Cells Flashcards
Three original tenets of cell theory
- All living things consist of cells
- The cell is the smallest and basic unit of life
- All cells originate from pre-existing cells
Tenets of modern Cell Theory
- All living things consist of cells
- The cell is the smallest and basic unit of life
- All cells originate from pre-existing cells
Modern additions:
- The activity of an organism depends on the total activity of independent cells.
- Energy flow (metabolism and biochemistry) occurs within cells.
- Cells contain DNA, the hereditary information.
- All cells are basically the same in chemical composition in organisms of similar species.
Function of chromatin network
- Made of DNA and proteins
- Contains genes (hereditary information)
- Instructs all the activities of the cell
- Packaged as chromosomes for cell division
All eukaryotic cells have…
- Cell membrane
- Cytoplasm
- Organelles
- Nucleus
Only plant cells have…
- Cell wall (though fungi also have a cell wall)
- Large central vacuole
- Plastids e.g. chloroplasts
Structures making up the cell wall of plants
- Primary cellulose wall
- Secondary lignin wall
- Middle pectin lamella
- Pits
- Plasmodesmata
Primary cellulose wall function
shape
Secondary lignin wall function
strength
Middle pectin lamella function
joins cells together
Pits in cell wall function
ease transport between cells
Plasmodesmata function
joint cell cytoplasms for communication and transport between plant cells
Useful substances made from plant cell walls
- Wood
- Paper
- Cork
- Cotton
Structures of cell membranes
- Phospholipid bi-layer
- Carrier and channel proteins
- Carbohydrates
Function of carrier and channel proteins in a cell membrane
control movement of larger substances into and out of a cell
Function of the carbohydrates on the surface of a cell membrane
cell recognition
Parts of the phospholipid bi-layer
- Hydrophilic head
- Hydrophobic tail
- Hydrophobic tail
- Hydrophilic head
Types of movement across a membrane
Diffusion
Osmosis
Facilitated transport
Active transport
Two types of osmosis
Endosmosis (water movement into cell)
Exosmosis (water movement out of cell)
Process of diffusion
- Passive process (no energy required)
- Non-selective movement along concentration gradient
- From high to low concentrations until equilibrium
- E.g. oxygen
Process of osmosis
- Selectively permeable membrane
- Passive process (no energy required)
- Movement of water into or out of cell
- Water moves along concentration gradient
- From high water potential to low water potential until equilibrium
Process of facilitated transport
- Living selectively permeable membrane
- Carrier proteins required
- passive process (no energy required)
- selective movement of substances along concentration gradient using carrier proteins until equilibrium
- e.g. Glucose
Process of active transport
- living selectively permeable membrane
- carrier proteins required
- active process ATP required
- selective movement of substances
- against a concentration gradient (from low to high)
- e.g. sodium and potassium ions
Endocytosis
- In animal cells
- Process of taking in food particles and nutrients
- Also called phagocytosis
- structure formed called a food vacuole (membrane bound)
Exocytosis
- In animal cells
- structure involved called secretory vesicle (membrane bound)
- Process or removing particles and metabolic wastes
- Also called elimination or secretion
Other cell membrane structures in animal cells
Microvilli - increase surface area
Pinocytic vesicles - take up liquids
Phagocytic vesicles - take up particles using pseudopodia
Structures of the nucleus
Double membrane
Nucleopores
Nucleoplasm
Chromatin network
Nucleolus
Two types of endoplasmic reticulum (ER)
Smooth ER - no ribosomes attached
Rough ER - ribosomes attached
Function of the endoplasmic reticulum
Connects cell membrane with nucleus
A network of membrane bound tubes
For transporting substances
Rough ER makes and transports proteins
Cytoplasm contents
- Water (90%)
- Enzymes
- Protein cytoskeleton
- Organelles
Function of ribosomes
Protein synthesis
Examples of vacuoles
Contractile vacuole - controls water content of cell
Lysosome - contains peroxidase enzyme
Phagocytic vesicle - contain food particles
Pinocytic vesicle - take up fluids
Tonoplast
Membrane that surrounds a vacuole
It can provide turgidity (support) to the cells
Structure of a mitochondrion
- Double membrane
- Cristae - internal folds
- Matrix - internal fluid
Function of the mitochondrion
- Where cellular respiration takes place
- Production of ATP (energy carrier molecules)
- Provides energy for the cell
Golgi body (animal cells) and dictyosomes (plants) structure and function
Stacked flapjack like membrane bound structure
Packaging centre of cell
Sort and store cellular secretions e.g. enzymes
Types of plastids (plant cells)
- Leucoplasts - no pigments (storage organelle)
- Chromoplasts - yellow-red pigments
- Chloroplasts - green pigments
Structure of a chloroplast
- Double membrane
- Stroma - inner fluid
- Thylakoids - membrane structures with chlorophyl
- Grana - stacked thylakoids
- Inter-granum lamella - membrane bridges between grana
- Occasionally: starch granules
Chlorophyll
- Green pigment
- Captures light energy
- Needed for photosynthesis
Structure and function of the centrosome
- Made of two centrioles
- act as anchors during cell division
- and form the spindle apparatus
Cell differentiation
- A process where cells change size, shape and composition
- to be able to perform specific function
- also called cell specialisation
Undifferentiated cells in plants and animals
- Stem cells - animals
- Meristem cells - plants
