Bio12AP: Cell Structure and Function

prokaryotes

prokaryotes

single-celled organisms that lack a membrane-bound nucleus and other membrane-bound organelles. Their genetic material is located in a region called the nucleoid, which is not enclosed by a membrane. Prokaryotic cells include bacteria and archaea.

• Cell wall: In bacteria, this is composed of peptidoglycan, a mesh-like structure that provides rigidity and protection. (In archaea, the cell wall structure differs and lacks peptidoglycan.)

• possess ribosomes

how are lysosomes and vacuoles related

Lysosomes and vacuoles are both involved in cellular digestion and are produced by the Golgi apparatus. They can combine to break down larger molecules like food, forming a secondary lysosome. Lysosomes contain enzymes to digest waste and cellular debris, while vacuoles primarily store substances but also aid in digestion, particularly in plant cells.

why are plant cells so unique?

• have a cell wall

• large central water vacuole (used for turgidity)

• possess chloroplasts and plastids

• ALSO HAVE mitochondria

how is the endoplasmic reticulum and golgi apparatus related

ER (Endoplasmic Reticulum) and Golgi Apparatus work together in protein and lipid synthesis. The ER produces proteins (rough ER) and lipids (smooth ER). They get sent to the Golgi that modifies, sorts, and packages them for transport inside or outside the cell.

how are ribosomes and the ER related

• Ribosomes and the endoplasmic reticulum (ER) are related because ribosomes attach to the rough ER, where they synthesize proteins. The rough ER helps process and transport these proteins. Ribosomes can also be free-floating in the cytoplasm, but those bound to the rough ER are specifically involved in making proteins for secretion or for use in membranes.

How are mitochondria and chloroplasts related?

Mitochondria and chloroplasts are both organelles involved in energy conversion. Mitochondria generate energy through cellular respiration, producing ATP from glucose and oxygen. Chloroplasts, found in plants and algae, carry out photosynthesis, converting light energy into chemical energy (glucose that the mitochondria needs produce ATP)

• Both organelles have their own DNA and are thought to have originated from endosymbiotic bacteria.

peripheral proteins

The proteins of a membrane that are not embedded in the lipid bilayer; they are appendages loosely bound to the surface of the membrane.

which organelle is found in the pituitary gland (produces hormones)?

golgi apparatus

which organelle is found in muscle cells?

mitochondria/rough er

integral proteins

penetrate the hydrophobic interior of the lipid bilayer

transmembrane proteins

Transmembrane proteins are integral proteins that do not extend all the way through the membrane.

fluid-mosaic model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.

adhesion proteins

Adhesion proteins are membrane proteins that form junctions between adjacent cells.

transport proteins

allow passage of hydrophilic substances across the membrane

A transmembrane protein that uses ATP

channel proteins

: Channel proteins are integral membrane proteins that form pores in the cell membrane, allowing specific ions or molecules to pass through the membrane. They facilitate the passive transport of substances, enabling the movement of ions (such as sodium, potassium, calcium) and small polar molecules across the membrane, down their concentration gradients

nucleolus

A dense structure within the nucleus responsible for producing and assembling ribosomal RNA (rRNA) and combining it with proteins to form ribosome subunits.

ribosomes

site of protein synthesis
- round structures of the large subunit. and the small subunit
- ribsomal RNA and proteins
-floating in the cell or attached to the endoplasmic reticulum

Endoplasmic Reticulum (Rough)

A system of membranes that is found in a cell's cytoplasm and that assists in the production, processing, and transport of proteins (golgi bodies, lysosomes, the ER) and in the production of lipids.
- attached to nucleus, studded with proteins (compartmentalizes the cell)

golgi complex

a cell organelle (in eukaryotic cells) that helps make and package materials to be transported out of the cell
- packages them in vesciles, which gets carried to the plasma membrane
-involved in production of lysosomes

cristae

Infoldings of the inner membrane of a mitochondrion that houses the electon transport chain and the enzyme catalyzing the synthesis of ATP.
- seperates the matrix (innermost area) from the intermembrane space
- having folds increases surface area for making ATP

how do cilia and flagella differ?

cilia are shorter than flagella

• often there are many cilia + one/two flagella

describe the internal structure of cilia and flagella

membrane bound cylinders; 9 microtubule pairs in a circle around 2 central microtubules - also called a '“9 + 2” pattern

how are basal bodies related to cilia? how is their internal structure different from that of cilia?

