Transcript Units of Life

Units of Life
Cell structure under light
Plant cell
• Cell wall
• Nucleus
• Cytoplasm
• Vacuole (food storage)
• chloroplast
Animal cell
• Cell membrane
• Cytoplasm
• Nucleus
Differences between plant and
animal cells
Plant cells
• Chloroplast
• Large vacuole
• Cellulose cell
wall
Animal cells
• No chloroplast
• Small vacuoles
• No cell wall
• Centrioles for
cells division
Differences between plant and
animal cells
Plant cells
• Cellulose cell wall
• Large vacuole
• chloroplasts
Animal Cell
• Cell membrane only
(no cell wall)
• Small vacuoles
• May be specialised
What a cell looks like
• Small and 3
• It needs organelles that
dimensional for
have specific functions
efficient diffusion of
eg mitochondrian for
particles
cell diffusion or
chloroplast for
• Cell membrane must
photosynthesis
be semi permeable to
allow some particles to • It needs some sort of
pass through eg
internal transport
oxygen and water but
system
stop others
Cell Organelles
Golgi body is (f)
involved in the
production and
packaging of
lysomes and other
secretory vesicles.
(s) looks like a stack
of pita bread or
naan or pancake
Contractile vacuole
Contractile vacuole
(shown here in a
paramecium)
Function: to pump
excess water out of
the cell by active
transport.
Chloroplast
Found only in plants
cells and (f) used by
plants to make food
via the process of
photosynthesis
(s) Shaped like CDs
in a stack (grana) in
jelly like substance
(stroma)
Mitochondria
Function:
(f) Used in the
process of
cellular
respiration,
(s)sausage
shaped with an
inner membrane
folded
Cell (Plasma) Membrane
F- Controls movement of substances into and
out of the cell, s- a phospholipid bilayer with
embedded proteins.
Other organelles
• Nucleus – in the cytoplasm, f- controls the
cells and carries the genetic code, s nuclear membrane with pores and contains
chromatin
• ER (endoplasmic reticulum) – f – transport
and site of synthesis of proteins and lipids srough with ribosomes and smooth tubes w/o
Other organelles
• Lysosome in cytoplasm, s- tough membrane
bag, f- contains enzymes for digestion
• Nucleolus in nucleus, f assembles
ribosomes
• Vacuoles in cytoplasm , s- membrane bag
containing, f – stored fluid for support in
plant of food in animals cells
• Cell walls outside plant cells, s layers of
cellulose and f - gives shape and support
Organelles involved in movement
• Cilia outside the cell sshort hair-like , fmove cells around
with wave like motion
• Flagella – s long and
f- move cell in a whiplike motion
Movement across the cell
membrane
There are two types of
movement of particles
1. Passive
a. happens across a
concentration gradient
(high to low)
b. requires no energy
c. only small particles
like oxygen and water
2. Active Transport
a. Against a
concentration
gradient from low to
high
b. So energy is needed
and some sort of
mechanism (protein
in cell membrane)
c.larger particles like
glucose and proteins
Osmosis and osmo-regulation
The movement of water across a cell
membrane is called osmosis. This happens
from high to low concentration so is passive
transport. Therefore it naturally happens.
So a cell in pure water will absorb water and
become turgid (tight and full of water)
while a cell in salt water will lose water and
become flaccid (floppy or shrivelled) - it
plasmolysed
Osmoregulation
• A cell tries to control the amount of water it
has to help with cell processes
• It does this by means of a water pump - or
contractile vacuole - that requires energy to
work
• Contractile vacuoles
pump water out of the
paramecium by active
transport which
requires energy
Cell process - structure
• Diffusion, osmosis, active transport - cell
wall, cell membrane, cytoplasm, contractile
vacuole
• cell respiration - mitochondrion, enzymes
• photosynthesis - chloroplast
• enzyme activity - enzyme, mitochondrion,
chloroplast, lysosome
• replication, cell division - chromosome
Cell process matched to structure
• replication, cell division chromosome
• feeding - oral groove,
phagocytosis (engulf food
particle), pinocytosis
(water droplet)
• sensitivity - eye spot
• excretion - anal pore,
contractile vacuole
• secretion - golgi body
• movement - cilia,
flagellum
Enzymes
Enzymes are biological catalysts. Their job is to
help make chemical reactions in the cell happen.
