The Cell

2025 Ap bio u2 Cell structure and function

Prokaryotes

have no nucleus, no membrane-bound organelles, unicellular, ex

Shared features of all prokaryotic cells

genetic materiel in nucleoid, cytoplasm, ribosomes, and cytosol

Eubacteria

true bacteria, most abundant form of life, can be single cells, chian or clusters, may be disease producing while others are involved in necessary processes such as decomposition, digestion, and nitrogen fixation, ex

Archaebacteria

live in extreme env similar to ancient earth usually places that are quite inhabitable like volcanic vents, permafrost, salt lakes, mostly anaerobic, DNa more similar ot eukaryotes than true bacteria

Thermophiles

“heat-loving”

Halophiles

“salt-loving’

Where would water go if a fish lived in the ocean (salty)

outside bc more solute outside

Where would water go if a fish lived in a river (freshwater)

inside bc more solute inside

Shared characteristics of Eukaryotic cells

cytoskeleton for cell movement, structural integrity, organelle transport, membrane- bound organelles

Eukaryotes

have nucleus to house DNA and membrane- bound organelles, may be unicellular or multicellular, ex

3 domains of life

Bacteria, Archae, and Eukarya (come from Archae)

Cytoskeleton

supports organelles and cell shape and plays a role in cell motion

Microtuble

tube of protein molecules present in cytoplasm, centrioles, cilia, and flagella

Intermediate filament

intertwined protein fibers that provide support and strength

Actin filament

twisted protein fibers that are responsible for cell movement

Centriole

complex assembly of microtubles that occurs in pairs

Mitochondrion

organelle in which energy is extracted from food during oxidative metabolism

Secretory Vesicle

vesicle fusing with the plasma membrane, releasing materials to be secreted from the cell

Lysosome

vesicle that breaks down macromolecules with hydrolytic enzymes and digests worn out cell components

Golgi Complex

collects, packages, and distributes molecules manufactured in the cell

Nucleus

common center of the cell

Nucleolus

site where ribosomes are produced

Nuclear Envelope

double membrane between nucleus and the cytoplasm

Nuclear Pore

opening embedded with proteins that regulates passage into and out of the nucleus

Ribosomes

small complexes of RNA that are sites of protein synthesis

Peroxisome

vesicle that contains enzymes that carry out particular reactions such as detoxifying potentially harmful molecules

Plasma Membrane

the lipid bilayer in which proteins are embedded

Cell wall

rigid outer covering made of carbohydrates which helps maintain shape of cell and prevents cell membrane from bursting; allows some things in (makes plants more efficient at getting sunlight) + found in prokaryotes and fungi

Chloroplast

organelle which uses light energy to convert carbon dioxide and water into glucose

Free Ribosomes

synthesize proteins for use WITHIN the cell

Membrane-bound Ribosomes

on the Endoplasmic Reticulum synthesize proteins for export (secretion) or for use in a lysosome

Function of Rough Endoplasmic Reiculum

modifies proteins that will be shipped to other locations in the endomembrane system, the cell surface, or outside the cell (the ribosomes that carry out protein synthesis)

Visual appearance of rough er (endoplasmic reticulum)

covered in ribosomes (like tiny dots in diagrams) - ribosomes are protein-making machines

Function of Smooth Endoplasmic Reticulum

Synthesizes lipids such as fatty acids, phospholipids, and steroid & detoxifies molecules such as alcohol, drugs, and metabolic waste products

Visual appearance of smooth er (endoplasmic reticulum)

smooth bc no ribosomes on the surface

Golgi Complex Modifications

correct folding and cuts of protein, chemical modification- glycosylation (tags made of sugar) which can create alternate folding, and storing and packaging for export (all are post-translational modifications)

Inner membrane system in eukaryotes

divide the cell into functional and structural areas for specialized tasks, increasing efficiency (ideal pH, smaller volume for enzyme reactions, etc)

Cells compartmentalize

when cells use membrane to compartmentalize to prevent reactants from contaminating the wanted reaction, increase interactions between substrates and enzymes. Increase efficiency for enzymes

Endomembrane system

is a network of organelles (like little organs) involved in manufacturing and material transport, allowing the cell to make, move and break down cellular products. It consists of the nuclear envelope, rough and smooth endoplasmic reticulum (ER), the Golgi apparatus as well as the cell's plasma membrane, and includes the vesicles that bud off these membranes for intracellular transport (moving stuff around inside the cell), exocytosis (stuff leaving the cell) and endocytosis (stuff coming into the cell)

Symbiosis

when 2 species benefit off living off one another

Endoysymbiosis

when one organism lives inside another

Examples of endosymbiosis

nitrogen fixing bacteria in legumes or algal protists that live inside coral polyps

Endosymbiont Theory

States that both mitochondria and chloroplasts both existed at some point as independent bacteria and formed an endosymbiotic relationship with what we know as eukaryotic cells. Today they are so interdependent on one another, both chloroplasts and mitochondria are simply considered organelles.