Basal bodies anchor cilia to the cell and help organize their formation. While cilia have a 9+2 arrangement of microtubules (nine doublets around two central microtubules), basal bodies have a 9+0 structure (nine triplets with no central microtubules)

structure of basal bodies and centrioles

9+0 structure (nine triplets with no central microtubules).

how are centrioles related to basal bodies

• also have a 9+0 pattern of microtubules

• gave rise to basal bodies

how are centrioles important for mitosis

• involved in appearance/disappearance of spindle apparatus (pulls apart chromatids)

centrioles

Cell organelle that aids in cell division in animal cells only

3 functions of microtubules and microfilaments

• cellular movement

• internal cytoskeleton

• anchors/moves organelles

peroxisomes

Contain oxidase enzymes that detoxify alcohol, hydrogen peroxide, and other harmful chemicals
- common in liver and kidney cells

cytoskeleton

A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement

where do we find microtubules?

• inside the structures of cilia/flagella

• in the centrioles

• cytoplasm/basal bodies

microtubules

made up of the protein tubulin
- cellular division and movement
Thick hollow tubes that make up the cilia, flagella, and spindle fibers. (centrioles)

microfilaments

- composed of actin; joined together adn pulled apart fo allow microfilaments to grow and shrink
- Long, thin fibers that function in the movement and support of the cell

eukaryotic ribosomes

80s, can be found attached to the endoplasmic reticulum

cell wall

A rigid layer of nonliving material that surrounds the cells of plants and some other organisms.
- in fungi, it is made of chitin

aquaporins

A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane

nucleus

enclosed by a double membrane called the nuclear envelope. This structure contains pores that control the movement of molecules in and out of the nucleus, like RNA and ribosome subunits. Inside, the nucleus houses chromatin (DNA and associated proteins) and the nucleolus, where ribosome production begins. This organization allows the nucleus to perform its critical job of storing genetic information, regulating gene expression, and coordinating cell activities like growth and reproduction.

simple diffusion

Diffusion that doesn't involve a direct input of energy or assistance by carrier proteins.
-hydrophobic molecule

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

plasmolysis

Collapse of a walled cell's cytoplasm due to a lack of water

isosmotic

solutions with the same concentrations of solute particles

adding a solute to water

Adding a solute to water lowers the water potential of the solution, making water less likely to leave and more likely to flow into the solution. The more solute molecules present, the more negative the solute potential becomes, driving water movement into the solution.

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

- 3 sodium ions out, two potassium ions in

primary active transport

Active transport that relies directly on the hydrolysis of ATP.

hydrolysis of ATP

releases energy

secondary active transport

use pre-existing gradient to drive transport of solute

resting membrane potential

An electrical potential established across the plasma membrane of all cells by the Na+/K+ ATPase and the K+ leak channels. IN most cells, the resting membrane potential is approximately -70 mV with respect to the outside of the cell.

endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

three types of endocytosis

phagocytosis, pinocytosis, receptor-mediated endocytosis

pincytosis

the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.

light microscopes

use light and glass lenses to magnify an image
- study stained or living cells

electron microscopes

use beams of electrons, rather than light, to produce images
- viruses, pores on nucleus

ADH

antidiuretic hormone (vasopressin)
posterior pituitary gland, produced by hypothalamus
- Dehydration (high ADH levels): decreased urine volume, darker and more concentrated urine.
Hydration (low ADH levels): increased urine volume, lighter and more dilute urine.

cisternae

Flattened, membrane-bound compartments that make up the Golgi apparatus.
- golgi stacks have around 3-20
- cis cisternae: close to RER
- medial: middle
- trans: farthest from the RER
-molecules can move between cisternae via vesicles

plasma membrane (cell membrane)

