composition between ICF and ECF
-Maintains homeostasis – things may change outside the cell but inside
remain constant
Plasma Membrane Function:
Cell-to-cell communication
-Contains receptors which bind signalling molecules
Plasma Membrane Function:
Structural Support
-Contains connections composed of proteins which anchor cells to each other or to extracellular materials
Plasma Membrane Function:
Transport
-Plasma membrane is selectively permeable- some substances may
simply move across the plasma membrane but most require specific transport proteins (transporters, carriers, channels etc.) to cross. It is therefore selectively permeable, allowing certain molecules to move across but not others.
Can cell organelles have membranes? What are they called?
Yes, they are called intracellular membranes
What is the cell/plasma membrane, and the intracellular membranes surrounding organelles composed of?
a double layer of lipid molecules with embedded proteins
What is the predominant lipid in the cell/plasma membrane, and the intracellular membranes?
The phospholipid
What are biological membranes that have the predominant lipid as phospholipids called?
Phospholipid Bilayers
Phospholipid Bilayer
2 layers of phospholipids with embedded proteins
2 Types of biological membranes:
-Cell/Plasma Membrane
-Membranes surrounding organelles
Biological Membrane lipids are:
amphipathic
amphipathic:
contains polar and none-polar regions
3 types of amphipathic lipids found in biological membranes
- Phospholipids
- Cholesterol
- Glycolipids
What composes the structure of a phospholipid?
- Polar head group
- Non-polar tail
Structure of a Phospholipid: Polar Head group
-Composed of phosphate attached to glycerol, a nitrogen-containing chemical group, and glycerol backbone
-Polar head group is hydrophilic (water-loving or dissolves in water)
Structure of a Phospholipid: Non-Polar tail
-Composed of 2 fatty acid chains composed of carbon and hydrogen atoms
-Fatty acid chains may be: saturated (no double bonds) or unsaturated
(containing 1 or more double bonds)
-Nonpolar tail is hydrophobic (water-fearing or does not dissolve in water)
What happens to phospholipids when you put them in water
-They spontaneously form a bilayer
-Polar heads face aqueous environment, either the ECF or ICF (REMEMBER DOUBLE-LAYERED SO CAN BOTH)
- Nonpolar tails form hydrophobic core
-Bilayer is the structure of the plasma membrane and the organelle membranes
Cholesterol
-Steroid Lipid
-Amphipathic
Polar/Nonpolar groups of cholesterol
Nonpolar: carbon-hydrogen rings and a carbon-hydrogen chemical group attached to one of the rings
Polar: hydroxyl group
Where is cholesterol found?
In the cell/plasma membrane
2 Functions of Cholesterol
-maintains proper membrane fluidity
-Very important part of plasma membrane: there is almost one molecule of cholesterol for each molecule of phospholipid in the cell/plasma membrane (organelle membranes contain very little cholesterol)
Glycolipids are lipids with ___________
CHO (carbohydrate) attached
Where are Glycolipids found?
On the outer leaflet of the plasma membrane (meaning the layer that faces the ECF)
Are Glycolipids Amphipathic? Why
Yes they are, due to the presence of sugar.
What do glycolipids do?
They form the glycocalyx
Glycocalyx
A layer of carbohydrates linked to lipids or membrane proteins
What are two types of proteins on the plasma/cell membrane?
Integral (Intrinsic)
Peripheral (Extrinsic)
Intrinsic Proteins
-Amphipathic
– inserted into phospholipid bilayer of plasma/cell membrane and partially span membrane or are transmembrane proteins (completely cross phospholipid bilayer of membrane)
-Penetrate the phospholipid bilayer
-Comprise the majority (70%) of all proteins
-Examples: transporters or channels
Extrinsic Proteins
-Not Amphipathic
-Attached at the outer or inner surface of the membrane, they do not penetrate into the phospholipid bilayer.
-Carbohydrates may be attached to proteins facing the extracellular surface of the
plasma membrane and these are called glycoproteins. They form the glycocalyx alongside with the glycolipids.
- Extrensic Proteins are distributed unequally between the two halves of the plasma membrane and this is related to the function of the protein.
Example highlighting the unequal distribution of extrensic proteins in the plasma membrane
A receptor in the membrane has binding sites facing the ECF, so signaling molecules may arrive at the cell and bind to the receptorsw. These binding sites do not face the inside of the cell.
Cell Junctions
Connections “bridges” that help connect, structurally support, and promote communication between cells.
Desmosomes
-Connections that secure cells together in tissues that are subject to considerable amount of stretching or mechanical stress. Like the heart muscle.
-Maintain Structural integrity of tissue
-Made of proteins called plaques, cadherins, intermediate filaments
Where are Plaques found in the cell
On the cytoplasmic surface of the cell (inner part of cell membrane).
Cadherins
Link cells together.
Intermediate Filaments
They secure the cytoplasmic surface of the desmosome to the components inside the cell to provide structural support.
Where are tight junctions found?
In epithelial tissue specialized for molecular transport
Epithelial tissue
Tissue that is composed of cells laid together in sheets with the cells tightly connected to one another.
