The Cell Flashcards
The plasma membrane
Forms a cells flexible outer surface and separates the cell’s internal environment from its external environment.
It regulates the flow of material into and out of the cell.
Plays a key role in communication between cells and with their external environment
Framework of the plasma membrane
lipid bilayer - two tail to tail layers made up of three types of lipid molecules: phospholipids, cholesterol and glycolipids
Integral protein in plasma membrane
extends through lipid bilayer and allows small and medium water soluble materials to cross the membrane
Peripheral protein in plasma membrane
loosely attached to exterior or interior surface of the membrane
Name of fluid in body cells
Intracellular fluid - 2/3 of the total fluid in our bodies
ICF
intracellular fluid - found in body cells
ECF
extracellular fluid - found outside cells
Interstitial fluid
ECF between cells in tissues
Blood plasma
ECF in blood vessels
Lymph
ECF in lymphatic vessels
CSF
cerebrospinal fluid- surrounds brain and spinal cord
Solute
any material dissolved in fluid
Solvent
fluid that dissolves materials
How much fluid is in our bodies?
8 pints or 4 litres
How permeable is the plasma membrane?
Selectively permeable - allows some substances but restricts the access of others
What is the lipid bilayer permeable to?
water and non polar molecules
Macrophages
eat anything that’s foreign - when they are overwhelmed, it causes glands to swell up
Passive processes
substance moves down its concentration gradient through the membrane, using only its own energy of motion.
Includes simple diffusion and osmosis
Active processes
cellular energy is used to push the substance through the membrane ‘uphill’ against its concentration gradient
e.g. active transport
Brownian motion
moving from an area of high concentration to an area of low concentration
Simple diffusion
when substances move across a membrane through the lipid bilayer e.g. fatty acids, steroids, O2, CO2
Facilitated diffusion
when substances that can’t move through the lipid bilayer by simple diffusion cross the plasma membrane by a passive process.
An integral membrane protein (a channel or a carrier) assists a specific substance to move across the membrane.
How do channel proteins open?
By a flow of electricity - they get excited
Osmosis
a net movement of water through a permeable membrane. high concentration –> low concentration
Phagocytosis
‘cell eating’. Large, solid particles such as bacteria are taken in by the cell
Bulk phase endocytosis
‘cell drinking’. Cells take up tiny droplets of extracellular fluid
Exocytosis
results in secretion or the liberation of materials out of a cell
Cytoplasm
The structural framework for the cell which generates movement. Cytosol is the liquid portion of the cytoplasm that surrounds organelles - 55% of total cell volume.
Composed of three different types of protein filaments - microfilaments, intermediate filaments and microtubules
Ribosomes
Ribosomes are the site of protein synthesis. Have a high content of RNA.
ER
Endoplasmic Reticulum - network of folded membrane of flattened tubules
Rough ER
extends from nuclear envelope and is studded with ribosomes. Function is to synthesise proteins
Smooth ER
extends from rough ER and lacks ribosomes. Fatty acids and steroids such as estrogens and testosterones are synthesised
Golgi complex
After proteins are synthesised on a ribosome attached to ER, most are transported to another region of the cell. First step of transport pathways is the golgi complex whose main function is to modify and package proteins. They are then sorted and packaged into vesicles
Mitochondria
site of most ATP production. A series of inner folds called mitochondrial cristae and a larg central fluid filled cavity is the mitochondrial matrix
ATP (3 phosphates) ADP (2 phosphates)
Nucelus
spherical or oval structure.
A double membrane called the nuclear envelope separates the nucleus and cytoplasm. Nuclear pores pierce the envelope and control the movement of substances between the nucleus and cytoplasm.
Contains DNA which allows replication of cells
Nucleoli
Inside nucleus. Clusters of protein, DNA and RNA which are the sites of the assembly of ribosomes
Genes
Within nucleus and control cellular structure and direct most cellular activities. Arranged along chemical chromosomes.
Protein Synthesis
Information contained in DNA is transcribed to produce a complementary sequence of codons in a strand of RNA. This is catalysed by enzyme RNA polymerase. RNA then attaches to a ribosome, where the information in RNA is translated into specific amino acids to form a new protein molecule.
How much ATP does the body produce?
Total ATP in an adult is approximately 0.1mol/L. We require 100-150mol/L daily so each ATP molecule is recyled 1000-1500 times per day.
Glycolysis
reactions that extract energy from glucose by splitting it into two 3-carbon molecules
Two main phases of the glycolytic pathway
Energy requiring phase - starting molecule of glucose is rearranged and two phosphate groups are attached. The phosphate groups make the fructose-1,6-biphosphate, which is unstable so it splits in half to form two phosphate bearing three carbon sugars. Two ATP molecules are used.
Energy releasing phase - each three carbon sugar is converted to another three carbon molecule, pyruvate, through a series of reactions. Two ATP molecules and one NADH molecule produced, but process is repeated twice for two of the carbon sugars so four ATP molecules and two NADH molecules produced overall.