Regulates what enters and leaves the cell and separates the internal environment of the cell from the external environment
- phospholipid bilayer
- smalll hydrophobic molecules canpass through it unaided

receptor proteins

Proteins that transmit information in and out of cells. They allow communication between cells.
- hormones

cell surface markers

glycoproteins and glycolipids
- a membrane protein that identifies the cell type

carbohydrate side chains

A carbohydrate side chain is attached to the surface of some proteins found only on the outer surface of the plasma membrane.

nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Smooth ER (SER)

type of endoplasmic reticulum (ER) in cells that lacks ribosomes on its surface, giving it a smooth appearance. It is involved in various metabolic processes, including lipid synthesis, detoxification of drugs and poisons, and calcium ion storage. The SER also plays a role in carbohydrate metabolism and steroid hormone production.

mitochondria

Powerhouse of the cell, organelle that is the site of ATP (energy) production

• smooth outer membrane, inner membrane forms folds called cristae

lysosomes

. They contain digestive enzymes that break down waste materials, cellular debris, and foreign invaders like bacteria. Lysosomes are often referred to as the cell's "waste disposal system" because they degrade and recycle macromolecules, playing a crucial role in cellular homeostasis and metabolism.

apoptosis

process of programmed cell death

vacuole

Cell organelle that stores materials such as water, salts, proteins, and carbohydrates

cilia and flagella

hairlike structures that extend from the surface of the cell, where they assist in movement

prokaryotic ribosomes

(70s) smaller than eukaryotic ribosomes, found in the cytoplasm

chloroplast

An organelle found in plant and algae cells where photosynthesis occurs

central vacuole in plants

stores excess water and provides extra support. The extra water in the vacuoles of plant cells keeps the plant from drying out.

ability of molecules to move across the cell membrane

1. semipermeability of the plasma membrane
2. size and charge of particles that want to get through

facilitated transport

Energy Requirement: Does not require energy (passive transport).

Direction: Moves substances down their concentration gradient (from high to low concentration).

Mechanism: Utilizes carrier proteins or channel proteins embedded in the cell membrane to help specific molecules or ions cross the membrane.

diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.
- movign down a concentration gradient

osmosis

Diffusion of water through a selectively permeable membrane
- water wants to move from high to low concentration

tonicity

The ability/strength of a solution surrounding a cell to cause that cell to gain or lose water.

• concentration given. as a % of solution

isotonic

- concentration of solute the same inside and outside
- cells in isotonic solutions won’t gain or lose H2O

-[outside cell] = [inside cell]

ex. 0.9% NaCl solution is ISOTONIC to red blood cells

hypertonic

A hypertonic solution has a higher concentration of solute compared to another solution, typically the cytoplasm of a cell. This causes water to move out of the cell to balance the solute concentrations on both sides of the membrane. As a result, the cell experiences dehydration and begins to lose water, leading to a shriveled appearance, known as crenation.

• cell contains 0.1% glucose; solution outside contains 0.5% glucose

hypotonic

A solution with a lower concentration of solute compared to another solution, leading to water moving into the cell, which may cause the cell to swell or even burst (lysis)

hyperosmotic

A solution with a higher concentration of solute compared to another solution, resulting in water moving into the hyperosmotic solution due to osmosis.

hyposomotic

Hyposmotic refers to a solution that has a lower concentration of solutes compared to another solution. When a cell is placed in a hyposmotic solution, water tends to move into the cell by osmosis, potentially causing the cell to swell or even burst due to the influx of water. This occurs because water moves from areas of low solute concentration (the hyposmotic solution) to areas of higher solute concentration (inside the cell).

water potential

The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.

red blood cell added to water

will explode, because water will move into the cell

active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells

receptor-mediated endocytosis

The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in (lined with the protein clathrin) ; enables a cell to acquire bulk quantities of specific substances.

bulk flow

The movement of a fluid due to a difference in pressure between two locations.

dialysis

diffusion of solutes across a selectively permeable membrane
- some membranes have holes of a certain size within them that can sort substances by using diffusion
-

exocytosis

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

hydrostatic pressure

water being pushed out by some force