Epithelial cells have _________ surfaces that differ in both structure and function
two
What are tight junctions made from
Proteins called Occludins
3 things Occludins do:
- Form nearly impermeable junctions (meaning tight junctions)
- Link adjacent cells together
- Limit the movement of molecules between cells, forcing molecules to pass through the cell, or cross the plasma membrane (molecules can only cross the plasma membrane if they can diffuse through the lipid bilayer or have specific proteins in the membrane).
Gap Junctions
Transmembrane channels linking the cytoplasms of adjacent cells
What are Gap Junctions made of?
Proteins called connexons
What do gap junctions do
They connect “couple” cells electrically, and metabolically.
Coupling cells electrically meaning
Connecting cells to allow ions to move through them
Coupling cells metabolically meaning
Connecting cells to allow small molecules to move between cells.
Why are gap junctions called communicating junctions?
Because they allow ions and molecules to move from one cell through the gap junction proteins (connexons) to another cell.
Nucleus function
Transmits genetic information to the next generation of cells and contains information needed for protein synthesis
What 4 things does the nucleus contain?
-Chromatin
-Nuclear Envelope
-Nuclear Pores
-Nucleolus
Chromatin
Complex of DNA and proteins found in the nucleus
Nuclear Envelope
Made up of two phospholipid bilayers, the inner and outer phospholipid bilayers.
Nuclear Pores
Watery channels made from proteins which allow molecules to move in and out of the nucleus (DNA too large to pass through the nuclear pores and remains in the nucleus)
Nucleolus
Site of synthesis of ribosomal DNA
Most cells have one nucleus except…
Red Blood Cells - No Nucleus
-Skeletal Muscles - Many Nuclei in one skeletal muscle cell (multinucleate)
What is not surrounded by phospholipid bilayer
Ribosomes
What is the function of ribosomes?
Protein Synthesis
What are ribosomes formed of?
A small and a large subunit
Large and small subunits of ribosomes are not ________________
functional when separate
Where are functional ribosomes found?
-They can be found free in the cytoplasm
-Rough Endoplasmic Reticulum (RER)
Large and small subunits join to form a _______________
functional ribosome, or one capable of protein synthesis
Proteins made in the cytoplasm have a _________________ than those made in the RER.
different final destination
Endoplasmic Reticulum (ER)
Fluid filled membranous system
2 types of Endoplasmic Reticulum (ER):
-Rough Endoplasmic Reticulum (RER)
-Smooth Endoplasmic Reticulum (SER)
Rough Endoplasmic Reticulum
flattened sacs with ribosomes attached to outer surface
Smooth Endoplasmic Reticulum
branched tubular structure with no ribosomes attached to outer surface
Rough Endoplasmic Reticulum Function
synthesizes proteins and performs post-translational modifications needed to produce a functional protein
Smooth Endoplasmic Reticulum Function
synthesizes lipids, stores calcium (in muscle; called the sarcoplasmic reticulum), drug detoxification (in liver)
Cisternae
Flattened sacs
What is the golgi apparatus made up of?
Cisternae
vesicle
small sack with a membrane
Golgi Apparatus functions
-Receives vesicles which contain proteins that were made at the RER
- Does Post-translational modifications of proteins made at the RER
-Sorts and packages proteins into vesicles
-Proteins packaged into vesicles by the golgi are then secreted from the cell, becoming integral membrane proteins, or becoming proteins of lysosomes, er or golgi itself.
What do lysosomes contain?
Hydrolytic enzymes
What do hydrolytic enzymes do?
They break large molecules into smaller subunits
Enzymes are only active at an acidic _________ in the lysosome
PH of 5
Lysosome function
Degrade extracellular and intracellular debris (worn out organelles) and destroy bacteria or viruses brought into the cell by fusing with them.
What do peroxisomes contain?
-Oxidative enzymes
-Catalase
What do oxidative enzymes do?
They use oxygen to remove hydrogen from molecules, thus breaking them down
What do peroxisomes do?
Break down fatty acids, alcohol, and drugs
Where are peroxisomes abundant?
In the liver and kidney
What is the toxic byproduct of the actions of oxidative enzymes
Hydrogen Peroxide
What does catalase do?
It breaks down hydrogen peroxide (H2O2) into water and oxygen
What is the function of the mitochondria
It does cellular respiration, makes nutrients into energy /ATP
What are the only organelles with double phospholipid membranes?
-Nucleus
-Mitochondria
Mitochondria layers
-Outer membrane
-Inner membrane is folded into tubules called cristae
Cells that need more energy have more _________
Mitochondrias
What are the two organelles that have their own DNA?
-Nucleus
-Mitochondria
What are the two organelles that are not membrane bound?
-Ribosome
-Cytoskeleton
What are cytoskeletons composed of?
Protein filaments or cytoskeletal filaments
What are the functions of the cytoskeleton
-Maintain cell shape
-Maintain the position of organelles in the cell
-Guides/Moves the cell, and organelles within it.
Cytoskeletal Filaments include:
- Microfilaments
- Intermediate filaments
- Microtubules
What are microfilaments made of?
A protein called actin
What are microtubules made of?
A protein called tubulin
Intermediate filaments are part of _____________
Desmosomes
______________ act as Intermediate filaments
Many Different proteins
