Cells Flashcards
Cell definition
a collection of living matter enclose by a membrane
Types of cells
Prokaryotic cells
- a cell that lacks a nucleus (still has DNA)
Eukaryotic cells
- a cell that contains a membrane-bound nucleus and other membrane-bound organelles
Cell Theory
- all organisms are composed of cells
- all cells arise from pre-existing cells
- The cell is the basic unit of life
Organelles
structures suspended in the cytoplasm that carry out a particular function
Cell membrane structure
- phospholipid bilayer -> a hydrophilic polar phosphate head and a hydrophobic non-polar lipid tail
Cell membrane function
- separates intracellular fluid from extracellular fluid (protects the cell)
- regulates what enters and exits the cell (selectively permeable membrane)
- supports the cell and is sensitive to changes
Homeostasis
maintaining a constant internal environment
achieved by:
- exchange of nutrients & waste
- maintaining a constant temperature
- blood glucose levels
- water
- concentration of fluids
- blood pressure
- heart rate
Fluid mosaic model of the cell membrane
Fluid - phospholipids are constantly moving
Mosaic - made up of individual parts joined together
Cytoplasm structure
- cystol: thick watery fluid that is 70-90% water
- contains dissolved ions, salts & carbs
Cytoplasm function
- supports floating organelles
- suspends non-water soluble proteins & lipids
Nucleus structure
- largest organelle
- contains genetic material (DNA)
- contains chromatin (contains DNA & proteins called histones)
Nucleus function
controls cell activity
Nucleolus structure
- suspended in nucleoplasm
- contains RNA
Nucleolus function
produces ribosomes -> role in protein synthesis
Nuclear envelope structure
- dense spherical structure
- made of an inner & outer membrane (two phospholipid bilayers)
- nuclear pores -> allow movement of molecules
Nuclear envelope function
seperate the cytoplasm from the contents of the nucleus
Ribosomes structure
- Composed of RNA & protein
- Consists of a large subunit and a small subunit
- Make in nucleolus
Ribosomes funtion
Site of protein synthesis - amino acids join to make proteins
ER Structure
- parallel membranes
- a system of membrane channels and flattened sacs continous with the outer membrane of the nuclear envelope
ER Function
- connects cell membrane with nuclear membrane
- Transports proteins around the cell and involved in the manufacture of lipids
Rough ER
- ribosomes on the surface -> move proteins into Rough ER so it can be transported through in vesicles (sacs)
- provides a surface for chemical reactions involving protein synthesis
Smooth ER
- no ribosomes
- synthesises lipids & steroids (e.g. cholesterol, estrogen)
Golgi body structure
- 3-20 flattened, stacked curved sacs (vesicles that are received from ER are broken down to form Golgi vesicles at the other end)
Golgi body function
- Modify & package proteins in vesicles for secretion
Golgi body location
- near nucleus
- surrounded by vesicles
Protein processing examples
- add sugars -> glycoproteins
- remove 1st amino acid from new proteins -> functioning proteins
Lysosome function
breakdown molecules and old organelles
Lysosome structure
- contains enzymes (made in Rough ER)
- made in Golgi body
- spherical sacs surrounded by single membrane
- more common in animal cells
- kind of like specialised vesicles
Enzymes in lysosomes
- highly acidic - powerful digestive
function: - digests large molecules
- recycle cellular resources (by apoptosis - programmed cell death of worn-out organelles)
Mitochondria structure
- contains ribosomes and own DNA
double membrane:
- inner: convoluted to form cristae and surrounds a liquid (matrix) and is coated in enzymes
- outer: contains transport protein and forms aqueous channels for molecules to enter
- intermembrane space: breaks down carbs
Mitochondria function
- release energy to the cell - cellular respiration
ATP process
adenine triphosphate
- matrix enzymes supply hydrogen and electrons to reactions in cristae
- energy is released by breaking the molecule to ADP - adenine triphosphate
- then recycles to conversion back to ATP during aerobic respiration
Endosymbiont theory
- some of the organelles in eukaryotic cells (mitochondria & chloroplasts) have evolved from organelles in prokaryotic cells
Centrioles structure
- pair of hollow cylindrical structures - make up of bundles microtubules
-* not found in plant cells*
Centrioles function
- help organise cell division - produces spindle to seperate cells
- aren’t always needed in the process
Vesicles structure
membrane-bound sac
Vesicles function
stores materials for transport
Microtubules function
rods that keep organelles in place or move them in and out of cell
Cilia structure
- hair like projections
- on outside of cell
Cilia function
beat to move cell or materials across the cell surface
Microvilli
- finger-like extensions of the cell surface membrane
- in epithelial cells
- increase surface area
Endomembrane system
restrict enzymatic reactions to specific compartments within the cell
consists of:
- nuclear envelope
- ER membranes
- golgi apparatus
- vesicles
Cholesterol function
keeps the structure of cell membrane
Peripheral proteins
Glycoprotein - (a.k.a recognition protein) cell signalling through antigens
Transmembrane proteins
span the entire membrane
a.k.a. integral proteins
- channel proteins: forms a channel through the membrane for smaller molecules to pass
- carrier proteins: binds to larger molecules and helps them move across the membrane (they are specific)
