Cells - lecture 2 Flashcards
cells
smallest unit of life that can function independently
who coined the term “cells?”
Robert Hooke (1660)
cell theory
all organisms are made up of cells; the cell is the base unit for all life; all cells come from pre-existing cells
what do all cells contain?
DNA, RNA, ribosomes, proteins, cytoplasm, and cell membrane
why are cells so small?
everything is transported across the cell membrane and the smaller the object, the smaller surface area to volume ratio
what are the two types of cells
prokaryotic and eukaryotic
prokaryotic cells
no membrane-bound nucleus (nucleoid), small with few structures
prokaryotic domain
bacteria and archaea
Eukaryotic cells
membrane-bound nucleus, internal structures bound by membranes called organelles
eukaryotic domain
Eukarya
Prokaryotes consist of
cell wall (sometimes a capsule), cell membrane, cytoplasm, and nucleoid (DNA)
Eukaryotes consist of
one or more cells, animal and plant cells, made up of organelles (‘little organs’) and each has its own function(s)
cell membrane
all cells have one, made of phospholipids, phospholipid bilayer (phospholipid head and fatty acid tails)
what would happen if phospholipids were added to water?
- form a layer on the surface
- form spherical droplets (single layer)
- orient so the heads interact with the water and tails point away from the water (double layer)
What can freely pass through cell membranes
lipids and small, non-polar molecules
what cannot freely pass through cell membranes
ions and polar molecules (due to hydrophobic interior)
Diffusion
the cell has no control over the movement of water and moves until equilibrium is reached
Fluid mosaic - what are cell membranes made up of
Sterols, phospholipids, proteins, and enzymes
what do the sterols and phospholipids provide for the cell membrane?
structural support
What do proteins provide for the cell membrane?
transport, adhesion, recognition, and receptor
What do enzymes provide for the cell membrane?
facilitate chemical reactions
Cell wall
plant cells and bacteria, made of carbohydrates which are structural and protective
Inside the cell
cytoplasm, organelles, and proteins
what does the nucleus contain?
enclosed by a membrane; contains a cells DNA (genetic material); control center; contains the nucleolus
what does the nucleolus do
assemble components of ribosomes - parts come together once they leave the nucleus to become ribosomes in the cytoplasm
Ribosomes
small (no membrane) - assembles amino acids into proteins
Endoplasmic Reticulum (ER)
network of sacs and tubules which make lipids and proteins
Rough ER
make proteins and studded with ribosomes (rough appearance)
Smooth ER
make lipids and detoxify drugs and poisons
Vesicles
Transport and store - consist of small sacs
Golgi apparatus
Flat sacs and process proteins by folding (makes them functional)
Digestive organelles
Lysosome, Vacuole and Peroxisome
Lysosome
Dismantle and digest damaged/old organelles and debris
External functions of lysosome
tail of frog and the head of sperm to help break through the egg wall
Vacuole
Dismantle and digest organelles and act as water storage/protect agains turgor pressure
Peroxisome
dispose of toxic substance
Chloroplast
where photosynthesis occurs and contain their own DNA and ribosomes
what are chloroplasts made of
Membrane - inner and outer, stroma, thylakoids, and grana
stroma
enzyme rich fluid
thylakoids
flattened sacs within stroma
grana
interconnected stacks of thylakoids
Mitochondria
powerhouse of the cell, extract energy from food, and contain their own DNA and ribosomes
What are mitochondria made up of
inner and outer membrane and Cristae
cristae
folds of inner membrane which increase surface area of mitochondria
Endosymbiosis theory
Evidence suggests that mitochondria and chloroplasts were once free-living organisms (bacteria)
Why do we think m and c were free-living organisms?
Similar in size, shape and membrane structure as some types of bacteria; double membrane: lysosome/vacuole; replicate via binary fission as bacteria do; photosynthetic pigments and cyanobacteria; and DNA shows a close relationship
DNA close relationships with mitochondria and chloroplasts
Mitochondria to aerobic bacteria and chloroplasts to cyanobacteria
How does the cytoskeleton contribute to the cell
structural and movement
3 components of the cytoskeleton
microfilament, intermediate filament, and microtubules
Microfilament
composed of actin, stretching and compression (movement)
intermediate filament
maintain cell shape
microtubules
composed of tubular, movement of proteins and organelles, and important in cell division
Centrosomes contain
centrioles
Cilia and flagella
allow a cell to move
cilia
shorter and lots of them
flagella
longer and 1-2 of them
How do plant cells communicate?
plasmodesmata
plasmodesmata
channels that connect adjacent cells - cytoplasm of one cell can interact with adjacent cell’s cytoplasm
how do animal cells communicate?
Can secrete a matrix that holds cells together (cells are not in direct contact with one another) and form junctions or direct contact
Tight junction
cells are fused together (impermeable), “blood-brain barrier”, and lipid-soluble drugs can still pass
anchoring junction
linking intermediate filaments together
gap junction
protein channel that links cytoplasm of adjacent cells and analogous to the plasmodesmata
