CELLS Flashcards
2 types of cell
Eukaryotic cells
Prokaryotic cells
difference between eukaryotic and prokaryotic cells
Prokaryotic
- lack nucleus
- include 2 groups of bacteria - eubacteria & archaebacterial
- Absence of mitochondria
- Circular DNA
Eukaryotic
- Have a nucleus
- include animals, fungi, plants, protists
- Linear DNA
- Presence of mitochondria
similarity between eukaryotic and prokaryotic cells
- presence of plasma membrane
2. both bear ribosomes for protein synthesis
what is present in prokaryotic cells
- nucleoid
- plasma membrane
- capsule
- flagellum
- ribosomes
what is present in eukaryotic cells
- nucleus
- cytoplasm
- plasma membrane
- SER
- RER
- mitochondria
memorise plasma membrane structure
refer to saved image
function and structure of muscle cells
Contain numerous organelles providing
energy needed for muscle contraction
function and structure of nerve cells
Long and thin to carry impulses over distance
characteristic of plasma membrane
- fluid mosaic model
- phospholipid bilayer
functions of plasma membrane
- physical isolation - barrier
- regulation of exchange of substances with environment - ions and nutrients enter, wastes eliminated, cellular products released
- sensitivity to environment - detect extracellular fluid composition and chemical signals
- structural support - anchors cells and tissues
characteristics of phospholipid bilayers
- hydrophilic heads - face outwards towards environment
- hydrophobic fatty acid tails - face inwards, sandwiched between heads
- barrier to ions and water-soluble compounds
function of cholesterol
helps to maintain cell membrane stability at varying
temperatures
function of membrane carbohydrates – glycoproteins and glycolipids
Identify the cell as “foreign” and act as receptors
Function of membrane proteins
Receptor proteins
• Bind and respond to ligands (ions, hormones)
– Carrier proteins
• Transport specific solutes through membrane
– Channels
• Regulate water flow and solutes passing through
membrane
• Channel ions for electrical impulse conduction
• Gated channels open or close to regulate
passage of substances
INFORMATION TRANSFERRED ACROSS PLASMA MEMBRANE
Receptor sites on receptor proteins are highly specific — interact specifically with signal molecules
• Receptors bind to molecules (such as hormones, drugs) with considerable specificity. The molecules and receptors fit like a key in a lock. Eg, Antidiuretic hormone only acts on kidneys.
• Different cell types have different receptor proteins
• A change is triggered within the cell as a result of
binding of signal molecule to receptor site
5 TYPES OF TRANSPORT ACROSS PLASMA MEMBRANE
- Diffusion.
- Osmosis.
- Facilitated diffusion.
- Active transport.
- Endocytosis and exocytosis
Diffusion
Random movement of molecules from a HIGHER CONCENTRATION to a LOWER CONCENTRATION down a CONCENTRATION GRADIENT.
Osmosis
Random movement of water molecules from a HIGHER CONCENTRATION to a LOWER CONCENTRATION down a CONCENTRATION GRADIENT VIA A SEMI PERMEABLE MEMBRANE.
Facilitated transport
The transport of molecules across the plasma
membrane from higher concentration to lower
concentration via a protein carrier
Active transport
The movement of molecules from a lower to
higher concentration.
• May be too large to travel through membrane channels
• May not be lipid soluble
• May have to move against a concentration gradient
Endocytosis
Transports molecules or cells into the cell via
invagination of the plasma membrane to form a
vesicle
Exocytosis
Exocytosis transports molecules outside the cell
via the fusion of a vesicle with the plasma
membrane
nucleus
• Control center of the cell
• Contains DNA
• DNA is made up of genes, which contain instructions
for the production of proteins.
• Nucleolus—dark region inside the nucleus.
• Produces ribosomes.
• Nuclear envelope —a double membrane around the nucleus.
• Nuclear pores —holes in the nuclear envelope; allow passage of substances in and out of nucleus
cytoplasm
– All materials inside the cell, outside of the nucleus In the cytoplasm, • Cytosol (intracellular fluid) – Contains dissolved materials » Nutrients, ions, proteins, and waste products – High protein and potassium levels – Low carbohydrate, lipid, amino acid, and sodium levels • Organelles – Structures with specific functions
ribosomes
Made of rRNA and protein.
• Sites of protein synthesis.
• Found attached to the endoplasmic reticulum or free floating in the cytoplasm.
2 categories endoplasmic reticulum
Rough endoplasmic reticulum (RER)—studded with
ribosomes used to make proteins. synthesise proteins and packages in them vesicles.
Smooth endoplasmic reticulum (SER)—lacks ribosomes;
synthesizes lipids and other macromolecules.
Golgi apparatus
Stack of flattened membranes associated with tiny vesicles
• modify and refine proteins and lipids from ER .
• Processes, packages, and secretes in vesicles
Vesicles
Small membranous sacs functions to store,
transport, or digest cellular products and waste.
- do not just float about in the cytoplasm & docked onto filaments as microtubules and move like conveyor belts on these microtubules
Lysosomes
contains digestive hydrolytic enzymes that break down cell parts or substances entering by vesicles into smaller parts.
• Prevalent in white blood cells that engulf disease causing microbes.
Transport vesicles
takes protein to golgi apparatus
Cytoskeleton
These are like bones in our body – only more easily
broken and fixed to form new shapes
• Dynamic structure of protein fibers that maintain cell
shape, anchor and/or move organelles in the cell.
• Plays important roles in both intracellular transport
(eg: the movement of vesicles and organelles)
• Cytoskeleton is responsible for chromosome movement during cell division
Centrioles
Rod-shaped bodies made of microtubules
Form spindle apparatus during cell division, which helps move chromosomes.
Centrosome
cytoplasm next to the nucleus that surrounds centrioles
Mitochondria
site of cellular respiration and production of ATP
Structure of Mitochondria
- Has inner and outer membrane.
- Inner membrane is folded into cristae that contain enzymes for cellular respiration reactions.
cilia
- Cilia in the respiratory tract move mucus toward the
throat. - Both are made of microtubules.
flagella
- Flagella on sperm propel them toward the egg
- Both are made of microtubules.