They work by helping collisions happen faster
than usual
Several things can affect enzyme action
• heat - gives molecules energy so they collide
more frequently
• substrate (amount or number of particles) - meet
more frequently
• pH- enzymes have a specific pH they work best at
• enzyme concentration - greater conc faster
reaction
Photosynthesis - make with light
The chloroplast is the site of
photosynthesis. This is where
the plant makes food for cell
processes.
Plants capture sunlight by
chlorophyll a green pigment
found within the chloroplast.
The chlorophyll is on small discs
(thylakoids) arranged in stacks
(grana) which are joined
together.
Chlorophyll absorbs light in the
blue and red areas of the light
spectrum hence reflects green.
Chlorophyll comes in two
main types a and b
Water + carbon dioxide ---->
glucose + oxygen
There are two steps
1. The light phase (photo
bit)- chlorophyll absorbs
the energy of light and
a. splits water into hydrogen
which is carried by NADP
changing it to NADPH2 and
oxygen is released as a
waste product
b. some energy changes ADP
to ATP (Adenine Tri
Phosphate)
this happens on grana
2. Calvin Cycle (the synthesis part)
This uses the NADPH2 and ATP (energy)
a. Carbon dioxide is captured from the air and
fixed into a molecule (CO2 fixation)
b. The Calvin cycle reduces the fixed carbon
with the hydrogen from the NADPH2 changing
it back to NADP and using energy of ATP
This is a cycle.
• The glucose formed is turned to insoluble starch
• At night the starch is changed to sugar and goes
down the phloem to roots or stems
• The process generally happens during the
day
Plant structures that help the process of
photosynthesis
• Leaf
- thin and transparent for light to pass through
- tubes to transport water (xylem) and food (phloem)
- holes in leaf surface (stomata) that open and shut
(guard cells) to let in CO2 and let out water (to
cool the leaves down) and O2
- waxy layer for protection - to stop drying out and
the epidermis that contain stomata
- cells with chloroplasts (palisade and spongy
mesophyll
• Roots
- absorb water which is then pulled up the plant by
transpiration and capillary tubes (as a drop of
water leaves the leaf another is pulled in the roots)
- storage of the produced food - roots (tubers potatoes)
• Stems
- phloem and xylem to carry food and water
- storage of food (sugar cane, or celery)
Respiration
• Respiration is the
release of energy from
foods to carry out cell
processes (growth,
repair, muscular
activity, and many
other things)
• Respiration takes
place in the
mitochondria.
Respiration
• The raw materials for respiration are
glucose and oxygen - glucose is oxidised to
release energy (a small fire!) - so oxygen is
needed via gas exchange it comes into the
cell by diffusion
• Plants make their own food (glucose) for
respiration but animals need to obtain a
food source (plants or other animals) to get
carbohydrates, proteins and fats.
• The source of energy is adenosine triphosphate (ATP) this is produced in the cell by the process of respiration.
• ATP exists in three states (it is the universal energy carrier)
- two concern us ATP and ADP (adenosine diphosphate)
• ADP is an empty energy carrier. In respiration another
phosphorous is added to create ATP which is stable and is
later used as an energy source to power cell processes.
• Once used ATP becomes ADP and the cycle continues.
Aerobic respiration
• Respiration with oxygen - a process guided by enzymes,
releasing energy and turning ADP to ATP.
• NAD carries hydrogen during respiration
• Co enzyme A - carries an acetyl group (broken down
glucose CHO) during respiration- called acetyl co enzyme
A when full
Aerobic Respiration has four steps
Step 1: Glycolysis
• Happens in the cytoplasm
• 2 ATP produced
• No oxygen
Step 2: Formation of Acetyl co enzyme A
• In the matrix
• An acetyl group
• Carbon dioxide waste product
Step 3 Kreb Cycle
• In the inner matrix
• NAD – NADH2
• Carbon dioxide is waste product
Step 4 Electron transport chain
• In the cristae
• ATP
• Water is waste product