Evidence for Endosymbiont Theory

Evidence that supports this is that 1. We presently have organisms that function like this (ex. coral), they both contain their own circular DNA (chloroplasts are most closely related to cyanobacteria), and they both produce their own unique enzymes.

Fluid Mosaic Model

thin double layer of phospholipid molecules (PO4 = polar, Lipid Tail = nonpolar), proteins float in the lipid bilyaer and control what passes thru the membrane, steroids such as cholestrol in eukaryotes (maintain fluidity), and glycoproteins and glycolipids extend out from the proteins (receptors/markers)

Glycosylation

the process that occurs in the Golgi Complex that places the glycosidic chains on the proteins

Functions of the Cell Membrane

(aka plasma membrane) separates internal/external environments, regulates transport (ions, gases, nutrients, waste, and cellular products), and identification which are markers on it to show that it is unique to a particular org

Property of membranes

they are fluid so proteins have the ability to move around the cell membrane

Transporters

use energy to move molecules across a membrane

Channels

open in response to a signal to allow certain molecules to pass in or out

Receptor Proteins

transmit messages into the cell

Diffusion

scattering or spreading of molecules or ions through rando movement, net movement from hi to lo, more particles hit the memrbance more often so go from high to low

What determines the rate at which particles diffuse?

Size of concentration gradient (imagine a slide) and the size or particles diffusing

How do cells import materials and export wastes?

Using passive transport

Passive Transport

no energy required; particles move from HIGH concentration to LOW concentration (“down concentration gradient”)

What allows the cell membrane to create concentration gradients?

it is selectively permeable

Membrane Potential

A difference in charge in a cell

Types of Passive transport

Simple diffusion, facilitated diffusion, and osmosis

Simple Diffusion

small, nonpolar molecules will diffuse through the lipid bilayer easily (Nc, O2 CO2)

Facilitated diffusion

diffusion with the help of transport proteins such as channel proteins and carrier proteins (ions and small compounds like Glucose, Sucrose, H+,Na+,HCO-3, K+, Ca+,Mg+

Osmosis

the diffusion of water molecules across a semipermeable membrane, moving from an area of lower solute concentration to an area of higher solute concentration.

Active Transport

Moves molecules and ions against concentration gradient (low to high) using carrier proteins and free energy used by proteins (often ATP)

Sodium Potassium Pump

an example of an active transport protein pump, arguably the most important protein in the whole body bc 40% of energy in body is used to power this pump

Vesicular transport

movement of large things into/out of the cell

Exocytosis

move out substances

Endocytosis

take in substances

Phagocytosis

LARGE material like bacteria

Pinocytosis

SMALL material like macromolecules

Receptor Endocytosis

Selective uptake of substances through specific cell surface receptors

Plasmolysis

When a cell is in a hypertonic solution

Cytolysis

When a cell is in a hypotonic solution

Which structure is found in both plants and animal cells, but is uncommon in animal cells, while very large in plant cells

vacuole

What structures are found in plant cells but not animal?

cell wall, chloroplasts, plastids, and a central vacuole

What structure is found in all forms of life?

ribosomes

Golgi Apparatus

Transport, sort, and modify proteins and lipids

Vesicles

Move molecules, secrete substances, digest materials, or regulate pressure in cell

Vacuole and its 2 roles

A membrane-bound organelle in plant and fungal cells that stores nutrients and waste products, and helps maintain turgor pressure.

Mitochondria

The powerhouse of the cell, they are organelles that generate ATP through cellular respiration, providing energy for various cellular processes. + Regulate metabolic activity and promote cell multiplication and growth

Chemical energy taken in by mitochondria to make ATP

food energy (glucose)

Name of energy used by chloroplasts to make ATP

Light Energy

What type of chemical energy is ATP converted to in the chloroplast

glucose

Calvin Cycle

the chemical process used by chloroplasts to both harvest light energy and make ATP then convert stored energy into glucose

Receptors (glycoproteins)

recognition sites on cell membranes, allows cells to identify and interact with other cells and molecules by binding

Cytoskeleton

helps cells maintain their shape and internal organization, also provides mechanical support for cell division and movement

Cytosol

provides structural support to the cell organelles (semifluid matrix that contains the nucleus and other organelles)

Isotonic

solutions on both sides of membrane are the same

Hypertonic

solution on one side of membrane has a higher concentration of solutes

Hypotonic

solution on one side of the membrane has a lower concentration of solute