- receptor proteins: binds with molecule out of cell to make a change inside cell (they are specific)
Cell transport
the movement of molecules across the membrane
- passive - doesn’t require energy
- active - requires energy
Simple diffusion
movement of lipid-soluble substances that can diffuse between the phospholipids of the membrane
Molecules that can undergo simple diffusion
lipid-soluble molecules:
- oxygen
- carbon dioxide
- fatty acids
- alcohol
- steroids
Diffusion
the net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient as a result of their random movement until they reach an equilibrium (equal)
most efficient way to get particles in and out of cell
Concentration gradient
difference in concentrations on either side of the membrane
- greater concentration gradient = steeper gradient on graph = faster reaction
Factors affecting the rate of diffusion
- distance particles travel
- concentration gradient
- surface area
Osmosis
diffusion of water across a semi-permeable membrane from an area of high water concentration to an area of low
water is small enough to fit between the phospholipids without touching (but can also go through channel proteins)
Osmotic pressure
- concentration of water depends on how much solute is dissolved
- low pressure = dilute solution
- high pressure = concentrated solution
Tonicity
a measure to compare water concentration in 2 diff solutions by comparing the concentration of solutes that can’t cross the cell membrane
Isotonic cell
concentration of solute is the same inside and outside of cell
water will move in and out of cell at equal rate
Hypertonic cell
concentration of solute is more outside cell
water moves out of cell
cell shrinks
Hypotonic cell
concentration of solute is less outside cell
water moves into cell
cell bursts
Facilitated Transport
the use of channel or carrier proteins to move across the membrane
Facilitated Diffusion
water-soluble molecules must pass through channel proteins
e.g. water & ions (calcium, sodium)
Carrier-mediated Transport
used for larger molecules (e.g. glucose, amino acids)
- carrier proteins open on one side on cell membrane
- binds to molecules, changes shape to release it to other side
- can become saturated when all the carriers are occupied - concentration will not increase the rate of movement
Carrier-mediated transport types
- facilitated diffusion -> with the concentration gradient through a protein carrier- no energy required
- active transport -> against the concentration gradient - energy required
Vesicular transport
movement of substances in and out of cell enclosed in vesicles
- vesicles can fuse with cell membrane or form from membrane
- a.k.a. bulk transport - transports large amounts of materials
Endocytosis
type of vesicular transports that brings material into the cell
- membrane surrounds & encloses extracellular material
- vesicle then pinches off and is suspended in cytoplasm
- phagocytosis (cell-eating)
- pinocytosis (cell-drinking)
Exocytosis
contents of a vesicle are pushed out of cell
- vesicle forms inside cell, migrates to membrane & fuses with it, contents are pushed out
Why are cells so small?
Cells must be small enough so they can have a higher/larger surface area to volume ratio in order to exchange materials efficiently
Structural levels of the body
cells -> tissues -> organs -> systems -> organisms
Types of tissues
- epithelial tissue
- connective tissue
- muscle tissue
- nervous tissue
Epithelial tissue function
covers/lines organs & all body surfaces - protective barrier
Connective tissue function
- connects or separates, and supports all other types of tissue in the body
- stores nutrients
- cushions organs
Non-cellular material
material not made of cells
Muscle tissue structure
- contains muscle fibers - contract to become shorter
- elastic
- excitable - respond to nerve impluses
Types of muscle tissue
Skeletal muscle
- attached to skeleton
- striated (striped appearance)
- voluntary control
Smooth muscle
- makes up organs
- no striation
- cannot be controlled voluntarily
Cardiac muscle
- heart muscle
- faint striations
- cannot be controlled voluntarily
Nervous Tissue
Function:
receives & transmits messages as electrical impulses
Structure:
- made up of neurons
- brain, spinal chord, nerves
Epithelial tissue structure
- cells are very close together with little intERcellular fluid between them
- vary in shape depending on tissue:
- smooth -> for things to get in and out (secretion)
- striated -> many layers (protection)
- cubodial
- columned
- squamous (squashed flat)
Epithelial examples
- layer of the skin
- lining of the intestines, heart, kidney, liver & lungs
Muscular tissues are responsible for
- movement
- process of digestion
- waste elimination
- breathing
- speech
- blood circulation
Connective tissue structure
- not as close together as epithelium - seperated by large amounts of non-cellular material (a.k.a. matrix)
Connective tissue types/examples
Proper:
- loose tissue (adipose)
- dense tissue (tendons)
Specialised:
- bone
- cartilage
- blood
Extracellular fluid
Fluid that is surrounding the cell
e.g. tissue fluid or blood plasma
Nutrients that cells need to take in
- water
- oxygen
- glucose for cell respiration
Tissue definition
A group of similar cells in the same place with the same function
Active Transport examples
- uptake of glucose in intestines
- sodium-potassium pump (sodium goes out of cell and potassium goes into cell)
