Cell Structure and Function - Part 1

cells

building blocks of all living organisms, smallest unit of organization

cell theory

1. all organisms are composed of cells

2. cells are the smallest living things

3. cells only form from pre-existing cells (through cell division)

two types of cells:

prokaryotic and eukaryotic

prokaryotic cells

single celled, no nucleus or other membrane-enclosed organelles; bacteria and archaea

eukaryotic cells

has membrane-enclosed organelles, largest is nucleus; animals, plants, and protists

4 common components of cells:

1. plasma membrane

2. cytoplasm

3. DNA

4. ribosomes

plasma membrane definition

outer covering that separates the cell’s interior from its surrounding environment

plasma membrane function

maintains internal state as cell gets nutrients from environment, eliminates waste, essentially decides what comes in and what goes out, detects and responds to environmental cues

cytoplasm definition

jelly-like cytosol within cell that contains other cellular components

cytoplasm function

substance between plasma membrane and nucleus/nucleoid, determines and maintains cell shape, aids cell division

DNA definition

cell’s genetic material (blueprint on how we survive)

DNA/chromosome function in both cell types

1. eukaryotes: housed inside nucleus, multiple, linear double strandS

2. prokaryotes: forms nucleoid, single, circular double strand

ribosome definition

synthesizes proteins (makes them)

ribosome function

made of RNA and proteins, made of large and small subunits

bacteria

small and very abundant cells in the environment and our bodies, most aren’t harmful to humans but some can cause disease

archaea (microbes)

similar size to bacteria, but less common and found in extreme environments

INSIDE plasma membrane

nucleoid, cytoplasm, ribosomes

nucleoid

where DNA is found in prokaryotes

OUTSIDE plasma membrane

cell wall, capsule & pili, flagellum

cell wall

provides support and protection

capsule & pili

for attachment, single celled organisms attach to other single celled organisms

flagellum

for movement

cell size comparison

prokaryotic cells are way smaller than eukaryotic cells

2 benefits of a small cell

1. quick exchange with surrounding environment

2. fast intracellular transport

as cell size increases…

it’s surface area-to-volume ratio decreases

the plasma membrane can’t keep up with…

diffusing molecules and waste in and out of the cell

if a cell gets too big…

it changes shape, divides, or dies